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Nanomaterials
Volume 8
Issue 6
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Nanomaterials, Volume 8, Issue 6 (June 2018) – 94 articles

Cover Story (view full-size image): Platinum nanoparticles (PtNPs) are internalized by THP-1 monocytes without affecting cell viability. The expression of CD14, CD11b, CCR2, and CCR5 is also not affected, nor is the basal release of inflammatory cytokines. However, PtNPs within THP-1 cells did not behave as a quiescent nanomaterial demonstrating catalytic activity by reducing reactive oxygen species (ROS) and modulating the transcription of 60 genes. We demonstrated that PtNPs are non-toxic, perform intracellular ROS scavenging, and possess good immune-compatibility, suggesting that they could be feasible synthetic nanozymes for applications in nanomedicine. View Paper here.
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12 pages, 2292 KiB  
Article
Spherical and Spindle-Like Abamectin-Loaded Nanoparticles by Flash Nanoprecipitation for Southern Root-Knot Nematode Control: Preparation and Characterization
by Zhinan Fu, Kai Chen, Li Li, Fang Zhao, Yan Wang, Mingwei Wang, Yue Shen, Haixin Cui, Dianhua Liu and Xuhong Guo
Nanomaterials 2018, 8(6), 449; https://doi.org/10.3390/nano8060449 - 20 Jun 2018
Cited by 27 | Viewed by 5327
Abstract
Southern root-knot nematode (Meloidogyne incognita) is a biotrophic parasite, causing enormous loss in global crop production annually. Abamectin (Abm) is a biological and high-efficiency pesticide against Meloidogyne incognita. In this study, a powerful method, flash nanoprecipitation (FNP), was adopted to [...] Read more.
Southern root-knot nematode (Meloidogyne incognita) is a biotrophic parasite, causing enormous loss in global crop production annually. Abamectin (Abm) is a biological and high-efficiency pesticide against Meloidogyne incognita. In this study, a powerful method, flash nanoprecipitation (FNP), was adopted to successfully produce Abm-loaded nanoparticle suspensions with high drug loading capacity (>40%) and encapsulation efficiency (>95%), where amphiphilic block copolymers (BCPs) poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-b-PEG), poly(d,l-lactide)-b-poly(ethylene glycol) (PLA-b-PEG), or poly(caprolactone)-b-poly(ethylene glycol) (PCL-b-PEG) were used as the stabilizer to prevent the nanoparticles from aggregation. The effect of the drug-to-stabilizer feed ratio on the particle stability were investigated. Moreover, the effect of the BCP composition on the morphology of Abm-loaded nanoparticles for controlling Meloidogyne incognita were discussed. Notably, spindle-like nanoparticles were obtained with PCL-b-PEG as the stabilizer and found significantly more efficient (98.4% mortality at 1 ppm particle concentration) than spherical nanoparticles using PLGA-b-PEG or PLA-b-PEG as the stabilizer. This work provides a more rapid and powerful method to prepare stable Abm-loaded nanoparticles with tunable morphologies and improved effectiveness for controlling Meloidogyne incognita. Full article
(This article belongs to the Special Issue Self-Assembled Bio-Nanomaterials: Synthesis, Characterization, and Applications)
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<p>(<b>a</b>) Illustration of the preparation of Abamectin (Abm)-loaded nanoparticles by flash nanoprecipitation. (<b>b</b>–<b>d</b>) Morphology of Abm-loaded nanoparticles with different stabilizers: poly(lactic-co-glycolic acid)-<span class="html-italic">b</span>-poly(ethylene glycol) (PLGA-<span class="html-italic">b</span>-PEG) (<b>b</b>), poly(<span class="html-small-caps">d</span>,<span class="html-small-caps">l</span>-lactide)-<span class="html-italic">b</span>-poly(ethylene glycol) (PLA-<span class="html-italic">b</span>-PEG) (<b>c</b>), and poly(caprolactone)-<span class="html-italic">b</span>-poly(ethylene glycol) (PCL-<span class="html-italic">b</span>-PEG) (<b>d</b>). (<b>e</b>) Biological assay of Abm-loaded nanoparticles to <span class="html-italic">Meloidogyne incognita</span>. THF = tetrahydrofuran.</p> Full article ">Figure 2
<p>TEM photographs of Abm-loaded nanoparticles prepared using (<b>a</b>) PLGA-<span class="html-italic">b</span>-PEG, (<b>b</b>) PLA-<span class="html-italic">b</span>-PEG, and (<b>c</b>) PCL-<span class="html-italic">b</span>-PEG as the stabilizer, respectively. The insets are the corresponding schematic diagrams.</p> Full article ">Figure 3
<p>Particle size and size distribution of Abm-loaded nanoparticles prepared using PLGA-<span class="html-italic">b</span>-PEG (<b>black</b>), PLA-<span class="html-italic">b</span>-PEG (<b>blue</b>), and PCL-<span class="html-italic">b</span>-PEG (<b>red</b>) as the stabilizer, respectively. The mean diameters derived from the Gaussian fits (solid lines) are 414, 314, and 72 nm, respectively.</p> Full article ">Figure 4
<p>Effect of various Abm-to-stabilizer ratios on particle stability for flash nanoprecipitation-nanoparticles (FNP-NPs) prepared with 10 mg/mL PLGA-b-PEG as the stabilizer. Stream 1 was 1, 2.5, 7.5, or 10 mg/mL of Abamectin dissolved in THF. Stream 2 was 10 mg/mL of PLGA-<span class="html-italic">b</span>-PEG dissolved in THF. The other two streams were both water.</p> Full article ">Figure 5
<p>Abm loading capacity of the nanoparticles prepared using PLGA-b-PEG as the stabilizer before and after storage at 0 °C for 7 days and 54 °C for 14 days.</p> Full article ">Figure 6
<p>Mortality of <span class="html-italic">Meloidogyne incognita</span> as a function of concentration of Abm-loaded nanoparticles prepared using different block copolymers (BCPs) as the stabilizer.</p> Full article ">
8 pages, 711 KiB  
Article
Measuring the Density of States of the Inner and Outer Wall of Double-Walled Carbon Nanotubes
by Benjamin A. Chambers, Cameron J. Shearer, LePing Yu, Christopher T. Gibson and Gunther G. Andersson
Nanomaterials 2018, 8(6), 448; https://doi.org/10.3390/nano8060448 - 19 Jun 2018
Cited by 5 | Viewed by 4195
Abstract
The combination of ultraviolet photoelectron spectroscopy and metastable helium induced electron spectroscopy is used to determine the density of states of the inner and outer coaxial carbon nanotubes. Ultraviolet photoelectron spectroscopy typically measures the density of states across the entire carbon nanotube, while [...] Read more.
The combination of ultraviolet photoelectron spectroscopy and metastable helium induced electron spectroscopy is used to determine the density of states of the inner and outer coaxial carbon nanotubes. Ultraviolet photoelectron spectroscopy typically measures the density of states across the entire carbon nanotube, while metastable helium induced electron spectroscopy measures the density of states of the outermost layer alone. The use of double-walled carbon nanotubes in electronic devices allows for the outer wall to be functionalised whilst the inner wall remains defect free and the density of states is kept intact for electron transport. Separating the information of the inner and outer walls enables development of double-walled carbon nanotubes to be independent, such that the charge transport of the inner wall is maintained and confirmed whilst the outer wall is modified for functional purposes. Full article
(This article belongs to the Special Issue Applications of Carbon Nanotubes)
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<p>Raman spectra for a single-walled carbon nanotube (SWCNT) and a double-walled carbon nanotube (DWCNT) with inset showing the radial breathing mode (RBM) region.</p> Full article ">Figure 2
<p>Comparison of ultraviolet photoelectron (UP) and metastable helium induced electron (MIE) spectra at low temperatures for both (<b>a</b>) SWCNT (113 K) and (<b>b</b>) DWCNT (173 K).</p> Full article ">
24 pages, 5532 KiB  
Article
Numerical Comparison of Prediction Models for Aerosol Filtration Efficiency Applied on a Hollow-Fiber Membrane Pore Structure
by Pavel Bulejko
Nanomaterials 2018, 8(6), 447; https://doi.org/10.3390/nano8060447 - 19 Jun 2018
Cited by 23 | Viewed by 6105
Abstract
Hollow-fiber membranes (HFMs) have been widely applied to many liquid treatment applications such as wastewater treatment, membrane contactors/bioreactors and membrane distillation. Despite the fact that HFMs are widely used for gas separation from gas mixtures, their use for mechanical filtration of aerosols is [...] Read more.
Hollow-fiber membranes (HFMs) have been widely applied to many liquid treatment applications such as wastewater treatment, membrane contactors/bioreactors and membrane distillation. Despite the fact that HFMs are widely used for gas separation from gas mixtures, their use for mechanical filtration of aerosols is very scarce. In this work, we compared mathematical models developed for the prediction of air filtration efficiency by applying them on the structural parameters of polypropylene HFMs. These membranes are characteristic of pore diameters of about 90 nm and have high solidity, thus providing high potential for nanoparticle removal from air. A single fiber/collector and capillary pore approach was chosen to compare between models developed for fibrous filters and capillary-pore membranes (Nuclepore filters) based on three main mechanisms occurring in aerosol filtration (inertial impaction, interception and diffusion). The collection efficiency due to individual mechanisms differs significantly. The differences are caused by the parameters for which the individual models were developed, i.e., given values of governing dimensionless numbers (Reynolds, Stokes and Peclet number) and also given values of filter porosity and filter fiber diameter. Some models can be used to predict the efficiency of HFMs based on assumptions depending on the conditions and exact membrane parameters. Full article
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<p>Polypropylene HFM pore structure.</p> Full article ">Figure 2
<p>Schematic presentation of individual collection mechanisms at a single collector.</p> Full article ">Figure 3
<p>Schematic filtration mechanisms involved in separation on a CPM.</p> Full article ">Figure 4
<p>Evaluation of collector diameter (<b>a</b>) and pore size (<b>b</b>) from SEM images using Stream Motion software.</p> Full article ">Figure 5
<p>Comparison of impaction efficiency based on different models and airflow velocity of 5 cm/s (<b>a</b>) and 20 cm/s (<b>b</b>) in relation to Stokes number.</p> Full article ">Figure 6
<p>SCE due to interception based on various models in relation to interception parameter.</p> Full article ">Figure 7
<p>Comparison of SCE due to diffusion mechanisms based on different models for an airflow velocity of 5 cm/s (<b>a</b>) and 20 cm/s (<b>b</b>) in relation to the Peclet number.</p> Full article ">Figure 8
<p>Collection efficiency due to the adhesion effect.</p> Full article ">Figure 9
<p>Single collector efficiency (<b>a</b>), overall filter efficiency (<b>b</b>) and overall penetration (<b>c</b>).</p> Full article ">Figure 9 Cont.
<p>Single collector efficiency (<b>a</b>), overall filter efficiency (<b>b</b>) and overall penetration (<b>c</b>).</p> Full article ">Figure 10
<p>Impaction efficiency based on CPM model.</p> Full article ">Figure 11
<p>Interception efficiency based on CPM model.</p> Full article ">Figure 12
<p>Collection efficiency due to diffusion in pores (<b>a</b>) and on the membrane surface (<b>b</b>).</p> Full article ">Figure 13
<p>Overall efficiency in relation to particle size based on CPM model for a velocity of 5 and 10 cm/s (<b>a</b>) and 15 and 20 cm/s (<b>b</b>).</p> Full article ">
11 pages, 3117 KiB  
Article
MIL-100(Al) Gels as an Excellent Platform Loaded with Doxorubicin Hydrochloride for pH-Triggered Drug Release and Anticancer Effect
by Yuge Feng, Chengliang Wang, Fei Ke, Jianye Zang and Junfa Zhu
Nanomaterials 2018, 8(6), 446; https://doi.org/10.3390/nano8060446 - 19 Jun 2018
Cited by 18 | Viewed by 5502
Abstract
Slow and controlled release systems for drugs have attracted increasing interest recently. A highly efficient metal-organic gel (MOGs) drug delivery carrier, i.e., MIL-100(Al) gel, has been fabricated by a facile, low cost, and environmentally friendly one-pot process. The unique structure of MIL-100(Al) gels [...] Read more.
Slow and controlled release systems for drugs have attracted increasing interest recently. A highly efficient metal-organic gel (MOGs) drug delivery carrier, i.e., MIL-100(Al) gel, has been fabricated by a facile, low cost, and environmentally friendly one-pot process. The unique structure of MIL-100(Al) gels has led to a high loading efficiency (620 mg/g) towards doxorubicin hydrochloride (DOX) as a kind of anticancer drug. DOX-loaded MOGs exhibited high stability under physiological conditions and sustained release capacity of DOX for up to three days (under acidic environments). They further showed sustained drug release behavior and excellent antitumor effects in in vitro experiments on HeLa cells, in contrast with the extremely low biotoxicity of MOGs. Our work provides a promising way for anticancer therapy by utilizing this MOGs-based drug delivery system as an efficient and safe vehicle. Full article
(This article belongs to the Special Issue Nanocolloids for Nanomedicine and Drug Delivery)
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Full article ">Figure 1
<p>TEM images of (<b>a</b>,<b>b</b>) MIL-100(Al) gels. (<b>c</b>,<b>d</b>) DOX-loaded MIL-100(Al) gels.</p> Full article ">Figure 2
<p>(<b>a</b>) Powder XRD patterns of MIL-100(Al) gels, DOX-loaded MOGs, and drug-released MOGs at pH 5.5; (<b>b</b>) FTIR spectra of MIL-100(Al) gels, DOX, and DOX-loaded MOGs.</p> Full article ">Figure 3
<p>Drug release profiles for DOX-loaded MOGs in PBS buffer solution at pH = 5.5 and pH = 7.4 within 100 h. (Inset are TEM images of DOX-loaded MOGs after 10 h, 50 h, and 100 h in release process at pH 5.5.) Bars denote the standard deviation (±SD, <span class="html-italic">n</span> = 5).</p> Full article ">Figure 4
<p>The effect of MIL-100(Al) gels and DOX-loaded MOGs with various concentrations on the cell viability of HeLa cells in 24 h (the orange and blue bars represent the viability of HeLa cancer cells incubated with MIL-100(Al) gels and DOX-loaded MOGs, respectively).</p> Full article ">Figure 5
<p>Cell viability of HeLa cells incubated with DOX-loaded MOGs and MOGs + free DOX for different time periods at concentrations of (<b>a</b>) 2.5 μg/mL, (<b>b</b>) 5 μg/mL, (<b>c</b>) 10 μg/mL, (<b>d</b>) 25 μg/mL, (<b>e</b>) 50 μg/mL, and (<b>f</b>) 100 μg/mL.</p> Full article ">Figure 6
<p>Flow cytometry experiments of HeLa cells when incubated with (<b>a</b>) Pure autoclave water as control, (<b>b</b>) MIL-100(Al) gels, and (<b>c</b>) DOX-loaded MOGs, respectively.</p> Full article ">Figure 7
<p>Confocal microscopy images of HeLa cells incubated with 12.5 μg/mL (<b>a</b>–<b>d</b>) MIL-100(Al) gels and (<b>e</b>–<b>h</b>) DOX-loaded MOGs, respectively. Blue fluorescence represents the living cell imaging. Red fluorescence represents the released DOX from DOX-loaded MOGs within the cancer cells. Green fluorescence represents the apoptosis of cells. (<b>d</b>,<b>h</b>) are the merged images of (<b>a</b>–<b>c</b>) and (<b>e</b>–<b>g</b>), respectively.</p> Full article ">
13 pages, 4875 KiB  
Article
Hydrophilic Chlorin e6-Poly(amidoamine) Dendrimer Nanoconjugates for Enhanced Photodynamic Therapy
by So-Ri Lee and Young-Jin Kim
Nanomaterials 2018, 8(6), 445; https://doi.org/10.3390/nano8060445 - 18 Jun 2018
Cited by 23 | Viewed by 5160
Abstract
In photodynamic therapy (PDT), chlorin e6 (Ce6), with its high phototoxic potential and strong absorption of visible light, penetrates deeply into photodamaged tissue. However, despite this fact, the direct application of Ce6 to PDT has been limited by its low water solubility and [...] Read more.
In photodynamic therapy (PDT), chlorin e6 (Ce6), with its high phototoxic potential and strong absorption of visible light, penetrates deeply into photodamaged tissue. However, despite this fact, the direct application of Ce6 to PDT has been limited by its low water solubility and poor cancer cell localization. To ameliorate this situation, we report herein on the use of a hydrophilic nanoconjugate (DC) comprised of Ce6 and poly(amidoamine) dendrimer, which improves the water solubility and intracellular uptake of Ce6, thereby enhancing PDT efficacy. The synthesis of DC was verified by 1H nuclear magnetic resonance (NMR) analysis, and the coupling ratio of Ce6 introduced onto DC was 2.64. The prepared DC was spherical, with an average diameter of 61.7 ± 3.5 nm. In addition, the characteristic ultraviolet-visible absorption bands of DC in distilled water were similar to those of free Ce6 in dimethyl sulfoxide (DMSO), indicating that the Ce6 chromophore did not change upon conjugation. Investigation using fluorescence spectroscopy and confocal microscopy revealed a greater intracellular uptake of DC than of Ce6 alone. Moreover, DC exhibited significantly increased phototoxicity to human cervical cancer cells, mostly because of apoptotic cell death. These results imply that DC is a candidate for the clinical treatment of PDT. Full article
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Full article ">Figure 1
<p>Schematic diagram of synthesis of hydrophilic Ce6-PAMAM dendrimer nanoconjugate (DC).</p> Full article ">Figure 2
<p>(<b>a</b>) TEM images and (<b>b</b>) particle size distribution of DC.</p> Full article ">Figure 3
<p>(<b>a</b>) Photographs of free chlorin e6 (Ce6) and DC dissolved in DMSO or DW (0.2 mg/mL Ce6). The arrow shows the precipitate of Ce6. (<b>b</b>) UV-visible absorbance spectra and (<b>c</b>) fluorescence emission spectra (λ<sub>ex</sub> = 360 nm) of free Ce6 and DC in DMSO or DW (10 μg/mL Ce6).</p> Full article ">Figure 4
<p>9,10-Dimethylnathracene (DMA) fluorescence change (F<sub>f</sub> − F<sub>s</sub>) due to singlet oxygen generation by free Ce6 and DC after laser irradiation in Dulbecco’s phosphate-buffered saline (DPBS) (pH 7.4), where F<sub>f</sub> and F<sub>s</sub> represent the fluorescence intensity of full DMA and each sample.</p> Full article ">Figure 5
<p>Change in fluorescence intensity due to intracellular uptake of free Ce6 and DC (4 μg/mL Ce6) in HeLa cells as a function of incubation time (<span class="html-italic">n</span> = 5).</p> Full article ">Figure 6
<p>Confocal laser scanning microscopy image of the intracellular distribution of (<b>a</b>) free Ce6 and (<b>b</b>) DC in HeLa cells after incubation for 2 h in the dark.</p> Full article ">Figure 7
<p>In vitro phototoxicity and dark-toxicity of various concentrations of Ce6 and DC on HeLa cells with and without laser irradiation (<span class="html-italic">n</span> = 6).</p> Full article ">Figure 8
<p>Fluorescence microscopy images of live HeLa cells and dead HeLa cells stained with calcein-AM (green) and ethidium homodimer-1 (EthD-1) (red) with (<b>a</b>) no drug, (<b>b</b>) free Ce6, and (<b>c</b>) DC (4 μg/mL Ce6) after irradiation by 2.5 J/cm<sup>2</sup>, 671 nm diode laser.</p> Full article ">Figure 9
<p>Flow cytometric analysis of ROS generation in HeLa cells treated with free Ce6 and DC (4 μg/mL Ce6). (<b>a</b>) Shift in fluorescence peak due to the ROS generation in the presence of free Ce6 and DC before irradiation (Ce6(−) and DC(−)) and after irradiation (Ce6(+) and DC(+)) with a 2.5-J/cm<sup>2</sup>, 671-nm diode laser. (<b>b</b>) DCF fluorescence intensity measured with the flow cytometer for investigating the ROS level with free Ce6 and DC before and after irradiation (<span class="html-italic">n</span> = 5).</p> Full article ">Figure 10
<p>Morphology of HeLa cells stained with neutral red and H-33258 (<b>a</b>) before photodynamic treatment (no drug and no light) and after treatment with (<b>b</b>) free Ce6 and (<b>c</b>) DC (4 μg/mL Ce6), followed by irradiation with a 2.5-J/cm<sup>2</sup>, 671-nm diode laser.</p> Full article ">
12 pages, 4385 KiB  
Article
In Situ Synthesis of Ag@Cu2O-rGO Architecture for Strong Light-Matter Interactions
by Shuang Guo, Yaxin Wang, Fan Zhang, Renxian Gao, Maomao Liu, Lirong Dong, Yang Liu, Yongjun Zhang and Lei Chen
Nanomaterials 2018, 8(6), 444; https://doi.org/10.3390/nano8060444 - 17 Jun 2018
Cited by 11 | Viewed by 4776
Abstract
Emerging opportunities based on two-dimensional (2D) layered structures can utilize a variety of complex geometric architectures. Herein, we report the synthesis and properties of a 2D+0D unique ternary platform-core-shell nanostructure, termed Ag@Cu2O-rGO, where the reduced graphene oxide (rGO) 2D acting as [...] Read more.
Emerging opportunities based on two-dimensional (2D) layered structures can utilize a variety of complex geometric architectures. Herein, we report the synthesis and properties of a 2D+0D unique ternary platform-core-shell nanostructure, termed Ag@Cu2O-rGO, where the reduced graphene oxide (rGO) 2D acting as a platform is uniformly decorated by Ag@Cu2O core-shell nanoparticles. Cu2O nanoparticles occupy the defect positions on the surface of the rGO platform and restore the conjugation of the rGO structure, which contributes to the significant decrease of the ID/IG intensity ratio. The rGO platform can not only bridge the isolated nanoparticles together but also can quickly transfer the free electrons arising from the Ag core to the Cu2O shell to improve the utilization efficiency of photogenerated electrons, as is verified by high efficient photocatalytic activity of Methyl Orange (MO). The multi-interface coupling of the Ag@Cu2O-rGO platform-core-shell nanostructure leads to the decrease of the bandgap with an increase of the Cu2O shell thickness, which broadens the absorption range of the visible light spectrum. Full article
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Full article ">Figure 1
<p>Schematic of the synthetic procedure for Ag@Cu<sub>2</sub>O-reduced graphene oxide (rGO) nanostructures.</p> Full article ">Figure 2
<p>SEM images of (<b>A</b>) Ag-rGO and Ag@Cu<sub>2</sub>O-rGO nanocomposites with different concentrations of Cu(NO<sub>3</sub>)<sub>2</sub> solution ((<b>B</b>–<b>F</b>), S-2 mM, S-4 mM, S-6 mM, S-8 mM, and S-10 mM). The insets are the corresponding TEM images.</p> Full article ">Figure 3
<p><b>Figure</b><b>3.</b> TEM image (<b>A</b>) and high-resolution TEM image (<b>B</b>) of the Ag@Cu<sub>2</sub>O-rGO (S-8 mM). The EDS line on the red segment in (<b>B</b>) corresponds to the different elements (<b>C</b>) and the corresponding element count-position curve (<b>D</b>).</p> Full article ">Figure 4
<p>The X-ray photoelectron spectroscopy (XPS) survey spectra (<b>A</b>) of Ag-rGO and Ag@Cu<sub>2</sub>O-rGO; high-resolution XPS spectra of C 1s for (<b>B</b>) Ag-rGO and (<b>C</b>) Ag@Cu<sub>2</sub>O-rGO. The XPS survey spectra of Cu element and Ag element (<b>D</b>) in Ag@Cu<sub>2</sub>O-rGO.</p> Full article ">Figure 4 Cont.
<p>The X-ray photoelectron spectroscopy (XPS) survey spectra (<b>A</b>) of Ag-rGO and Ag@Cu<sub>2</sub>O-rGO; high-resolution XPS spectra of C 1s for (<b>B</b>) Ag-rGO and (<b>C</b>) Ag@Cu<sub>2</sub>O-rGO. The XPS survey spectra of Cu element and Ag element (<b>D</b>) in Ag@Cu<sub>2</sub>O-rGO.</p> Full article ">Figure 5
<p>(<b>A</b>) Raman spectra of GO, Ag-rGO, and Ag@Cu<sub>2</sub>O-rGO; (<b>B</b>) Raman spectra of Ag@Cu<sub>2</sub>O-rGO nanocomposites for S-2 mM to S-10 mM, the inset shows the dependence of the intensity of Ag@Cu<sub>2</sub>O-rGO on Cu<sub>2</sub>O content.</p> Full article ">Figure 6
<p>(<b>A</b>) UV-VIS absorption spectra of Ag-rGO and the Ag@Cu<sub>2</sub>O-rGO nanocomposites S-2 mM, S-4 mM, S-6 mM, S-8 mM, and S-10 mM; (<b>B</b>) the plots of (αhν)<sup>2</sup> vs. photon energy (hν).</p> Full article ">Figure 7
<p>(<b>A</b>) Photocatalytic degradation of Methyl Orange (MO) (4 mg/L) under visible-light irradiation at room temperature with different catalysts: Ag-rGO and the Ag@Cu<sub>2</sub>O-rGO nanocomposites S-2 mM, S-4 mM, S-6 mM, S-8 mM, and S-10 mM; (<b>B</b>) absorption spectra of the photocatalytic degradation of MO in the presence of Ag@Cu<sub>2</sub>O-rGO (S-8 mM) the inset is the corresponding digital camera photographs of MO dye.</p> Full article ">Figure 8
<p>Schematic illustration of the Ag@Cu<sub>2</sub>O-rGO charge transfer in the photocatalytic degradation process of MO.</p> Full article ">
12 pages, 3633 KiB  
Communication
Nitrogen-Doped Carbon Nanoparticles Derived from Silkworm Excrement as On–Off–On Fluorescent Sensors to Detect Fe(III) and Biothiols
by Xingchang Lu, Chen Liu, Zhimin Wang, Junyi Yang, Mengjing Xu, Jun Dong, Ping Wang, Jiangjiang Gu and Feifei Cao
Nanomaterials 2018, 8(6), 443; https://doi.org/10.3390/nano8060443 - 17 Jun 2018
Cited by 30 | Viewed by 5014
Abstract
On–off–on fluorescent sensors based on emerging carbon nanoparticles (CNPs) or carbon dots (CDs) have attracted extensive attention for their convenience and efficiency. In this study, dumped silkworm excrement was used as a novel precursor to prepare fluorescent nitrogen-doped CNPs (N-CNPs) through hydrothermal treatment. [...] Read more.
On–off–on fluorescent sensors based on emerging carbon nanoparticles (CNPs) or carbon dots (CDs) have attracted extensive attention for their convenience and efficiency. In this study, dumped silkworm excrement was used as a novel precursor to prepare fluorescent nitrogen-doped CNPs (N-CNPs) through hydrothermal treatment. The obtained N-CNPs showed good photoluminescent properties and excellent water dispersibility. Thus, they were applied as fluorescence “on–off–on” probes for the detection of Fe(III) and biothiols. The “on–off” process was achieved by adding Fe(III) into N-CNP solution, which resulted in the selective fluorescence quenching, with the detection limit of 0.20 μM in the linear range of 1–500 μM. Following this, the introduction of biothiols could recover the fluorescence efficiently, in order to realize the “off–on” process. By using glutathione (GSH) as the representative, the linear range was in the range of 1–1000 μM, and the limit of detection was 0.13 μM. Moreover, this useful strategy was successfully applied for the determination of amounts of GSH in fetal calf serum samples. Full article
(This article belongs to the Special Issue Nanostructured Biosensors)
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Figure 1

Figure 1
<p>A schematic illustration of the formation of nitrogen-doped CNPs (N-CNPs) from silkworm excrement, and the fluorescence “on–off–on” detection of Fe(III) and biothiols.</p> Full article ">Figure 2
<p>Transmission electron microscopy (TEM) image (<b>a</b>); the particle size distribution histogram (<b>b</b>); X-ray diffraction (XRD) pattern (<b>c</b>); and fourier transform infrared (FT-IR) spectrum (<b>d</b>) of N-CNPs.</p> Full article ">Figure 3
<p>X-ray photoelectron spectroscopy (XPS) full survey (<b>a</b>); C 1s (<b>b</b>); N 1s (<b>c</b>) and O 1s (<b>d</b>) spectra of N-CNPs. Black line: raw, navy line: background, other lines: fitting.</p> Full article ">Figure 4
<p>Ultraviolet-visible (UV-vis) absorption spectrum (<b>a</b>) and photoluminescent (PL) emission spectra at different excitation wavelengths (<b>b</b>) of N-CNPs. Inset: photographs of N-CNPs in water under daylight and UV irradiation.</p> Full article ">Figure 5
<p>(<b>a</b>) Selectivity of N-CNPs with different ions at the same concentration (500 μM); (<b>b</b>) The linear relationship between F<sub>0</sub>/F and Fe(III) concentration. F and F<sub>0</sub> were the PL intensities (424 nm) of N-CNPs at 340 nm excitation in the presence and absence of ions, respectively.</p> Full article ">Figure 6
<p>(<b>a</b>) Selectivity of N-CNPs/Fe(III) to different biological molecules at the same concentration (1 mM); (<b>b</b>) The linear relationship between (F’/F’<sub>0</sub>) and the square root of glutathione (GSH) concentration. F’ and F’<sub>0</sub> were the PL intensities (424 nm) of N-CNPs/Fe(III) at 340 nm excitation in the absence and presence of biological molecules, respectively.</p> Full article ">
18 pages, 4007 KiB  
Article
Emergence of Quantum Phase-Slip Behaviour in Superconducting NbN Nanowires: DC Electrical Transport and Fabrication Technologies
by Nicolas G. N. Constantino, Muhammad Shahbaz Anwar, Oscar W. Kennedy, Manyu Dang, Paul A. Warburton and Jonathan C. Fenton
Nanomaterials 2018, 8(6), 442; https://doi.org/10.3390/nano8060442 - 16 Jun 2018
Cited by 27 | Viewed by 4973
Abstract
Superconducting nanowires undergoing quantum phase-slips have potential for impact in electronic devices, with a high-accuracy quantum current standard among a possible toolbox of novel components. A key element of developing such technologies is to understand the requirements for, and control the production of, [...] Read more.
Superconducting nanowires undergoing quantum phase-slips have potential for impact in electronic devices, with a high-accuracy quantum current standard among a possible toolbox of novel components. A key element of developing such technologies is to understand the requirements for, and control the production of, superconducting nanowires that undergo coherent quantum phase-slips. We present three fabrication technologies, based on using electron-beam lithography or neon focussed ion-beam lithography, for defining narrow superconducting nanowires, and have used these to create nanowires in niobium nitride with widths in the range of 20–250 nm. We present characterisation of the nanowires using DC electrical transport at temperatures down to 300 mK. We demonstrate that a range of different behaviours may be obtained in different nanowires, including bulk-like superconducting properties with critical-current features, the observation of phase-slip centres and the observation of zero conductance below a critical voltage, characteristic of coherent quantum phase-slips. We observe critical voltages up to 5 mV, an order of magnitude larger than other reports to date. The different prominence of quantum phase-slip effects in the various nanowires may be understood as arising from the differing importance of quantum fluctuations. Control of the nanowire properties will pave the way for routine fabrication of coherent quantum phase-slip nanowire devices for technology applications. Full article
(This article belongs to the Special Issue Synthesis and Characterization of Nanowires)
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Figure 1
<p>Measurements and analysis of <math display="inline"> <semantics> <mrow> <mi>R</mi> <mo>(</mo> <mi>T</mi> <mo>)</mo> </mrow> </semantics> </math> for NbN films with thickness <span class="html-italic">d</span> in the range 10–103 nm. (<b>a</b>) Sheet resistance <math display="inline"> <semantics> <mrow> <msub> <mi>R</mi> <mo>□</mo> </msub> <mrow> <mo>(</mo> <mi>T</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math>. The films with thickness of 10 nm and 26 nm were patterned into structures with 90-μm-wide, 2.4-mm-long tracks prior to measurement; the other measurements were carried out on unpatterned films. (<b>b</b>) The same data as (a) at low <span class="html-italic">T</span>, normalised to the maximum resistance <math display="inline"> <semantics> <msub> <mi>R</mi> <mi>max</mi> </msub> </semantics> </math>. (<b>c</b>) Variation of <math display="inline"> <semantics> <msub> <mi>T</mi> <mi mathvariant="normal">c</mi> </msub> </semantics> </math> with low-temperature maximum <math display="inline"> <semantics> <msub> <mi>R</mi> <mo>□</mo> </msub> </semantics> </math>. The line shows a fit to <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi mathvariant="normal">c</mi> </msub> <mo>/</mo> <msub> <mi>T</mi> <mrow> <mi mathvariant="normal">c</mi> <mn>0</mn> </mrow> </msub> <mo>=</mo> <mo form="prefix">exp</mo> <mrow> <mo>(</mo> <mi>γ</mi> <mo>)</mo> </mrow> <msup> <mrow> <mo>(</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>/</mo> <mi>γ</mi> <mo>−</mo> <msqrt> <mrow> <mi>t</mi> <mo>/</mo> <mn>2</mn> </mrow> </msqrt> <mo>+</mo> <mi>t</mi> <mo>/</mo> <mn>4</mn> <mo>)</mo> </mrow> <mo>/</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>/</mo> <mi>γ</mi> <mo>+</mo> <msqrt> <mrow> <mi>t</mi> <mo>/</mo> <mn>2</mn> </mrow> </msqrt> <mo>+</mo> <mi>t</mi> <mo>/</mo> <mn>4</mn> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mrow> <mn>1</mn> <mo>/</mo> <mi>γ</mi> </mrow> </msup> </mrow> </semantics> </math> with <math display="inline"> <semantics> <mrow> <mi>t</mi> <mo>=</mo> <msub> <mi>R</mi> <mo>□</mo> </msub> <mo>/</mo> <mrow> <mo>(</mo> <mn>4</mn> <mi>π</mi> <msub> <mi>R</mi> <mi mathvariant="normal">Q</mi> </msub> <mo>)</mo> </mrow> </mrow> </semantics> </math> and where the fit coefficient <math display="inline"> <semantics> <mi>γ</mi> </semantics> </math> is related to the elastic scattering time <math display="inline"> <semantics> <mi>τ</mi> </semantics> </math> by <math display="inline"> <semantics> <mrow> <mi>τ</mi> <mo>=</mo> <mo>(</mo> <mi>h</mi> <mo>/</mo> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi mathvariant="normal">B</mi> </msub> <msub> <mi>T</mi> <mrow> <mi mathvariant="normal">c</mi> <mn>0</mn> </mrow> </msub> <mo>)</mo> </mrow> <mo>)</mo> <mo form="prefix">exp</mo> <mrow> <mo>(</mo> <mo>−</mo> <mi>γ</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math> [<a href="#B31-nanomaterials-08-00442" class="html-bibr">31</a>], and we also treat <math display="inline"> <semantics> <msub> <mi>T</mi> <mrow> <mi mathvariant="normal">c</mi> <mn>0</mn> </mrow> </msub> </semantics> </math> as a fit coefficient, obtaining <math display="inline"> <semantics> <msub> <mi>T</mi> <mrow> <mi mathvariant="normal">c</mi> <mn>0</mn> </mrow> </msub> </semantics> </math> = 13.4 K. (The fit parameter <math display="inline"> <semantics> <mi>γ</mi> </semantics> </math> is related to the fit parameter <math display="inline"> <semantics> <msub> <mi>γ</mi> <mrow> <mo>[</mo> <mn>31</mn> <mo>]</mo> </mrow> </msub> </semantics> </math> in [<a href="#B31-nanomaterials-08-00442" class="html-bibr">31</a>] by <math display="inline"> <semantics> <mrow> <mi>γ</mi> <mo>=</mo> <mo>−</mo> <mn>1</mn> <mo>/</mo> <msub> <mi>γ</mi> <mrow> <mo>[</mo> <mn>31</mn> <mo>]</mo> </mrow> </msub> </mrow> </semantics> </math>.) Inset: Variation of <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi mathvariant="normal">c</mi> </msub> <mi>d</mi> </mrow> </semantics> </math> with <math display="inline"> <semantics> <msub> <mi>R</mi> <mo>□</mo> </msub> </semantics> </math>; the line shows a fit to <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi mathvariant="normal">c</mi> </msub> <mrow> <mo>(</mo> <mi mathvariant="normal">K</mi> <mo>)</mo> </mrow> <mo>.</mo> <mspace width="0.166667em"/> <mi>d</mi> <mrow> <mo>(</mo> <mi>nm</mi> <mo>)</mo> </mrow> <mo>=</mo> <mi>A</mi> <msup> <mrow> <mo>[</mo> <msub> <mi>R</mi> <mo>□</mo> </msub> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">Ω</mi> <mo>)</mo> </mrow> <mo>]</mo> </mrow> <mrow> <mo>−</mo> <mi>B</mi> </mrow> </msup> </mrow> </semantics> </math> as applied in [<a href="#B32-nanomaterials-08-00442" class="html-bibr">32</a>].</p> Full article ">Figure 2
<p>Schematic side view cross-sections through nanowire showing the fabrication technologies employed. (<b>a</b>) Fabrication by negative resist, electron-beam lithography (EBL) and reactive ion etching (RIE). (<b>b</b>) Nanowire cut-out using positive resist, EBL and RIE. (<b>c</b>) Nanowire definition by neon focussed ion-beam milling (Ne-FIB).</p> Full article ">Figure 3
<p>Plan-view micrographs of nanowires we have fabricated via three different processes. (<b>a</b>) He-FIB image of a nanowire fabricated using a hydrogen silsesquioxane (HSQ) negative-resist mask. Kinks in the nanowire shape may arise from strain relief of the nanowire resist mask during processing [<a href="#B34-nanomaterials-08-00442" class="html-bibr">34</a>]. Inset: An enlarged view of the part of the image indicated by the upper red box. (<b>b</b>) Scanning electron micrograph of a nanowire fabricated by cut-out using a polymethyl methacrylate (PMMA) mask. (<b>c</b>) He-FIB image of a nanowire defined by Ne-FIB. In all images, light contrast shows the niobium nitride, and dark contrast shows the substrate. Note that not all the images show the narrowest nanowire obtained using this strategy.</p> Full article ">Figure 4
<p><math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> measurements at 4.2 K for five nanowires with widths in the range 20–250 nm in a film of a thickness of 10 nm. (<b>a</b>) <math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> at 4.2 K for nanowires of widths of 250 nm, 100 nm and 75 nm. Lines join consecutive points. (<b>b</b>) Same data zoomed-in at low bias and also showing data for nanowires of widths of 50 nm and 25 nm. (<b>c</b>) Data for the three narrowest nanowires on a further expanded scale. Notice that the data for the 50-nm-wide and 75-nm-wide nanowires contain small jumps for <math display="inline"> <semantics> <mrow> <mi>V</mi> <mo>&lt;</mo> <mn>20</mn> </mrow> </semantics> </math> mV.</p> Full article ">Figure 5
<p>Measurements on sample NbN81/2. (<b>a</b>) <math display="inline"> <semantics> <mrow> <mi>R</mi> <mo>(</mo> <mi>T</mi> <mo>)</mo> </mrow> </semantics> </math>. The inset shows the same data on an expanded scale. (<b>b</b>) <math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> at 330 mK. The lines show fits to the form <math display="inline"> <semantics> <mrow> <mi>V</mi> <mo>=</mo> <msub> <mi>V</mi> <mi>i</mi> </msub> <mo form="prefix">sinh</mo> <mrow> <mo>(</mo> <mi>I</mi> <mo>/</mo> <msub> <mi>I</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> </mrow> </semantics> </math>: the dashed line shows the best fit to thermally activated phase-slips (TAPS), with <math display="inline"> <semantics> <mrow> <msub> <mi>V</mi> <mi>TAPS</mi> </msub> <mo>=</mo> <mn>45.7</mn> </mrow> </semantics> </math> mV, and the dashed line shows the best fit as a model of incoherent quantum phase-slips (IQPS), with <math display="inline"> <semantics> <mrow> <msub> <mi>V</mi> <mi>IQPS</mi> </msub> <mo>=</mo> <mn>467</mn> </mrow> </semantics> </math> mV and <math display="inline"> <semantics> <mrow> <msub> <mi>I</mi> <mi>IQPS</mi> </msub> <mo>=</mo> <mn>77.9</mn> </mrow> </semantics> </math> mA. The inset shows the same data on an expanded scale.</p> Full article ">Figure 6
<p><math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> for nanowire NbN65/1 at 320 mK, which has a width of 40 nm and a length of 220 nm and was fabricated using Ne-FIB. The <math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> shows possible phase-slip-centre behaviour. Solid lines join consecutive points; arrows show the direction of current sweep; and dashed red lines show resistance multiples of 6.5 kΩ.</p> Full article ">Figure 7
<p>Measurements of sample NbN25/A1. (<b>a</b>) <math display="inline"> <semantics> <mrow> <mi>R</mi> <mo>(</mo> <mi>T</mi> <mo>)</mo> </mrow> </semantics> </math>, found by fitting to <math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> taken with <math display="inline"> <semantics> <mrow> <mo>|</mo> <mi>I</mi> <mo>|</mo> <mo>≤</mo> <mn>10</mn> </mrow> </semantics> </math> nA. (<b>b</b>) <math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> at 330 mK. (<b>c</b>) Low-bias sweep at 330 mK, showing a critical voltage feature.</p> Full article ">Figure 8
<p>Measurements on sample NbN80/1. (<b>a</b>) <math display="inline"> <semantics> <mrow> <mi>R</mi> <mo>(</mo> <mi>T</mi> <mo>)</mo> </mrow> </semantics> </math>. Inset: the same data on an expanded scale showing the low-temperature region. (<b>b</b>) High-bias <math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> at 330 mK. (<b>c</b>) <math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>V</mi> <mo>)</mo> </mrow> </semantics> </math> at three temperatures above and below <math display="inline"> <semantics> <msub> <mi>T</mi> <mi mathvariant="normal">c</mi> </msub> </semantics> </math>, 350 mK, 1.92 K and 12.98 K. In all sub-plots, lines join consecutive data points. Voltage- and current-offsets of −1.25 mV, 0.5 mV and −0.28 mV and 5.5 pA, 6.0 pA and 5.5 pA, respectively, have been subtracted from the respective datasets in (c). The slight hysteresis observed in the measurement at 12.98 K is not a property of the sample, but rather an artefact associated with carrying out the measurement relatively rapidly (see <a href="#sec3dot2-nanomaterials-08-00442" class="html-sec">Section 3.2</a>).</p> Full article ">
14 pages, 5629 KiB  
Article
Synthesis of Magnetic Wood Fiber Board and Corresponding Multi-Layer Magnetic Composite Board, with Electromagnetic Wave Absorbing Properties
by Zhichao Lou, Yao Zhang, Ming Zhou, He Han, Jiabin Cai, Lintian Yang, Chenglong Yuan and Yanjun Li
Nanomaterials 2018, 8(6), 441; https://doi.org/10.3390/nano8060441 - 16 Jun 2018
Cited by 45 | Viewed by 4561
Abstract
With the rapid growth in the use of wireless electronic devices, society urgently needs electromagnetic wave (EMW) absorbing material with light weight, thin thickness, wide effective absorbing band width, and strong absorption capacity. Herein, the multi-layer magnetic composite boards are fabricated by hot-pressing [...] Read more.
With the rapid growth in the use of wireless electronic devices, society urgently needs electromagnetic wave (EMW) absorbing material with light weight, thin thickness, wide effective absorbing band width, and strong absorption capacity. Herein, the multi-layer magnetic composite boards are fabricated by hot-pressing magnetic fiber boards and normal veneer layer-by-layer. The magnetic fibers obtained using in-situ chemical co-precipitation are used to fabricate magnetic fiber board by hot-pressing. The magnetic wave absorbing capacities of the magnetic fiber boards obtained with 72 h impregnation time exhibit strongest adsorption capacities of −51.01 dB with a thickness of 3.00 mm. It is proved that this outstanding EMW absorption property is due to the strongest dielectric loss, the optimal magnetic loss, and the dipole relaxation polarization. Meanwhile, the EMW absorbing capacities of the corresponding multi-layer composite magnetic board increases from −14.14 dB (3-layer) to −60.16 dB (7-layer). This is due to the generated multi-interfaces between magnetic fiber board and natural wood veneer in the EMW propagation direction, which significantly benefit multireflection and attenuation of the incident waves. The results obtained in this work indicate that natural wood fibers are of great potential in the fabrication of magnetic multi-layer boards treated as EMW absorbers via a low cost, green, and scalable method. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>A</b>) Schematic diagram of the three different magnetic fiber multi-layer board. (<b>B</b>) The experimental components the network analyzer: 1. EMW generator; 2. attenuator; 3. specimen holder; 4. attenuator; 5. EMW receiving terminal; 6. test sample.</p> Full article ">Figure 2
<p>SEM and EDS images of the (<b>A</b>) untreated and (<b>B</b>) treated wood fibers. (3), (4) are EDS mappings of O and Fe for the separate wood fibers in <b>A</b>(2) and <b>B</b>(2), respectively. Insert: macro-structures of two samples. (<b>C</b>) is the SEM image of treated wood fibers in a large view. The typical particles and clusters in the spaces among the fibers and on the fiber surface are pointed to with yellow and green arrows, respectively.</p> Full article ">Figure 3
<p>(<b>A</b>) XRD patterns of the untreated (black) and treated (red) wood fibers. (<b>B</b>) VSM curves of the untreated wood fibers (black), and magnetic wood fibers with impregnation time of 24 h (green), 48 h (blue), and 72 h (red), respectively.</p> Full article ">Figure 4
<p>The reflection loss curves of the 3-layer composite magnetic board fabricated by a magnetic fiber core with the thickness from 2 mm to 5 mm.</p> Full article ">Figure 5
<p>The reflection loss curves of the three-layer composite magnetic board fabricated by a magnetic fiber core with the thickness of 3 mm. The impregnation time was 24 h, 48 h, and 72 h, respectively.</p> Full article ">Figure 6
<p>Frequency dependences of real parts (<b>A</b>) and imaginary parts (<b>B</b>) of complex permittivities, and the real parts (<b>C</b>) and imaginary parts (<b>D</b>) of complex permeabilities of the magnetic fiber boards with different impregnation time, 24 h, 48 h and 72 h, respectively.</p> Full article ">Figure 7
<p>Plots of <math display="inline"> <semantics> <mrow> <msup> <mi>μ</mi> <mo>″</mo> </msup> <msup> <mrow> <mrow> <mo>(</mo> <msup> <mi>μ</mi> <mo>′</mo> </msup> <mo>)</mo> </mrow> </mrow> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> <msup> <mi>f</mi> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </semantics> </math> vs. frequency for all the as-prepared magnetic wood fibers.</p> Full article ">Figure 8
<p>Frequency dependences of <math display="inline"> <semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>ε</mi> </msub> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>μ</mi> </msub> </mrow> </semantics> </math> of magnetic wood: 24 h (black), 48 h (blue), and 72 h (red).</p> Full article ">Figure 9
<p>Scheme of primary EMI absorbing processes in the magnetic fiber board (Left): interfacial polarization (Right) at the interfaces between Fe<sub>3</sub>O<sub>4</sub> nanoparticles and the carbohydrates from the wood fiber surface, and conductive network (Middle) constructed by magnetic nanoparticles. The nanoparticles attached on the wood fiber surface and in the spaces among these fibers (as observed in <a href="#nanomaterials-08-00441-f003" class="html-fig">Figure 3</a>C) are labeled as black.</p> Full article ">Figure 10
<p>(<b>A</b>) The reflection loss curves of 3-, 5-, and 7-layer magnetic composite boards. (<b>B</b>) Schematic illustrating the EMW absorbing mechanisms for multi-layer magnetic composite boards perpendicular to the plane.</p> Full article ">
14 pages, 5211 KiB  
Article
Hazy Al2O3-FTO Nanocomposites: A Comparative Study with FTO-Based Nanocomposites Integrating ZnO and S:TiO2 Nanostructures
by Shan-Ting Zhang, Guy Vitrant, Etienne Pernot, Carmen Jiménez, David Muñoz-Rojas and Daniel Bellet
Nanomaterials 2018, 8(6), 440; https://doi.org/10.3390/nano8060440 - 16 Jun 2018
Cited by 3 | Viewed by 4943
Abstract
In this study, we report the use of Al2O3 nanoparticles in combination with fluorine doped tin oxide (F:SnO2, aka FTO) thin films to form hazy Al2O3-FTO nanocomposites. In comparison to previously reported FTO-based nanocomposites [...] Read more.
In this study, we report the use of Al2O3 nanoparticles in combination with fluorine doped tin oxide (F:SnO2, aka FTO) thin films to form hazy Al2O3-FTO nanocomposites. In comparison to previously reported FTO-based nanocomposites integrating ZnO and sulfur doped TiO2 (S:TiO2) nanoparticles (i.e., ZnO-FTO and S:TiO2-FTO nanocomposites), the newly developed Al2O3-FTO nanocomposites show medium haze factor HT of about 30%, while they exhibit the least loss in total transmittance Ttot. In addition, Al2O3-FTO nanocomposites present a low fraction of large-sized nanoparticle agglomerates with equivalent radius req > 1 μm; effectively 90% of the nanoparticle agglomerates show req < 750 nm. The smaller feature size in Al2O3-FTO nanocomposites, as compared to ZnO-FTO and S:TiO2-FTO nanocomposites, makes them more suitable for applications that are sensitive to roughness and large-sized features. With the help of a simple optical model developed in this work, we have simulated the optical scattering by a single nanoparticle agglomerate characterized by bottom radius r0, top radius r1, and height h. It is found that r0 is the main factor affecting the HT(λ), which indicates that the haze factor of Al2O3-FTO and related FTO nanocomposites is mainly determined by the total surface coverage of all the nanoparticle agglomerates present. Full article
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Figure 1
<p>(<b>a</b>) Scanning electron microscopy (SEM) image of a 2 wt % Al<sub>2</sub>O<sub>3</sub> nanoparticle suspension spin-coated on glass substrate; (<b>b</b>) Cross-sectional and (<b>c</b>) plane-view SEM images of a 1 wt % Al<sub>2</sub>O<sub>3</sub>-FTO nanocomposite with its region B examined in (<b>d</b>) atomic force microscopy (AFM) (2 × 2 μm<sup>2</sup>) image; (<b>e</b>) Plane-view SEM and (<b>f</b>) AFM (1 × 1 μm<sup>2</sup>) images of a reference flat FTO.</p> Full article ">Figure 2
<p>(<b>a</b>) Root-mean-square (RMS) roughness and (<b>b</b>) total surface coverage plotted against nanoparticle suspension concentration for Al<sub>2</sub>O<sub>3</sub>-FTO, S:TiO<sub>2</sub>-FTO (as reported in [<a href="#B11-nanomaterials-08-00440" class="html-bibr">11</a>]), and ZnO-FTO nanocomposites. At least five different areas were measured on each sample to deduce the corresponding values and associated error bars.</p> Full article ">Figure 3
<p>Surface coverages calculated for all eight groups (classified based on the equivalent radius r<sub>eq</sub>) of nanoparticle agglomerates for (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>-FTO nanocomposites; (<b>b</b>) S:TiO<sub>2</sub>-FTO nanocomposites (as reported in [<a href="#B11-nanomaterials-08-00440" class="html-bibr">11</a>]); and (<b>c</b>) ZnO-FTO nanocomposites. For each series, the top and bottom panels show the surface coverage of groups with r<sub>eq</sub> inferior and superior to 1 μm, respectively.</p> Full article ">Figure 4
<p>(<b>a</b>) X-ray diffraction (XRD) θ-2θ patterns of Al<sub>2</sub>O<sub>3</sub> nanocomposites and respective reference flat FTO. The dashed lines mark the diffraction peaks of FTO (PDF: SnO<sub>2</sub> 00-041-1445); (<b>b</b>) Texture coefficient C<sub>hkl</sub> plotted against nanoparticle suspension concentration for Al<sub>2</sub>O<sub>3</sub>-FTO nanocomposites. The inset shows the evolution of the degree of preferred orientation σ.</p> Full article ">Figure 5
<p>Sheet resistance (R<sub>s</sub>) with respect to nanoparticle suspension concentration plotted for Al<sub>2</sub>O<sub>3</sub>-FTO nanocomposites. The error bar of each specimen was obtained from statistical analysis on measurements at five different regions. The dashed line is a guide to the eye.</p> Full article ">Figure 6
<p>(<b>a</b>) Total transmittance (T<sub>tot</sub>) and diffuse transmittance (T<sub>diff</sub>) for Al<sub>2</sub>O<sub>3</sub>-FTO nanocomposites and respective reference flat FTO as well as the bare glass substrate; (<b>b</b>) Haze factor (H<sub>T</sub>) for Al<sub>2</sub>O<sub>3</sub>-FTO nanocomposites and respective reference flat FTO as well as the bare glass substrate.</p> Full article ">Figure 7
<p>Haze factor (H<sub>T</sub>), total transmittance (T<sub>tot</sub>), and absorptance at 635 nm for Al<sub>2</sub>O<sub>3</sub>-FTO, S:TiO<sub>2</sub>-FTO (as reported in [<a href="#B11-nanomaterials-08-00440" class="html-bibr">11</a>]), and ZnO-FTO nanocomposites plotted as a function of nanoparticle suspension concentration. Dashed lines help to guide the eyes.</p> Full article ">Figure 8
<p>(<b>a</b>) Mathematical representation of an individual nanoparticle agglomerate approximated as a truncated circular pyramid described by three parameters: bottom radius r<sub>0</sub>, top radius r<sub>1</sub>, and height h; (<b>b</b>) The profile of total transmission for light passing through FTO nanocomposite containing a ZnO nanoparticle agglomerate parameterized as r<sub>0</sub> = 600 nm, r<sub>1</sub> = 200 nm, and h = 150 nm; (<b>c</b>) 3D-plot of light intensity in k-space; and (<b>d</b>) 2D-plot of light intensity, deduced as cross section at k<sub>y</sub>/k<sub>0</sub> = 0 (or equivalently, k<sub>x</sub>/k<sub>0</sub> = 0) in (<b>c</b>). The specularly (corresponding to about 3°) and diffusely transmitted light are pointed out, respectively.</p> Full article ">Figure 9
<p>(<b>a</b>) AFM image of 40 × 40 μm<sup>2</sup> for a 0.5 wt % ZnO-FTO nanocomposite. Here the nanoparticle agglomerates are colored in red with the help of Gwyddion software [<a href="#B28-nanomaterials-08-00440" class="html-bibr">28</a>]; (<b>b</b>) Plot of H<sub>T</sub>(λ) (measured experimentally) for 0.5 wt % ZnO-FTO nanocomposite; (<b>c</b>) Simulated H<sub>T</sub>(λ) of FTO nanocomposite containing a single grain of those marked 1–12 in (<b>a</b>), respectively. Here the specular light is considered as the central one pixel only.</p> Full article ">Figure 10
<p>Simulated H<sub>T</sub>(λ) of FTO nanocomposite containing a single ZnO nanoparticle agglomerate: (<b>a</b>) r<sub>0</sub> varies while r<sub>1</sub> and h are fixed to 196 and 178 nm, respectively; (<b>b</b>) r<sub>1</sub> varies while r<sub>0</sub> and h are fixed to 572 and 178 nm, respectively; and (<b>c</b>) h varies while r<sub>0</sub> and r<sub>1</sub> are fixed to 572 and 196 nm, respectively. The specular light is considered as the central one pixel only.</p> Full article ">Figure 11
<p>Haze factor (H<sub>T</sub>) at 635 nm as a function of the total surface coverage for Al<sub>2</sub>O<sub>3</sub>-FTO, S:TiO<sub>2</sub>-FTO (reported in [<a href="#B11-nanomaterials-08-00440" class="html-bibr">11</a>]), and ZnO-FTO nanocomposites.</p> Full article ">
9 pages, 1849 KiB  
Short Note
Time-Dependent Growth of Silica Shells on CdTe Quantum Dots
by Pavlína Modlitbová, Karel Klepárník, Zdeněk Farka, Pavel Pořízka, Petr Skládal, Karel Novotný and Jozef Kaiser
Nanomaterials 2018, 8(6), 439; https://doi.org/10.3390/nano8060439 - 16 Jun 2018
Cited by 8 | Viewed by 4183
Abstract
The purpose of this study is to investigate the time dependent growth of silica shells on CdTe quantum dots to get their optimum thicknesses for practical applications. The core/shell structured silica-coated CdTe quantum dots (CdTe/SiO2 QDs) were synthesized by the Ströber process, [...] Read more.
The purpose of this study is to investigate the time dependent growth of silica shells on CdTe quantum dots to get their optimum thicknesses for practical applications. The core/shell structured silica-coated CdTe quantum dots (CdTe/SiO2 QDs) were synthesized by the Ströber process, which used CdTe QDs co-stabilized by mercaptopropionic acid. The coating procedure used silane primer (3-mercaptopropyltrimethoxysilane) in order to make the quantum dots (QDs) surface vitreophilic. The total size of QDs was dependent on both the time of silica shell growth in the presence of sodium silicate, and on the presence of ethanol during this growth. The size of particles was monitored during the first 72 h using two principally different methods: Dynamic Light Scattering (DLS), and Scanning Electron Microscopy (SEM). The data obtained by both methods were compared and reasons for differences discussed. Without ethanol precipitation, the silica shell thickness grew slowly and increased the nanoparticle total size from approximately 23 nm up to almost 30 nm (DLS data), and up to almost 60 nm (SEM data) in three days. During the same time period but in the presence of ethanol, the size of CdTe/SiO2 QDs increased more significantly: up to 115 nm (DLS data) and up to 83 nm (SEM data). The variances occurring between silica shell thicknesses caused by different methods of silica growth, as well as by different evaluation methods, were discussed. Full article
(This article belongs to the Special Issue Preparation, Characterization and Utility of Quantum Dots)
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<p>The emission spectra of as-synthesized CdTe quantum dots(QDs) and the silanized aliquots of CdTe QDs with and without presence of ethanol in specific times (1, 24, and 72 h).</p> Full article ">Figure 2
<p>Transmission Electron Microscopy (TEM) picture of CdTe QDs.</p> Full article ">Figure 3
<p>Dependence of CdTe/SiO<sub>2</sub> QDs average hydrodynamic particle diameter (nm) on time (hours) of silica shell growth. The number of Dynamic Light Scattering (DLS) measurements per one exposure time was 5, error bars correspond to standard deviations. Scanning Electron Microscopy (SEM) photograh (<b>a</b>) after 24 h growth (diameter 53.7 ± 4.2 nm) and (<b>b</b>) after 72 h growth (diameter 59.7 ± 4.0 nm).</p> Full article ">Figure 4
<p>Dependence of CdTe/SiO<sub>2</sub> QDs average hydrodynamic particle diameter (nm) on time (hours) of silica shell growth in ethanol presence. The number of DLS measurements per one exposure time was 5; error bars correspond to standard deviations. SEM photograh (<b>a</b>) after 24 h growth (diameter 62.3 ± 7.5 nm) and (<b>b</b>) after 72 h growth (diameter 83.1 ± 6.9 nm).</p> Full article ">
17 pages, 3121 KiB  
Article
Functionalized Tyrosinase-Lignin Nanoparticles as Sustainable Catalysts for the Oxidation of Phenols
by Eliana Capecchi, Davide Piccinino, Ines Delfino, Paolo Bollella, Riccarda Antiochia and Raffaele Saladino
Nanomaterials 2018, 8(6), 438; https://doi.org/10.3390/nano8060438 - 15 Jun 2018
Cited by 39 | Viewed by 6184
Abstract
Sustainable catalysts for the oxidation of phenol derivatives under environmentally friendly conditions were prepared by the functionalization of lignin nanoparticles with tyrosinase. Lignin, the most abundant polyphenol in nature, is the main byproduct in the pulp and paper manufacturing industry and biorefinery. Tyrosinase [...] Read more.
Sustainable catalysts for the oxidation of phenol derivatives under environmentally friendly conditions were prepared by the functionalization of lignin nanoparticles with tyrosinase. Lignin, the most abundant polyphenol in nature, is the main byproduct in the pulp and paper manufacturing industry and biorefinery. Tyrosinase has been immobilized by direct adsorption, encapsulation, and layer-by-layer deposition, with or without glutaraldehyde reticulation. Lignin nanoparticles were found to be stable to the tyrosinase activity. After the enzyme immobilization, they showed a moderate to high catalytic effect in the synthesis of catechol derivatives, with the efficacy of the catalyst being dependent on the specific immobilization procedures. Full article
(This article belongs to the Special Issue Sustainable Nanoparticles - Their Synthesis and Catalytic Applications)
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<p>SEM images of catalyst <b>I</b> and catalyst <b>II</b>. (<b>a</b>) General overview of catalyst <b>I</b>; (<b>b</b>) Selected magnification of catalyst <b>I</b>; (<b>c</b>) General overview of catalyst <b>II</b>.</p> Full article ">Figure 2
<p>Representative particle diameter distributions of OL nanocapsules and Catalyst <b>I</b>–<b>IV</b>.</p> Full article ">Figure 3
<p>Confocal images of (<b>a</b>) Catalyst <b>I</b>; (<b>b</b>) Catalyst <b>II</b>.</p> Full article ">Figure 4
<p>Zeta potential values of OL nanoparticles, OL PDDA nanoparticles, and catalysts <b>I</b>–<b>IV</b>.</p> Full article ">Figure 5
<p>SEM images of catalyst <b>III</b> in the first panel (<b>a</b>) and of catalyst <b>IV</b> in the second panel (<b>b</b>).</p> Full article ">Figure 6
<p>Cyclic voltammograms of OL nanocapsules (black line, <b>A</b>–<b>D</b>), Catalyst I (red line, (<b>A</b>)), Catalyst II (red line, (<b>B</b>)), Catalyst III (red line, (<b>C</b>)), and Catalyst IV (red line, (<b>D</b>)) performed in 250 µM catechol solution (50 mM PBS buffer pH 6.5 + 100 mM KCl) at a scan rate of 5 mV s<sup>−1</sup>.</p> Full article ">Scheme 1
<p>Schematic representation for the preparation of catalysts <b>I</b>–<b>IV</b>.</p> Full article ">Scheme 2
<p>Oxidation of phenols <b>1</b>–<b>4</b> with catalysts <b>I</b>–<b>IV</b>.</p> Full article ">
12 pages, 2981 KiB  
Article
Stable and High Piezoelectric Output of GaN Nanowire-Based Lead-Free Piezoelectric Nanogenerator by Suppression of Internal Screening
by Muhammad Ali Johar, Mostafa Afifi Hassan, Aadil Waseem, Jun-Seok Ha, June Key Lee and Sang-Wan Ryu
Nanomaterials 2018, 8(6), 437; https://doi.org/10.3390/nano8060437 - 14 Jun 2018
Cited by 39 | Viewed by 5398
Abstract
A piezoelectric nanogenerator (PNG) that is based on c-axis GaN nanowires is fabricated on flexible substrate. In this regard, c-axis GaN nanowires were grown on GaN substrate using the vapor-liquid-solid (VLS) technique by metal organic chemical vapor deposition. Further, Polydimethylsiloxane (PDMS) was coated [...] Read more.
A piezoelectric nanogenerator (PNG) that is based on c-axis GaN nanowires is fabricated on flexible substrate. In this regard, c-axis GaN nanowires were grown on GaN substrate using the vapor-liquid-solid (VLS) technique by metal organic chemical vapor deposition. Further, Polydimethylsiloxane (PDMS) was coated on nanowire-arrays then PDMS matrix embedded with GaN nanowire-arrays was transferred on Si-rubber substrate. The piezoelectric performance of nanowire-based flexible PNG was measured, while the device was actuated using a cyclic stretching-releasing agitation mechanism that was driven by a linear motor. The piezoelectric output was measured as a function of actuation frequency ranging from 1 Hz to 10 Hz and a linear tendency was observed for piezoelectric output current, while the output voltages remained constant. A maximum of piezoelectric open circuit voltages and short circuit current were measured 15.4 V and 85.6 nA, respectively. In order to evaluate the feasibility of our flexible PNG for real application, a long term stability test was performed for 20,000 cycles and the device performance was degraded by less than 18%. The underlying reason for the high piezoelectric output was attributed to the reduced free carriers inside nanowires due to surface Fermi-level pinning and insulating metal-dielectric-semiconductor interface, respectively; the former reduced the free carrier screening radially while latter reduced longitudinally. The flexibility and the high aspect ratio of GaN nanowire were the responsible factors for higher stability. Such higher piezoelectric output and the novel design make our device more promising for the diverse range of real applications. Full article
(This article belongs to the Special Issue 1D Nanostructure-Based Piezo-Generators)
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<p>Schematic illustration of GaN NWs based piezoelectric nanogenerator (PNG) (<b>a</b>) c-axis GaN NWs after polydimethylsiloxane (PDMS) deposition on sapphire substrate; and, (<b>b</b>) transfer of PDMS matrix embedded with c-axis GaN NWs on Si-rubber substrate, NiO deposition and ITO electrode formation on complete device.</p> Full article ">Figure 2
<p>Scanning electron micrographs (<b>a</b>) vertical GaN NW on GaN thin film, inset shows the high magnification micrograph; (<b>b</b>) after deposition of PDMS on GaN NWs; and, (<b>c</b>) peeled-off PDMS matrix embedded with GaN NWs, bottom side of NWs is exposed while tope side is covered with PDMS.</p> Full article ">Figure 3
<p>Piezoelectric outputs of PNG (<b>a</b>) open circuit voltages; (<b>b</b>) short circuit current; and, (<b>c</b>) magnified view of output current with decreasing frequency.</p> Full article ">Figure 4
<p>Piezoelectric output as a function of actuation frequency (<b>a</b>) open circuit voltages, high frequency (HF), medium frequency (MF), and low frequency (LF); (<b>b</b>) short circuit current; and, (<b>c</b>) the trend of output current by increasing the frequency of actuation source.</p> Full article ">Figure 5
<p>Schematic illustration of energy band diagram of Ni-PDMS-GaN (<b>a</b>) band positions of GaN and work function Ni in vacuum before contact; (<b>b</b>) metal-dielectric-semiconductor (MDS) interface in thermal equilibrium; (<b>c</b>) the effect of positive piezoelectric charges on band bending of GaN at PDMS-GaN interface; and, (<b>d</b>) formation of negative charges when the stress was relieved and their effect on band bending of GaN at PDMS-GaN interface. Φ—work function, χ—Electron affinity, E<sub>F</sub>—Fermi level, E<sub>Fi</sub>—Intrinsic Fermi level, E<sub>g</sub>—bandgap, E<sub>c</sub>—lower level of conduction band, E<sub>v</sub>—upper level of valance band, E<sub>Fm</sub>—metal fermi level.</p> Full article ">Figure 6
<p>The long-term stability test of PNG with an actuation frequency of 8.0 Hz, piezoelectric output current for 20,000 cycles.</p> Full article ">
8 pages, 1626 KiB  
Article
Ag Nanotwin-Assisted Grain Growth-Induced by Stress in SiO2/Ag/SiO2 Nanocap Arrays
by Fan Zhang, Yaxin Wang, Yongjun Zhang, Lei Chen, Yang Liu and Jinghai Yang
Nanomaterials 2018, 8(6), 436; https://doi.org/10.3390/nano8060436 - 14 Jun 2018
Cited by 5 | Viewed by 3346
Abstract
A trilayer SiO2/Ag/SiO2 nanocap array was prepared on a two-dimensional template. When annealed at different temperatures, the curvature of the SiO2/Ag/SiO2 nanocap arrays increased, which led to Ag nanocap shrinkage. The stress provided by the curved SiO [...] Read more.
A trilayer SiO2/Ag/SiO2 nanocap array was prepared on a two-dimensional template. When annealed at different temperatures, the curvature of the SiO2/Ag/SiO2 nanocap arrays increased, which led to Ag nanocap shrinkage. The stress provided by the curved SiO2 layer induced the formation of Ag nanotwins. Ag nanotwins assisted the growth of nanoparticles when the neighboring nanotwins changed the local misorientations. Nanocap shrinkage reduced the surface plasmon resonance (SPR) coupling between neighboring nanocaps; concurrently, grain growth decreased the SPR coupling between the particles in each nanocap, which led to a red shift of the localized surface plasmon resonance (LSPR) bands and decreased the surface-enhanced Raman scattering (SERS) signals. Full article
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<p>(<b>A</b>) SEM, (<b>B</b>) TEM, and (<b>C</b>) HRTEM images of a SiO<sub>2</sub>/Ag/SiO<sub>2</sub> nanocap arrays. The insets are the size distribution and the Ag SAED pattern.</p> Full article ">Figure 2
<p>(<b>A</b>) SEM, (<b>B</b>) TEM and (<b>C</b>) HRTEM images of SiO<sub>2</sub>/Ag/SiO<sub>2</sub> nanocap arrays annealed at 400 °C and (<b>D</b>–<b>F</b>) 800 °C. The inserts are the fast Fourier transform (FFT) of the Ag nanotwins; T, G, and M are the abbreviations for twin, grain, and matrix.</p> Full article ">Figure 3
<p>XRD patterns of the SiO<sub>2</sub>/Ag/SiO<sub>2</sub> nanocap arrays at different temperatures.</p> Full article ">Figure 4
<p>UV-Vis absorbed spectra (<b>A</b>) and SERS spectra (<b>B</b>) of the SiO<sub>2</sub>/Ag/SiO<sub>2</sub> nanocap arrays at different temperatures.</p> Full article ">
17 pages, 4504 KiB  
Article
Gelled Electrolyte Containing Phosphonium Ionic Liquids for Lithium-Ion Batteries
by Mélody Leclère, Laurent Bernard, Sébastien Livi, Michel Bardet, Armel Guillermo, Lionel Picard and Jannick Duchet-Rumeau
Nanomaterials 2018, 8(6), 435; https://doi.org/10.3390/nano8060435 - 14 Jun 2018
Cited by 17 | Viewed by 4871
Abstract
In this work, new gelled electrolytes were prepared based on a mixture containing phosphonium ionic liquid (IL) composed of trihexyl(tetradecyl)phosphonium cation combined with bis(trifluoromethane)sulfonimide [TFSI] counter anions and lithium salt, confined in a host network made from an epoxy prepolymer and amine hardener. [...] Read more.
In this work, new gelled electrolytes were prepared based on a mixture containing phosphonium ionic liquid (IL) composed of trihexyl(tetradecyl)phosphonium cation combined with bis(trifluoromethane)sulfonimide [TFSI] counter anions and lithium salt, confined in a host network made from an epoxy prepolymer and amine hardener. We have demonstrated that the addition of electrolyte plays a key role on the kinetics of polymerization but also on the final properties of epoxy networks, especially thermal, thermo-mechanical, transport, and electrochemical properties. Thus, polymer electrolytes with excellent thermal stability (>300 °C) combined with good thermo-mechanical properties have been prepared. In addition, an ionic conductivity of 0.13 Ms·cm−1 at 100 °C was reached. Its electrochemical stability was 3.95 V vs. Li0/Li+ and the assembled cell consisting in Li|LiFePO4 exhibited stable cycle properties even after 30 cycles. These results highlight a promising gelled electrolyte for future lithium ion batteries. Full article
(This article belongs to the Special Issue Polymers and Ionic Liquids: Shaping up a New Generation of High Performances Nanomaterials)
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<p>Ionic conductivity of phosphonium electrolytes with two types of anion: (a) [P<sub>66614</sub>][TFSI] with 0.75 M of LiTFSI and (b) [P<sub>66614</sub>][TMP] with 0.2 M of LiTMP.</p> Full article ">Figure 2
<p><sup>7</sup>Li NMR (<b>a</b>) and <sup>31</sup>P NMR (<b>b</b>) of electrolyte [TMP] ([P<sub>66614</sub>][TMP] + 0.2 M LiTMP) at different temperatures.</p> Full article ">Figure 3
<p>Evolution of the normalized relative intensity of the phosphinate anion compared to the relative intensity of the cation as a function of the temperature for the electrolyte [TMP] ([P<sub>66614</sub>][TMP] + 0.2 M LiTMP).</p> Full article ">Figure 4
<p>Epoxy conversion (E), and primary amine (PA) and evolution of secondary amine (SA) during the reaction time at 110 °C for 6 h and at 120 °C for 6 h of (<b>a</b>) neat PPO-Jeffamine networks compared to (<b>b</b>) PPO-Jeffamine/Electrolyte system with 50 wt % of ([P<sub>66614</sub>][TFSI] + 0.75 M LiTFSI).</p> Full article ">Figure 5
<p>Thermo-gravimetric analyses (TGA) (<b>a</b>) and dynamical mechanical analysis (DTG) (<b>b</b>) of electrolyte ([P<sub>66614</sub>][TFSI] + 0.75 M LiTFSI) alone and introduced in PPO-Jeffamine networks prepared with an electrolyte varying content (heating ramp: 10 K·min<sup>−1</sup>; atmosphere: Nitrogen).</p> Full article ">Figure 6
<p>Ionic conductivity of gelled electrolyte with different amount of electrolyte ([P<sub>66614</sub>][TFSI] with 0.75 M of LiTFSI).</p> Full article ">Figure 7
<p>Cyclic voltammetry of gelled electrolyte prepared with 70 wt % of electrolyte (<b>a</b>) in reduction to 0.05 V vs. Li<sup>+</sup>/Li<sup>0</sup> and (<b>b</b>) in oxidation to 4 V vs. Li<sup>+</sup>/Li<sup>0.</sup></p> Full article ">Figure 8
<p>Cycling performances of Li|LiFePO<sub>4</sub> cell at different current densities (C/100, C/50 and C/20) between 2.5 V and 4 V at 100 °C of gelled electrolyte prepared with 70 wt % of electrolyte.</p> Full article ">Figure 9
<p>Cycling performance of the Li|PPO [TFSI]−70|LiFePO<sub>4</sub> cell at indicating rates at 100 °C.</p> Full article ">Scheme 1
<p>Model circuit used for the fitting of Nyquist plots.</p> Full article ">
26 pages, 6345 KiB  
Article
Applications of Nanomaterials Based on Magnetite and Mesoporous Silica on the Selective Detection of Zinc Ion in Live Cell Imaging
by Roghayeh Sadeghi Erami, Karina Ovejero, Soraia Meghdadi, Marco Filice, Mehdi Amirnasr, Antonio Rodríguez-Diéguez, María Ulagares De La Orden and Santiago Gómez-Ruiz
Nanomaterials 2018, 8(6), 434; https://doi.org/10.3390/nano8060434 - 14 Jun 2018
Cited by 19 | Viewed by 5910
Abstract
Functionalized magnetite nanoparticles (FMNPs) and functionalized mesoporous silica nanoparticles (FMSNs) were synthesized by the conjugation of magnetite and mesoporous silica with the small and fluorogenic benzothiazole ligand, that is, 2(2-hydroxyphenyl)benzothiazole (hpbtz). The synthesized fluorescent nanoparticles were characterized by FTIR, XRD, XRF, [...] Read more.
Functionalized magnetite nanoparticles (FMNPs) and functionalized mesoporous silica nanoparticles (FMSNs) were synthesized by the conjugation of magnetite and mesoporous silica with the small and fluorogenic benzothiazole ligand, that is, 2(2-hydroxyphenyl)benzothiazole (hpbtz). The synthesized fluorescent nanoparticles were characterized by FTIR, XRD, XRF, 13C CP MAS NMR, BET, and TEM. The photophysical behavior of FMNPs and FMSNs in ethanol was studied using fluorescence spectroscopy. The modification of magnetite and silica scaffolds with the highly fluorescent benzothiazole ligand enabled the nanoparticles to be used as selective and sensitive optical probes for zinc ion detection. Moreover, the presence of hpbtz in FMNPs and FMSNs induced efficient cell viability and zinc ion uptake, with desirable signaling in the normal human kidney epithelial (Hek293) cell line. The significant viability of FMNPs and FMSNs (80% and 92%, respectively) indicates a potential applicability of these nanoparticles as in vitro imaging agents. The calculated limit of detections (LODs) were found to be 2.53 × 10−6 and 2.55 × 10−6 M for Fe3O4-H@hpbtz and MSN-Et3N-IPTMS-hpbtz-f1, respectively. FMSNs showed more pronounced zinc signaling relative to FMNPs, as a result of the more efficient penetration into the cells. Full article
(This article belongs to the Special Issue Nanostructured Biosensors)
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<p>Low angle XRD patterns of (a) MSNs and FMSNs includes the following: (b) MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b>, (c) MSN-pyridine-IPTMS-hpbtz-<b>f2</b>, (d) MSN-NaOH-IPTMS-hpbtz-<b>f3</b>, (e) MSN-Et<sub>3</sub>N-NCO-hpbtz-<b>e1</b>, (f) MSN-pyridine-NCO-hpbtz-<b>e2,</b> and (g) MSN-NaOH-NCO-hpbtz-<b>e3</b>.</p> Full article ">Figure 2
<p>Wide angle X-Ray powder diffraction (XRD) patterns of (a) Fe<sub>3</sub>O<sub>4</sub>-H, (b) Fe<sub>3</sub>O<sub>4</sub>-C, (c) Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz, (d) Fe<sub>3</sub>O<sub>4</sub>-C@hpbtz (prepared in method I), and (e) Fe<sub>3</sub>O<sub>4</sub>@hpbtz (prepared in method II).</p> Full article ">Figure 3
<p>Nitrogen adsorption/desorption isotherms of MSNs and MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b>. For both materials, a mixture between type IV and type VI isotherms are exhibited.</p> Full article ">Figure 4
<p>Nitrogen adsorption/desorption isotherms of MNPs (Fe<sub>3</sub>O<sub>4</sub>-H and Fe<sub>3</sub>O<sub>4</sub>-C). For both materials, type III isotherms are exhibited.</p> Full article ">Figure 5
<p><sup>13</sup>C CP-MAS NMR spectra of <b>hpbtz</b> ligand and MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b>.</p> Full article ">Figure 6
<p>TEM analysis of MNPs and FMNPs for (<b>a</b>) Fe<sub>3</sub>O<sub>4</sub>-C, (<b>b</b>) Fe<sub>3</sub>O<sub>4</sub>-C@hpbtz, (<b>c</b>) Fe<sub>3</sub>O<sub>4</sub>-H, (<b>d</b>) Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz, (<b>e</b>) Fe<sub>3</sub>O<sub>4</sub>@hpbtz, (<b>f</b>) Fe<sub>3</sub>O<sub>4</sub>-H, (<b>g</b>) MSNs, and (<b>h</b>) MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1,</b> as well as the corresponding particle size distribution.</p> Full article ">Figure 7
<p>UV-vis titration of an ethanolic solution of <b>hpbtz</b> (1 × 10<sup>−4</sup> M) with Zn<sup>2+</sup> ion (1 × 10<sup>−3</sup> M).</p> Full article ">Figure 8
<p>Comparative fluorescence spectra of (a) <b>hpbtz</b>, (b) Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz, (c) Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz + Zn<sup>2+</sup>, (d) Fe<sub>3</sub>O<sub>4</sub>-C@hpbtz, (e) Fe<sub>3</sub>O<sub>4</sub>-C@hpbtz + Zn<sup>2+</sup>, (f) Fe<sub>3</sub>O<sub>4</sub>@hpbtz, and (g) Fe<sub>3</sub>O<sub>4</sub>@hpbtz + Zn<sup>2+</sup>, upon the addition of Zn<sup>2+</sup> (7.8 equivalent, 300 μL), at a concentration of 10<sup>−3</sup> M in an ethanol solution (λ<sub>ex</sub> = 350 nm) (Inset: <b>f</b> in higher concentration, 3 mg mL<sup>−1</sup>).</p> Full article ">Figure 9
<p>Comparative fluorescence spectra of (a) MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b>, (b) MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b> + Zn<sup>2+</sup>, (c) MSN-pyridine-IPTMS-hpbtz-<b>f2</b>, (d) MSN-pyridine-IPTMS-hpbtz-<b>f2</b> + Zn<sup>2+</sup>, (e) MSN-NaOH-IPTMS-hpbtz-<b>f3</b>, and (f) MSN-NaOH-IPTMS-hpbtz-<b>f3</b> + Zn<sup>2+</sup>, upon the addition of Zn<sup>2+</sup> (15.4 equivalent, 350 μL) at a concentration of 10<sup>−3</sup> M in ethanol (λ<sub>ex</sub> = 305 nm).</p> Full article ">Figure 10
<p>Fluorescence intensity changes observed in (<b>A</b>) Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz (2 mg mL<sup>−1</sup>) and (<b>B</b>) MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b> (2 mg mL<sup>−1</sup>) upon the addition of Zn<sup>2+</sup> (0–7.8 equivalent, 0–130 μM and 300 μL for A, and 0–15.4 equivalents, 0–130 μM and 350 μL for B) at λ<sub>ex</sub> = 350 nm for Aa and 305 nm for B in the ethanol (a and b: plot of the fluorescence intensity at 460 nm as a function of the Zn<sup>2+</sup> concentration.</p> Full article ">Figure 11
<p>Job’s plot indicating the 2:1 stoichiometry for [Zn<sup>2+</sup>: Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz] (<b>A</b>) and 1:2 for [Zn<sup>2+</sup>: MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b>] (<b>B</b>). The total concentration of (L) and Zn<sup>2+</sup> is 10 µM (λ<sub>ex</sub> = 350 and 305 for Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz and MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b>, respectively).</p> Full article ">Figure 12
<p>The association constant (K<sub>a</sub>) of each sensor with Zn<sup>2+</sup> was calculated by Benesi–Hildebrand equation for Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz (<b>A</b>) and MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b> (<b>B</b>).</p> Full article ">Figure 13
<p>Fluorescence emission spectra for (<b>A</b>) Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz in the presence of 7.8 equivalent, 300 μL and (<b>B</b>) MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b> in the presence of 15.4 equivalent, 350 μL of various metal ions at λ = 350 and 305 nm, respectively, in ethanol.</p> Full article ">Figure 14
<p>Variation of the fluorescence intensity of Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz (2 mg mL<sup>−1</sup>) with Zn<sup>2+</sup> (7.8 equivalent, 300 μL) and various metal ions (2 times more in equivalent) at 460 nm (λ<sub>ex</sub>= 350 nm) in ethanol.</p> Full article ">Figure 15
<p>Variation of the fluorescence intensity of MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b> (2 mg mL<sup>−1</sup>), with Zn<sup>2+</sup> (15.4 equivalent, 350 μL) and various metal ions (two times more in equivalent) at 460 nm (λ<sub>ex</sub>= 305 nm) in ethanol.</p> Full article ">Figure 16
<p>Toxicity of tested nanomaterials on HEK293 cells.</p> Full article ">Figure 17
<p>Fluorescence images of the HEK293 cells treated with different functionalized materials in absence of Zn<sup>2+</sup> supplementation (Column I), in the presence of supplemented Zn<sup>2+</sup> (Column II) and 3D reconstruction of cells treated with nanomaterials in the presence of Zn<sup>2+</sup> (Column III).</p> Full article ">Scheme 1
<p>Synthesis of functionalized mesoporous silica nanoparticles (FMSNs). Reaction of benzothiazole ligand (<b>hpbtz</b>) with 3-isocyanatopropyltriethoxysilane (ICTES) and 3-iodopropyltrimethoxysilane (IPTMS) generates <b>c</b> and <b>d</b> in the presence of different bases. The reaction of the post functionalized materials with ICTES and IPTMS under a nitrogen atmosphere with MSNs, forms the <b>hpbtz</b> loaded materials, <b>e1–e3</b> and <b>f1–f3</b>, respectively. The resulting products are labeled as MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b>, MSN-pyridine-IPTMS-hpbtz-<b>f2</b>, MSN-NaOH-IPTMS-hpbtz-<b>f3</b>, MSN-Et<sub>3</sub>N-NCO-hpbtz-<b>e1</b>, MSN-pyridine-NCO-hpbtz-<b>e2</b>, and MSN-NaOH-NCO-hpbtz-<b>e3</b>.</p> Full article ">Scheme 2
<p>Synthesis of <b>hpbtz</b>-functionalized magnetite nanoparticles (FMNPs) by different methods.</p> Full article ">Scheme 3
<p>Proposed binding mechanism of Fe<sub>3</sub>O<sub>4</sub>-H@hpbtz or MSN-Et<sub>3</sub>N-IPTMS-hpbtz-<b>f1</b> and Zn<sup>2+.</sup></p> Full article ">
13 pages, 1970 KiB  
Article
Construction of Hyaluronic Tetrasaccharide Clusters Modified Polyamidoamine siRNA Delivery System
by Yingcong Ma, Meng Sha, Shixuan Cheng, Wang Yao, Zhongjun Li and Xian-Rong Qi
Nanomaterials 2018, 8(6), 433; https://doi.org/10.3390/nano8060433 - 14 Jun 2018
Cited by 13 | Viewed by 3714
Abstract
The CD44 protein, as a predominant receptor for hyaluronan (HA), is highly expressed on the surface of multiple tumor cells. HA, as a targeting molecule for a CD44-contained delivery system, increases intracellular drug concentration in tumor tissue. However, due to the weak binding [...] Read more.
The CD44 protein, as a predominant receptor for hyaluronan (HA), is highly expressed on the surface of multiple tumor cells. HA, as a targeting molecule for a CD44-contained delivery system, increases intracellular drug concentration in tumor tissue. However, due to the weak binding ability of hyaluronan oligosaccharide to CD44, targeting for tumor drug delivery has been restricted. In this study, we first use a HA tetrasaccharide cluster as the target ligand to enhance the binding ability to CD44. A polyamidoamine (PAMAM) dendrimer was modified by a HA tetrasaccharide cluster as a nonviral vector for small interfering RNA (siRNA) delivery. The dendrimer/siRNA nanocomplexes increased the cellular uptake capacity of siRNA through the CD44 receptor-mediated endocytosis pathway, allowing the siRNA to successfully escape the endosome/lysosome. Compared with the control group, nanocomplexes effectively reduced the expression of GFP protein and mRNA in MDA-MB-231-GFP cells. This delivery system provides a foundation to increase the clinical applications of PAMAM nanomaterials. Full article
(This article belongs to the Special Issue Pharmaceutical Nanotechnology)
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<p>Synthetic scheme of polyamidoamine (PAMAM)-gallic acid triethylene glycol (GATG)- hyaluronan tetrasaccharide clusters (HA4).</p> Full article ">Figure 2
<p>(<b>a</b>) Agarose gel electrophoresis of PAMAM-3GATG-HA4/siRNA and PAMAM-6GATG-HA4/siRNA nanocomplexes at different N/P ratios. (<b>b</b>) Particle size and zeta potential of PAMAM-3GATG-HA4/siRNA and PAMAM-6GATG-HA4/siRNA nanocomplexes at different N/P ratios. siRNA concentration in nanocomplexes was 100 nM. (<b>c</b>) Transmission electron microscopy (TEM) images of PAMAM-3GATG-HA4/siRNA and PAMAM-6GATG-HA4/siRNA nanocomplexes. The scale was 2 μm in the original and 100 nm in the magnified image. (<b>d</b>) Serum stability of nanocomposites at 37 °C for 24 h. Results are expressed as mean ± SD (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 3
<p>(<b>a</b>) Effects of vectors PAMAM, PAMAM-3GATG-HA4 and PAMAM-6GATG-HA4 on cell viability within 48 h of MDA-MB-231 cells and MCF-7 cells. Results are expressed as mean ± SD (<span class="html-italic">n</span> = 4). (<b>b</b>) Uptake of nanocomplexes in MDA-MB-231 cells and MCF-7 cells by flow cytometry. FAM-siRNA concentration was 200 nM. In the competition experiments, pre-incubated with free HA was added for incubation. Results are expressed as mean ± SD (<span class="html-italic">n</span> = 3). (<b>c</b>) Laser confocal images used to observe uptake of nanocomplexes in MDA-MB-231 cells. FAM-siRNA concentration was 200 nM. Blue denotes the nucleus and †green denotes FAM-siRNA (scale 25 μm). (<b>d</b>) The lysosomal escape of siRNA after 0.5 and 2 h uptake of PAMAM-6GATG-HA4/siRNA nanocomplexes in MDA-MB-231 cells. FAM-siRNA concentration was 200 nM. Green denotes siRNA and red denotes lysosome (scale 25 μm). Statistical analysis was performed with one-way ANOVA and Bonferroni post-hoc testing with * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, and *** <span class="html-italic">p</span> &lt; 0.005.</p> Full article ">Figure 4
<p>The gene silencing efficacy of PAMAM-GATG-HA4 nanocomplexes analyzed by flow-cytometry and quantitative real-time polymerase chain reaction (qRT-PCR) in MDA-MB-231-GFP cells. The gene silencing efficacy without adding hyaluronan tetrasaccharide was analyzed (<b>a</b>) by flow-cytometry and (<b>b</b>) with adding hyaluronan tetrasaccharide analyzed by flow-cytometry. (<b>c</b>) The gene silencing efficacy without adding hyaluronan tetrasaccharide analyzed by qRT-PCR and (<b>d</b>) with adding hyaluronan tetrasaccharide analyzed by qRT-PCR. Statistical analysis was performed with one-way ANOVA and Bonferroni post-hoc testing with * <span class="html-italic">p</span> &lt; 0.05 and *** <span class="html-italic">p</span> &lt; 0.01. The “negative” represents the blank control group using MDA-MB-231 cells without GFP; the “control” means the MDA-MB-231-GFP cells were not treated with siGFP or nanocomplexes; and the “free” and “lipo” mean the MDA-MB-231-GFP cells were treated with free siGFP or lipofectamine 2000 containing siGFP respectively.</p> Full article ">
16 pages, 3669 KiB  
Article
Carbon Nitride Materials as Efficient Catalyst Supports for Proton Exchange Membrane Water Electrolyzers
by Ana Belen Jorge, Ishanka Dedigama, Thomas S. Miller, Paul Shearing, Daniel J. L. Brett and Paul F. McMillan
Nanomaterials 2018, 8(6), 432; https://doi.org/10.3390/nano8060432 - 13 Jun 2018
Cited by 18 | Viewed by 5421
Abstract
Carbon nitride materials with graphitic to polymeric structures (gCNH) were investigated as catalyst supports for the proton exchange membrane (PEM) water electrolyzers using IrO2 nanoparticles as oxygen evolution electrocatalyst. Here, the performance of IrO2 nanoparticles formed and deposited in situ onto [...] Read more.
Carbon nitride materials with graphitic to polymeric structures (gCNH) were investigated as catalyst supports for the proton exchange membrane (PEM) water electrolyzers using IrO2 nanoparticles as oxygen evolution electrocatalyst. Here, the performance of IrO2 nanoparticles formed and deposited in situ onto carbon nitride support for PEM water electrolysis was explored based on previous preliminary studies conducted in related systems. The results revealed that this preparation route catalyzed the decomposition of the carbon nitride to form a material with much lower N content. This resulted in a significant enhancement of the performance of the gCNH-IrO2 (or N-doped C-IrO2) electrocatalyst that was likely attributed to higher electrical conductivity of the N-doped carbon support. Full article
(This article belongs to the Special Issue Graphitic Carbon Nitride Nanostructures: Catalysis and Beyond)
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<p><b>Left</b>: The structure of Liebig’s melon that provides a crystalline model for polymeric gCNH structures. The structure contains chains of linked heptazine (tri-<span class="html-italic">s</span>-triazine) units; <b>Right</b>: When precursors such as melamine, dicyandiamide, or urea are treated above 550 °C in an inert (e.g., N<sub>2</sub>) atmosphere, they undergo condensation reactions with the release of ammonia molecules to form series of amorphous or nanocrystalline polymeric C<sub>x</sub>N<sub>y</sub>H<sub>z</sub> structures known generally as the graphitic carbon nitride (gCNH) family of materials. A drawing of a laterally polymerized unit formed from “sideways” condensation of melon-like polyheptazine chains is shown. Blue balls represent N atoms; black balls represent C atoms; H atoms are not illustrated, for clarity. The picture under the arrows illustrates the deepening color of different gCNH materials formed as a function of increasing synthesis temperature, from left to right.</p> Full article ">Figure 2
<p>(<b>a</b>) TGA/DSC of the reaction between (NH<sub>4</sub>)Ir<sub>2</sub>Cl<sub>6</sub> and NaNO<sub>3</sub> conducted in air at a 5 °C min<sup>−1</sup> heating rate; (<b>b</b>) the XRD of the IrO<sub>2</sub> NPs produced at 400, 600, and 900 °C by the Adams’ fusion method; (<b>c</b>) the TGA/DSC of (NH<sub>4</sub>)Ir<sub>2</sub>Cl<sub>6</sub>, NaNO<sub>3</sub>, and gCNH support conducted in air at a 5 °C min<sup>−1</sup> heating rate; (<b>d</b>) XRD of the gCNH-IrO<sub>2</sub> prepared at 300, 350, 400, and 450 °C. Note: the NaCl formed in the reaction was washed out prior to the XRD acquisition. The weak feature for gCNH occurs at ~27° 2θ. The characteristic strong (111) and (200) reflections for metallic Ir are indexed in red.</p> Full article ">Figure 3
<p><b>Left</b>: TGA/DSC traces of (<b>a</b>) (NH<sub>4</sub>)Ir<sub>2</sub>Cl<sub>6</sub>, (<b>c</b>) gCNH-(NH<sub>4</sub>)<sub>2</sub>IrCl<sub>6</sub>, (<b>e</b>) Vulcan-(NH<sub>4</sub>)<sub>2</sub>IrCl<sub>6</sub> conducted in air at 5 °C min<sup>−1</sup> heating rate. <b>Right:</b> the XRD of products of TGA analysis at different temperatures for (<b>b</b>) (NH<sub>4</sub>)<sub>2</sub>IrCl<sub>6</sub>, (<b>d</b>) gCNH-(NH<sub>4</sub>)<sub>2</sub>IrCl<sub>6</sub> and (<b>f</b>) Vulcan-(NH<sub>4</sub>)<sub>2</sub>IrCl<sub>6</sub>. Peaks due to metallic Ir are indexed in red.</p> Full article ">Figure 4
<p>HRTEM images of (<b>a</b>,<b>b</b>) gCNH-IrO<sub>2</sub> obtained through Adams’ fusion method at 450 °C.</p> Full article ">Figure 5
<p>TEM images and corresponding energy-dispersive X-ray spectroscopy (EDX) mapping for (<b>a</b>) gCNH-IrO<sub>2</sub> (40%) prepared by the ball-milling of pre-prepared IrO<sub>2</sub> and gCNH materials; (<b>b</b>) gCNH-IrO<sub>2</sub> (20%) prepared by in situ deposition of IrO<sub>2</sub> on gCNH support following an adaptation of Adams’ fusion method at 450 °C.</p> Full article ">Figure 6
<p>XPS spectra: C 1s (<b>a</b>) and N 1s (<b>b</b>) spectra of gCNH-IrO<sub>2</sub> (20 wt %) prepared by ball-milling; C 1s (<b>c</b>) and N 1s (<b>d</b>) spectra of gCNH-IrO<sub>2</sub> (450 °C); the inset shows an expansion of the N 1s peak.</p> Full article ">Figure 7
<p>Polarization measurements of PEMWEs with MEAs containing anodes made from (<b>a</b>) IrO<sub>2</sub>, (<b>b</b>) gCNH-IrO<sub>2</sub> prepared at 400 °C, and (<b>c</b>) gCNH-IrO<sub>2</sub> prepared at 450 °C. Measurements conducted at 80 °C and atmospheric pressure.</p> Full article ">Figure 8
<p>EIS Nyquist plots conducted in a PEM water electrolyzer at 80 °C, using Pt black as the cathode and gCNH-IrO<sub>2</sub> prepared at 400 and 450 °C as anode at (<b>a</b>) 0.1 A cm<sup>−2</sup> and (<b>b</b>) 1 A cm<sup>−2</sup>. Commercial IrRuO<sub>x</sub> anode results are included for comparison. (<b>c</b>) Equivalent circuit used for data fitting. <span class="html-italic">R<sub>ct</sub></span> is the charge transfer resistance described in the text.</p> Full article ">
9 pages, 3491 KiB  
Article
Preparation of TiO2/Carbon Nanotubes/Reduced Graphene Oxide Composites with Enhanced Photocatalytic Activity for the Degradation of Rhodamine B
by Yanzhen Huang, Dongping Chen, Xinling Hu, Yingjiang Qian and Dongxu Li
Nanomaterials 2018, 8(6), 431; https://doi.org/10.3390/nano8060431 - 13 Jun 2018
Cited by 61 | Viewed by 9002
Abstract
In this report, ternary titanium dioxide (TiO2)/carbon nanotubes (CNTs)/reduced graphene oxide (rGO) composites were fabricated by a facile and environmentally friendly one-pot solvethermal method for the removal of Rhodamine B (RhB). Its structures were represented by X-ray powder diffraction (XRD), Raman [...] Read more.
In this report, ternary titanium dioxide (TiO2)/carbon nanotubes (CNTs)/reduced graphene oxide (rGO) composites were fabricated by a facile and environmentally friendly one-pot solvethermal method for the removal of Rhodamine B (RhB). Its structures were represented by X-ray powder diffraction (XRD), Raman spectrometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic performance was tested by the degradation efficiency of RhB under UV-vis light irradiation. The experimental results indicated that photocatalytic activity improved as the ratio of CNTs:TiO2 ranged from 0.5% to 3% but reduced when the content increased to 5% and 10%, and the TiO2/CNTs/rGO-3% composites showed superior photocatalytic activity compared with the binary ones (i.e., TiO2/CNTs, TiO2/rGO) and pristine TiO2. The rate constant k of the pseudo first-order reaction was about 1.5 times that of TiO2. The improved photocatalytic activity can be attributed to the addition of rGO and CNTs, which reduced the recombination of photo-induced electron-hole pairs, and the fact that CNTs and rGO, with a high specific surface area and high adsorption ability to efficiently adsorb O2, H2O and organics, can increase the hydroxyl content of the photocatalyst surface. Full article
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<p>The schematic illustration of TiO<sub>2</sub>/carbon nanotubes (CNTs)/ reduced graphene oxide (rGO) composites.</p> Full article ">Figure 2
<p>X-ray powder diffraction (<b>a</b>) (XRD) patterns; (<b>b</b>) Raman spectra of TiO<sub>2</sub>, TiO<sub>2</sub>/rGO, TiO<sub>2</sub>/CNTs and TiO<sub>2</sub>/CNTs/rGO-3%.</p> Full article ">Figure 3
<p>(<b>a</b>) Scanning electron microscopy (SEM) image of TiO<sub>2</sub>/rGO; (<b>b</b>) SEM image of TiO<sub>2</sub>/CNTs; (<b>c</b>) High resolution- transmission electron microscopy (HR-TEM) of TiO<sub>2</sub>; (<b>d</b>) transmission electron microscopy (TEM) image of TiO<sub>2</sub>/CNTs/rGO-3%.</p> Full article ">Figure 4
<p>Blank test, TiO<sub>2</sub>, TiO<sub>2</sub>/rGO, TiO<sub>2</sub>/CNTs and TiO<sub>2</sub>/CNTs/rGO-3%: (<b>a</b>) plot of <span class="html-italic">C</span>/<span class="html-italic">C<sub>0</sub></span> vs. irradiation time of RhB degradation; (<b>b</b>) linear transform ln(<span class="html-italic">C</span><sub>0</sub>/<span class="html-italic">C</span>) = <span class="html-italic">kt</span> of the kinetic curves of RhB degradation.</p> Full article ">
15 pages, 6664 KiB  
Article
Easy Synthesis and Characterization of Holmium-Doped SPIONs
by Magdalena Osial, Paulina Rybicka, Marek Pękała, Grzegorz Cichowicz, Michał K. Cyrański and Paweł Krysiński
Nanomaterials 2018, 8(6), 430; https://doi.org/10.3390/nano8060430 - 13 Jun 2018
Cited by 34 | Viewed by 4850
Abstract
The exceptional magnetic properties of superparamagnetic iron oxide nanoparticles (SPIONs) make them promising materials for biomedical applications like hyperthermia, drug targeting and imaging. Easy preparation of SPIONs with the controllable, well-defined properties is a key factor of their practical application. In this work, [...] Read more.
The exceptional magnetic properties of superparamagnetic iron oxide nanoparticles (SPIONs) make them promising materials for biomedical applications like hyperthermia, drug targeting and imaging. Easy preparation of SPIONs with the controllable, well-defined properties is a key factor of their practical application. In this work, we report a simple synthesis of Ho-doped SPIONs by the co-precipitation route, with controlled size, shape and magnetic properties. To investigate the influence of the ions ratio on the nanoparticles’ properties, multiple techniques were used. Powder X-ray diffraction (PXRD) confirmed the crystallographic structure, indicating formation of an Fe3O4 core doped with holmium. In addition, transmission electron microscopy (TEM) confirmed the correlation of the crystallites’ shape and size with the experimental conditions, pointing to critical holmium content around 5% for the preparation of uniformly shaped grains, while larger holmium content leads to uniaxial growth with a prism shape. Studies of the magnetic behaviour of nanoparticles show that magnetization varies with changes in the initial Ho3+ ions percentage during precipitation, while below 5% of Ho in doped Fe3O4 is relatively stable and sufficient for biomedicine applications. The characterization of prepared nanoparticles suggests that co-precipitation is a simple and efficient technique for the synthesis of superparamagnetic, Ho-doped SPIONs for hyperthermia application. Full article
(This article belongs to the Special Issue Nanocolloids for Nanomedicine and Drug Delivery)
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<p>Image of the co-precipitation of Ho-doped ferrite nanoparticles under NH<sub>3</sub> addition.</p> Full article ">Figure 2
<p>TEM images of (<b>a</b>) undoped iron oxide SPIONs, and doped with (<b>b</b>) 1%; (<b>c</b>) 2.5%; (<b>d</b>) 5%; (<b>e</b>) 7.5%; (<b>f</b>) 10% of holmium obtained by co-precipitation (scale bar: 50 nm).</p> Full article ">Figure 3
<p>Histogram for Fe<sub>3</sub>O<sub>4</sub>@2.5%Ho.</p> Full article ">Figure 4
<p>Size distribution by volume for Fe<sub>3</sub>O<sub>4</sub>@2.5%Ho unmodified (blue curve) and modified with CEPA (black curve).</p> Full article ">Figure 5
<p>Thermograms of the SPIONs modified with 3-phosphoropropionic acid: (<b>a</b>) Fe<sub>3</sub>O<sub>4</sub>@1%Ho@CEPA, and (<b>b</b>) Fe<sub>3</sub>O<sub>4</sub>@2.5%Ho@CEPA.</p> Full article ">Figure 6
<p>PXRD patterns of undoped and Ho-doped nanoferrite crystallites.</p> Full article ">Figure 7
<p>XPS survey spectrum of Fe<sub>3</sub>O<sub>4</sub>@2.5 at. % Ho nanoparticles.</p> Full article ">Figure 8
<p>XPS spectra of (<b>a</b>) Fe 2p and (<b>b</b>) Ho 4d region for Fe<sub>3</sub>O<sub>4</sub>@2.5%Ho SPIONs.</p> Full article ">Figure 9
<p>Magnetization isotherms for SPIONs with different Ho content measured at (<b>a</b>) 100 K and (<b>b</b>) 300 K.</p> Full article ">Figure 10
<p>Magnetization loops K for (<b>a</b>) Fe<sub>3</sub>O<sub>4</sub>, (<b>b</b>) Fe<sub>3</sub>O<sub>4</sub>@1% Ho registered at 100 K and 300 K from −200 Oe to 200 Oe.</p> Full article ">Figure 11
<p>Values of (<b>a</b>) saturation magnetization at 20.000 Oe and (<b>b</b>) coercive field as a function of holmium content in SPIONs measured at 100 K and 300 K. Error bars are smaller than the data symbols.</p> Full article ">Figure 12
<p>Temperature dependence of ZFC and FC magnetization at 100 Oe for nanoparticles doped with (<b>a</b>) 1% and (<b>b</b>) 2.5% of holmium.</p> Full article ">
14 pages, 4557 KiB  
Article
Copper Nanoparticle and Nitrogen Doped Graphite Oxide Based Biosensor for the Sensitive Determination of Glucose
by Kulandaivel Sivasankar, Karuppasamy Kohila Rani, Sea-Fue Wang, Rajkumar Devasenathipathy and Chia-Her Lin
Nanomaterials 2018, 8(6), 429; https://doi.org/10.3390/nano8060429 - 13 Jun 2018
Cited by 18 | Viewed by 5620
Abstract
Copper nanoparticles with the diameter of 50 ± 20 nm decorated nitrogen doped graphite oxide (NGO) have been prepared through a simple single step carbonization method using copper metal-organic framework (MOF), [Cu2(BDC)2(DABCO)] (where BDC is 1,4-benzenedicarboxylate, and DABCO is [...] Read more.
Copper nanoparticles with the diameter of 50 ± 20 nm decorated nitrogen doped graphite oxide (NGO) have been prepared through a simple single step carbonization method using copper metal-organic framework (MOF), [Cu2(BDC)2(DABCO)] (where BDC is 1,4-benzenedicarboxylate, and DABCO is 1,4-Diazabicyclo[2.2.2]octane) as precursor. The surface morphology, porosity, surface area and elemental composition of CuNPs/NGO were characterized by various techniques. The as-synthesized CuNPs/NGO nanomaterials were coated on commercially available disposable screen-printed carbon electrode for the sensitive determination of glucose. We find that the modified electrode can detect glucose between 1 μM and 1803 μM (linear range) with good sensitivity (2500 μA mM−1 cm−2). Our glucose sensor also possesses low limits of detection (0.44 μM) towards glucose determination. The highly selective nature of the fabricated electrode was clearly visible from the selectivity studies. The practicability of CuNPs/NGO modified electrode has been validated in the human serum samples. The storage stability along with better repeatability and reproducibility results additionally substantiate the superior electrocatalytic activity of our constructed sensor towards glucose. Full article
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<p>Crystal structure of [Cu<sub>2</sub>(BDC)<sub>2</sub>(DABCO)] along the <span class="html-italic">b</span>-axis (hydrogen atoms are not given for the sake of clarity).</p> Full article ">Figure 2
<p>SEM images of only MOF (<b>A</b>); CuNPs/NGO (carbonized at 600 °C (<b>B</b>); 700 °C (<b>C</b>); 800 °C (<b>D</b>); 900 °C (<b>E</b>); and TEM image (<b>F</b>) of CuNPs/NGO (900 °C)).</p> Full article ">Figure 3
<p>XRD pattern of CuNPs/NGO (carbonized at 600 °C (<b>a</b>), 700 °C (<b>b</b>), 800 °C (<b>c</b>) and 900 °C (<b>d</b>)).</p> Full article ">Figure 4
<p>(<b>A</b>) N<sub>2</sub> adsorption analysis of CuNPs/NGO (600 (a), 700 (b), 800 (c) and 900 °C (d)); (<b>B</b>) pore size distribution curves of CuNPs/NGO (600 (a), 700 (b), 800 (c) and 900 °C (d)).</p> Full article ">Figure 5
<p>CVs obtained at CuNPs/NGO (600 (<b>A</b>), 700 (<b>B</b>), 800 (<b>C</b>) and 900 °C (<b>D</b>)) modified SPCEs in 0.1 NaOH with and without 3 mM glucose at the scan rate of 50 mV/s.</p> Full article ">Figure 6
<p>CVs observed without (<b>a</b>) and with each addition (<b>b</b>–<b>k</b>) of 1 mM glucose at CuNPs/NGO/SPCE in 0.1 M NaOH at the scan rate of 50 mV/s.</p> Full article ">Figure 7
<p>(<b>A</b>) amperometric response at CuNPs/NGO/SPCE upon successive additions of glucose (1, 10, 50, 100 and 200 μM (a–e)) of glucose in 0.1 M NaOH (scan rate = 50 mV s<sup>−1</sup>, applied potential = 0.4 V); (<b>B</b>) calibration plot of <span class="html-italic">I</span><sub>p</sub> vs. (<span class="html-italic">glucose</span>).</p> Full article ">
11 pages, 1992 KiB  
Article
Optimization of Malachite Green Removal from Water by TiO2 Nanoparticles under UV Irradiation
by Yongmei Ma, Maofei Ni and Siyue Li
Nanomaterials 2018, 8(6), 428; https://doi.org/10.3390/nano8060428 - 13 Jun 2018
Cited by 46 | Viewed by 4642
Abstract
TiO2 nanoparticles with surface porosity were prepared by a simple and efficient method and presented for the removal of malachite green (MG), a representative organic pollutant, from aqueous solution. Photocatalytic degradation experiments were systematically conducted to investigate the influence of TiO2 [...] Read more.
TiO2 nanoparticles with surface porosity were prepared by a simple and efficient method and presented for the removal of malachite green (MG), a representative organic pollutant, from aqueous solution. Photocatalytic degradation experiments were systematically conducted to investigate the influence of TiO2 dosage, pH value, and initial concentrations of MG. The kinetics of the reaction were monitored via UV spectroscopy and the kinetic process can be well predicted by the pseudo first-order model. The rate constants of the reaction kinetics were found to decrease as the initial MG concentration increased; increased via elevated pH value at a certain amount of TiO2 dosage. The maximum efficiency of photocatalytic degradation was obtained when the TiO2 dosage, pH value and initial concentrations of MG were 0.6 g/L, 8 and 10−5 mol/L (M), respectively. Results from this study provide a novel optimization and an efficient strategy for water pollutant treatment. Full article
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<p>(<b>A</b>) TEM image of the TiO<sub>2</sub> particle; (<b>B</b>) enlarged HRTEM image of details of the TiO<sub>2</sub> particle.</p> Full article ">Figure 2
<p>XRD patterns of TiO<sub>2</sub> and the standard XRD patterns of anatase-phase TiO<sub>2</sub> (JCPDS 21-1272).</p> Full article ">Figure 3
<p>(<b>A</b>) Time-course UV-Vis absorbance spectra of MG (10<sup>−5</sup> M) photocatalyzed by 0.6 g/L TiO<sub>2</sub> under UV light; (<b>B</b>–<b>D</b>) The calculated time-dependent ratios of <span class="html-italic">C<sub>t</sub></span>/<span class="html-italic">C</span><sub>0</sub>, first-order degradation rates, and reaction rate constants under UV light with different TiO<sub>2</sub> dosage.</p> Full article ">Figure 4
<p>(<b>A</b>) Time-course UV-vis absorbance spectra of MG (10<sup>−5</sup> M) photocatalyzed by 0.6 g/L TiO<sub>2</sub> under UV light; (<b>B</b>–<b>D</b>) The calculated time-dependent ratios of <span class="html-italic">C<sub>t</sub></span>/<span class="html-italic">C</span><sub>0</sub>, first-order degradation rates, and reaction rate constants for different concentration of MG photocatalyzed by 0.6 g/L TiO<sub>2</sub> under UV light.</p> Full article ">Figure 5
<p>(<b>A</b>) Time-course UV-Vis absorbance spectra of MG (10<sup>−5</sup> M) photocatalyzed by 0.6 g/L TiO<sub>2</sub> under UV light at pH = 8. (<b>B</b>–<b>D</b>) The calculated time-dependent ratios of <span class="html-italic">C<sub>t</sub></span>/<span class="html-italic">C</span><sub>0</sub>, first-order degradation rates and reaction rate constants for MG (10<sup>−5</sup> M) photocatalyzed by 0.6 g/L TiO<sub>2</sub> with different pH values.</p> Full article ">Scheme 1
<p>Illustrated mechanism of UV-activated photocatalysis on TiO<sub>2</sub>.</p> Full article ">
13 pages, 3062 KiB  
Article
Construction of g-C3N4-mNb2O5 Composites with Enhanced Visible Light Photocatalytic Activity
by Meiyin Wang, Hui Wang, Yuanhang Ren, Cheng Wang, Zhewei Weng, Bin Yue and Heyong He
Nanomaterials 2018, 8(6), 427; https://doi.org/10.3390/nano8060427 - 12 Jun 2018
Cited by 15 | Viewed by 4089
Abstract
A series of composites consisting of g-C3N4 sheet and mesoporous Nb2O5 (mNb2O5) microsphere were fabricated by in situ hydrolysis deposition of NbCl5 onto g-C3N4 sheet followed by solvothermal treatment. [...] Read more.
A series of composites consisting of g-C3N4 sheet and mesoporous Nb2O5 (mNb2O5) microsphere were fabricated by in situ hydrolysis deposition of NbCl5 onto g-C3N4 sheet followed by solvothermal treatment. The samples were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The photocatalytic activity of the composites was studied by degradation of rhodamine B (RhB) and tetracycline hydrochloride (TC-HCl) in aqueous solution under visible light irradiation (λ > 420 nm). Compared with g-C3N4 and mNb2O5, g-C3N4-mNb2O5 composites have higher photocatalytic activity due to synergistic effect between g-C3N4 and mNb2O5. Among these composites, 4% g-C3N4-mNb2O5 has the highest efficiency and good recyclability for degradation of both RhB and TC-HCl. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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Graphical abstract
Full article ">Figure 1
<p>XRD patterns for mNb<sub>2</sub>O<sub>5</sub>, g-C<sub>3</sub>N<sub>4</sub> and g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub> composites with different contents of g-C<sub>3</sub>N<sub>4</sub>.</p> Full article ">Figure 2
<p>(<b>a</b>) FT-IR spectra of mNb<sub>2</sub>O<sub>5</sub>, g-C<sub>3</sub>N<sub>4</sub> and g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub> composites with different contents of g-C<sub>3</sub>N<sub>4</sub>. (a, mNb<sub>2</sub>O<sub>5</sub>; b, 1% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>; c, 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>; d, 10% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>; e, 20% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>; f, 50% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>; g, g-C<sub>3</sub>N<sub>4</sub>); and (<b>b</b>) enlarged FT-IR spectra corresponding to rectangle region from (<b>a</b>).</p> Full article ">Figure 3
<p>TEM images of: (<b>a</b>) mNb<sub>2</sub>O<sub>5</sub>; (<b>b</b>,<b>c</b>) g-C<sub>3</sub>N<sub>4</sub>; and (<b>d</b>,<b>e</b>) 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>; (<b>f</b>) EDS analysis of 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub> corresponding to (<b>e</b>).</p> Full article ">Figure 4
<p>Nitrogen adsorption–desorption isotherms of g-C<sub>3</sub>N<sub>4</sub>, mNb<sub>2</sub>O<sub>5</sub>, 1% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>, 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>, 10% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub> and 50% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>.</p> Full article ">Figure 5
<p>(<b>a</b>) UV-vis diffuse reflectance spectra; and (<b>b</b>) plots of the (<span class="html-italic">α</span>h<span class="html-italic">υ</span>)<sup>2</sup> vs. (h<span class="html-italic">υ</span>) of mNb<sub>2</sub>O<sub>5</sub>, g-C<sub>3</sub>N<sub>4</sub>, and g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub> composites with different content of g-C<sub>3</sub>N<sub>4</sub>.</p> Full article ">Figure 6
<p>(<b>a</b>) XPS survey spectra of g-C<sub>3</sub>N<sub>4</sub>, mNb<sub>2</sub>O<sub>5</sub> and 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>; and (<b>b</b>) Nb 3d spectra for mNb<sub>2</sub>O<sub>5</sub> and 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>.</p> Full article ">Figure 7
<p>PL spectra of mNb<sub>2</sub>O<sub>5</sub>, 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>, 10% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>, 20% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub>, 50% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub> and g-C<sub>3</sub>N<sub>4</sub>.</p> Full article ">Figure 8
<p>(<b>a</b>) Photolysis of RhB and photocatalytic activity over as-prepared photocatalysts for RhB; and (<b>b</b>) recyclability for the photodegradation of RhB in the presence of 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub> under visible light irradiation.</p> Full article ">Figure 9
<p>(<b>a</b>) Photolysis of TC-HCl and photocatalytic activity over as-prepared photocatalysts for TC-HCl; and (<b>b</b>) recyclability for the photodegradation of TC-HCl in the presence of 4% g-C<sub>3</sub>N<sub>4</sub>-mNb<sub>2</sub>O<sub>5</sub> under visible light irradiation.</p> Full article ">
16 pages, 4661 KiB  
Article
Piezo-Potential Generation in Capacitive Flexible Sensors Based on GaN Horizontal Wires
by Amine El Kacimi, Emmanuelle Pauliac-Vaujour, Olivier Delléa and Joël Eymery
Nanomaterials 2018, 8(6), 426; https://doi.org/10.3390/nano8060426 - 12 Jun 2018
Cited by 5 | Viewed by 3962
Abstract
We report an example of the realization of a flexible capacitive piezoelectric sensor based on the assembly of horizontal c¯-polar long Gallium nitride (GaN) wires grown by metal organic vapour phase epitaxy (MOVPE) with the Boostream® technique spreading wires on [...] Read more.
We report an example of the realization of a flexible capacitive piezoelectric sensor based on the assembly of horizontal c¯-polar long Gallium nitride (GaN) wires grown by metal organic vapour phase epitaxy (MOVPE) with the Boostream® technique spreading wires on a moving liquid before their transfer on large areas. The measured signal (<0.6 V) obtained by a punctual compression/release of the device shows a large variability attributed to the dimensions of the wires and their in-plane orientations. The cause of this variability and the general operating mechanisms of this flexible capacitive device are explained by finite element modelling simulations. This method allows considering the full device composed of a metal/dielectric/wires/dielectric/metal stacking. We first clarify the mechanisms involved in the piezo-potential generation by mapping the charge and piezo-potential in a single wire and studying the time-dependent evolution of this phenomenon. GaN wires have equivalent dipoles that generate a tension between metallic electrodes only when they have a non-zero in-plane projection. This is obtained in practice by the conical shape occurring spontaneously during the MOVPE growth. The optimal aspect ratio in terms of length and conicity (for the usual MOVPE wire diameter) is determined for a bending mechanical loading. It is suggested to use 60–120 µm long wires (i.e., growth time less than 1 h). To study further the role of these dipoles, we consider model systems with in-plane 1D and 2D regular arrays of horizontal wires. It is shown that a strong electrostatic coupling and screening occur between neighbouring horizontal wires depending on polarity and shape. This effect, highlighted here only from calculations, should be taken into account to improve device performance. Full article
(This article belongs to the Special Issue 1D Nanostructure-Based Piezo-Generators)
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Figure 1

Figure 1
<p>(<b>a</b>) Scanning electron microscopy (SEM) image of metal organic vapour phase epitaxy (MOVPE) grown ultra-long wires (~300 µm) grown on sapphire substrate [<a href="#B23-nanomaterials-08-00426" class="html-bibr">23</a>]. (<b>b</b>) Schematics of the Boostream© process used for the wire assembly. (<b>c</b>) SEM image of about 300 µm long GaN wire encapsulated by a thin layer of Parylene-C after Boostream<sup>®</sup> assembly. (<b>d</b>) Schematics for the capacitive device structure using horizontally assembled GaN (in red) and parylene-C dielectric.</p> Full article ">Figure 2
<p>(<b>a</b>) Stripes of GaN wires assembled with the Boostream<sup>®</sup> process. (<b>b</b>) Optical microscopy image of the wires. (<b>c</b>) Piezoelectric signal measured on three different regions of a flexible devices made of 104 µm long wires (see <a href="#nanomaterials-08-00426-f001" class="html-fig">Figure 1</a>d). The sensor is subjected to a cycled local compression load/release of 1 N/cm² on 1 cm-diameter disk at the speed of 900 mm/min.</p> Full article ">Figure 3
<p>Schematics of the wire geometry (length <span class="html-italic">L</span> and conicity angle α) and definition of axes. The left inset gives a front view of the simulated structure consisting of a single conical wire embedded into a dielectric layer of height <span class="html-italic">h</span> and with <span class="html-italic">w</span>. The right inset is a front view of the conical wire showing its top and bottom diameter <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mrow> <mi>t</mi> <mi>o</mi> <mi>p</mi> </mrow> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mrow> <mi>b</mi> <mi>o</mi> <mi>t</mi> </mrow> </msub> </mrow> </semantics></math>.</p> Full article ">Figure 4
<p>Maximum displacement and output voltage as function of the curvature radius <math display="inline"><semantics> <mi mathvariant="sans-serif">ρ</mi> </semantics></math> for a single wire embedded in a capacitive structure. The maximum displacement occurs at the wire extremities and the potential value is taken at the middle of the top facet of the wire (see point M in <a href="#nanomaterials-08-00426-f003" class="html-fig">Figure 3</a>).</p> Full article ">Figure 5
<p>Calculated potential along the top dielectric facet with <span class="html-italic">L</span> = 120 and 200 µm long wires embedded in <span class="html-italic">h</span> = 2 µm dielectric layer with α = 1° conicity angle and <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">ρ</mi> <mo>=</mo> </mrow> </semantics></math> 10 cm curvature radius bending.</p> Full article ">Figure 6
<p>(<b>a</b>) Piezo-potential calculated at center of the wire as a function of the wire length for α = 1° and <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">ρ</mi> <mo>=</mo> </mrow> </semantics></math> 10 cm curvature radius; (<b>b</b>) the related variation of the wire surface and volume.</p> Full article ">Figure 7
<p>Two-dimensional finite element calculation of non-conical (α = 0°) and conical (α = 1°) embedded GaN wires bended under 10 cm radius curvature. (<b>a</b>) Piezoelectric charge density mappings (note the different scales along X and Y). (<b>b</b>) Piezo-potential taken at the top m-plane facet al.ong the length for (lines) and the corresponding cross-section mappings of the potential across the structure in insets.</p> Full article ">Figure 8
<p>Time-dependent behaviour of the wire-based sensor obtained by finite element modelling simulation for a structure with a single cone-shaped wire of 120 µm length and 1° conicity angle under 10 cm curvature radius bending. The voltage is taken on the top electrode while the bottom is grounded. The inset shows the equivalent electrical circuit of the device. (<span class="html-italic">R</span><sub>1</sub>, <span class="html-italic">C</span><sub>1</sub>) correspond to the internal impedance of the sensor and (<span class="html-italic">R</span><sub>C</sub>, <span class="html-italic">C</span><sub>C</sub>) to the measurement setup.</p> Full article ">Figure 9
<p>(<b>a</b>) Piezo-potential evolution as function of the conicity angle <math display="inline"><semantics> <mi mathvariant="sans-serif">α</mi> </semantics></math> for wires with <span class="html-italic">L</span> = 50, 120, 200 µm and and <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mrow> <mi>t</mi> <mi>o</mi> <mi>p</mi> </mrow> </msub> <mo>=</mo> <mn>700</mn> <mo> </mo> <mi>nm</mi> </mrow> </semantics></math>. (<b>b</b>) The related variation of the surface over volume ratio.</p> Full article ">Figure 10
<p>(<b>a</b>) Schematics of a regular horizontal assembly of wires. (<b>b</b>) Elementary cell structure composed of two wires illustrating the boundary condition calculation method.</p> Full article ">Figure 11
<p>(<b>a</b>) Schematics of the wire relative crystallographic orientation: (<b>a</b>) parallel and (<b>b</b>) anti-parallel configurations of the <math display="inline"><semantics> <mrow> <mover accent="true"> <mi>c</mi> <mo>¯</mo> </mover> </mrow> </semantics></math> growth axis. The m-planes of GaN are parallel to the bottom electrode. The black arrows in the center of the wires are the in-plane representations of the equivalent electric dipoles schematized in <a href="#nanomaterials-08-00426-f007" class="html-fig">Figure 7</a>. (<b>b</b>) Potential per surface area measured between metal electrodes as function of wire inter-distance d for parallel and anti-parallel configuration of the wire orientation. A bending deformation of 10 cm curvature radius is applied to the bottom part of the simulated structure.</p> Full article ">Figure 12
<p>Surface potential as function of the parameter <span class="html-italic">h/d</span> for a two-wires in parallel and anti-parallel configurations under a bending with <math display="inline"><semantics> <mi mathvariant="sans-serif">ρ</mi> </semantics></math> = 10 cm curvature radius. The potential is taken at the top electrode while the bottom one is grounded (see <a href="#nanomaterials-08-00426-f008" class="html-fig">Figure 8</a>). The graph focuses on values of <span class="html-italic">h/d</span> lower than 1. The inset graph shows a zoom out for the whole range of values of <span class="html-italic">h/d</span> from 0.25 to 8.</p> Full article ">Figure 13
<p>(<b>a</b>) Schematics of three in-plane arrays of two-dimensional wire assemblies. The black arrows sketch the equivalent electric dipoles shown in <a href="#nanomaterials-08-00426-f007" class="html-fig">Figure 7</a> and <a href="#nanomaterials-08-00426-f011" class="html-fig">Figure 11</a>. (<b>b</b>) Comparison of the evolution of the normalized potential by unit surface as function of <span class="html-italic">h/d</span> for configurations shown in (<b>a</b>). The value of <span class="html-italic">h</span> is fixed at 2 µm while d is varied between 2 and 10 µm.</p> Full article ">
13 pages, 4992 KiB  
Article
Mesoscopic Modeling of the Encapsulation of Capsaicin by Lecithin/Chitosan Liposomal Nanoparticles
by Ketzasmin A. Terrón-Mejía, Evelin Martínez-Benavidez, Inocencio Higuera-Ciapara, Claudia Virués, Javier Hernández, Zaira Domínguez, Waldo Argüelles-Monal, Francisco M. Goycoolea, Roberto López-Rendón and Armando Gama Goicochea
Nanomaterials 2018, 8(6), 425; https://doi.org/10.3390/nano8060425 - 12 Jun 2018
Cited by 15 | Viewed by 5541
Abstract
The transport of hydrophobic drugs in the human body exhibits complications due to the low solubility of these compounds. With the purpose of enhancing the bioavailability and biodistribution of such drugs, recent studies have reported the use of amphiphilic molecules, such as phospholipids, [...] Read more.
The transport of hydrophobic drugs in the human body exhibits complications due to the low solubility of these compounds. With the purpose of enhancing the bioavailability and biodistribution of such drugs, recent studies have reported the use of amphiphilic molecules, such as phospholipids, for the synthesis of nanoparticles or nanocapsules. Given that phospholipids can self-assemble in liposomes or micellar structures, they are ideal candidates to function as vehicles of hydrophobic molecules. In this work, we report mesoscopic simulations of nanoliposomes, constituted by lecithin and coated with a shell of chitosan. The stability of such structures and the efficiency of the encapsulation of capsaicin, as well as the internal and superficial distribution of capsaicin and chitosan inside the nanoliposome, were analyzed. The characterization of the system was carried out through density maps and the potentials of mean force for the lecithin-capsaicin, lecithin-chitosan, and capsaicin-chitosan interactions. The results of these simulations show that chitosan is deposited on the surface of the nanoliposome, as has been reported in some experimental works. It was also observed that a nanoliposome of approximately 18 nm in diameter is stable during the simulation. The deposition behavior was found to be influenced by a pattern of N-acetylation of chitosan. Full article
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Graphical abstract

Graphical abstract
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<p>Schematic representation of the coarse-grained models adopted in this work. Mesoscopic models for lecithin (C<sub>42</sub>H<sub>82</sub>NO<sub>8</sub>P, <b>left)</b>, chitosan (CS) (<b>top center</b>), water as solvent (<b>bottom center</b>), and capsaicin (C<sub>18</sub>H<sub>27</sub>NO<sub>3</sub>, <b>right</b>). The exact division of every functional group is presented in the SI. As an overview, the molecular structure of lecithin is composed of three different beads, which we have labelled as <span class="html-italic">L</span>1, <span class="html-italic">L</span>2, and <span class="html-italic">L</span>3, that correspond to the head, neck and tail groups, respectively. The same nomenclature is used for capsaicin, where the beads <span class="html-italic">C</span>1, <span class="html-italic">C</span>2, and <span class="html-italic">C</span>3 correspond to the head, neck, and tail groups, respectively. The CS model consists of two types of beads: the first bead represents the glucosamine units (C<sub>6</sub>H<sub>13</sub>NO<sub>5</sub>), which are labelled <span class="html-italic">G</span>, while the second bead represents the <span class="html-italic">N</span>-acetyl-glucosamine units (C<sub>8</sub>H<sub>15</sub>NO<sub>6</sub>), which are labelled <span class="html-italic">A</span>. Finally, the solvent (water) is represented by bead <span class="html-italic">W</span>. These figures were prepared with the Visual Molecular Dynamics (VMD) package [<a href="#B53-nanomaterials-08-00425" class="html-bibr">53</a>].</p> Full article ">Figure 2
<p>Initial configuration of nanoliposome. A snapshot of the initial configuration of lecithin molecules in the structure of a liposome bilayer (<b>left</b>). The yellow spheres represent the hydrophobic part of the lecithin, while the red spheres represent the hydrophilic part. The capsaicin and CS molecules were placed in a random configuration around the lecithin (<b>right</b>). The orange chains represent the CS polymers, while the turquoise chains represent the capsaicin molecules. These Figures were prepared with the VMD package [<a href="#B53-nanomaterials-08-00425" class="html-bibr">53</a>].</p> Full article ">Figure 3
<p>Density maps of lecithin on the <span class="html-italic">xy</span> plane at different concentration of CS. (<b>A</b>) 50 chains of CS (6 mM); (<b>B</b>) 100 chains of CS (12 mM); (<b>C</b>) 150 chains of CS (18 mM); (<b>D</b>) 200 chains of CS (24 mM). The scale of density bars starts at 0.0 (black regions) and reaches a maximum of 2.0 (yellow regions). All quantities are expressed in reduced dissipative particle dynamics (DPD) units.</p> Full article ">Figure 4
<p>Distribution of CS on liposome on the <span class="html-italic">xy</span> plane. (<b>A</b>) 50 chains of CS; (<b>B</b>) 100 chains of CS; (<b>C</b>) 150 chains of CS; (<b>D</b>) 200 chains of CS. All quantities are reported in reduced DPD units.</p> Full article ">Figure 5
<p>Influence of CS concentration on capsaicin on the <span class="html-italic">xy</span> plane at different concentrations of the CS polymer. (<b>A</b>) 50 chains of CS; (<b>B</b>) 100 chains of CS; (<b>C</b>) 150 chains of CS; (<b>D</b>) 200 chains of CS. All quantities are reported in reduced DPD units.</p> Full article ">Figure 6
<p>Potentials of mean force (PMF) for different concentration of CS, as function of separation distance between mass centers of each molecule. (<b>A</b>) Lecithin-CS; (<b>B</b>) lecithin-capsaicin; and (<b>C</b>) capsaicin-CS. All quantities are expressed in reduced DPD units.</p> Full article ">Figure 7
<p>PMF for the two sequences of CS used in this work, S1 (red line) and S2 (blue dotted line), to concentrations of CS reaching 6 mM. PMF for (<b>A</b>) lecithin-CS; (<b>B</b>) CS-capsaicin; and (<b>C</b>) lecithin-capsaicin. All quantities are expressed in reduced DPD units.</p> Full article ">Figure 8
<p>Snapshots of adsorption of CS on the nanoliposome at various times during simulation. In these pictures, the conformation of the nanocapsule along different times can be observed. The color code in this figure is the same as the one in <a href="#nanomaterials-08-00425-f002" class="html-fig">Figure 2</a>. The solvent molecules are not shown for clarity purposes. These figures were prepared with the VMD package [<a href="#B53-nanomaterials-08-00425" class="html-bibr">53</a>].</p> Full article ">
9 pages, 2752 KiB  
Article
Complex Magnetization Harmonics of Polydispersive Magnetic Nanoclusters
by Suko Bagus Trisnanto and Yasushi Takemura
Nanomaterials 2018, 8(6), 424; https://doi.org/10.3390/nano8060424 - 11 Jun 2018
Cited by 7 | Viewed by 4059
Abstract
Understanding magnetic interparticle interactions within a single hydrodynamic volume of polydispersed magnetic nanoparticles and the resulting nonlinear magnetization properties is critical for their implementation in magnetic theranostics. However, in general, the field-dependent static and dynamic magnetization measurements may only highlight polydispersity effects including [...] Read more.
Understanding magnetic interparticle interactions within a single hydrodynamic volume of polydispersed magnetic nanoparticles and the resulting nonlinear magnetization properties is critical for their implementation in magnetic theranostics. However, in general, the field-dependent static and dynamic magnetization measurements may only highlight polydispersity effects including magnetic moment and size distributions. Therefore, as a complement to such typical analysis of hysteretic magnetization curves, we spectroscopically examined the complex magnetization harmonics of magnetic nanoclusters either dispersed in a liquid medium or immobilized by a hydrocolloid polymer, later to emphasize the harmonic characteristics for different core sizes. In the case of superparamagnetic nanoclusters with a 4-nm primary size, particularly, we correlated the negative quadrature components of the third-harmonic susceptibility with an insignificant cluster rotation induced by the oscillatory field. Moreover, the field-dependent in-phase components appear to be frequency-independent, suggesting a weak damping effect on the moment dynamics. The characteristic of the Néel time constant further supports this argument by showing a smaller dependence on the applied dc bias field, in comparison to that of larger cores. These findings show that the complex harmonic components of the magnetization are important attributes to the interacting cores of a magnetic nanocluster. Full article
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Full article ">Figure 1
<p>(<b>a</b>) Transmission electron microscopy images and dynamic light scattering measurements of the characterized ferrofluid samples; (<b>b</b>) Phase-sensitive detection system to measure the complex magnetization harmonics of a 0.1-mL ferrofluid sample placed within an area with a spatially uniform field-distribution. The signal amplitude and phase differences at the fundamental and third-harmonic frequencies (<math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>R</mi> <mn>1</mn> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>φ</mi> <mn>1</mn> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>R</mi> <mn>3</mn> </msub> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>φ</mi> <mn>3</mn> </msub> </mrow> </semantics></math>, respectively) were recorded while varying field strength and frequency of the applied fields.</p> Full article ">Figure 2
<p>Dynamic magnetization curves of the ferrofluid samples at 1 kHz. The different coercive fields <math display="inline"><semantics> <mrow> <msub> <mi>H</mi> <mi>C</mi> </msub> </mrow> </semantics></math> and remanences <math display="inline"><semantics> <mrow> <msub> <mi>M</mi> <mi>R</mi> </msub> </mrow> </semantics></math> within low-field regimes (e.g., ±50, ±100, ±200, and ±300 Oe) indicate magnetization reversal. The measured magnetization <math display="inline"><semantics> <mi>M</mi> </semantics></math> has been normalized by the saturated magnetization <math display="inline"><semantics> <mrow> <msub> <mi>M</mi> <mi>S</mi> </msub> </mrow> </semantics></math> of the respective samples.</p> Full article ">Figure 3
<p>(<b>a</b>) Frequency-dependent complex magnetic susceptibilities at 50 Oe. The field-induced cluster rotation is recognized from the spectral shift of the imaginary peaks between the imaginary <math display="inline"><semantics> <mrow> <msubsup> <mi>χ</mi> <mn>1</mn> <mrow> <mo>″</mo> </mrow> </msubsup> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msubsup> <mi>χ</mi> <mn>3</mn> <mrow> <mo>″</mo> </mrow> </msubsup> </mrow> </semantics></math> parts (open circles), in addition the larger real <math display="inline"><semantics> <mrow> <msubsup> <mi>χ</mi> <mn>1</mn> <mo>′</mo> </msubsup> </mrow> </semantics></math>’ and <math display="inline"><semantics> <mrow> <msubsup> <mi>χ</mi> <mn>3</mn> <mo>′</mo> </msubsup> </mrow> </semantics></math>’ parts (solid circles) than those of the solidified samples (solid triangles). The imaginary parts for the solid samples (open triangles) are later attributed to the moment dynamics; (<b>b</b>) Illustrative <math display="inline"><semantics> <mrow> <msubsup> <mi>M</mi> <mi>n</mi> <mrow> <mo>″</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <mrow> <msubsup> <mi>M</mi> <mi>n</mi> <mo>′</mo> </msubsup> </mrow> <mo>)</mo> </mrow> </mrow> </semantics></math> plot of an empirical relaxation model with <math display="inline"><semantics> <mi>a</mi> </semantics></math> and <math display="inline"><semantics> <mi>b</mi> </semantics></math> fitting parameters [<a href="#B16-nanomaterials-08-00424" class="html-bibr">16</a>]. The semicircle Cole-Cole model can be partially fitted to the <math display="inline"><semantics> <mrow> <msubsup> <mi>M</mi> <mn>1</mn> <mrow> <mo>″</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <mrow> <msubsup> <mi>M</mi> <mn>1</mn> <mo>′</mo> </msubsup> </mrow> <mo>)</mo> </mrow> </mrow> </semantics></math> plots of the ferrofluid samples, whereas <math display="inline"><semantics> <mrow> <msubsup> <mi>M</mi> <mn>3</mn> <mrow> <mo>″</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <mrow> <msubsup> <mi>M</mi> <mn>3</mn> <mo>′</mo> </msubsup> </mrow> <mo>)</mo> </mrow> </mrow> </semantics></math> appears to have unique patterns.</p> Full article ">Figure 4
<p>Field-dependent third-harmonic susceptibility at 1, 2, 5, and 10 kHz. The real <math display="inline"><semantics> <mrow> <msubsup> <mi>χ</mi> <mn>3</mn> <mo>′</mo> </msubsup> </mrow> </semantics></math> and the imaginary <math display="inline"><semantics> <mrow> <msubsup> <mi>χ</mi> <mn>3</mn> <mrow> <mo>″</mo> </mrow> </msubsup> </mrow> </semantics></math> parts of the liquid samples (solid and open circles, respectively), as well as those of the solidified samples (solid and open triangles), distinguish the superparamagnetism of CMEAD-γFe<sub>2</sub>O<sub>3</sub> nanoclusters from the frequency independence.</p> Full article ">Figure 5
<p>Field-dependent effective Néel time constant <math display="inline"><semantics> <mrow> <msubsup> <mi>τ</mi> <mi>N</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>H</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> of the immobilized CMEAD-γFe<sub>2</sub>O<sub>3</sub> (solid squares) and AOS-Fe<sub>3</sub>O<sub>4</sub> (solid circles) nanoparticles representing the damping behavior of the particle moment <math display="inline"><semantics> <mrow> <msub> <mi>m</mi> <mi>p</mi> </msub> </mrow> </semantics></math>.</p> Full article ">
13 pages, 2636 KiB  
Article
Facet-Dependent Cuprous Oxide Nanocrystals Decorated with Graphene as Durable Photocatalysts under Visible Light
by Shou-Heng Liu and Jun-Sheng Lu
Nanomaterials 2018, 8(6), 423; https://doi.org/10.3390/nano8060423 - 11 Jun 2018
Cited by 11 | Viewed by 3593
Abstract
Three morphologies (octahedral, hierarchical and rhombic dodecahedral) of crystal Cu2O with different facets ({111}, {111}/{110}, and {110}) incorporating graphene sheets (denoted as o-Cu2O-G, h-Cu2O-G and r-Cu2O-G, respectively) have been fabricated by using simple solution-phase techniques. [...] Read more.
Three morphologies (octahedral, hierarchical and rhombic dodecahedral) of crystal Cu2O with different facets ({111}, {111}/{110}, and {110}) incorporating graphene sheets (denoted as o-Cu2O-G, h-Cu2O-G and r-Cu2O-G, respectively) have been fabricated by using simple solution-phase techniques. Among these photocatalysts, the r-Cu2O-G possesses the best photocatalytic performance of 98% removal efficiency of methyl orange (MO) with outstanding kinetics for 120 min of visible light irradiation. This enhancement is mainly due to the dangling “Cu” atoms in the highly active {110} facets, resulting in the increased adsorption of negatively charged MO. More importantly, the unique interfacial structures of Cu2O rhombic dodecahedra connected to graphene nanosheets can not only decrease the recombination of electron-hole pairs but also stabilize the crystal structure of Cu2O, as verified by a series of spectroscopic analyses (e.g., X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)). The effective photocatalysts developed in this work could be applied to the efficient decolorization of negatively charged organic dyes by employing solar energy. Full article
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Full article ">Figure 1
<p>X-ray diffraction (XRD) patterns of different photocatalysts.</p> Full article ">Figure 2
<p>Scanning electron microscope (SEM) images of (<b>a</b>) o-Cu<sub>2</sub>O; (<b>b</b>) h-Cu<sub>2</sub>O; (<b>c</b>) r-Cu<sub>2</sub>O; (<b>d</b>) o-Cu<sub>2</sub>O-G; (<b>e</b>) h-Cu<sub>2</sub>O-G and (<b>f</b>) r-Cu<sub>2</sub>O-G.</p> Full article ">Figure 3
<p>Transmission electron microscope (TEM) images of (<b>a</b>) o-Cu<sub>2</sub>O-G; (<b>b</b>) h-Cu<sub>2</sub>O-G; (<b>c</b>) r-Cu<sub>2</sub>O-G and high-resolution TEM (HRTEM) of (<b>d</b>) o-Cu<sub>2</sub>O-G; (<b>e</b>) h-Cu<sub>2</sub>O-G; (<b>f</b>) r-Cu<sub>2</sub>O-G. Inset: selected area electron diffraction (SAED) from the circle area.</p> Full article ">Figure 4
<p>X-ray photoelectron spectroscopy (XPS) spectra of different photocatalysts at the (<b>a</b>) high-resolution C 1s core-level; (<b>b</b>) Cu 2p core-level; and (<b>c</b>) O 1s core-level.</p> Full article ">Figure 5
<p>(<b>a</b>) Ultraviolet-visible (UV-Vis) absorption spectra for different samples and (<b>b</b>) the corresponding Kubelka–Munk plots of photocatalysts.</p> Full article ">Figure 6
<p>(<b>a</b>) Relative concentration of methyl orange (MO) versus time by various photocatalysts under visible light and (<b>b</b>) kinetic plots from the data in (<b>a</b>).</p> Full article ">Figure 7
<p>(<b>a</b>) Cyclic tests of r-Cu<sub>2</sub>O and r-Cu<sub>2</sub>O-G photocatalysts for MO photodegradation under visible light; (<b>b</b>) XRD patterns of the fresh and used r-Cu<sub>2</sub>O-G.</p> Full article ">Figure 8
<p>Possible mechanism of MO photodegradation over r-Cu<sub>2</sub>O-G under visible-light illumination.</p> Full article ">
10 pages, 3593 KiB  
Article
A Thin Film Flexible Supercapacitor Based on Oblique Angle Deposited Ni/NiO Nanowire Arrays
by Jing Ma, Wen Liu, Shuyuan Zhang, Zhe Ma, Peishuai Song, Fuhua Yang and Xiaodong Wang
Nanomaterials 2018, 8(6), 422; https://doi.org/10.3390/nano8060422 - 11 Jun 2018
Cited by 16 | Viewed by 5240
Abstract
With high power density, fast charging-discharging speed, and a long cycling life, supercapacitors are a kind of highly developed novel energy-storage device that has shown a growing performance and various unconventional shapes such as flexible, linear-type, stretchable, self-healing, etc. Here, we proposed a [...] Read more.
With high power density, fast charging-discharging speed, and a long cycling life, supercapacitors are a kind of highly developed novel energy-storage device that has shown a growing performance and various unconventional shapes such as flexible, linear-type, stretchable, self-healing, etc. Here, we proposed a rational design of thin film, flexible micro-supercapacitors with in-plane interdigital electrodes, where the electrodes were fabricated using the oblique angle deposition technique to grow oblique Ni/NiO nanowire arrays directly on polyimide film. The obtained electrodes have a high specific surface area and good adhesion to the substrate compared with other in-plane micro-supercapacitors. Meanwhile, the as-fabricated micro-supercapacitors have good flexibility and satisfactory energy-storage performance, exhibiting a high specific capacity of 37.1 F/cm3, a high energy density of 5.14 mWh/cm3, a power density of up to 0.5 W/cm3, and good stability during charge-discharge cycles and repeated bending-recovery cycles, respectively. Our micro-supercapacitors can be used as ingenious energy storage devices for future portable and wearable electronic applications. Full article
(This article belongs to the Special Issue Metallic Nanostructures)
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Full article ">Figure 1
<p>The schematic fabrication process of flexible micro-supercapacitors (MSCs). (<b>a</b>–<b>f</b>) Steps of preparing substrate, lithography, sputtering Ti/Au, oblique angle-depositing Ni nanowires annealing and packaging, respectively; (<b>g</b>) photograph of the as-fabricated flexible supercapacitor device.</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) Top-view and cross-section images of the nanostructured layer prepared on a polyimide (PI) substrate; (<b>c</b>) transmission electron microscopy (TEM) image of the oblique nanowire arrays; (<b>d</b>) high-resolution TEM (HRTEM) image of the nanowire; (<b>e</b>) X-ray diffractometer (XRD) patterns of the nanowires on the substrate; (<b>f</b>) Raman spectra measured on the surface of nanowires using a 532-nm laser; (<b>g</b>) Ni 2p; (<b>h</b>) O 1s and (<b>i</b>) C 1s X-ray photoelectron spectroscopy (XPS) spectra.</p> Full article ">Figure 3
<p>(<b>a</b>) Photos of the MSC devices; (<b>b</b>) capacitance-voltage (CV) curves at various scan rates; (<b>c</b>) Galvanostatic charge-discharge (GCD) at different currents measured in the voltage window of 0–1 V; (<b>d</b>) comparison of capacitances of the MSC devices at varied galvanostatic charge-discharge current densities; (<b>e</b>) capacitance retention on cycle number at a current of 4 A/cm<sup>3</sup>; (<b>f</b>) energy and powder densities of the MSC devices.</p> Full article ">Figure 4
<p>(<b>a</b>) Photos of a MSC at different bending states; (<b>b</b>) CV curves at 100 mV/s in straight and different bending states, respectively; (<b>c</b>) charge/discharge curves at a current of 2 A/cm<sup>3</sup> in straight and different bending states, respectively; (<b>d</b>) capacitance performance under the different bending states.</p> Full article ">Figure 5
<p>The integrated MSCs system based on six individual devices: (<b>a</b>) device position on the substrate; (<b>b</b>) CV curves of one MSC and an integrated arrays of six MSCs at scan rates of 100 mV/s and 300 mV/s, respectively; (<b>c</b>) galvanostatic CD curves of an array system of one MSC and six MSCs at the currents of 2 A/cm<sup>3</sup> and 4 A/cm<sup>3</sup>, respectively; (<b>d</b>) photos of an integrated MSCs system; (<b>e</b>) flexibility performance of the integrated MSCs system based on six individual devices at different bending states; (<b>f</b>) the capacitance stability of the MSCs during repeated bending-recovery cycles at a galvanostatic current of 4 A/cm<sup>3</sup>.</p> Full article ">
16 pages, 7423 KiB  
Article
Interfacial Model and Characterization for Nanoscale ReB2/TaN Multilayers at Desired Modulation Period and Ratios: First-Principles Calculations and Experimental Investigations
by Shangxiao Jin and Dejun Li
Nanomaterials 2018, 8(6), 421; https://doi.org/10.3390/nano8060421 - 10 Jun 2018
Cited by 3 | Viewed by 3578
Abstract
The interfacial structure of ReB2/TaN multilayers at varied modulation periods (Λ) and modulation ratios (tReB2:tTaN) was investigated using key experiments combined with first-principles calculations. A maximum hardness of 38.7 GPa occurred at Λ [...] Read more.
The interfacial structure of ReB2/TaN multilayers at varied modulation periods (Λ) and modulation ratios (tReB2:tTaN) was investigated using key experiments combined with first-principles calculations. A maximum hardness of 38.7 GPa occurred at Λ = 10 nm and tReB2:tTaN = 1:1. The fine nanocrystalline structure with small grain sizes remained stable for individual layers at Λ= 10 nm and tReB2:tTaN = 1:1. The calculation of the interfacial structure model and interfacial energy was performed using the first principles to advance the in-depth understanding of the relationship between the mechanical properties, residual stresses, and the interfacial structure. The B-Ta interfacial configuration was calculated to have the highest adsorption energy and the lowest interfacial energy. The interfacial energy and adsorption energy at different tReB2:tTaN followed the same trend as that of the residual stress. The 9ReB2/21TaN interfacial structure in the B-Ta interfacial configuration was found to be the most stable interface in which the highest adsorption energy and the lowest interfacial energy were obtained. The chemical bonding between the neighboring B atom and the Ta atom in the interfaces showed both covalency and iconicity, which provided a theoretical interpretation of the relationship between the residual stress and the stable interfacial structure of the ReB2/TaN multilayer. Full article
(This article belongs to the Special Issue Design and Development of Nanostructured Thin Films)
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Figure 1
<p>X-ray reflection (XRR) patterns of rhenium diboride (ReB<sub>2</sub>)/tantalum nitride (TaN) multilayers at (<b>a</b>) <span class="html-italic">Λ</span>~8 nm, <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub> = 1:2; and (<b>b</b>) <span class="html-italic">Λ</span>~21 nm, <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub> = 1:1. The insets are the linear least squares fit of sin<sup>2</sup><span class="html-italic">θ</span> vs. <span class="html-italic">n</span><sup>2</sup>.</p> Full article ">Figure 2
<p>Cross-sectional scanning electron microscopy (SEM) images of ReB<sub>2</sub>/TaN multilayer at (<b>a</b>) <span class="html-italic">Λ</span>~7 nm at low magnification; (<b>b</b>) 7 nm, <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub> = 1:2 at high magnification; (<b>c</b>) X-ray photoelectron spectrometer (XPS) depth profile of ReB<sub>2</sub>/TaN multilayer at <span class="html-italic">Λ</span>~7 nm, <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub> = 1:2; (<b>d</b>) 20 nm, <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub> = 1:1 at high magnification.</p> Full article ">Figure 3
<p>Hardness and Elastic modulus of ReB<sub>2</sub>/TaN multilayers vs. (<b>a</b>) <span class="html-italic">Λ</span>; (<b>b</b>) <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub>.</p> Full article ">Figure 4
<p>Residual stresses of ReB<sub>2</sub>/TaN multilayers vs. <span class="html-italic">Λ</span>, <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub>.</p> Full article ">Figure 5
<p>Surface profiles of the scratch scan, post scan, and scratch tracks on ReB<sub>2</sub>/TaN multilayers at different <span class="html-italic">t</span><sub>ZrB2</sub>:<span class="html-italic">t</span><sub>AlN</sub> and <span class="html-italic">Λ</span>, (<b>a</b>) 1:1, 10 nm; (<b>b</b>) 1:4, 10 nm; (<b>c</b>) 2:1, 10 nm; and (<b>d</b>) 1:1, 28 nm.</p> Full article ">Figure 6
<p>(<b>a</b>) Comparison of load <span class="html-italic">vs</span> displacement data of ReB<sub>2</sub>/TaN multilayer (<span class="html-italic">Λ</span>~10 nm) with monolithic ReB<sub>2</sub> and TaN coatings; (<b>b</b>) Comparison of load vs. displacement data for ReB<sub>2</sub>/TaN multilayer (<span class="html-italic">Λ</span>~10 nm) with monolithic ReB<sub>2</sub> and TaN coatings at shallow indentation depths; and, (<b>c</b>) Comparison of load vs. displacement data of ReB<sub>2</sub>/TaN multilayers at different <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub> and <span class="html-italic">Λ</span>.</p> Full article ">Figure 7
<p>Supercell of BB-Ta interface (<b>a1</b>), crystal structures of TaN (<b>a2</b>) and ReB<sub>2</sub> (<b>a4</b>) and the interface bands (<b>a3</b>); Structures of BB-Ta-top configuration (<b>b1</b>), BB-Ta-bridge configuration (<b>b2</b>) and BB-Ta-hcp configuration (<b>b3</b>), respectively; Unit cell structures of 15ReB<sub>2</sub>/15TaN interface (<b>c1</b>), and 9ReB<sub>2</sub>/21TaN interface.(<b>c2</b>).</p> Full article ">Figure 8
<p>Adsorption energy (<span class="html-italic">E<sub>ad</sub></span>) and interfacial energy of ReB<sub>2</sub>/TaN multilayers at different <span class="html-italic">t</span><sub>ReB2</sub>:<span class="html-italic">t</span><sub>TaN</sub> based on five B-Ta interfacial models.</p> Full article ">Figure 9
<p>Charge density of 9ReB<sub>2</sub>/21TaN interface (<b>a</b>) and charge density difference of 9ReB<sub>2</sub>/21TaN interface (<b>b</b>), respectively, based on five B-Ta interfacial models.</p> Full article ">Figure 10
<p>Density of states (DOS) of 9ReB<sub>2</sub>/21TaN interface (<b>a</b>) and interface atoms of 9ReB<sub>2</sub>/21TaN interface (<b>b</b>), respectively, based on five B-Ta interfacial models.</p> Full article ">
13 pages, 12952 KiB  
Article
Piezoelectric Response of Aligned Electrospun Polyvinylidene Fluoride/Carbon Nanotube Nanofibrous Membranes
by Chang-Mou Wu, Min-Hui Chou and Wun-Yuan Zeng
Nanomaterials 2018, 8(6), 420; https://doi.org/10.3390/nano8060420 - 10 Jun 2018
Cited by 123 | Viewed by 7518
Abstract
Polyvinylidene fluoride (PVDF) shows piezoelectricity related to its β-phase content and mechanical and electrical properties influenced by its morphology and crystallinity. Electrospinning (ES) can produce ultrafine and well-aligned PVDF nanofibers. In this study, the effects of the presence of carbon nanotubes (CNT) and [...] Read more.
Polyvinylidene fluoride (PVDF) shows piezoelectricity related to its β-phase content and mechanical and electrical properties influenced by its morphology and crystallinity. Electrospinning (ES) can produce ultrafine and well-aligned PVDF nanofibers. In this study, the effects of the presence of carbon nanotubes (CNT) and optimized ES parameters on the crystal structures and piezoelectric properties of aligned PVDF/CNT nanofibrous membranes were examined. The optimal β content and piezoelectric coefficient (d33) of the aligned electrospun PVDF reached 88% and 27.4 pC/N; CNT addition increased the β-phase content to 89% and d33 to 31.3 pC/N. The output voltages of piezoelectric units with aligned electrospun PVDF/CNT membranes increased linearly with applied loading and showed good stability during cyclic dynamic compression and tension. The sensitivities of the piezoelectric units with the membranes under dynamic compression and tension were 2.26 mV/N and 4.29 mV/%, respectively. In bending tests, the output voltage increased nonlinearly with bending angle because complicated forces were involved. The output of the aligned membrane-based piezoelectric unit with CNT was 1.89 V at the bending angle of 100°. The high electric outputs indicate that the aligned electrospun PVDF/CNT membranes are potentially effective for flexible wearable sensor application with high sensitivity. Full article
(This article belongs to the Special Issue Smart Nanogenerators)
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Full article ">Figure 1
<p>SEM images of: (<b>a</b>) randomly oriented electrospun PVDF; (<b>b</b>) aligned electrospun PVDF; and (<b>c</b>) aligned electrospun PVDF/CNT. (<b>d</b>) TEM image of aligned electrospun PVDF/CNT nanofiber.</p> Full article ">Figure 2
<p>FTIR spectra for the PVDF samples.</p> Full article ">Figure 3
<p>Tensile load-displacement curves of PVDF samples.</p> Full article ">Figure 4
<p>Piezoelectric output voltage waves of the piezoelectric units with: (<b>a</b>) randomly oriented electrospun PVDF; (<b>b</b>) aligned electrospun PVDF; and (<b>c</b>) aligned electrospun PVDF/CNT under compressive forces from 200 N to 350 N.</p> Full article ">Figure 5
<p>Applied compressive force vs. output voltage of the piezoelectric PVDF units.</p> Full article ">Figure 6
<p>Piezoelectric output voltage waves of the piezoelectric units with: (<b>a</b>) randomly oriented electrospun PVDF; (<b>b</b>) aligned electrospun PVDF; and (<b>c</b>) aligned electrospun PVDF/CNT under tensile strains from 4% to 10%.</p> Full article ">Figure 7
<p>Applied tensile strain vs. output voltage of the piezoelectric PVDF units.</p> Full article ">Figure 8
<p>Bending angle vs. output voltage of the piezoelectric PVDF units.</p> Full article ">Figure 9
<p>(<b>a</b>) Output voltage waves of the piezoelectric units with aligned electrospun PVDF/CNT under 100° bending in series connection. (<b>b</b>) Output current waves of the piezoelectric units with aligned electrospun PVDF/CNT under 100° bending in parallel connection.</p> Full article ">
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