Nanomaterials

12 pages, 3616 KiB

Open AccessFeature PaperArticle

Robust Topographical Micro-Patterning of Nanofibrillar Collagen Gel by In Situ Photochemical Crosslinking-Assisted Collagen Embossing

by Hyeonjun Hong and Dong Sung Kim

Nanomaterials 2020, 10(12), 2574; https://doi.org/10.3390/nano10122574 - 21 Dec 2020

Cited by 5 | Viewed by 2990

Abstract

The topographical micro-patterning of nanofibrillar collagen gels is promising for the fabrication of biofunctional constructs mimicking topographical cell microenvironments of in vivo extracellular matrices. Nevertheless, obtaining structurally robust collagen micro-patterns through this technique is still a challenging issue. Here, we report a novel [...] Read more.

The topographical micro-patterning of nanofibrillar collagen gels is promising for the fabrication of biofunctional constructs mimicking topographical cell microenvironments of in vivo extracellular matrices. Nevertheless, obtaining structurally robust collagen micro-patterns through this technique is still a challenging issue. Here, we report a novel in situ photochemical crosslinking-assisted collagen embossing (IPC-CE) process as an integrative fabrication technique based on collagen compression-based embossing and UV–riboflavin crosslinking. The IPC-CE process using a micro-patterned polydimethylsiloxane (PDMS) master mold enables the compaction of collagen nanofibrils into micro-cavities of the mold and the simultaneous occurrence of riboflavin-mediated photochemical reactions among the nanofibrils, resulting in a robust micro-patterned collagen construct. The micro-patterned collagen construct fabricated through the IPC-CE showed a remarkable mechanical resistivity against rehydration and manual handling, which could not be achieved through the conventional collagen compression-based embossing alone. Micro-patterns of various sizes (minimum feature size <10 μm) and shapes could be obtained by controlling the compressive pressure (115 kPa) and the UV dose (3.00 J/cm²) applied during the process. NIH 3T3 cell culture on the micro-patterned collagen construct finally demonstrated its practical applicability in biological applications, showing a notable effect of anisotropic topography on cells in comparison with the conventional construct. Full article

(This article belongs to the Special Issue Development of Functional Polymer Surfaces with Nanomaterials)

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Fabrication of the in situ photochemical crosslinking-assisted collagen embossing (IPC-CE) construct. (a) Schematic illustration of the IPC-CE process. (b) Photographs of (i) the IPC-CE construct and (ii) its magnified surface. (iii) Manual handling of the IPC-CE construct. (iv) The conventional construct and (v) its magnified surface. (vi) Structural weakness of conventional construct for manual handling. White arrows in inset indicated damages induced by manual handling. Full article ">Figure 2
Effects of processing parameters on micro-ridge patterns. Microscopic images of the IPC-CE constructs for (a) different compressive pressures at the same UV dose of 3.00 J/cm2 and (b) different UV doses at same compressive pressure of 115 kPa in (i) rehydrated and (ii) dried state. All scale bars are 200 μm. (c) Quantitative measurement of micro-ridge pattern width for rehydrated and dried IPC-CE construct according to (i) compressive pressure and (ii) UV-dose. Full article ">Figure 3
Microstructures of the IPC-CE constructs. SEM images of micro-ridge patterns with different widths of (a) 100, (b) 80, (c) 60, and (d) 20 μm at (i) low and (ii) high magnifications. White and black scale bars are 100 and 2 μm, respectively. Full article ">Figure 4
Robustness and topographical effect of the IPC-CE construct. (a) Microscopic observation of conventional (2 and 115 kPa without UV dose) and IPC-CE construct, right after fabrication and after immersion in PBS solution. Green and yellow arrows indicate defects by partial replication and wrinkled structure, respectively. (b) NIH 3T3 cells cultured on each construct on day 2 (DAPI, blue; phalloidin, red). (c) Aspect ratio and orientation of NIH 3T3 cells. Blue arrow indicates direction of micro-ridge patterns. All scale bars are 100 μm. Full article ">

17 pages, 2667 KiB

Open AccessArticle

Ipriflavone-Loaded Mesoporous Nanospheres with Potential Applications for Periodontal Treatment

by Laura Casarrubios, Natividad Gómez-Cerezo, María José Feito, María Vallet-Regí, Daniel Arcos and María Teresa Portolés

Nanomaterials 2020, 10(12), 2573; https://doi.org/10.3390/nano10122573 - 21 Dec 2020

Cited by 27 | Viewed by 3009

Abstract

The incorporation and effects of hollow mesoporous nanospheres in the system SiO₂–CaO (nanoMBGs) containing ipriflavone (IP), a synthetic isoflavone that prevents osteoporosis, were evaluated. Due to their superior porosity and capability to host drugs, these nanoparticles are designed as a potential [...] Read more.

The incorporation and effects of hollow mesoporous nanospheres in the system SiO₂–CaO (nanoMBGs) containing ipriflavone (IP), a synthetic isoflavone that prevents osteoporosis, were evaluated. Due to their superior porosity and capability to host drugs, these nanoparticles are designed as a potential alternative to conventional bioactive glasses for the treatment of periodontal defects. To identify the endocytic mechanisms by which these nanospheres are incorporated within the MC3T3-E1 cells, five inhibitors (cytochalasin B, cytochalasin D, chlorpromazine, genistein and wortmannin) were used before the addition of these nanoparticles labeled with fluorescein isothiocyanate (FITC–nanoMBGs). The results indicate that nanoMBGs enter the pre-osteoblasts mainly through clathrin-dependent mechanisms and in a lower proportion by macropinocytosis. The present study evidences the active incorporation of nanoMBG–IPs by MC3T3-E1 osteoprogenitor cells that stimulate their differentiation into mature osteoblast phenotype with increased alkaline phosphatase activity. The final aim of this study is to demonstrate the biocompatibility and osteogenic behavior of IP-loaded bioactive nanoparticles to be used for periodontal augmentation purposes and to shed light on internalization mechanisms that determine the incorporation of these nanoparticles into the cells. Full article

(This article belongs to the Special Issue Nano-Engineering Solutions for Dental Implant Applications)

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Characterization of mesoporous nanospheres. (a) scanning electron micrograph of hollow mesoporous nanospheres in the system SiO2–CaO (nanoMBG) spheres. (b) Transmission electron image of nanoMBG spheres. (c) Nitrogen adsorption/desorption isotherm of nanoMBG spheres. (d) FTIR spectra of nanoMBG and IP-loaded nanospheres (nanoMBG–IP) spheres (* indicates the absorption bands corresponding to ipriflavone). Full article ">Figure 2
Effects of nanoMBGs and nanoMBG–IPs on cell cycle phases of MC3T3-E1 pre-osteoblasts and apoptosis percentage (Sub G1 fraction) after 24 h of treatment with 50 μg/mL of nanospheres. Control conditions without nanospheres were performed at the same time. Statistical significance: *** p < 0.005. Full article ">Figure 3
Effects of 50 μg/mL of nanoMBG and nanoMBG–IP nanospheres on viability, intracellular content of reactive oxygen species (ROS) and cytosolic calcium of MC3T3-E1 pre-osteoblasts, after 24 h of incubation. Control conditions without nanospheres were performed at the same time. Fluorescence profiles of control cells, cells with Fluo4 and cells with Fluo4 plus A23187 ionophore are shown in the lower-left figure. Statistical significance: *** p < 0.005. Full article ">Figure 4
Effects of several doses of nanoMBGs and nanoMBG–IPs on MC3T3-E1 pre-osteoblast differentiation after 11 days, evaluated through the measurement of alkaline phosphatase (ALP) activity. Control conditions without nanospheres were performed at the same time. Statistical significance: *** p < 0.005, * p < 0.05. Full article ">Figure 5
Effects of nanoMBGs and nanoMBG–IPs on interleukin 6 (IL-6) production by cultured MC3T3-E1 pre-osteoblasts after treatment with 50 μg/mL of nanospheres for 24 h. Control conditions without nanospheres were performed at the same time. Full article ">Figure 6
Intracellular uptake of nanoMBG nanospheres labeled with FITC by MC3T3-E1 pre-osteoblasts. (A) flow cytometric analysis of fluorescence intensity of cells with intracellular FITC–nanoMBG nanospheres after incubation with 10 (●), 30 (○) and 50 µg/mL (▼) for different times (15, 30 and 60 min). Statistical significance: *** p < 0.005. (B) Confocal microscopy images of MC3T3-E1 pre-osteoblasts after 24 h of incubation with 50 μg/mL of nanoMBG nanospheres labeled with fluorescein isothiocyanate (FITC). Nuclei were stained with DAPI (blue), F-actin filaments were stained with rhodamine-phalloidin (red), and FITC–nanoMBGs are observed in green. Full article ">Figure 7
Inhibitory effects of several endocytosis inhibitors on FITC–nanoMBG uptake by MC3T3-E1 pre-osteoblasts. Cells were incubated with each inhibitor for 2 h, the medium was then removed, and the cultures were treated with 50 µg/mL FITC–nanoMBGs for 2 h. Statistical significance: * p < 0.05, *** p < 0.005. Full article ">

10 pages, 2208 KiB

Open AccessArticle

Photocatalytic Overall Water Splitting by SrTiO₃ with Surface Oxygen Vacancies

by Yanfei Fan, Yan Liu, Hongyu Cui, Wen Wang, Qiaoyan Shang, Xifeng Shi, Guanwei Cui and Bo Tang

Nanomaterials 2020, 10(12), 2572; https://doi.org/10.3390/nano10122572 - 21 Dec 2020

Cited by 38 | Viewed by 4782

Abstract

Strontium Titanate has a typical perovskite structure with advantages of low cost and photochemical stability. However, the wide bandgap and rapid recombination of electrons and holes limited its application in photocatalysis. In this work, a SrTiO₃ material with surface oxygen vacancies was [...] Read more.

Strontium Titanate has a typical perovskite structure with advantages of low cost and photochemical stability. However, the wide bandgap and rapid recombination of electrons and holes limited its application in photocatalysis. In this work, a SrTiO₃ material with surface oxygen vacancies was synthesized via carbon reduction under a high temperature. It was successfully applied for photocatalytic overall water splitting to produce clean hydrogen energy under visible light irradiation without any sacrificial reagent for the first time. The photocatalytic overall water splitting ability of the as-prepared SrTiO₃-C950 is attributed to the surface oxygen vacancies that can make suitable energy levels for visible light response, improving the separation and transfer efficiency of photogenerated carriers. Full article

(This article belongs to the Section Energy and Catalysis)

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Morphology and Structure characterizations of SrTiO3. (a), Scanning Electron Microscope (SEM) image of SrTiO3; (b), SEM of SrTiO3-C950; (c), XRD of SrTiO3 and SrTiO3-C950. Full article ">Figure 2
Transmission Electron Microscope (TEM) image (a), High Resolution Transmission Electron Microscope (HRTEM) image (b) and Electron Paramagnetic Resonance (EPR) image (c) of SrTiO3-C950. Full article ">Figure 3
XPS spectra of Sr3d (a), O1s (b), Ti2p (c) and C1s (d) of SrTiO3 and SrTiO3-C950. Full article ">Figure 4
Photocatalytic activity of SrTiO3-C950 under full-spectrum light irradiation (a) or visible light irradiation (b) without sacrificial reagent. No photocatalytic water splitting activity was observed for pristine SrTiO3 and SrTiO3-C300 under the same conditions. Full article ">Figure 5
Ultraviolet–visible diffuse reflectance spectrum (UV-Vis DRS) (a), XPS Valence Band Spectrum and Energy band structure of SrTiO3 (left) and SrTiO3-C950 (right) (b), Electrochemical impedance spectroscopy (c) and Photocurrent density (d) of SrTiO3-C950 and SrTiO3. Full article ">

26 pages, 4899 KiB

Open AccessReview

A Guided Walk through the World of Mesoporous Bioactive Glasses (MBGs): Fundamentals, Processing, and Applications

by Carla Migneco, Elisa Fiume, Enrica Verné and Francesco Baino

Nanomaterials 2020, 10(12), 2571; https://doi.org/10.3390/nano10122571 - 21 Dec 2020

Cited by 55 | Viewed by 5241

Abstract

Bioactive glasses (BGs) are traditionally known to be able to bond to living bone and stimulate bone regeneration. The production of such materials in a mesoporous form allowed scientists to dramatically expand the versatility of oxide-based glass systems as well as their applications [...] Read more.

Bioactive glasses (BGs) are traditionally known to be able to bond to living bone and stimulate bone regeneration. The production of such materials in a mesoporous form allowed scientists to dramatically expand the versatility of oxide-based glass systems as well as their applications in biomedicine. These nanostructured materials, called mesoporous bioactive glasses (MBGs), not only exhibit an ultrafast mineralization rate but can be used as vehicles for the sustained delivery of drugs, which are hosted inside the mesopores, and therapeutic ions, which are released during material dissolution in contact with biological fluids. This review paper summarizes the main strategies for the preparation of MBGs, as well as their properties and applications in the biomedical field, with an emphasis on the methodological aspects and the promise of hierarchical systems with multiscale porosity. Full article

(This article belongs to the Special Issue Preparation and Application of Nanostructured Glass–Ceramics and Nanocomposites)

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14 pages, 2591 KiB

Open AccessArticle

Temperature-Dependent Photoluminescent Properties of PbSe Nanoplatelets

by Ivan Skurlov, Anastasiia Sokolova, Tom Galle, Sergei Cherevkov, Elena Ushakova, Alexander Baranov, Vladimir Lesnyak, Anatoly Fedorov and Aleksandr Litvin

Nanomaterials 2020, 10(12), 2570; https://doi.org/10.3390/nano10122570 - 21 Dec 2020

Cited by 14 | Viewed by 4672

Abstract

Semiconductor colloidal nanoplatelets (NPLs) are a promising new class of nanostructures that can bring much impact on lightning technologies, light-emitting diodes (LED), and laser fabrication. Indeed, great progress has been made in optimizing the optical properties of the NPLs for the visible spectral [...] Read more.

Semiconductor colloidal nanoplatelets (NPLs) are a promising new class of nanostructures that can bring much impact on lightning technologies, light-emitting diodes (LED), and laser fabrication. Indeed, great progress has been made in optimizing the optical properties of the NPLs for the visible spectral range, which has already made the implementation of a number of effective devices on their basis possible. To date, state-of-the-art near-infrared (NIR)-emitting NPLs are significantly inferior to their visible-range counterparts, although it would be fair to say that they received significantly less research attention so far. In this study, we report a comprehensive analysis of steady-state and time-dependent photoluminescence (PL) properties of four monolayered (ML) PbSe NPLs. The PL measurements are performed in a temperature range of 78–300 K, and their results are compared to those obtained for CdSe NPLs and PbSe quantum dots (QDs). We show that multiple emissive states, both band-edge and trap-related, are responsible for the formation of the NPLs’ PL band. We demonstrate that the widening of the PL band is caused by the inhomogeneous broadening rather than homogeneous one, and analyze the possible contributions to PL broadening. Full article

(This article belongs to the Special Issue Electronic and Optical Properties of Nanostructures)

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24 pages, 3778 KiB

Open AccessReview

Recent Developments in Lead and Lead-Free Halide Perovskite Nanostructures towards Photocatalytic CO₂ Reduction

by Chaitanya B. Hiragond, Niket S. Powar and Su-Il In

Nanomaterials 2020, 10(12), 2569; https://doi.org/10.3390/nano10122569 - 21 Dec 2020

Cited by 47 | Viewed by 6436

Abstract

Perovskite materials have been widely considered as emerging photocatalysts for CO₂ reduction due to their extraordinary physicochemical and optical properties. Perovskites offer a wide range of benefits compared to conventional semiconductors, including tunable bandgap, high surface energy, high charge carrier lifetime, and [...] Read more.

Perovskite materials have been widely considered as emerging photocatalysts for CO₂ reduction due to their extraordinary physicochemical and optical properties. Perovskites offer a wide range of benefits compared to conventional semiconductors, including tunable bandgap, high surface energy, high charge carrier lifetime, and flexible crystal structure, making them ideal for high-performance photocatalytic CO₂ reduction. Notably, defect-induced perovskites, for example, crystallographic defects in perovskites, have given excellent opportunities to tune perovskites’ catalytic properties. Recently, lead (Pb) halide perovskite and their composites or heterojunction with other semiconductors, metal nanoparticles (NPs), metal complexes, graphene, and metal-organic frameworks (MOFs) have been well established for CO₂ conversion. Besides, various halide perovskites have come under focus to avoid the toxicity of lead-based materials. Therefore, we reviewed the recent progress made by Pb and Pb-free halide perovskites in photo-assisted CO₂ reduction into useful chemicals. We also discussed the importance of various factors like change in solvent, structure defects, and compositions in the fabrication of halide perovskites to efficiently convert CO₂ into value-added products. Full article

(This article belongs to the Special Issue Nanomaterials toward CO₂ Reduction and Conversion)

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10 pages, 6287 KiB

Open AccessArticle

Van der Waals Integrated Silicon/Graphene/AlGaN Based Vertical Heterostructured Hot Electron Light Emitting Diodes

by Nallappagari Krishnamurthy Manjunath, Chang Liu, Yanghua Lu, Xutao Yu and Shisheng Lin

Nanomaterials 2020, 10(12), 2568; https://doi.org/10.3390/nano10122568 - 21 Dec 2020

Cited by 1 | Viewed by 2656

Abstract

Silicon-based light emitting diodes (LED) are indispensable elements for the rapidly growing field of silicon compatible photonic integration platforms. In the present study, graphene has been utilized as an interfacial layer to realize a unique illumination mechanism for the silicon-based LEDs. We designed [...] Read more.

Silicon-based light emitting diodes (LED) are indispensable elements for the rapidly growing field of silicon compatible photonic integration platforms. In the present study, graphene has been utilized as an interfacial layer to realize a unique illumination mechanism for the silicon-based LEDs. We designed a Si/thick dielectric layer/graphene/AlGaN heterostructured LED via the van der Waals integration method. In forward bias, the Si/thick dielectric (HfO₂-50 nm or SiO₂-90 nm) heterostructure accumulates numerous hot electrons at the interface. At sufficient operational voltages, the hot electrons from the interface of the Si/dielectric can cross the thick dielectric barrier via the electron-impact ionization mechanism, which results in the emission of more electrons that can be injected into graphene. The injected hot electrons in graphene can ignite the multiplication exciton effect, and the created electrons can transfer into p-type AlGaN and recombine with holes resulting a broadband yellow-color electroluminescence (EL) with a center peak at 580 nm. In comparison, the n-Si/thick dielectric/p-AlGaN LED without graphene result in a negligible blue color EL at 430 nm in forward bias. This work demonstrates the key role of graphene as a hot electron active layer that enables the intense EL from silicon-based compound semiconductor LEDs. Such a simple LED structure may find applications in silicon compatible electronics and optoelectronics. Full article

(This article belongs to the Special Issue State-of-the-Art Optoelectronic and Electronic Nanodevices in China)

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(a) Cross-sectional high-resolution Transmission Electron Microscope (HR-TEM) image of the interface of n-Si/HfO2 heterostructure. (a1) Transmission Electron Microscope (TEM) image of cross-sectional view of the interface of n-Si/HfO2 with 100 nm scale. (a2) and (a3) TEM magnified view of the interface of n-Si/HfO2, from which a thickness of 54.5 nm for the HfO2 layer, SiO2 interface layer, and a hetero-layered stacking of Si and HfO2 can be read out respectively. (b) STEM-EDX elemental mapping of (b1) Si, (b2) Hf, (b3) Pt, and (b4) O in the hetero-layered structure of n-Si/HfO2. Full article ">Figure 2
(a) Pictorial view of the graphene free n-Si/HfO2/p-AlGaN LED. (b) Current-Voltage (I–V) characteristic curve of the LED. (c) Electroluminescence (EL) of the LED at forward bias applied voltages. Full article ">Figure 3
(a) Structure of n-Si/HfO2/DLG/p-AlGaN LED. (b) Current-Voltage (I–V) characteristics of the LED. (c) Electroluminescence (EL) of the LED at applied forward bias voltages. Defects based broadband yellow color with peak center at 580 nm. Full article ">Figure 4
(a) Energy band profile of n-Si/HfO2/DLG/p-AlGaN vertical semiconductor heterostructure under zero bias condition. (b) The illumination mechanism of the LED at forward bias voltages. (c) Pictorial view of the electronic band profile of graphene in the LED at zero bias. (d) Pictorial view of the band profile of graphene in the LED at forward bias. Electric field induced hot electron accumulation at the graphene led to the n-type doped graphene and rise in Fermi level of the graphene. Full article ">Figure 5
(a) Schematic representation of the structure of graphene free n-Si/SiO2/p-AlGaN LED. (b) Current-Voltage (I–V) curve of the graphene free LED. (c) Electroluminescence (EL) of the graphene free LED at forward bias applied voltages. (d) Pictorial view of the graphene based Si/SiO2/DLG/AlGaN LED. (e) I–V curve of the graphene based LED. (f) EL from the graphene based LED in forward bias. The illumination from the graphene based LED was a defect based broadband yellow color with a wavelength maxima (λmax) at 580 nm. Full article ">

20 pages, 3406 KiB

Open AccessReview

Biodegradable Poly(Lactic Acid) Nanocomposites for Fused Deposition Modeling 3D Printing

by Madison Bardot and Michael D. Schulz

Nanomaterials 2020, 10(12), 2567; https://doi.org/10.3390/nano10122567 - 21 Dec 2020

Cited by 71 | Viewed by 7905

Abstract

3D printing by fused deposition modelling (FDM) enables rapid prototyping and fabrication of parts with complex geometries. Unfortunately, most materials suitable for FDM 3D printing are non-degradable, petroleum-based polymers. The current ecological crisis caused by plastic waste has produced great interest in biodegradable [...] Read more.

3D printing by fused deposition modelling (FDM) enables rapid prototyping and fabrication of parts with complex geometries. Unfortunately, most materials suitable for FDM 3D printing are non-degradable, petroleum-based polymers. The current ecological crisis caused by plastic waste has produced great interest in biodegradable materials for many applications, including 3D printing. Poly(lactic acid) (PLA), in particular, has been extensively investigated for FDM applications. However, most biodegradable polymers, including PLA, have insufficient mechanical properties for many applications. One approach to overcoming this challenge is to introduce additives that enhance the mechanical properties of PLA while maintaining FDM 3D printability. This review focuses on PLA-based nanocomposites with cellulose, metal-based nanoparticles, continuous fibers, carbon-based nanoparticles, or other additives. These additives impact both the physical properties and printability of the resulting nanocomposites. We also detail the optimal conditions for using these materials in FDM 3D printing. These approaches demonstrate the promise of developing nanocomposites that are both biodegradable and mechanically robust. Full article

(This article belongs to the Special Issue Functional Biodegradable Nanocomposites)

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18 pages, 29842 KiB

Open AccessArticle

Graphene Quantum Dot-TiO₂ Photonic Crystal Films for Photocatalytic Applications

by Maria-Athina Apostolaki, Alexia Toumazatou, Maria Antoniadou, Elias Sakellis, Evangelia Xenogiannopoulou, Spiros Gardelis, Nikos Boukos, Polycarpos Falaras, Athanasios Dimoulas and Vlassis Likodimos

Nanomaterials 2020, 10(12), 2566; https://doi.org/10.3390/nano10122566 - 21 Dec 2020

Cited by 16 | Viewed by 3935

Abstract

Photonic crystal structuring has emerged as an advanced method to enhance solar light harvesting by metal oxide photocatalysts along with rational compositional modifications of the materials’ properties. In this work, surface functionalization of TiO₂ photonic crystals by blue luminescent graphene quantum dots [...] Read more.

Photonic crystal structuring has emerged as an advanced method to enhance solar light harvesting by metal oxide photocatalysts along with rational compositional modifications of the materials’ properties. In this work, surface functionalization of TiO₂ photonic crystals by blue luminescent graphene quantum dots (GQDs), n–π* band at ca. 350 nm, is demonstrated as a facile, environmental benign method to promote photocatalytic activity by the combination of slow photon-assisted light trapping with GQD-TiO₂ interfacial electron transfer. TiO₂ inverse opal films fabricated by the co-assembly of polymer colloidal spheres with a hydrolyzed titania precursor were post-modified by impregnation in aqueous GQDs suspension without any structural distortion. Photonic band gap engineering by varying the inverse opal macropore size resulted in selective performance enhancement for both salicylic acid photocatalytic degradation and photocurrent generation under UV–VIS and visible light, when red-edge slow photons overlapped with the composite’s absorption edge, whereas stop band reflection was attenuated by the strong UVA absorbance of the GQD-TiO₂ photonic films. Photoelectrochemical and photoluminescence measurements indicated that the observed improvement, which surpassed similarly modified benchmark mesoporous P25 TiO₂ films, was further assisted by GQDs electron acceptor action and visible light activation to a lesser extent, leading to highly efficient photocatalytic films. Full article

(This article belongs to the Section 2D and Carbon Nanomaterials)

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17 pages, 8008 KiB

Open AccessArticle

Photoinduced Enhancement of Photoluminescence of Colloidal II-VI Nanocrystals in Polymer Matrices

by Volodymyr Dzhagan, Oleksandr Stroyuk, Oleksandra Raievska, Oksana Isaieva, Olga Kapush, Oleksandr Selyshchev, Volodymyr Yukhymchuk, Mykhailo Valakh and Dietrich R. T. Zahn

Nanomaterials 2020, 10(12), 2565; https://doi.org/10.3390/nano10122565 - 21 Dec 2020

Cited by 7 | Viewed by 3059

Abstract

The environment strongly affects both the fundamental physical properties of semiconductor nanocrystals (NCs) and their functionality. Embedding NCs in polymer matrices is an efficient way to create a desirable NC environment needed for tailoring the NC properties and protecting NCs from adverse environmental [...] Read more.

The environment strongly affects both the fundamental physical properties of semiconductor nanocrystals (NCs) and their functionality. Embedding NCs in polymer matrices is an efficient way to create a desirable NC environment needed for tailoring the NC properties and protecting NCs from adverse environmental factors. Luminescent NCs in optically transparent polymers have been investigated due to their perspective applications in photonics and bio-imaging. Here, we report on the manifestations of photo-induced enhancement of photoluminescence (PL) of aqueous colloidal NCs embedded in water-soluble polymers. Based on the comparison of results obtained on bare and core/shell NCs, NCs of different compounds (CdSe, CdTe, ZnO) as well as different embedding polymers, we conclude on the most probable mechanism of the photoenhancement for these sorts of systems. Contrary to photoenhancement observed earlier as a result of surface photocorrosion, we do not observe any change in peak position and width of the excitonic PL. Therefore, we suggest that the saturation of trap states by accumulated photo-excited charges plays a key role in the observed enhancement of the radiative recombination. This suggestion is supported by the unique temperature dependence of the trap PL band as well as by power-dependent PL measurement. Full article

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

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12 pages, 875 KiB

Open AccessArticle

Strategies to Improve the Properties of Amaranth Protein Isolate-Based Thin Films for Food Packaging Applications: Nano-Layering through Spin-Coating and Incorporation of Cellulose Nanocrystals

by Amparo López-Rubio, Adriana Blanco-Padilla, Kristiina Oksman and Sandra Mendoza

Nanomaterials 2020, 10(12), 2564; https://doi.org/10.3390/nano10122564 - 21 Dec 2020

Cited by 18 | Viewed by 3431

Abstract

In this work, two different strategies for the development of amaranth protein isolate (API)-based films were evaluated. In the first strategy, ultrathin films were produced through spin-coating nanolayering, and the effects of protein concentration in the spin coating solution, rotational speed, and number [...] Read more.

In this work, two different strategies for the development of amaranth protein isolate (API)-based films were evaluated. In the first strategy, ultrathin films were produced through spin-coating nanolayering, and the effects of protein concentration in the spin coating solution, rotational speed, and number of layers deposited on the properties of the films were evaluated. In the second strategy, cellulose nanocrystals (CNCs) were incorporated through a casting methodology. The morphology, optical properties, and moisture affinity of the films (water contact angle, solubility, water content) were characterized. Both strategies resulted in homogeneous films with good optical properties, decreased hydrophilic character (as deduced from the contact angle measurements and solubility), and improved mechanical properties when compared with the neat API-films. However, both the processing method and film thickness influenced the final properties of the films, being the ones processed through spin coating more transparent, less hydrophilic, and less water-soluble. Incorporation of CNCs above 10% increased hydrophobicity, decreasing the water solubility of the API films and significantly enhancing material toughness. Full article

(This article belongs to the Special Issue Nanocomposites for Food Packaging)

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11 pages, 599 KiB

Open AccessArticle

Plasmon-Enhanced Fluorescence of EGFP on Short-Range Ordered Ag Nanohole Arrays

by Vladimir E. Bochenkov, Ekaterina M. Lobanova, Aleksander M. Shakhov, Artyom A. Astafiev, Alexey M. Bogdanov, Vadim A. Timoshenko and Anastasia V. Bochenkova

Nanomaterials 2020, 10(12), 2563; https://doi.org/10.3390/nano10122563 - 20 Dec 2020

Cited by 2 | Viewed by 3602

Abstract

Fluorescence of organic molecules can be enhanced by plasmonic nanostructures through coupling to their locally amplified electromagnetic field, resulting in higher brightness and better photostability of fluorophores, which is particularly important for bioimaging applications involving fluorescent proteins as genetically encoded biomarkers. Here, we [...] Read more.

Fluorescence of organic molecules can be enhanced by plasmonic nanostructures through coupling to their locally amplified electromagnetic field, resulting in higher brightness and better photostability of fluorophores, which is particularly important for bioimaging applications involving fluorescent proteins as genetically encoded biomarkers. Here, we show that a hybrid bionanosystem comprised of a monolayer of Enhanced Green Fluorescent Protein (EGFP) covalently linked to optically thin Ag films with short-range ordered nanohole arrays can exhibit up to 6-fold increased brightness. The largest enhancement factor is observed for nanohole arrays with a propagating surface plasmon mode, tuned to overlap with both excitation and emission of EGFP. The fluorescence lifetime measurements in combination with FDTD simulations provide in-depth insight into the origin of the fluorescence enhancement, showing that the effect is due to the local amplification of the optical field near the edges of the nanoholes. Our results pave the way to improving the photophysical properties of hybrid bionanosystems based on fluorescent proteins at the interface with easily fabricated and tunable plasmonic nanostructures. Full article

(This article belongs to the Special Issue Photonic Nanomaterials)

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Simplified schematic of the experiment showing the short-range ordered (SRO) nanoholes in the optically thin silver film with immobilized Enhanced Green Fluorescent Protein (EGFP) and the illumination configuration. Full article ">Figure 2
EGFP fluorescence enhancement by the Ag nanohole arrays. (A) Normalized extinction spectra of various Ag nanohole arrays (NHAs) (colored lines) and normalized absorption (blue) and emission (green) of EGFP (filled area). (B) Relative emission intensity of EGFP immobilized on glass (black) and on AgNHAs (colored lines). The legend indicates the SPR peak positions. (C) Fluorescence enhancement factors. The same color code is used in all panels. Full article ">Figure 3
Fluorescence decay kinetics of EGFP immobilized on glass (red dots) and AgNHA (green dots) with the corresponding fits (red and green lines, respectively). Shown is also the instrument response function (blue line). Full article ">Figure 4
Simulation of the EGFP fluorescence enhancement near periodic 100 nm AgNHA. (A) Top and section views of the simulated periodic box; the blue and red dots indicate the positions of a dipole source during the scan (the same color code is used in panels B,C) Extinction (1-T) spectrum of Ag NHA (blue line). The excitation and oscillating dipole emission wavelengths are shown by the blue and green dashed lines, respectively. (C) Excited state lifetime. (D) Fluorescence enhancement factor. Full article ">

14 pages, 16363 KiB

Open AccessArticle

Impact of Inductively Coupled Plasma Etching Conditions on the Formation of Semi-Polar (\({11\overline{2}2}\)) and Non-Polar (\({11\overline{2}0}\)) GaN Nanorods

by Pierre-Marie Coulon, Peng Feng, Tao Wang and Philip A. Shields

Nanomaterials 2020, 10(12), 2562; https://doi.org/10.3390/nano10122562 - 20 Dec 2020

Cited by 3 | Viewed by 3860

Abstract

The formation of gallium nitride (GaN) semi-polar and non-polar nanostructures is of importance for improving light extraction/absorption of optoelectronic devices, creating optical resonant cavities or reducing the defect density. However, very limited studies of nanotexturing via dry etching have been performed, in comparison [...] Read more.

The formation of gallium nitride (GaN) semi-polar and non-polar nanostructures is of importance for improving light extraction/absorption of optoelectronic devices, creating optical resonant cavities or reducing the defect density. However, very limited studies of nanotexturing via dry etching have been performed, in comparison to wet etching. In this paper, we investigate the formation and morphology of semi-polar (

11 \bar{2} 2

) and non-polar (

11 \bar{2} 0

) GaN nanorods using inductively coupled plasma (ICP) etching. The impact of gas chemistry, pressure, temperature, radio-frequency (RF) and ICP power and time are explored. A dominant chemical component is found to have a significant impact on the morphology, being impacted by the polarity of the planes. In contrast, increasing the physical component enables the impact of crystal orientation to be minimized to achieve a circular nanorod profile with inclined sidewalls. These conditions were obtained for a small percentage of chlorine (Cl₂) within the Cl₂ + argon (Ar) plasma combined with a low pressure. Damage to the crystal was reduced by lowering the direct current (DC) bias through a reduction of the RF power and an increase of the ICP power. Full article

(This article belongs to the Special Issue Nano-Fabrication Technology and Applications)

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25 pages, 5147 KiB

Open AccessArticle

Biodegradable PLA/PBSA Multinanolayer Nanocomposites: Effect of Nanoclays Incorporation in Multinanolayered Structure on Mechanical and Water Barrier Properties

by Tiphaine Messin, Nadège Follain, Quentin Lozay, Alain Guinault, Nicolas Delpouve, Jérémie Soulestin, Cyrille Sollogoub and Stéphane Marais

Nanomaterials 2020, 10(12), 2561; https://doi.org/10.3390/nano10122561 - 20 Dec 2020

Cited by 8 | Viewed by 3493

Abstract

Biodegradable PLA/PBSA multinanolayer nanocomposites were obtained from semi-crystalline poly(butylene succinate-co-butylene adipate) (PBSA) nanolayers filled with nanoclays and confined against amorphous poly(lactic acid) (PLA) nanolayers in a continuous manner by applying an innovative coextrusion technology. The cloisite 30B (C30B) filler incorporation in [...] Read more.

Biodegradable PLA/PBSA multinanolayer nanocomposites were obtained from semi-crystalline poly(butylene succinate-co-butylene adipate) (PBSA) nanolayers filled with nanoclays and confined against amorphous poly(lactic acid) (PLA) nanolayers in a continuous manner by applying an innovative coextrusion technology. The cloisite 30B (C30B) filler incorporation in nanolayers was considered to be an improvement of barrier properties of the multilayer films additional to the confinement effect resulting to forced assembly during the multilayer coextrusion process. 2049-layer films of ~300 µm thick were processed containing loaded PBSA nanolayers of ~200 nm, which presented certain homogeneity and were mostly continuous for the 80/20 wt% PLA/PBSA composition. The nanocomposite PBSA films (monolayer) were also processed for comparison. The presence of exfoliated and intercalated clay structure and some aggregates were observed within the PBSA nanolayers depending on the C30B content. A greater reduction of macromolecular chain segment mobility was measured due to combined effects of confinement effect and clays constraints. The absence of both polymer and clays interdiffusions was highlighted since the PLA glass transition was unchanged. Besides, a larger increase in local chain rigidification was evidenced through RAF values due to geometrical constraints initiated by close nanoclay contact without changing the crystallinity of PBSA. Tortuosity effects into the filled PBSA layers adding to confinement effects induced by PLA layers have caused a significant improvement of water barrier properties through a reduction of water permeability, water vapor solubility and water vapor diffusivity. The obtaining barrier properties were successfully correlated to microstructure, thermal properties and mobility of PBSA amorphous phase. Full article

(This article belongs to the Special Issue Functional Biodegradable Nanocomposites)

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20 pages, 4763 KiB

Open AccessArticle

Thiolation of Chitosan Loaded over Super-Magnetic Halloysite Nanotubes for Enhanced Laccase Immobilization

by Avinash A. Kadam, Bharat Sharma, Surendra K. Shinde, Gajanan S. Ghodake, Ganesh D. Saratale, Rijuta G. Saratale, Do-Yeong Kim and Jung-Suk Sung

Nanomaterials 2020, 10(12), 2560; https://doi.org/10.3390/nano10122560 - 20 Dec 2020

Cited by 18 | Viewed by 3780

Abstract

This study focuses on the development of a nanosupport based on halloysite nanotubes (HNTs), Fe₃O₄ nanoparticles (NPs), and thiolated chitosan (CTs) for laccase immobilization. First, HNTs were modified with Fe₃O₄ NPs (HNTs-Fe₃O₄) by [...] Read more.

This study focuses on the development of a nanosupport based on halloysite nanotubes (HNTs), Fe₃O₄ nanoparticles (NPs), and thiolated chitosan (CTs) for laccase immobilization. First, HNTs were modified with Fe₃O₄ NPs (HNTs-Fe₃O₄) by the coprecipitation method. Then, the HNTs-Fe₃O₄ surface was tuned with the CTs (HNTs-Fe₃O₄-CTs) by a simple refluxing method. Finally, the HNTs- Fe₃O₄-CTs surface was thiolated (-SH) (denoted as; HNTs- Fe₃O₄-CTs-SH) by using the reactive NHS-ester reaction. The thiol-modified HNTs (HNTs- Fe₃O₄-CTs-SH) were characterized by FE-SEM, HR-TEM, XPS, XRD, FT-IR, and VSM analyses. The HNTs-Fe₃O₄-CTs-SH was applied for the laccase immobilization. It gave excellent immobilization of laccase with 100% activity recovery and 144 mg/g laccase loading capacity. The immobilized laccase on HNTs-Fe₃O₄-CTs-SH (HNTs-Fe₃O₄-CTs-S-S-Laccase) exhibited enhanced biocatalytic performance with improved thermal, storage, and pH stabilities. HNTs-Fe₃O₄-CTs-S-S-Laccase gave outstanding repeated cycle capability, at the end of the 15th cycle, it kept 61% of the laccase activity. Furthermore, HNTs-Fe₃O₄-CTs-S-S-Laccase was applied for redox-mediated removal of textile dye DR80 and pharmaceutical compound ampicillin. The obtained result marked the potential of the HNTs-Fe₃O₄-CTs-S-S-Laccase for the removal of hazardous pollutants. This nanosupport is based on clay mineral HNTs, made from low-cost biopolymer CTs, super-magnetic in nature, and can be applied in laccase-based decontamination of environmental pollutants. This study also gave excellent material HNTs-Fe₃O₄-CTs-SH for other enzyme immobilization processes. Full article

(This article belongs to the Special Issue Advanced Magnetic Nanocomposites: Structural, Physical Properties and Application)

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11 pages, 2245 KiB

Open AccessArticle

Combined Toxicity of TiO₂ Nanospherical Particles and TiO₂ Nanotubes to Two Microalgae with Different Morphology

by Zhuang Wang, Shiguang Jin, Fan Zhang and Degao Wang

Nanomaterials 2020, 10(12), 2559; https://doi.org/10.3390/nano10122559 - 20 Dec 2020

Cited by 11 | Viewed by 3129

Abstract

The joint activity of multiple engineered nanoparticles (ENPs) has attracted much attention in recent years. Many previous studies have focused on the combined toxicity of different ENPs with nanostructures of the same dimension. However, the mixture toxicity of multiple ENPs with different dimensions [...] Read more.

The joint activity of multiple engineered nanoparticles (ENPs) has attracted much attention in recent years. Many previous studies have focused on the combined toxicity of different ENPs with nanostructures of the same dimension. However, the mixture toxicity of multiple ENPs with different dimensions is much less understood. Herein, we investigated the toxicity of the binary mixture of TiO₂ nanospherical particles (NPs) and TiO₂ nanotubes (NTs) to two freshwater algae with different morphology, namely, Scenedesmus obliquus and Chlorella pyrenoidosa. The physicochemical properties, dispersion stability, and the generation of reactive oxygen species (ROS) were determined in the single and binary systems. Classical approaches to assessing mixture toxicity were applied to evaluate and predict the toxicity of the binary mixtures. The results show that the combined toxicity of TiO₂ NPs and NTs to S. obliquus was between the single toxicity of TiO₂ NTs and NPs, while the combined toxicity to C. pyrenoidosa was higher than their single toxicity. Moreover, the toxicity of the binary mixtures to C. pyrenoidosa was higher than that to S. obliquus. A toxic unit assessment showed that the effects of TiO₂ NPs and NTs were additive to the algae. The combined toxicity to S. obliquus and C. pyrenoidosa can be effectively predicted by the concentration addition model and the independent action model, respectively. The mechanism of the toxicity caused by the binary mixtures of TiO₂ NPs and NTs may be associated with the dispersion stability of the nanoparticles in aquatic media and the ROS-induced oxidative stress effects. Our results may offer a new insight into evaluating and predicting the combined toxicological effects of ENPs with different dimensions and of probing the mechanisms involved in their joint toxicity. Full article

(This article belongs to the Special Issue Advances in Nanotoxicology)

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Full article ">Figure 1
TEM images of the TiO2 NPs (A), TiO2 NTs (B), and TiO2 NPs + NTs (C) in the algae medium. Full article ">Figure 2
Total potential energy (VT) curves for the TiO2 particles in the single and binary systems at 0 h (A) and 96 h (B). Full article ">Figure 3
Concentration-response curves for Scenedesmus obliquus (A) and Chlorella pyrenoidosa (B) exposed to TiO2 NPs, TiO2 NTs, and TiO2 NPs + NTs. Full article ">Figure 4
Observed toxic units (TUs) as converted from the toxicity data of Scenedesmus obliquus and Chlorella pyrenoidosa following exposure to mixtures of TiO2 NPs and NTs, and subsequently plotted against expected TUs calculated on the basis of the median effect concentrations from the individual constituents present in the mixtures. Full article ">Figure 5
Comparison between regression models of the observed (OBS) combined nanotoxicity and expected toxicity of the mixtures to Scenedesmus obliquus (A) and Chlorella pyrenoidosa (B) according to concentration addition (CA) and independent action (IA). The dashed-line and dotted-line represent the 95% confidence band and 95% prediction band of the experimental data points, respectively. Full article ">Figure 6
Relative levels of reactive oxygen species (ROS) detected using 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) staining in Scenedesmus obliquus (A) and Chlorella pyrenoidosa (B) exposed to single TiO2 NPs and TiO2 NTs at each EC10 or EC50 value, as well as TiO2 NPs + NTs at the EC10 or EC50 ratios. Statistical significance versus control group: * p < 0.05, ** p < 0.01, and *** p < 0.001. Full article ">

13 pages, 3496 KiB

Open AccessArticle

Self-Assembled Few-Layered MoS₂ on SnO₂ Anode for Enhancing Lithium-Ion Storage

by Thang Phan Nguyen and Il Tae Kim

Nanomaterials 2020, 10(12), 2558; https://doi.org/10.3390/nano10122558 - 20 Dec 2020

Cited by 21 | Viewed by 3538

Abstract

SnO₂ nanoparticles (NPs) have been used as reversible high-capacity anode materials in lithium-ion batteries, with reversible capacities reaching 740 mAh·g⁻¹. However, large SnO₂ NPs do not perform well in charge–discharge cycling. In this work, we report the incorporation of [...] Read more.

SnO₂ nanoparticles (NPs) have been used as reversible high-capacity anode materials in lithium-ion batteries, with reversible capacities reaching 740 mAh·g⁻¹. However, large SnO₂ NPs do not perform well in charge–discharge cycling. In this work, we report the incorporation of MoS₂ nanosheet (NS) layers with SnO₂ NPs. SnO₂ NPs of ~5 nm in diameter synthesized by a facile hydrothermal precipitation method. Meanwhile, MoS₂ NSs of a few hundreds of nanometers to a few micrometers in lateral size were produced by top-down chemical exfoliation. The self-assembly of the MoS₂ NS layer on the gas–liquid interface was first demonstrated to achieve up to 80% coverage of the SnO₂ NP anode surface. The electrochemical properties of the pure SnO₂ NPs and MoS₂-covered SnO₂ NP anodes were investigated. The results showed that the SnO₂ electrode with a single-layer MoS₂ NS film exhibited better electrochemical performance than the pure SnO₂ anode in lithium storage applications. Full article

(This article belongs to the Special Issue Nanomaterials for Ion Battery Applications)

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10 pages, 3038 KiB

Open AccessArticle

Plasmonic Gold Nanohole Arrays for Surface-Enhanced Sum Frequency Generation Detection

by Wei Guo, Bowen Liu, Yuhan He, Enming You, Yongyan Zhang, Shengchao Huang, Jingjing Wang and Zhaohui Wang

Nanomaterials 2020, 10(12), 2557; https://doi.org/10.3390/nano10122557 - 19 Dec 2020

Cited by 8 | Viewed by 3904

Abstract

Nobel metal nanohole arrays have been used extensively in chemical and biological systems because of their fascinating optical properties. Gold nanohole arrays (Au NHAs) were prepared as surface plasmon polariton (SPP) generators for the surface-enhanced sum-frequency generation (SFG) detection of 4-Mercaptobenzonitrile (4-MBN). The [...] Read more.

Nobel metal nanohole arrays have been used extensively in chemical and biological systems because of their fascinating optical properties. Gold nanohole arrays (Au NHAs) were prepared as surface plasmon polariton (SPP) generators for the surface-enhanced sum-frequency generation (SFG) detection of 4-Mercaptobenzonitrile (4-MBN). The angle-resolved reflectance spectra revealed that the Au NHAs have three angle-dependent SPP modes and two non-dispersive localized surface plasmon resonance (LSPR) modes under different structural orientation angles (sample surface orientation). An enhancement factor of ~30 was achieved when the SPP and LSPR modes of the Au NHAs were tuned to match the incident visible (VIS) and output SFG, respectively. This multi-mode matching strategy provided flexible controls and selective spectral windows for surface-enhanced measurements, and was especially useful in nonlinear spectroscopy where more than one light beam was involved. The structural orientation- and power-dependent performance demonstrated the potential of plasmonic NHAs in SFG and other nonlinear sensing applications, and provided a promising surface molecular analysis development platform. Full article

(This article belongs to the Special Issue Plasmonic Nanostructures and Their Applications)

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Figure 1
Schematic illustration of the preparation processes of the gold nanohole arrays (Au NHAs). Full article ">Figure 2
(a) SEM and (b) AFM images of the Au NHAs. (c) Cross-sections profile along the blue line in the AFM image. Full article ">Figure 3
Angle-resolved reflection spectrum of the Au NHAs at different structural orientation angles (a) ϕ = 0° and (b) ϕ = 90°. Insets are the optical measurement configuration. Full article ">Figure 4
SFG spectra of 4-MBN on Au NHAs (black) at ϕ = 90° and flat gold film (red) at ~57° incident angle (with 1 mW VIS, 5 mW IR, and 30 s acquisition time). Full article ">Figure 5
(a) SFG spectra of 4-Mercaptobenzonitrile (4-MBN) on Au NHAs with different structural orientation angles (with 1 mW VIS, 5 mW IR, and 60 s acquisition time). Insets are the SFG optical configurations. (b) Structural orientation dependent reflectance spectra of Au NHAs at a 57.4° incident angle. Full article ">Figure 6
VIS power-dependent (a) SFG intensity of 4-MBN and (b) SFG enhancement factor of the Au NHAs at τ = 1 ps (with 5 mW IR and 60 s acquisition time). Full article ">

58 pages, 10060 KiB

Open AccessReview

Multimodal/Multifunctional Nanomaterials in (Bio)electrochemistry: Now and in the Coming Decade

by Paloma Yáñez-Sedeño, Araceli González-Cortés, Susana Campuzano and José Manuel Pingarrón

Nanomaterials 2020, 10(12), 2556; https://doi.org/10.3390/nano10122556 - 19 Dec 2020

Cited by 14 | Viewed by 4154

Abstract

Multifunctional nanomaterials, defined as those able to achieve a combined effect or more than one function through their multiple functionalization or combination with other materials, are gaining increasing attention in the last years in many relevant fields, including cargo targeted delivery, tissue engineering, [...] Read more.

Multifunctional nanomaterials, defined as those able to achieve a combined effect or more than one function through their multiple functionalization or combination with other materials, are gaining increasing attention in the last years in many relevant fields, including cargo targeted delivery, tissue engineering, in vitro and/or in vivo diseases imaging and therapy, as well as in the development of electrochemical (bio)sensors and (bio)sensing strategies with improved performance. This review article aims to provide an updated overview of the important advances and future opportunities exhibited by electrochemical biosensing in connection to multifunctional nanomaterials. Accordingly, representative aspects of recent approaches involving metal, carbon, and silica-based multifunctional nanomaterials are selected and critically discussed, as they are the most widely used multifunctional nanomaterials imparting unique capabilities in (bio)electroanalysis. A brief overview of the main remaining challenges and future perspectives in the field is also provided. Full article

(This article belongs to the Special Issue Electrochemistry of Nanomaterials and/or Nanostructures)

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15 pages, 2043 KiB

Open AccessArticle

Synergic Effect of Novel WS₂ Carriers Holding Spherical Cobalt Ferrite @cubic Fe₃O₄ (WS₂/s-CoFe₂O₄@c-Fe₃O₄) Nanocomposites in Magnetic Resonance Imaging and Photothermal Therapy for Ocular Treatments and Investigation of Corneal Endothelial Cell Migration

by Shadie Hatamie, Po-Jen Shih, Bo-Wei Chen, I-Jong Wang, Tai-Horng Young and Da-Jeng Yao

Nanomaterials 2020, 10(12), 2555; https://doi.org/10.3390/nano10122555 - 19 Dec 2020

Cited by 9 | Viewed by 3354

Abstract

The design of novel materials to use simultaneously in an ocular system for driven therapeutics and wound healing is still challenging. Here, we produced nanocomposites of tungsten disulfide carriers with spherical cobalt ferrite nanoparticles (NPs) as core inside a cubic iron oxide NPs [...] Read more.

The design of novel materials to use simultaneously in an ocular system for driven therapeutics and wound healing is still challenging. Here, we produced nanocomposites of tungsten disulfide carriers with spherical cobalt ferrite nanoparticles (NPs) as core inside a cubic iron oxide NPs shell (WS₂/s-CoFe₂O₄@c-Fe₃O₄). Transmission electron microscopy (TEM) confirmed that 10 nm s-CoFe₂O₄@c-Fe₃O₄ NPs were attached on the WS₂ sheet surfaces. The cytotoxicity of the WS₂ sheets and nanocomposites were evaluated on bovine cornea endothelial cells (BCECs) using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for a duration of three days. The MTT assay results showed low toxicity of the WS₂ sheets on BCECs by 67% cell viability at 100 μg/mL in 24 h, while the nanocomposites show 50% cell viability in the same conditions. The magnetic resonance imaging (MRI) of nanocomposites revealed the excellent T₂-weighted imaging with an r₂ contrast of 108 mM⁻¹ S⁻¹. The in vitro photothermal therapy based on WS₂ sheets and WS₂/s-CoFe₂O₄ @c-Fe₃O₄ nanocomposites using 808 nm laser showed that the maximum thermal energy dispatched in medium at different applied power densities (1200 mw, 1800, 2200, 2600 mW) was for 0.1 mg/mL of the sample solution. The migration assay of BCECs showed that the wound healing was approximately 20% slower for the cell exposed by nanocomposites compared with the control (no exposed BCECs). We believe that WS₂/s-CoFe₂O₄@c-Fe₃O₄ nanocomposites have a synergic effect as photothermal therapy agents for eye diseases and could be a target in an ocular system using MRI. Full article

(This article belongs to the Special Issue Transition Metal Dichalcogenides: From Fundamentals to Nanoelectronics)

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Figure 1
Transmission Electron Microscopy (TEM) images of the (a) WS2 sheets, (b) s-CoFe2O4@c-Fe3O4 NPs and (c) WS2/s-CoFe2O4@c-Fe3O4 nanocomposites shows the layered structure of WS2 and the size of the nanoparticles (NPs) is observed to be 10 nm, (d) the energy dispersive spectrometer (EDS) structural study of the s-CoFe2O4@c-Fe3O4 NPs. The inset of figure (c) showed its corresponding selected area electron diffraction (SAED) pattern. (d) The EDS structural study of the s-CoFe2O4@ c-Fe3O4 NPs confirmed the presence of the cobalt, iron and oxygen elements in the core-shell magnetic nanoparticles (MNPs). Full article ">Figure 2
3-[4,5-dimethylthiazol-2yl]-2,5-diphenyl tetrazolium bromide (MTT) assay of the (a) WS2 sheets and (b) WS2/s-CoFe2O4@c-Fe3O4 nanocomposites on bovine cornea endothelial cells for duration of the 24, 48, and 72 h. The data were represented as mean ± SD (n = 3). Full article ">Figure 3
(a) The cell migration scratching assay on bovine cornea endothelial cells (b) quantitative analysis of BCECs migration represent the relative wound width calculated in relation to initial time (0 h). Results are expressed as mean ± SD repeated n = 3 experiments. Full article ">Figure 4
The photothermal evaluations of laser absorption of WS2 sheets in various laser power densities of (a) 1200, (b) 1800, (c) 2200 and (d) 2600 mW at concentration 1, 0.5 and 0.1 mg/mL. Full article ">Figure 5
The photothermal evaluations of laser absorption of WS2/CoFe2O4 @Fe3O4 nanocomposites in various laser power densities of (a) 1200, (b) 1800, (c) 2200 and (d) 2600 mW at concentration 1, 0.5, and 0.1 mg/mL. Full article ">Figure 6
(a) T1 and T2-weighted MR images at five different concentrations of nanocomposites. (b) The linear fitting of relaxation rates (1/T2) of versus nanocomposites concentrations. (c) The linear fitting of relaxation rates (1/T1) of versus nanocomposites concentrations. The relaxivity values of r2 and r1 were obtained from the slopes. Full article ">Scheme 1
Shows the synthesis process of WS2/s-CoFe2O4@c-Fe3O4 nanocomposites. Full article ">

17 pages, 4499 KiB

Open AccessEditor’s ChoiceArticle

Highly Sensitive Gas Sensing Material for Environmentally Toxic Gases Based on Janus NbSeTe Monolayer

by Deobrat Singh and Rajeev Ahuja

Nanomaterials 2020, 10(12), 2554; https://doi.org/10.3390/nano10122554 - 19 Dec 2020

Cited by 21 | Viewed by 3816

Abstract

Recently, a new family of the Janus NbSeTe monolayer has exciting development prospects for two-dimensional (2D) asymmetric layered materials that demonstrate outstanding properties for high-performance nanoelectronics and optoelectronics applications. Motivated by the fascinating properties of the Janus monolayer, we have studied the gas [...] Read more.

Recently, a new family of the Janus NbSeTe monolayer has exciting development prospects for two-dimensional (2D) asymmetric layered materials that demonstrate outstanding properties for high-performance nanoelectronics and optoelectronics applications. Motivated by the fascinating properties of the Janus monolayer, we have studied the gas sensing properties of the Janus NbSeTe monolayer for CO, CO

_{2}

, NO, NO

_{2}

, H

_{2}

S, and SO

_{2}

gas molecules using first-principles calculations that will have eminent application in the field of personal security, protection of the environment, and various other industries. We have calculated the adsorption energies and sensing height from the Janus NbSeTe monolayer surface to the gas molecules to detect the binding strength for these considered toxic gases. In addition, considerable charge transfer between Janus monolayer and gas molecules were calculated to confirm the detection of toxic gases. Due to the presence of asymmetric structures of the Janus NbSeTe monolayer, the projected density of states, charge transfer, binding strength, and transport properties displayed distinct behavior when these toxic gases absorbed at Se- and Te-sites of the Janus monolayer. Based on the ultra-low recovery time in the order of

? s

for NO and NO

_{2}

and

p s

for CO, CO

_{2}

, H

_{2}

S, and SO

_{2}

gas molecules in the visible region at room temperature suggest that the Janus monolayer as a better candidate for reusable sensors for gas sensing materials. From the transport properties, it can be observed that there is a significant variation of

I ? V

characteristics and sensitivity of the Janus NbSeTe monolayer before and after adsorbing gas molecules demonstrates the feasibility of NbSeTe material that makes it an ideal material for a high-sensitivity gas sensor. Full article

(This article belongs to the Special Issue Advances in Janus Nanoparticles: Synthesis, Characterization and Applications)

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15 pages, 4408 KiB

Open AccessArticle

Role of Thermodynamics and Kinetics in the Composition of Ternary III-V Nanowires

by Egor D. Leshchenko and Jonas Johansson

Nanomaterials 2020, 10(12), 2553; https://doi.org/10.3390/nano10122553 - 18 Dec 2020

Cited by 11 | Viewed by 2291

Abstract

We explain the composition of ternary nanowires nucleating from a quaternary liquid melt. The model we derive describes the evolution of the solid composition from the nucleated-limited composition to the kinetic one. The effect of the growth temperature, group V concentration and Au/III [...] Read more.

We explain the composition of ternary nanowires nucleating from a quaternary liquid melt. The model we derive describes the evolution of the solid composition from the nucleated-limited composition to the kinetic one. The effect of the growth temperature, group V concentration and Au/III concentration ratio on the solid-liquid dependence is studied. It has been shown that the solid composition increases with increasing temperature and Au concentration in the droplet at the fixed In/Ga concentration ratio. The model does not depend on the site of nucleation and the geometry of monolayer growth and is applicable for nucleation and growth on a facet with finite radius. The case of a steady-state (or final) solid composition is considered and discussed separately. While the nucleation-limited liquid-solid composition dependence contains the miscibility gap at relevant temperatures for growth of In_xGa_1−xAs NWs, the miscibility gap may be suppressed completely in the steady-state growth regime at high supersaturation. The theoretical results are compared with available experimental data via the combination of the here described solid-liquid and a simple kinetic liquid-vapor model. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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15 pages, 5395 KiB

Open AccessArticle

Organic–Inorganic Ternary Nanohybrids of Single-Walled Carbon Nanohorns for Room Temperature Chemiresistive Ethanol Detection

by Cornel Cobianu, Bogdan-Catalin Serban, Niculae Dumbravescu, Octavian Buiu, Viorel Avramescu, Cristina Pachiu, Bogdan Bita, Marius Bumbac, Cristina-Mihaela Nicolescu and Cosmin Cobianu

Nanomaterials 2020, 10(12), 2552; https://doi.org/10.3390/nano10122552 - 18 Dec 2020

Cited by 20 | Viewed by 2896

Abstract

Organic–inorganic ternary nanohybrids consisting of oxidized-single walled carbon nanohorns-SnO₂-polyvinylpyrrolidone (ox-SWCNH/SnO₂/PVP) with stoichiometry 1/1/1 and 2/1/1 and ox-SWCNH/ZnO/PVP = 5/2/1 and 5/3/2 (all mass ratios) were synthesized and characterized as sensing films of chemiresistive test structures for ethanol vapor detection [...] Read more.

Organic–inorganic ternary nanohybrids consisting of oxidized-single walled carbon nanohorns-SnO₂-polyvinylpyrrolidone (ox-SWCNH/SnO₂/PVP) with stoichiometry 1/1/1 and 2/1/1 and ox-SWCNH/ZnO/PVP = 5/2/1 and 5/3/2 (all mass ratios) were synthesized and characterized as sensing films of chemiresistive test structures for ethanol vapor detection in dry air, in the range from 0 up to 50 mg/L. All the sensing films had an ox-SWCNH concentration in the range of 33.3–62.5 wt%. A comparison between the transfer functions and the response and recovery times of these sensing devices has shown that the structures with ox-SWCNH/SnO₂/PVP = 1/1/1 have the highest relative sensitivities of 0.0022 (mg/L)⁻¹, while the devices with ox-SWCNH/SnO₂/PVP = 2/1/1 have the lowest response time (15 s) and recovery time (50 s) for a room temperature operation, proving the key role of carbonic material in shaping the static and dynamic performance of the sensor. These response and recovery times are lower than those of “heated” commercial sensors. The sensing mechanism is explained in terms of the overall response of a p-type semiconductor, where ox-SWCNH percolated between electrodes of the sensor, shunting the heterojunctions made between n-type SnO₂ or ZnO and p-type ox-SWCNH. The hard–soft acid–base (HSAB) principle supports this mechanism. The low power consumption of these devices, below 2 mW, and the sensing performances at room temperature may open new avenues towards ethanol sensors for passive samplers of environment monitoring, alcohol test portable instruments and wireless network sensors for Internet of Things applications. Full article

(This article belongs to the Special Issue Advanced Carbon Nanostructures: Synthesis, Properties and Applications)

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Figure 1
Raman spectra of solid-state films of single walled carbon nanohorns-SnO2-polyvinylpyrrolidone (SWCNH/SnO2/PVP) = 1/1/1 (mass ratio) deposited on silicon substrate. Full article ">Figure 2
SEM images of the sensing ternary films deposited on the sensing area of the test structure. (a) Oxidized-single walled carbon nanohorns-SnO2-polyvinylpyrrolidone (ox-SWCNH/SnO2/PVP) = 1/1/1; (b) and ox-SWCNH/SnO2 = 2/1/1. Full article ">Figure 3
Transfer functions of the chemiresistive ethanol sensors with sensing films kept at room temperature and consisting of (a) ox-SWCNH/SnO2/PVP = 1/1/1 (mass ratio) and (b) ox-SWCNH/SnO2/PVP = 2/1/1 (mass ratio). For both cases, the flow rate of air passing through liquid ethanol was varied, while the total flow rate was kept constant at 1 L/min. The inset shows the automatic recording of the sensor resistance as a function of time and ethanol vapor concentration. Full article ">Figure 4
Transfer functions of the chemiresistive ethanol sensors with sensing films kept at room temperature and consisting of (a) ox-SWCNH/ZnO/PVP = 5/2/1 (mass ratio) and (b) ox-SWCNH/ZnO/PVP = 5/3/2. For both cases, the flow rate of air passing through liquid ethanol was varied, while the total flow rate was kept constant at 1 L/min. The inset shows the automatic recording of the sensor resistance as a function of time and ethanol vapor concentration. Full article ">Figure 5
Response and the recovery times of the chemiresistive ethanol sensors with sensing films kept at room temperature and consisting of (a) ox-SWCNH/SnO2/PVP = 1/1/1 (mass ratio), where (a1) is response time, and (a2) is recovery time and (b) ox-SWCNH/SnO2/PVP = 2/1/1 (mass ratio), where (b1) is response time, and (b2) is recovery time. Response time was measured for a change in ethanol vapor concentration from 2 to 5 mg/L, while the recovery time was measured for a change in ethanol vapor concentration from 25 mg/L to 0 mg/L. For both cases, the flow rate of air passing through liquid ethanol was varied, while the total flow rate in the test chamber was kept constant at 1 L/min. Full article ">Figure 6
Response and recovery times of the chemiresistive ethanol sensors with sensing films kept at room temperature and consisting of (a) ox-SWCNH/ZnO/PVP = 5/2/1 (mass ratio); (a1) response time, and (a2) recovery time, and (b) ox-SWCNH/ZnO/PVP = 5/3/2 (mass ratio); (b1) response time, and (b2) recovery time. Response time was measured for a change in ethanol vapor concentration from 2 to 5 mg/L, while the recovery time was measured for a change in ethanol vapor concentration from 25 mg/L to 0 mg/L. For both cases, the flow rate of air passing through liquid ethanol was varied, while the total flow rate was kept constant at 1 L/min. Full article ">

24 pages, 4626 KiB

Open AccessArticle

An Organic–Inorganic Hybrid Nanocomposite as a Potential New Biological Agent

by Mateusz Dulski, Katarzyna Malarz, Michał Kuczak, Karolina Dudek, Krzysztof Matus, Sławomir Sułowicz, Anna Mrozek-Wilczkiewicz and Anna Nowak

Nanomaterials 2020, 10(12), 2551; https://doi.org/10.3390/nano10122551 - 18 Dec 2020

Cited by 9 | Viewed by 3246 | Correction

Abstract

To solve the problem of human diseases caused by a combination of genetic and environmental factors or by microorganisms, intense research to find completely new materials is required. One of the promising systems in this area is the silver-silica nanocomposites and their derivatives. [...] Read more.

To solve the problem of human diseases caused by a combination of genetic and environmental factors or by microorganisms, intense research to find completely new materials is required. One of the promising systems in this area is the silver-silica nanocomposites and their derivatives. Hence, silver and silver oxide nanoparticles that were homogeneously distributed within a silica carrier were fabricated. Their average size was d = (7.8 ± 0.3) nm. The organic polymers (carboxymethylcellulose (CMC) and sodium alginate (AS)) were added to improve the biological features of the nanocomposite. The first system was prepared as a silver chlorine salt combination that was immersed on a silica carrier with coagulated particles whose size was d = (44.1 ± 2.3) nm, which coexisted with metallic silver. The second system obtained was synergistically interacted metallic and oxidized silver nanoparticles that were distributed on a structurally defective silica network. Their average size was d = (6.6 ± 0.7) nm. Physicochemical and biological experiments showed that the tiny silver nanoparticles in Ag/SiO₂ and Ag/SiO₂@AS inhibited E. coli, P. aeruginosa, S. aureus, and L. plantarum’s cell growth as well as caused a high anticancer effect. On the other hand, the massive silver nanoparticles of Ag/SiO₂@CMC had a weaker antimicrobial effect, although they highly interacted against PANC-1. They also generated reactive oxygen species (ROS) as well as the induction of apoptosis via the p53-independent mechanism. Full article

(This article belongs to the Special Issue Hybrid Nanomaterials Synthesis and Application)

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20 pages, 6222 KiB

Open AccessArticle

Cytotoxicity and Bioimaging Study for NHDF and HeLa Cell Lines by Using Graphene Quantum Pins

by Seong-Beom Jeon, Monica Samal, Saravanan Govindaraju, Rupasree Ragini Das and Kyusik Yun

Nanomaterials 2020, 10(12), 2550; https://doi.org/10.3390/nano10122550 - 18 Dec 2020

Cited by 4 | Viewed by 2977

Abstract

Herein, we report the synthesis of an interesting graphene quantum material called “graphene quantum pins (GQPs)”. Morphological analysis revealed the interesting pin shape (width: ~10 nm, length: 50–100 nm) and spectral analysis elucidated the surface functional groups, structural features, energy levels, and photoluminescence [...] Read more.

Herein, we report the synthesis of an interesting graphene quantum material called “graphene quantum pins (GQPs)”. Morphological analysis revealed the interesting pin shape (width: ~10 nm, length: 50–100 nm) and spectral analysis elucidated the surface functional groups, structural features, energy levels, and photoluminescence properties (blue emission under 365 nm). The difference between the GQPs and graphene quantum dos (GQDs) isolated from the same reaction mixture as regards to their morphological, structural, and photoluminescence properties are also discussed along with the suggestion of a growth mechanism. Cytotoxicity and cellular responses including changes in biophysical and biomechanical properties were evaluated for possible biomedical applications of GQPs. The studies demonstrated the biocompatibility of GQPs even at a high concentration of 512 μg/mL. Our results suggest GQPs can be used as a potential bio-imaging agent with desired photoluminescence property and low cytotoxicity. Full article

(This article belongs to the Section 2D and Carbon Nanomaterials)

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15 pages, 3090 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Eco-Friendly 1,3-Dipolar Cycloaddition Reactions on Graphene Quantum Dots in Natural Deep Eutectic Solvent

by Salvatore V. Giofrè, Matteo Tiecco, Consuelo Celesti, Salvatore Patanè, Claudia Triolo, Antonino Gulino, Luca Spitaleri, Silvia Scalese, Mario Scuderi and Daniela Iannazzo

Nanomaterials 2020, 10(12), 2549; https://doi.org/10.3390/nano10122549 - 18 Dec 2020

Cited by 35 | Viewed by 3743

Abstract

Due to their outstanding physicochemical properties, the next generation of the graphene family—graphene quantum dots (GQDs)—are at the cutting edge of nanotechnology development. GQDs generally possess many hydrophilic functionalities which allow their dispersibility in water but, on the other hand, could interfere with [...] Read more.

Due to their outstanding physicochemical properties, the next generation of the graphene family—graphene quantum dots (GQDs)—are at the cutting edge of nanotechnology development. GQDs generally possess many hydrophilic functionalities which allow their dispersibility in water but, on the other hand, could interfere with reactions that are mainly performed in organic solvents, as for cycloaddition reactions. We investigated the 1,3-dipolar cycloaddition (1,3-DCA) reactions of the C-ethoxycarbonyl N-methyl nitrone 1a and the newly synthesized C-diethoxyphosphorylpropilidene N-benzyl nitrone 1b with the surface of GQDs, affording the isoxazolidine cycloadducts isox-GQDs 2a and isox-GQDs 2b. Reactions were performed in mild and eco-friendly conditions, through the use of a natural deep eutectic solvent (NADES), free of chloride or any metal ions in its composition, and formed by the zwitterionic trimethylglycine as the -bond acceptor, and glycolic acid as the hydrogen-bond donor. The results reported in this study have for the first time proved the possibility of performing cycloaddition reactions directly to the p-cloud of the GQDs surface. The use of DES for the cycloaddition reactions on GQDs, other than to improve the solubility of reactants, has been shown to bring additional advantages because of the great affinity of these green solvents with aromatic systems. Full article

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Full article ">Figure 1
Eco-friendly synthesis of isox-graphene quantum dots (GQDs) 2a,b by 1,3-DCA reactions in natural deep eutectic solvent (NADES) medium. Full article ">Figure 2
(a) Representative HRTEM image of a GQDs cluster with mean particle size of 4.8 nm and the corresponding fast Fourier transform (FTT) on the inset showing planes at 0.21 nm; (b) DLS measurement of GQDs dispersion in deionized water; (c) optical properties of GQDs dispersions in deionized water: UV—vis absorption spectrum of GQDs (blue line) and photoluminescence (PL) spectrum of GQDs at the excitation wavelengths of 360 nm (red line). Full article ">Figure 3
(a) TGA curves of GQDs, isox-GQDs 2a and isox-GQDs 2b, performed in Ar atmosphere; (b) FTIR spectra of GQDs, isox-GQDs 2a and isox-GQDs 2b. Full article ">Figure 4
Al-Kα excited XPS of: (a,b) isox-GQDs 2a in the C 1s and O 1s binding energy regions; (c) overlapped XPS of the isox-GQDs 2b (black line) and isox-GQDs 2a (red line) in the N 1s binding energy region; (d,e) isox-GQDs 2b in the C 1s and O 1s binding energy regions; (f) isox-GQDs 2b in the P 2p binding energy region. Full article ">Figure 5
PL spectra of GQDs, isox-GQDs 2a and isox-GQDs 2b, at the λexc of 360 nm. All samples were tested at a concentration of 100 ng/mL. Full article ">Figure 6
Raman spectra of: (a) GQDs, (b) isox-GQDs 2a and (c) isox-GQDs 2b. Full article ">Figure 7
(a) Atomic force microscopy (AFM) image of the GQDs deposited on the Si substrate and (b) line profile referring to the green line in figure (a); (c) AFM image of isox-GQDs 2a deposited on the Si substrate and (d) line profile referring to the green line in (c); (e) AFM image of isox-GQDs 2b deposited on the Si substrate and (f) line profile referring to the green line in (e). Full article ">Scheme 1
Synthesis of cycloadducts isox-GQDs 2a and isox-GQDs 2b. Reagents and conditions: GA/TMG (2:1 molar ratio), MW, 1 h, 90 °C, 150 W. Full article ">

15 pages, 5738 KiB

Open AccessArticle

Effect of Water and Glycerol in Deoxygenation of Coconut Oil over Bimetallic NiCo/SAPO-11 Nanocatalyst under N₂ Atmosphere

by Rungnapa Kaewmeesri, Jeeranan Nonkumwong, Thongthai Witoon, Navadol Laosiripojana and Kajornsak Faungnawakij

Nanomaterials 2020, 10(12), 2548; https://doi.org/10.3390/nano10122548 - 18 Dec 2020

Cited by 3 | Viewed by 2757

Abstract

The catalytic deoxygenation of coconut oil was performed in a continuous-flow reactor over bimetallic NiCo/silicoaluminophosphate-11 (SAPO-11) nanocatalysts for hydrocarbon fuel production. The conversion and product distribution were investigated over NiCo/SAPO-11 with different applied co-reactants, i.e., water (H₂O) or glycerol solution, performed [...] Read more.

The catalytic deoxygenation of coconut oil was performed in a continuous-flow reactor over bimetallic NiCo/silicoaluminophosphate-11 (SAPO-11) nanocatalysts for hydrocarbon fuel production. The conversion and product distribution were investigated over NiCo/SAPO-11 with different applied co-reactants, i.e., water (H₂O) or glycerol solution, performed under nitrogen (N₂) atmosphere. The hydrogen-containing co-reactants were proposed here as in-situ hydrogen sources for the deoxygenation, while the reaction tests under hydrogen (H₂) atmosphere were also applied as a reference set of experiments. The results showed that applying co-reactants to the reaction enhanced the oil conversion as the following order: N₂ (no co-reactant) < N₂ (H₂O) < N₂ (aqueous glycerol) < H₂ (reference). The main products formed under the existence of H₂O or glycerol solution were free fatty acids (FFAs) and their corresponding C_n−1 alkanes. The addition of H₂O aids the triglyceride breakdown into FFAs, whereas the glycerol acts as hydrogen donor which is favourable to initiate hydrogenolysis of triglycerides, causing higher amount of FFAs than the former case. Consequently, those FFAs can be deoxygenated via decarbonylation/decarboxylation to their corresponding C_n−1 alkanes, showing the promising capability of the NiCo/SAPO-11 to produce hydrocarbon fuels even in the absence of external H₂ source. Full article

(This article belongs to the Special Issue Nanotechnologies and Nanomaterials: Selected Papers from CCMR)

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Figure 1
Schematic diagram of continuous-flow reactor system for catalytic testing. Full article ">Figure 2
(a) XRD patterns, * 2θ = 44.41°, 51.78°, and 76.09° (powder diffraction file (PDF) for Ni-Co alloy (01-074-5694)); (b) N2 adsorption-desorption isotherms; and (c) pore-size distributions of SAPO-11 and the reduced NiCo/SAPO-11 catalyst. Full article ">Figure 3
(a) Scanning electron microscopy (SEM) image; (b) transmission electron microscopy (TEM) image; (c,d) corresponding energy dispersive X-ray spectrometer (EDS) elemental mappings of Ni and Co; (e,f) EDS line profile of the NiCo/SAPO-11 catalyst. Full article ">Figure 4
Oil conversion and product yield of coconut oil deoxygenation under different atmospheres with (w/) and without (w/o) co-reactant feeds. (Condition: Coconut oil, LHSV of 1 h−1, 330 °C, and 50 bar of reaction gas, Gly = glycerol solution). Full article ">Figure 5
Distribution of liquid hydrocarbon products of coconut oil deoxygenation under different atmospheres with (w/) and without (w/o) co-reactant feeds. (Condition: Coconut oil, LHSV of 1 h−1, 330 °C, and 50 bar of reaction gas, Gly = glycerol solution). Full article ">Figure 6
Distribution of gas species of coconut oil deoxygenation under different atmospheres with (w/) and without (w/o) co-reactant feeds. (Condition: Coconut oil, LHSV of 1 h−1, 330 °C, and 50 bar of reaction gas, Gly = glycerol solution). Full article ">

10 pages, 4352 KiB

Open AccessArticle

Direct Laser Writing of Transparent Polyimide Film for Supercapacitor

by Fei Huang, Guoying Feng, Jiajia Yin, Sikun Zhou, Li Shen, Shutong Wang and Yun Luo

Nanomaterials 2020, 10(12), 2547; https://doi.org/10.3390/nano10122547 - 18 Dec 2020

Cited by 21 | Viewed by 4143

Abstract

Direct laser writing (DLW) is a convenient approach for fabricating graphene-based flexible electronic devices. In this paper, laser-induced graphene was successfully prepared on a thin and transparent polyimide film through the DLW process. Experiments have demonstrated that interdigital thin film capacitor prepared by [...] Read more.

Direct laser writing (DLW) is a convenient approach for fabricating graphene-based flexible electronic devices. In this paper, laser-induced graphene was successfully prepared on a thin and transparent polyimide film through the DLW process. Experiments have demonstrated that interdigital thin film capacitor prepared by the DLW method has a high specific capacitance of 8.11 mF/cm² and volume capacitance density of 3.16 F/cm³ (0.05 mA/cm²) due to the doped fluoride in the laser-induced graphene. The capacitance is about 20 times larger than the super-capacitor based non-transparent polyimide film of the same thickness. Owing to its thin, flexible, higher electrochemical characteristics, the transparent polyimide film is promising for integrating and powering portable and wearable electronics. Full article

(This article belongs to the Section Nanofabrication and Nanomanufacturing)

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Schematic illustration of fabrication process of (a–d) supercapacitor and (e) is physical image of supercapacitor. Full article ">Figure 2
(a–c) The scanning electron microscope (SEM) images of the porous carbon materials prepared by DLW on transparent PI (DLWT)’s; (a–b) surface and (c) thickness cross-section; (d–g) the electron diffraction spectroscopy (EDS) mapping of C, N, O, F of DLWT surface; (h–k) the EDS mapping of C, N, O, F of thickness cross-section. Full article ">Figure 3
(a) the Raman spectra of the porous carbon materials prepared by DLW on transparent PI and non-transparent PI (DLWT and DLWP) (Embedded graph is the Raman spectra of transparent polyimide film (PI)); (b) the X-ray photoelectron spectroscopy (XPS) spectra; (c) the high-resolution C 1s of DLWT; (d) the high-resolution F 1s of DLWT. Full article ">Figure 4
The cyclic voltammetry (CV) curve of (a) DLWP and (b) DLWT with the scan rates of 5, 10, 20, 50, and 100 mV/s; (c) the CV curve comparison between DLWT and DLWP (scan rates is 100 mV/s); The galvanostatic charge/discharge (GCD) curve of (d) DLWP and (e) DLWT with the current density of 0.05, 0.1, 0.2, and 0.5 mA/cm2; (f) the GCD curve comparison of DLWT and DLWP (current density is 0.05 mA/cm2); specific capacitance (g) calculated from CV data (h) calculated from GCD data; (i) the Nyquist plots of DLWP and DLWT; (j) Ragone plot. Full article ">Figure 5
(a) Normalized capacitance plot with 2500 charge/discharge cycles (Embedded graph is the initial CV curve after 500, 1000, 1500, 2000, and 2500 cycles number of DLWT with the scan rate of 0.1 V/s.); (b) DLWT CV curves of various bending radius under 0.1 V/s scan rate. Full article ">

14 pages, 627 KiB

Open AccessArticle

Exposure to Ultrafine Particles in the Ferroalloy Industry Using a Logbook Method

by Rikke Bramming Jørgensen, Ida Teresia Kero, Aleksander Blom, Esten Eide Grove and Kristin von Hirsch Svendsen

Nanomaterials 2020, 10(12), 2546; https://doi.org/10.3390/nano10122546 - 17 Dec 2020

Cited by 8 | Viewed by 3017

Abstract

Background: It is difficult to assess workers’ exposure to ultrafine particles (UFP) due to the lack of personal sampling equipment available for this particle fraction. The logbook method has been proposed as a general method for exposure assessment. This method measures the time [...] Read more.

Background: It is difficult to assess workers’ exposure to ultrafine particles (UFP) due to the lack of personal sampling equipment available for this particle fraction. The logbook method has been proposed as a general method for exposure assessment. This method measures the time and concentration components of the time-weighted average concentration separately and could be suitable for investigation of UFP exposure. Objectives: In this study, we have assessed workers’ exposure to UFP in a ferrosilicon plant. The main tasks of the furnace workers were identified, and the logbook method was used in combination with stationary measurements of UFP taken as close to the identified task areas as possible. In order to verify the results, respirable particles were collected using stationary sampling in close proximity to the UFP measuring instrument, and personal full-shift sampling of respirable particles was performed simultaneously. Thus, exposure to respirable particles determined using the logbook method could be compared to the results of standard measurement. Methods: The particle number concentration of ultrafine particles was determined using a NanoScan SMPS. Respirable particle concentration and exposure were determined using a sampling train consisting of a pump, filter, filter cassettes, and SKC Cyclone for the respirable fraction. Attendance times for workers at each work location were registered via thorough observations made by the research team. Results: The logbook method for exposure estimation based on stationary sampling equipment made it possible to calculate UFP exposure for workers operating the furnaces at a ferrosilicon plant. The mid-size furnace and the large furnace were evaluated separately. The workers operating the largest furnace were exposed to 1.47 × 10⁴ particles/cm³, while workers operating the mid-size furnace were exposed to 2.06 × 10⁴ particles/cm³, with a mean of 1.74 × 10⁴ particles/cm³. Substantial contributions from the casting area, ladle transport corridor, and both tapping areas were made. Exposure to respirable particles was 2.04 mg/m³ (logbook); 2.26 mg/m³ (personal sampling) for workers operating the large-sized furnace, 3.24 mg/m³ (logbook); 2.44 mg/m³ (personal sampling) for workers operating the medium-sized furnace, and 2.57 mg/m³ (logbook); 2.53 mg/m³(personal sampling) on average of all tappers. The average ratio of these two methods’ results was 1.02, which indicates that the logbook method could be used as a substitute for personal sampling when it is not possible to perform personal sampling, at least within this industry. Conclusions: The logbook method is a useful supplement for exposure assessment of UFP, able to identify the most polluted areas of the workplace and the contribution of different work tasks to the total exposure of workers, enabling companies to take action to reduce exposure. Full article

(This article belongs to the Special Issue Safety and Biocompatibility of Metallic Nanoparticles)

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34 pages, 7567 KiB

Open AccessFeature PaperArticle

The Kinetics and Stoichiometry of Metal Cation Reduction on Multi-Crystalline Silicon in a Dilute Hydrofluoric Acid Matrix

by Stefan Schönekerl and Jörg Acker

Nanomaterials 2020, 10(12), 2545; https://doi.org/10.3390/nano10122545 - 17 Dec 2020

Cited by 4 | Viewed by 2567

Abstract

In this study, the process of metal cation reduction on multi-crystalline silicon in a dilute hydrofluoric acid (HF) matrix is described using Ag(I), Cu(II), Au(III) and Pt(IV). The experimental basis utilized batch tests with various solutions of different metal cation and HF concentrations [...] Read more.

In this study, the process of metal cation reduction on multi-crystalline silicon in a dilute hydrofluoric acid (HF) matrix is described using Ag(I), Cu(II), Au(III) and Pt(IV). The experimental basis utilized batch tests with various solutions of different metal cation and HF concentrations and multi-crystalline silicon wafers. The metal deposition kinetics and the stoichiometry of metal deposition and silicon dissolution were calculated by means of consecutive sampling and analysis of the solutions. Several reaction mechanisms and reaction steps of the process were discussed by overlaying the results with theoretical considerations. It was deduced that the metal deposition was fastest if the holes formed during metal ion reduction could be transferred to the valence bands of the bulk and surface silicon with hydrogen termination. By contrast, the kinetics were lowest when the redox levels of the metal ion/metal half-cells were weak and the equilibrium potential of the H₃O⁺/H₂ half-cells was high. Further minima were identified at the thresholds where H₃O⁺ reduction was inhibited, the valence transfer via valence band mechanism was limited by a Schottky barrier and the dissolution of oxidized silicon was restricted by the activity of the HF species F⁻, HF₂⁻ and H₂F₃⁻. The findings of the stoichiometric conditions provided further indications of the involvement of H₃O⁺ and H₂O as oxidizing agents in addition to metal ions, and the hydrogen of the surface silicon termination as a reducing agent in addition to the silicon. The H₃O⁺ reduction is the predominant process in dilute metal ion solutions unless it is disabled due to the metal-dependent equilibrium potential of the H₃O⁺/H₂ half-cell and the energetic level of the valence bands of the silicon. As silicon is not oxidized up to the oxidation state +IV by the reduction of the metal ions and H₃O⁺, water is suspected of acting as a secondary oxidant. The stoichiometric ratios increased up to a maximum with higher molalities of the metal ions, in the manner of a sigmoidal function. If, owing to the redox level of the metal half-cells and the energetic level of the valence band at the metal–silicon contact, the surface silicon can be oxidized, the hydrogen of the termination is the further reducing agent. Full article

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