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Nanomaterials
Volume 5
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Nanomaterials, Volume 5, Issue 4 (December 2015) – 47 articles , Pages 1556-2390

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1760 KiB  
Communication
Freestanding rGO-SWNT-STN Composite Film as an Anode for Li Ion Batteries with High Energy and Power Densities
by Taeseup Song, Junghyun Choi and Ungyu Paik
Nanomaterials 2015, 5(4), 2380-2390; https://doi.org/10.3390/nano5042380 - 18 Dec 2015
Cited by 5 | Viewed by 6911
Abstract
Freestanding Si-Ti-Ni alloy particles/reduced graphene oxide/single wall carbon nanotube composites have been prepared as an anode for lithium ion batteries via a simple filtration method. This composite electrode showed a 9% increase in reversible capacity, a two-fold higher cycle retention at 50 cycles [...] Read more.
Freestanding Si-Ti-Ni alloy particles/reduced graphene oxide/single wall carbon nanotube composites have been prepared as an anode for lithium ion batteries via a simple filtration method. This composite electrode showed a 9% increase in reversible capacity, a two-fold higher cycle retention at 50 cycles and a two-fold higher rate capability at 2 C compared to pristine Si-Ti-Ni (STN) alloy electrodes. These improvements were attributed to the suppression of the pulverization of the STN active material by the excellent mechanical properties of the reduced graphene oxide-single wall carbon nanotube networks and the enhanced kinetics associated with both electron and Li ion transport. Full article
(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)
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Figure 1

Figure 1
<p>Schematic illustration of (<b>a</b>) advantages of freestanding reduced graphene oxide /single wall carbon nanotube/Si-Ti-Ni (rGO-SWNT-STN) composite film and (<b>b</b>) its fabrication process.</p> Full article ">Figure 2
<p>(<b>a</b>) Photograph and (<b>b</b>) field emission scanning electron microscopy (FE-SEM) image of freestanding GO-SWNT-STN composite film. Elementary mapping images of (<b>c</b>) carbon, (<b>d</b>) silicon, (<b>e</b>) titanium, and (<b>f</b>) nickel in the composite film.</p> Full article ">Figure 3
<p>(<b>a</b>) SEM and (<b>b</b>) transmission electron microscope (TEM) images of rGO-SWNT-STN composite film.</p> Full article ">Figure 4
<p>(<b>a</b>) X-ray diffraction patterns of Si-Ti-Ni (STN) and rGO-SWNT-STN, (<b>b</b>) Raman spectra of freestanding films, before and after annealing.</p> Full article ">Figure 5
<p>Electrochemical performances of the pristine STN and the rGO-SWNT-STN electrodes. (<b>a</b>) Initial cycle voltage profiles at a rate of 0.1 <span class="html-italic">C</span>, (<b>b</b>) Cycle retentions at a rate of 1 <span class="html-italic">C</span>, (<b>c</b>) Coulombic efficiency at a rate of 1 <span class="html-italic">C</span>, (<b>d</b>) Rate capabilities at various <span class="html-italic">C</span> rates.</p> Full article ">Figure 6
<p>SEM images of rGO-SWNT-STN electrode for (<b>a</b>) full lithiation, and (<b>b</b>) delithiation at the first cycle.</p> Full article ">Figure 7
<p>Electrochemical impedance spectra of the pristine STN and the rGO-SWNT-STN electrodes.</p> Full article ">
2255 KiB  
Article
Non-Cytotoxic Quantum Dot–Chitosan Nanogel Biosensing Probe for Potential Cancer Targeting Agent
by Tyler Maxwell, Tahmina Banu, Edward Price, Jeremy Tharkur, Maria Gabriela Nogueira Campos, Andre Gesquiere and Swadeshmukul Santra
Nanomaterials 2015, 5(4), 2359-2379; https://doi.org/10.3390/nano5042359 - 18 Dec 2015
Cited by 19 | Viewed by 7289
Abstract
Quantum dot (Qdot) biosensors have consistently provided valuable information to researchers about cellular activity due to their unique fluorescent properties. Many of the most popularly used Qdots contain cadmium, posing the risk of toxicity that could negate their attractive optical properties. The design [...] Read more.
Quantum dot (Qdot) biosensors have consistently provided valuable information to researchers about cellular activity due to their unique fluorescent properties. Many of the most popularly used Qdots contain cadmium, posing the risk of toxicity that could negate their attractive optical properties. The design of a non-cytotoxic probe usually involves multiple components and a complex synthesis process. In this paper, the design and synthesis of a non-cytotoxic Qdot-chitosan nanogel composite using straight-forward cyanogen bromide (CNBr) coupling is reported. The probe was characterized by spectroscopy (UV-Vis, fluorescence), microscopy (Fluorescence, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering. This activatable (“OFF”/“ON”) probe contains a core–shell Qdot (CdS:Mn/ZnS) capped with dopamine, which acts as a fluorescence quencher and a model drug. Dopamine capped “OFF” Qdots can undergo ligand exchange with intercellular glutathione, which turns the Qdots “ON” to restore fluorescence. These Qdots were then coated with chitosan (natural biocompatible polymer) functionalized with folic acid (targeting motif) and Fluorescein Isothiocyanate (FITC; fluorescent dye). To demonstrate cancer cell targetability, the interaction of the probe with cells that express different folate receptor levels was analyzed, and the cytotoxicity of the probe was evaluated on these cells and was shown to be nontoxic even at concentrations as high as 100 mg/L. Full article
(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>A</b>) UV-vis absorbance of dopamine HCl, bare CdS:Mn/ZnS Qdots, dopamine-Qdot conjugate, and the full probe. The peak at 278 nm is attributed to absorption by dopamine. This peak is evidence of dopamine remaining bound to the Qdot surface after washing and coating with chitosan; (<b>B</b>) FTIR spectra of dopamine HCl, dopamine-Qdot conjugate, and the full probe; (<b>C</b>) Normalized fluorescence emission spectra of the full probe in the “OFF” state, the full probe in the “ON” state (Probe + 10 mM glutathione (GSH)), folic acid (FA), Fluorescein isothiocyanate (FITC), and hydrothermally treated chitosan (CS) in PBS buffer obtained with 375 nm excitation; (<b>D</b>) Fluorescence intensity of Qdots in PBS over time after addition of 10 mM GSH. Full restoration of Qdots is observed 40 min after addition of GSH. This shows the extent to which fluorescence can be restored for the probe. A polynomial function was fitted to the data to determine the linearity of fluorescence restoration.</p> Full article ">Figure 2
<p>Scanning Electron Microscopy (SEM) images and Energy Dispersive Spectroscopy (EDS) spectrum of the gel probe. The full probe is composed of small particles that are embedded in a cross-linked chitosan matrix. The particle pictured above could possibly be multiple aggregated particles. The EDS spectrum shows small peaks for cadmium and zinc, which confirm the presence of Qdots in the chitosan matrix.</p> Full article ">Figure 3
<p>(<b>A</b>) Transmission Electron Microscopy (TEM) images of the bare CdS:Mn/ZnS Qdots. Three Qdots are circled for clarity in the image on the right; (<b>B</b>) The Qdot size distribution as determined by the observation of the lattice planes of 23 of the most clearly observed individual Qdots. Data were taken from multiple images (not shown). A normal distribution was fitted to the data to determine the average Qdot size; (<b>C</b>) Size distribution of the full probe dispersed in water as measured by DLS. The size scale is logarithmic. The apparent cutoff on the right hand side of the histogram is due to the absence of particles with diameter greater than 2000 nm.</p> Full article ">Figure 3 Cont.
<p>(<b>A</b>) Transmission Electron Microscopy (TEM) images of the bare CdS:Mn/ZnS Qdots. Three Qdots are circled for clarity in the image on the right; (<b>B</b>) The Qdot size distribution as determined by the observation of the lattice planes of 23 of the most clearly observed individual Qdots. Data were taken from multiple images (not shown). A normal distribution was fitted to the data to determine the average Qdot size; (<b>C</b>) Size distribution of the full probe dispersed in water as measured by DLS. The size scale is logarithmic. The apparent cutoff on the right hand side of the histogram is due to the absence of particles with diameter greater than 2000 nm.</p> Full article ">Figure 4
<p>(<b>A</b>) Observed cytotoxicity towards TE71; (<b>B</b>) OVCAR3; and (<b>C</b>) J774a.1 macrophage cells after 24 h incubation with bare Qdots and the full probe as measured by MTS assay. Bare Qdots and full probe with folic acid (+) FA and without folic acid (−) FA bound to the chitosan at 100, 10, 1, and 0.1 μg/mL Qdot concentration. The growth control (negative) is untreated cells in media. The positive control for cell death was completed by adding water to the cells. The cytotoxicity data are plotted relative to the negative control, which was assigned to have 100% viability. Error bars are standard deviation of the mean.</p> Full article ">Figure 5
<p>Confocal microscopy images of OVCAR3 cells incubated with the full probe with (+) FA and without folic acid (−) FA, and with media without probe (control). The right column images display the fluorescence of the Qdots only. The middle column images show just the fluorescence from FITC. The left images are phase images merged with Qdot and FITC fluorescence images. Qdots fluorescence is seen co-localized with fluorescence of chitosan bound FITC. Increased binding of the probe to OVCAR3 cells was observed with samples containing attached folic acid (Probe (+) FA). The full Z-stack images can be viewed in the supplemental section (<a href="#app1-nanomaterials-05-02359" class="html-app">Figures S3–S6</a>).</p> Full article ">Figure 6
<p>Fluorescence microscopy images of TE71 cells incubated with the probe with bound folic acid (+) FA and without folic acid (−) FA, and with media without probe (control). The left images are phase images merged with the fluorescence images. The middle images are only the FITC fluorescence. The right images are only the Qdot fluorescence. Only a small increase in binding of the full probe to the TE71 cells was seen from the probe (+) FA. This is most likely because TE71 does have some folate receptors but has not been shown to overexpress them.</p> Full article ">Figure 7
<p>Confocal microscopy images of J774a.1 macrophage cells incubated with the full probe with (+) FA and without folic acid (−) FA, and with media without probe (control). The left images are merged phase and fluorescence images. The middle image are only FITC fluorescence and right images are only Qdot fluorescence. A large amount of the full probe was bound and some internalized by the cells. Macrophages are known to nonspecifically internalize particles which contribute largely to internalization of the probe by these cells.</p> Full article ">Figure 8
<p>Fluorescence images of OVCAR3 cells after incubation with the full probe. (<b>Left</b>): Cells were incubated with regular DMEM media. (<b>Right</b>): Cells were incubated with media that had extra folic acid added (1 mM). The high concentration of free folic acid binds to the folate receptors blocking them from interacting with the folic acid bound to the probe.</p> Full article ">Figure 9
<p>Schematic representation of the overall design of the probe.</p> Full article ">
546 KiB  
Article
Size Effect of Ordered Mesoporous Carbon Nanospheres for Anodes in Li-Ion Battery
by Pei-Yi Chang, Kartick Bindumadhavan and Ruey-An Doong
Nanomaterials 2015, 5(4), 2348-2358; https://doi.org/10.3390/nano5042348 - 18 Dec 2015
Cited by 23 | Viewed by 8010
Abstract
The present work demonstrates the application of various sizes of ordered mesoporous carbon nanospheres (OMCS) with diameters of 46–130 nm as an active anode material for Li-ion batteries (LIB). The physical and chemical properties of OMCS have been evaluated by performing scanning electron [...] Read more.
The present work demonstrates the application of various sizes of ordered mesoporous carbon nanospheres (OMCS) with diameters of 46–130 nm as an active anode material for Li-ion batteries (LIB). The physical and chemical properties of OMCS have been evaluated by performing scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption analysis; small-angle scattering system (SAXS) and X-ray diffraction (XRD). The electrochemical analysis of using various sizes of OMCS as anode materials showed high capacity and rate capability with the specific capacity up to 560 mA·h·g−1 at 0.1 C after 85 cycles. In terms of performance at high current rate compared to other amorphous carbonaceous materials; a stable and extremely high specific capacity of 240 mA·h·g−1 at 5 C after 15 cycles was achieved. Such excellent performance is mainly attributed to the suitable particle size distribution of OMCS and intimate contact between OMCS and conductive additives; which can be supported from the TEM images. Results obtained from this study clearly indicate the excellence of size distribution of highly integrated mesoporous structure of carbon nanospheres for LIB application. Full article
(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)
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Figure 1
<p>Scanning electron microscopy (SEM) images of (<b>a</b>) OMCS<sub>7</sub>, (<b>b</b>) OMCS<sub>9</sub>, (<b>c</b>) and (<b>d</b>) OMCS<sub>11</sub> obtained by dilution of phenolic resol/F127 to different volumes followed by hydrothermal method and calcination at 700 °C in N<sub>2</sub> atmosphere.</p> Full article ">Figure 2
<p>Transmission electron microscopy (TEM) images of (<b>a</b>) OMCS<sub>7</sub>, (<b>b</b>) OMCS<sub>9</sub>, (<b>c</b>) OMCS<sub>11</sub>, and (<b>d</b>) small-angle scattering system (SAXS) patterns of OMCS<span class="html-italic"><sub>x</sub></span>.</p> Full article ">Figure 3
<p>(<b>a</b>) The N<sub>2</sub> adsorption-desorption isothermals and (<b>b</b>) pore size distributions of OMCS<span class="html-italic"><sub>x</sub></span>.</p> Full article ">Figure 4
<p>The Li-ion batteries (LIB) half cell performances of (<b>a</b>) discharge capacity and (<b>b</b>) coulombic efficiency of OMCS<span class="html-italic"><sub>x</sub></span> under various <span class="html-italic">C</span> rates from 0.1 <span class="html-italic">C</span> to 5 <span class="html-italic">C</span>.</p> Full article ">Figure 5
<p>(<b>a</b>) Galvanostatic discharge-charge profiles under various <span class="html-italic">C</span>-rate from 0.1 <span class="html-italic">C</span> to 5 <span class="html-italic">C</span>; and (<b>b</b>) cyclic voltammograms in the potential window of 0.01–3 V (<span class="html-italic">vs.</span> Li<sup>+</sup>/Li) at a scan rate of 0.1 mV·s<sup>−1</sup> of OMCS<sub>11</sub>.</p> Full article ">Figure 6
<p>TEM images of OMCS<sub>11</sub> electrodes (<b>a</b>) before and (<b>b</b>) after assigned charging-discharging processes under various <span class="html-italic">C</span>-rate from 0.1 <span class="html-italic">C</span> to 5 <span class="html-italic">C</span> for 85 cycles.</p> Full article ">
827 KiB  
Article
Facile and Eco-Friendly Synthesis of Finger-Like Co3O4 Nanorods for Electrochemical Energy Storage
by Shijiao Sun, Xiangyu Zhao, Meng Yang, Liqun Ma and Xiaodong Shen
Nanomaterials 2015, 5(4), 2335-2347; https://doi.org/10.3390/nano5042335 - 17 Dec 2015
Cited by 23 | Viewed by 5927
Abstract
Co3O4 nanorods were prepared by a facile hydrothermal method. Eco-friendly deionized water rather than organic solvent was used as the hydrothermal media. The as-prepared Co3O4 nanorods are composed of many nanoparticles of 30–50 nm in diameter, forming [...] Read more.
Co3O4 nanorods were prepared by a facile hydrothermal method. Eco-friendly deionized water rather than organic solvent was used as the hydrothermal media. The as-prepared Co3O4 nanorods are composed of many nanoparticles of 30–50 nm in diameter, forming a finger-like morphology. The Co3O4 electrode shows a specific capacitance of 265 F g−1 at 2 mV s−1 in a supercapacitor and delivers an initial specific discharge capacity as high as 1171 mAh g−1 at a current density of 50 mA g−1 in a lithium ion battery. Excellent cycling stability and electrochemical reversibility of the Co3O4 electrode were also obtained. Full article
(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)
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Figure 1

Figure 1
<p>X-ray diffraction (XRD) pattern of the as-prepared Co<sub>3</sub>O<sub>4</sub> nanorods.</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) Scanning electron microscopy (SEM) and (<b>c</b>,<b>d</b>) transmission electron microscopy (TEM) images of the as-prepared Co<sub>3</sub>O<sub>4</sub> nanorods.</p> Full article ">Figure 3
<p>N<sub>2</sub> adsorption-desorption isotherm and Barrett-Joyner-Halenda (BJH) pore size distribution (inset) curve of the as-prepared Co<sub>3</sub>O<sub>4</sub> nanorods.</p> Full article ">Figure 4
<p>Capacitive performance of the as-prepared Co<sub>3</sub>O<sub>4</sub> nanorods in a potential range of 0–0.45 V. (<b>a</b>) Cyclic voltammetric (CV) curve at a scan rate of 5 mV s<sup>−1</sup>; (<b>b</b>) CV curves at different scan rates; (<b>c</b>) peak current as a function of scan rate from (<b>b</b>); (<b>d</b>) rate dependent specific capacitance.</p> Full article ">Figure 5
<p>The lithium storage performance of the as-prepared Co<sub>3</sub>O<sub>4</sub> nanorods at a current density of 50 mA g<sup>−1</sup>. (<b>a</b>) The first three charge-discharge curves; (<b>b</b>) cycling performance; (<b>c</b>) rate performance.</p> Full article ">Figure 6
<p>(<b>a</b>) Enlarged Nyquist plot of the fresh Co<sub>3</sub>O<sub>4</sub> nanorod electrode at high frequency and Nyquist plot of the cycled electrode in the whole frequency region; the dot and the line are related to the experimental and fitting results, respectively; the inset is the Nyquist plot of the fresh electrode in the whole frequency region. (<b>b</b>) Equivalent circuit for the fresh and cycled electrodes; <span class="html-italic">R</span><sub>1</sub> represents the solution resistance (<span class="html-italic">R</span><sub>s</sub>) for both electrodes; <span class="html-italic">R</span><sub>2</sub> is the contact resistance (<span class="html-italic">R</span><sub>c</sub>) for the fresh electrode or the resistance caused by the SEI layer (<span class="html-italic">R</span><sub>SEI</sub>) for the cycled electrode; <span class="html-italic">R</span><sub>3</sub> corresponds to the Li<sup>+</sup> charge-transfer resistance (<span class="html-italic">R</span><sub>ct</sub>); CPE1 and CPE2 are constant phase elements; W represents the Warburg resistance.</p> Full article ">
788 KiB  
Article
Nanocarriers for DNA Vaccines: Co-Delivery of TLR-9 and NLR-2 Ligands Leads to Synergistic Enhancement of Proinflammatory Cytokine Release
by Johanna Poecheim, Simon Heuking, Livia Brunner, Christophe Barnier-Quer, Nicolas Collin and Gerrit Borchard
Nanomaterials 2015, 5(4), 2317-2334; https://doi.org/10.3390/nano5042317 - 17 Dec 2015
Cited by 11 | Viewed by 6425
Abstract
Adjuvants enhance immunogenicity of vaccines through either targeted antigen delivery or stimulation of immune receptors. Three cationic nanoparticle formulations were evaluated for their potential as carriers for a DNA vaccine, and muramyl dipeptide (MDP) as immunostimulatory agent, to induce and increase immunogenicity of [...] Read more.
Adjuvants enhance immunogenicity of vaccines through either targeted antigen delivery or stimulation of immune receptors. Three cationic nanoparticle formulations were evaluated for their potential as carriers for a DNA vaccine, and muramyl dipeptide (MDP) as immunostimulatory agent, to induce and increase immunogenicity of Mycobacterium tuberculosis antigen encoding plasmid DNA (pDNA). The formulations included (1) trimethyl chitosan (TMC) nanoparticles, (2) a squalene-in-water nanoemulsion, and (3) a mineral oil-in-water nanoemulsion. The adjuvant effect of the pDNA-nanocomplexes was evaluated by serum antibody analysis in immunized mice. All three carriers display a strong adjuvant effect, however, only TMC nanoparticles were capable to bias immune responses towards Th1. pDNA naturally contains immunostimulatory unmethylated CpG motifs that are recognized by Toll-like receptor 9 (TLR-9). In mechanistic in vitro studies, activation of TLR-9 and the ability to enhance immunogenicity by simultaneously targeting TLR-9 and NOD-like receptor 2 (NLR-2) was determined by proinflammatory cytokine release in RAW264.7 macrophages. pDNA in combination with MDP was shown to significantly increase proinflammatory cytokine release in a synergistic manner, dependent on NLR-2 activation. In summary, novel pDNA-Ag85A loaded nanoparticle formulations, which induce antigen specific immune responses in mice were developed, taking advantage of the synergistic combinations of TLR and NLR agonists to increase the adjuvanticity of the carriers used. Full article
(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)
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Figure 1

Figure 1
<p>Scanning electron microscopy (SEM) images of plain TMC nanoparticles alone (<b>a</b>) and loaded with pDNA (<b>A</b>), transmission electron microscopy (TEM) images of SWE06 alone (<b>b</b>) and loaded with pDNA (<b>B</b>), and TEM images of Cationorm<sup>®</sup> alone (<b>c</b>) and loaded with pDNA (<b>C</b>). The scale bars represent a size of 200 nm.</p> Full article ">Figure 1 Cont.
<p>Scanning electron microscopy (SEM) images of plain TMC nanoparticles alone (<b>a</b>) and loaded with pDNA (<b>A</b>), transmission electron microscopy (TEM) images of SWE06 alone (<b>b</b>) and loaded with pDNA (<b>B</b>), and TEM images of Cationorm<sup>®</sup> alone (<b>c</b>) and loaded with pDNA (<b>C</b>). The scale bars represent a size of 200 nm.</p> Full article ">Figure 2
<p>Immune responses in mice to pDNA (50 μg per dose) with/without TMC nanoparticles one week after the second booster injection (i.m.). Ag85A-specific serum immunoglobulin G (IgG) titers were analyzed by endpoint enzyme-linked immunosorbent assay (ELISA). (<b>A</b>) Bars represent mean <span class="html-italic">n</span> = 4 ± SEM, <b>*</b> <span class="html-italic">p</span> &lt; 0.05, compared to pDNA alone. (<b>B</b>,<b>C</b>) Corresponding average Log IgG2b/Log IgG1 and Log IgG2c/Log IgG1 ratios are indicative for the quality of the immune response, where values higher than 1 (dotted line) characterize Th1 biased immune responses.</p> Full article ">Figure 3
<p>Cell viability of RAW264.7 macrophages, detected with XTT reagent, after 24 h of incubation with the following formulations: unloaded TMC nanoparticles, SWE06 and Cationorm<sup>®</sup> (∘) and each nanoformulation loaded either with pDNA (∗), MDP (▲), or pDNA + MDP (⋄). Percentages above 80% (dotted line) were considered as minimum levels of acceptable viability.</p> Full article ">Figure 4
<p>Tumor necrosis factor-alpha (TNF-α) release from RAW264.7 murine macrophages on exposure to different stimulating agents: pDNA and MDP applied either alone or in combination in solution, or with TMC nanoparticles (TMC-NP), SWE06, and Cationorm<sup>®</sup>, respectively. Bars represent mean values (<span class="html-italic">n</span> = 3) ± SEM. pDNA loaded nanoformulations were compared with either pDNA alone (<b>*</b>) or with [pDNA + MDP] loaded nanoformulations (<b>*</b>), and [pDNA + MDP] in solution with [nanocarrier + pDNA + MDP] (x). Significant differences were indicated with <b>**</b> (<span class="html-italic">p</span> &lt; 0.01), <b>***</b> (<span class="html-italic">p</span> &lt; 0.001), and ns (not significant).</p> Full article ">Figure 5
<p>TNF-α release from RAW264.7 murine macrophages treated with pDNA and/or MDP and their inactive controls pCpGfree and/or D-MDP, respectively. The ligands were applied either in solution, as single components, or combined with TMC nanoparticles (TMC-NP), SWE06, or Cationorm<sup>®</sup>, respectively. Significantly reduced activity by control ligands compared to their active ligands are indicated with <b>**</b> (<span class="html-italic">p</span> &lt; 0.01), <b>***</b> (<span class="html-italic">p</span> &lt; 0.001), and <b>****</b> (<span class="html-italic">p</span> &lt; 0.0001).</p> Full article ">Figure 6
<p>TNF-α release from RAW264.7 murine macrophages treated with or without RIP2 tyrosine kinase blocker gefitinib. Stimulants were pDNA and MDP in combination, applied either in solution or with TMC nanoparticles, SWE06, or Cationorm<sup>®</sup>, respectively. Significantly reduced activity by receptor-interacting serine/threonine-protein kinase 2 (RIP2) blocking compared to unblocked NLR-2 pathway are indicated with <b>*</b> (<span class="html-italic">p</span> &lt; 0.05), <b>**</b> (<span class="html-italic">p</span> &lt; 0.01), and <b>***</b> (<span class="html-italic">p</span> &lt; 0.001).</p> Full article ">
1862 KiB  
Article
Mesoporous Silica Nanoparticles Loaded with Cisplatin and Phthalocyanine for Combination Chemotherapy and Photodynamic Therapy in vitro
by Juan L. Vivero-Escoto and Maram Elnagheeb
Nanomaterials 2015, 5(4), 2302-2316; https://doi.org/10.3390/nano5042302 - 16 Dec 2015
Cited by 55 | Viewed by 7959
Abstract
Mesoporous silica nanoparticles (MSNs) have been synthesized and loaded with both aluminum chloride phthalocyanine (AlClPc) and cisplatin as combinatorial therapeutics for treating cancer. The structural and photophysical properties of the MSN materials were characterized by different spectroscopic and microscopic techniques. Intracellular uptake and [...] Read more.
Mesoporous silica nanoparticles (MSNs) have been synthesized and loaded with both aluminum chloride phthalocyanine (AlClPc) and cisplatin as combinatorial therapeutics for treating cancer. The structural and photophysical properties of the MSN materials were characterized by different spectroscopic and microscopic techniques. Intracellular uptake and cytotoxicity were evaluated in human cervical cancer (HeLa) cells by confocal laser scanning microscopy (CLSM) and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays, respectively. The CLSM experiments showed that the MSN materials can be readily internalized in HeLa cells. The cytotoxic experiments demonstrated that, after light exposure, the combination of both AlClPc and cisplatin compounds in the same MSN platform potentiate the toxic effect against HeLa cells in comparison to the control AlClPc-MSN and cisplatin-MSN materials. These results show the potential of using MSN platforms as nanocarriers for combination photodynamic and chemotherapies to treat cancer. Full article
(This article belongs to the Special Issue Nanoparticles in Theranostics)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Nitrogen sorption isotherms of MSNs (<b>black</b>), AlClPc-MSNs (<b>blue</b>), cisplatin-MSNs (<b>red</b>), and AlClPc/cisplatin-MSNs (<b>green</b>).</p> Full article ">Figure 2
<p>(<b>a</b>) Scanning electron microscopy (SEM) micrograph of MSNs (Scale bar: 1 µm). Inset: close up of MSNs (scale bar: 100 nm). (<b>b</b>) Transmission electron microscopy (TEM) image of MSNs (scale bar: 20 nm).</p> Full article ">Figure 3
<p>UV-VIS spectra of AlClPc molecules (<b>black</b>) and AlClPc-MSNs (<b>gray</b>).</p> Full article ">Figure 4
<p>Singlet oxygen generation, without irradiation, by AlClPc-MSNs (<b>dark blue</b>), cisplatin-MSNs (<b>dark red</b>) and AlClPc/cisplatin-MSNs (<b>dark green</b>); and after irradiation, with red light, by AlClPc-MSNs (<b>light blue</b>), cisplatin-MSNs (<b>light red</b>), and AlClPc/cisplatin-MSNs (<b>light green</b>).</p> Full article ">Figure 5
<p>Confocal micrographs of HeLa cells incubated in the presence of 20 µg/mL of AlClPc-MSNs and AlClPc/cisplatin-MSNs for 4 h at 37 °C. (<b>a</b> and <b>d</b>) Red fluorescence from the internalized AlClPc-MSN and AlClPc/cisplatin-MSN materials; (<b>b</b> and <b>e</b>) DAPI-stained nuclei; and (<b>c</b> and <b>f</b>) overlapped image of DAPI-stained nuclei, red fluorescence, and DIC channel. White arrows indicate the localization of MSN materials. Scale bar = 20 μm.</p> Full article ">Figure 6
<p>Cytotoxicity of AlClPc-MSNs (<b>dark blue</b>), cisplatin-MSNs (<b>dark red</b>), AlClPc/cisplatin-MSNs (<b>dark green</b>) and physical mixture of cisplatin/AlClPc molecules (<b>dark orange</b>) under dark conditions. Phototoxicity of AlClPc-MSNs (<b>light blue</b>), cisplatin-MSNs (<b>light red</b>), AlClPc/cisplatin-MSNs (<b>light green</b>) and physical mixture of cisplatin/AlClPc molecules (<b>light orange</b>) after red light exposure (570–690 nm; 89 mW/cm<sup>2</sup>) for 20 min. Asterisk indicates <span class="html-italic">p</span> &lt; 0.05.</p> Full article ">
3186 KiB  
Article
Nanoscience Supporting the Research on the Negative Electrodes of Li-Ion Batteries
by Alain Mauger and Christian M. Julien
Nanomaterials 2015, 5(4), 2279-2301; https://doi.org/10.3390/nano5042279 - 16 Dec 2015
Cited by 17 | Viewed by 6569
Abstract
Many efforts are currently made to increase the limited capacity of Li-ion batteries using carbonaceous anodes. The way to reach this goal is to move to nano-structured material because the larger surface to volume ratio of particles and the reduction of the electron [...] Read more.
Many efforts are currently made to increase the limited capacity of Li-ion batteries using carbonaceous anodes. The way to reach this goal is to move to nano-structured material because the larger surface to volume ratio of particles and the reduction of the electron and Li path length implies a larger specific capacity. Additionally, nano-particles can accommodate such a dilatation/contraction during cycling, resulting in a calendar life compatible with a commercial use. In this review attention is focused on carbon, silicon, and Li4Ti5O12 materials, because they are the most promising for applications. Full article
(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Electrochemical performance of the doped hierarchically porous graphene electrodes. Reproduced with permission from [<a href="#B30-nanomaterials-05-02279" class="html-bibr">30</a>]. Copyright The American Chemical Society, 2013. (<b>a</b>) Cyclic voltammograms at a scan rate of 0.1 mV·s<sup>−1</sup>; (<b>b</b>) charge-discharge curves at 0.1 A·g<sup>−1</sup>; (<b>c</b>) capacity over cycling at different current densities; and (<b>d</b>) cycling and Coulombic efficiency at current density of 5 A·g<sup>−1</sup>.</p> Full article ">Figure 2
<p>Capacity retention of 500 Å thick n-Si film during charge/discharge cycling with 30 <span class="html-italic">C</span> rate charge/discharge in propylene carbonate containing 1 mol·L<sup>−1</sup> LiClO<sub>4</sub>. The scanning electron microscopy (SEM) image of the Si film is shown after 1000 cycles. Reproduced with permission from [<a href="#B54-nanomaterials-05-02279" class="html-bibr">54</a>]. Copyright Elsevier, 2004.</p> Full article ">Figure 3
<p>Half-cell lithium ion battery based on Si anodes, produced by microfabrication. Reproduced with permission from [<a href="#B58-nanomaterials-05-02279" class="html-bibr">58</a>]. Copyright Wiley, 2012. (<b>A</b>) Schematic steps to fabricate the Si anodes on Poly(dimethylsiloxane) (PDMS) substrates; (<b>B</b>) A SEM image of Si anode on PDMS; (<b>C</b>) Optical images of fabricated anode before assembling; and (<b>D</b>) an illustration of the battery cell assembly.</p> Full article ">Figure 4
<p>Electrochemical performance of a battery using porous silicon nanowires as the anode and lithium metal as the current collector (SEM and transmission electron microscopy (TEM) images of the nanowires are shown in <a href="#nanomaterials-05-02279-f005" class="html-fig">Figure 5</a>). Reproduced with permission from [<a href="#B32-nanomaterials-05-02279" class="html-bibr">32</a>]. Copyright Wiley, 2012. Si mass loading was around 0.3 mg·cm<sup>−2</sup>. (<b>a</b>) Charge/discharge profile within a voltage window of 0.01−2 V <span class="html-italic">vs.</span> Li<sup>0</sup>/Li<sup>+</sup> for the first cycle at a current rate of 0.4 A·g<sup>−1</sup> and the 50th, 100th, and 200th cycles at 2 A·g<sup>−1</sup>; (<b>b</b>) cyclic voltammetry curves of porous silicon nanowire electrode for the first and second cycles using a voltage window 0.01−2 V at rate of 0.1 mV·s<sup>−1</sup>; (<b>c</b>) charge/discharge capacity and coulombic efficiency of porous silicon nanowire electrode at current rates of 0.6, 1.2, 2.4, 3.6, 4.8, and 9.6 A·g<sup>−1</sup>; (<b>d</b>) charge/discharge capacity of a porous silicon nanowire electrode at current rates of 2, 4, and 18 A·g<sup>−1</sup> for 250 cycles; and (<b>e</b>) charge/discharge capacity of a porous silicon nanowire electrode at current rates of 2 A·g<sup>−1</sup> (0.5 <span class="html-italic">C</span>) and 4 A·g<sup>−1</sup> (1 <span class="html-italic">C</span>) with an additional 2000 cycles.</p> Full article ">Figure 4 Cont.
<p>Electrochemical performance of a battery using porous silicon nanowires as the anode and lithium metal as the current collector (SEM and transmission electron microscopy (TEM) images of the nanowires are shown in <a href="#nanomaterials-05-02279-f005" class="html-fig">Figure 5</a>). Reproduced with permission from [<a href="#B32-nanomaterials-05-02279" class="html-bibr">32</a>]. Copyright Wiley, 2012. Si mass loading was around 0.3 mg·cm<sup>−2</sup>. (<b>a</b>) Charge/discharge profile within a voltage window of 0.01−2 V <span class="html-italic">vs.</span> Li<sup>0</sup>/Li<sup>+</sup> for the first cycle at a current rate of 0.4 A·g<sup>−1</sup> and the 50th, 100th, and 200th cycles at 2 A·g<sup>−1</sup>; (<b>b</b>) cyclic voltammetry curves of porous silicon nanowire electrode for the first and second cycles using a voltage window 0.01−2 V at rate of 0.1 mV·s<sup>−1</sup>; (<b>c</b>) charge/discharge capacity and coulombic efficiency of porous silicon nanowire electrode at current rates of 0.6, 1.2, 2.4, 3.6, 4.8, and 9.6 A·g<sup>−1</sup>; (<b>d</b>) charge/discharge capacity of a porous silicon nanowire electrode at current rates of 2, 4, and 18 A·g<sup>−1</sup> for 250 cycles; and (<b>e</b>) charge/discharge capacity of a porous silicon nanowire electrode at current rates of 2 A·g<sup>−1</sup> (0.5 <span class="html-italic">C</span>) and 4 A·g<sup>−1</sup> (1 <span class="html-italic">C</span>) with an additional 2000 cycles.</p> Full article ">Figure 5
<p>(<b>a</b>) SEM and (<b>b</b>) TEM images of porous Si nanowires; (<b>c</b>,<b>d</b>) High-resolution transmission electron microscopy (HRTEM) image of a nanowire in (<b>b</b>), leading to the results in <a href="#nanomaterials-05-02279-f004" class="html-fig">Figure 4</a>. Reproduced with permission from [<a href="#B32-nanomaterials-05-02279" class="html-bibr">32</a>]. Copyright Wiley, 2012.</p> Full article ">Figure 6
<p>Top: SEM images of the silicon nanowires (Si Nws) (<b>a</b>) with and (<b>b</b>) without copper-coating after 100 cycles at the rate of 0.5 <span class="html-italic">C</span>; Bottom: capacity–cycle number curves for Si nanowires (<b>a</b>) without and (<b>b</b>) with copper-coating at different rates. Reproduced with permission from [<a href="#B97-nanomaterials-05-02279" class="html-bibr">97</a>]. Copyright Elsevier, 2011.</p> Full article ">Figure 7
<p>SEM images for nanocrystalline Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> at different magnifications synthesized by combustion method. Reproduced with permission from [<a href="#B110-nanomaterials-05-02279" class="html-bibr">110</a>]. Copyright American Chemical Society, 2013.</p> Full article ">Figure 8
<p>Capacity-voltage profile for nanocrystalline Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> (SEM images in <a href="#nanomaterials-05-02279-f007" class="html-fig">Figure 7</a>) synthesized by the combustion method at different <span class="html-italic">C</span>-rates. Inset shows capacity voltage profile for bulk Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> prepared by the solid-state method. Reproduced with permission from [<a href="#B108-nanomaterials-05-02279" class="html-bibr">108</a>]. Copyright Elsevier, 2014.</p> Full article ">
1981 KiB  
Article
Simulation of the Impact of Si Shell Thickness on the Performance of Si-Coated Vertically Aligned Carbon Nanofiber as Li-Ion Battery Anode
by Susobhan Das, Jun Li and Rongqing Hui
Nanomaterials 2015, 5(4), 2268-2278; https://doi.org/10.3390/nano5042268 - 15 Dec 2015
Cited by 4 | Viewed by 5356
Abstract
Micro- and nano-structured electrodes have the potential to improve the performance of Li-ion batteries by increasing the surface area of the electrode and reducing the diffusion distance required by the charged carriers. We report the numerical simulation of Lithium-ion batteries with the anode [...] Read more.
Micro- and nano-structured electrodes have the potential to improve the performance of Li-ion batteries by increasing the surface area of the electrode and reducing the diffusion distance required by the charged carriers. We report the numerical simulation of Lithium-ion batteries with the anode made of core-shell heterostructures of silicon-coated carbon nanofibers. We show that the energy capacity can be significantly improved by reducing the thickness of the silicon anode to the dimension comparable or less than the Li-ion diffusion length inside silicon. The results of simulation indicate that the contraction of the silicon electrode thickness during the battery discharge process commonly found in experiments also plays a major role in the increase of the energy capacity. Full article
(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)
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<p>Schematic of Si coating on vertically aligned carbon nanofibers (<b>a</b>) before and (<b>b</b>) after Lithium insertion, and scanning electron microscopic images showing of the morphology of Si shells in (<b>c</b>) in the non-lithiated condition with an average tip diameter of ~460 nm and (<b>d</b>) in lithiated conditions with the average tip diameter expanded to ~1.5 µm. All images were taken at 45° perspective view. All scale bars are 1.0 µm. (Reproduced with permission of [<a href="#B16-nanomaterials-05-02268" class="html-bibr">16</a>]. Copyright The Royal Society of Chemistry, 2013).</p> Full article ">Figure 2
<p>Simulation Schematic (inset shows details of the silicon anode coated on carbon nanofiber (CNF)).</p> Full article ">Figure 3
<p>(<b>a</b>) Discharge graph with <span class="html-italic">L</span> = 5 µm, <span class="html-italic">H</span> = 30 µm, and a constant current density of 4000 A/m<sup>2</sup> without considering thickness contraction of silicon layer. Dotted line: calculated with time-sectioning and redistribution of electrolyte salt concentration at the beginning of each time window. Solid line: calculated with standard COMSOL [<a href="#B18-nanomaterials-05-02268" class="html-bibr">18</a>] procedure without time-sectioning. (<b>b</b>) Same condition as (<b>a</b>) but with thickness contraction of silicon layer indicated by the right axis. Dotted line: calculated with time-sectioning, redistribution of electrolyte salt concentration and thickness reduction at the beginning of each time window. Solid line: a smoothed best fit to the dotted line.</p> Full article ">Figure 4
<p>Distribution of electrolyte salt concentration within silicon anode at different times of discharge process (<b>a</b>) without and (<b>b</b>) with thickness contraction.</p> Full article ">Figure 5
<p>Discharge graph calculated with different thickness <span class="html-italic">L</span> of silicon anode and with a constant discharge current density of 4000 A/m<sup>2</sup>, without (<b>a</b>) and with (<b>b</b>) the contraction of silicon anode.</p> Full article ">Figure 6
<p>Discharge graph calculated with different thickness of silicon anode and with a constant discharge current density of 400 A/m<sup>2</sup>, (<b>a</b>) without and (<b>b</b>) with the contraction of silicon anode.</p> Full article ">Figure 7
<p>Normalized discharge capacity calculated with different thickness of silicon anode with (open triangles) and without (stars) considering the contraction of silicon anode. Discharge current densities used in the simulations are (<b>a</b>) 4000 A/m<sup>2</sup> and (<b>b</b>) 400 A/m<sup>2</sup>.</p> Full article ">Figure 8
<p>(<b>a</b>) Triangle shaped silicon anode (shaded area) coated on 30 µm long CNF, and normalized distribution of electrolyte salt concentration calculated at within silicon anode at different times of discharge process (<b>a</b>) without and (<b>b</b>) with thickness contraction 250 s after the start of discharging at three different cross sections along the CNF (3 µm, 15 µm, and 24 µm, respectively, from the bottom). (<b>b</b>) Discharge graph calculated with a constant discharge current density of 4000 A/m<sup>2</sup> for triangle anode shape (solid line) and uniform anode thickness with the same silicon volume.</p> Full article ">
2337 KiB  
Review
Electric Field-Responsive Mesoporous Suspensions: A Review
by Seung Hyuk Kwon, Shang Hao Piao and Hyoung Jin Choi
Nanomaterials 2015, 5(4), 2249-2267; https://doi.org/10.3390/nano5042249 - 15 Dec 2015
Cited by 26 | Viewed by 7329
Abstract
This paper briefly reviews the fabrication and electrorheological (ER) characteristics of mesoporous materials and their nanocomposites with conducting polymers under an applied electric field when dispersed in an insulating liquid. Smart fluids of electrically-polarizable particles exhibit a reversible and tunable phase transition from [...] Read more.
This paper briefly reviews the fabrication and electrorheological (ER) characteristics of mesoporous materials and their nanocomposites with conducting polymers under an applied electric field when dispersed in an insulating liquid. Smart fluids of electrically-polarizable particles exhibit a reversible and tunable phase transition from a liquid-like to solid-like state in response to an external electric field of various strengths, and have potential applications in a variety of active control systems. The ER properties of these mesoporous suspensions are explained further according to their dielectric spectra in terms of the flow curve, dynamic moduli, and yield stress. Full article
(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)
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<p>Schematic diagram of the electrorheological (ER) phenomenon under an applied electric field.</p> Full article ">Figure 2
<p>(<b>a</b>) Proposed schematic diagram of conducting polymer/Mobil Composition of Matter No. 41 (MCM-41) nanocomposite particles (Reproduced with permission from [<a href="#B58-nanomaterials-05-02249" class="html-bibr">58</a>]. Copyright Elsevier, 2009); (<b>b</b>) in which the conducting polymer can be polyaniline (Reproduced with permission from [<a href="#B56-nanomaterials-05-02249" class="html-bibr">56</a>]. Copyright American Chemical Society, 2004).</p> Full article ">Figure 3
<p>(<b>a</b>) Scanning electron microscopy (SEM) and (<b>b</b>) transmission electron microscopy (TEM) image of MCM-41 particles (Reproduced with permission from [<a href="#B47-nanomaterials-05-02249" class="html-bibr">47</a>]. Copyright Elsevier, 2000); (<b>c</b>) SEM images of copolyaniline (COPANI)/MCM-41 particles (Reproduced with permission from [<a href="#B58-nanomaterials-05-02249" class="html-bibr">58</a>]. Copyright Elsevier, 2009); (<b>d</b>) PPy/MCM-41 particles (Reproduced with permission from [<a href="#B60-nanomaterials-05-02249" class="html-bibr">60</a>]. Copyright Elsevier, 2008).</p> Full article ">Figure 4
<p>(<b>a</b>) X-Ray diffraction (XRD) patterns of pure and swollen MCM-41 (Reproduced with permission from [<a href="#B57-nanomaterials-05-02249" class="html-bibr">57</a>]. Copyright Elsevier, 2005); (<b>b</b>) polymer modification MCM-41 particles (Reproduced with permission from [<a href="#B55-nanomaterials-05-02249" class="html-bibr">55</a>]. Copyright Elsevier, 2008).</p> Full article ">Figure 5
<p>N<sub>2</sub> adsorption-desorption isotherm plots before polymerization, MCM-41 (●) and swollen MCM-41 (▼); after polymerization, COPANI/swollen MCM-41 (▲) and PANI/MCM-41 (■), respectively (Reproduced with permission from [<a href="#B58-nanomaterials-05-02249" class="html-bibr">58</a>]. Copyright Elsevier, 2009).</p> Full article ">Figure 6
<p>(<b>a</b>) Shear stress curve as a function of the shear rate for PPy/MCM-41 ER fluids (triangle) and MCM-41-based ER fluid (circle) under different applied electric fields. (Reproduced with permission from [<a href="#B78-nanomaterials-05-02249" class="html-bibr">78</a>]. Copyright Elsevier, 2006); (<b>b</b>) Fitting curve of the model equations to shear stress curves for PPy/MCM-41 nanocomposite-based ER fluids under three different electric field strengths (Reproduced with permission from [<a href="#B59-nanomaterials-05-02249" class="html-bibr">59</a>]. Copyright Elsevier, 2010).</p> Full article ">Figure 7
<p>(<b>a</b>) Dynamic yield stress of MCM-41-based ER fluids at four different electric field strengths; (<b>b</b>) Dynamic yield stress of PPy/MCM-41-based ER fluids at seven different electric field strengths (Reproduced with permission from [<a href="#B59-nanomaterials-05-02249" class="html-bibr">59</a>]. Copyright Elsevier, 2010); (<b>c</b>) <math display="inline"> <semantics> <mover accent="true"> <mi mathvariant="sans-serif">τ</mi> <mo>^</mo> </mover> </semantics> </math> <span class="html-italic">vs.</span> <math display="inline"> <semantics> <mover accent="true"> <mi>E</mi> <mo stretchy="false">^</mo> </mover> </semantics> </math> for pure MCM-41 and PPy/MCM-41-based ER fluids. The solid line is drawn with Equation (5).</p> Full article ">Figure 8
<p>(<b>a</b>) Strain amplitude sweep of PANI/MCM-41 particles; (<b>b</b>) Angular frequency sweep of PANI/MCM-41 particle under 1 (■) and 2 (●) kV/mm using a strain of 3 × 10<sup>−5</sup>: Storage modulus (closed) and loss modulus (open) (Reproduced with permission from [<a href="#B56-nanomaterials-05-02249" class="html-bibr">56</a>]. Copyright American Chemical Society, 2004).</p> Full article ">Figure 9
<p>(<b>a</b>) Dielectric spectra (permittivity <span class="html-italic">versus</span> frequency); (<b>b</b>) Cole-Cole plot for each ER fluid (Reproduced with permission from [<a href="#B56-nanomaterials-05-02249" class="html-bibr">56</a>]. Copyright American Chemical Society, 2004).</p> Full article ">
1539 KiB  
Review
Magnetic Nanoparticles Cross the Blood-Brain Barrier: When Physics Rises to a Challenge
by Maria Antònia Busquets, Alba Espargaró, Raimon Sabaté and Joan Estelrich
Nanomaterials 2015, 5(4), 2231-2248; https://doi.org/10.3390/nano5042231 - 11 Dec 2015
Cited by 67 | Viewed by 9544
Abstract
The blood-brain barrier is a physical and physiological barrier that protects the brain from toxic substances within the bloodstream and helps maintain brain homeostasis. It also represents the main obstacle in the treatment of many diseases of the central nervous system. Among the [...] Read more.
The blood-brain barrier is a physical and physiological barrier that protects the brain from toxic substances within the bloodstream and helps maintain brain homeostasis. It also represents the main obstacle in the treatment of many diseases of the central nervous system. Among the different approaches employed to overcome this barrier, the use of nanoparticles as a tool to enhance delivery of therapeutic molecules to the brain is particularly promising. There is special interest in the use of magnetic nanoparticles, as their physical characteristics endow them with additional potentially useful properties. Following systemic administration, a magnetic field applied externally can mediate the capacity of magnetic nanoparticles to permeate the blood-brain barrier. Meanwhile, thermal energy released by magnetic nanoparticles under the influence of radiofrequency radiation can modulate blood-brain barrier integrity, increasing its permeability. In this review, we present the strategies that use magnetic nanoparticles, specifically iron oxide nanoparticles, to enhance drug delivery to the brain. Full article
(This article belongs to the Special Issue Nanoparticles in Theranostics)
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<p>Magnetic regimes of ferromagnetic materials as a function of their size (superparamagnetic, single domain, multidomain).</p> Full article ">Figure 2
<p>After disrupting the blood-brain barrier (BBB), nanoparticles (NPs) can accumulate at the tumor site. Receptor-mediated endocytosis of the functionalized NPs by cells overexpressing a receptor can retain NPs inside the tumor.</p> Full article ">Figure 3
<p>Cellular model for checking the passage of drugs or NPs across the BBB. The Transwell filter consists of a porous membrane support submerged in a culture medium. Two different Transwell co-culture modes exist: non-contact and contact culture. In non-contact culture, the cells (for instance, brain endothelial cells and astrocytes) are co-cultured in two different compartments (insert membrane in well). In contact culture, astrocytes are first seeded onto the abluminal side of the inverted Transwell filter, and after adhering, the filter is flipped back, and the astrocytes are cultured for 2 days. At the end of the second day, brain cells are seeded onto the luminal side of the Transwell filter and co-cultured with astrocytes for an additional 3–4 days. The number of NPs is determined in both compartments. Superparamagnetic IONs (SPIONs) are depicted as red dots. The passage through the BBB model can be mediated by the effect of a magnet located underneath the plate.</p> Full article ">Figure 4
<p>Magnetically vectored magnetic nanoparticles (MNPs) accumulate in the brain. (<b>A</b>) A small magnet was implanted in the right hemisphere of the brains of mice by stereotactic injection. (Blue represents the inserted magnet and green shade represents MNPs in cartoon). One week after implantation, MNPs were administered by IV injection. Confocal analysis demonstrated accumulation of the MNPs in the ipsilateral hemisphere, whereas a background level of MNPs was found in the contralateral hemisphere. Scale bar: 500 μm. (<b>B</b>) Confocal analysis of coronal sections of brain demonstrated enrichment of the MNPs near the magnet. Scale bar: 100 μm. Reproduced with permission of [<a href="#B59-nanomaterials-05-02231" class="html-bibr">59</a>]. Copyright Elsevier Science, 2012.</p> Full article ">
3462 KiB  
Article
Structural and Morphological Tuning of LiCoPO4 Materials Synthesized by Solvo-Thermal Methods for Li-Cell Applications
by Jessica Manzi, Mariangela Curcio and Sergio Brutti
Nanomaterials 2015, 5(4), 2212-2230; https://doi.org/10.3390/nano5042212 - 10 Dec 2015
Cited by 23 | Viewed by 5920
Abstract
Olivine-type lithium metal phosphates (LiMPO4) are promising cathode materials for lithium-ion batteries. LiFePO4 (LFP) is commonly used in commercial Li-ion cells but the Fe3+/Fe2+ couple can be usefully substituted with Mn3+/Mn2+, Co3+ [...] Read more.
Olivine-type lithium metal phosphates (LiMPO4) are promising cathode materials for lithium-ion batteries. LiFePO4 (LFP) is commonly used in commercial Li-ion cells but the Fe3+/Fe2+ couple can be usefully substituted with Mn3+/Mn2+, Co3+/Co2+, or Ni3+/Ni2+, in order to obtain higher redox potentials. In this communication we report a systematic analysis of the synthesis condition of LiCoPO4 (LCP) using a solvo-thermal route at low temperature, the latter being a valuable candidate to overcome the theoretical performances of LFP. In fact, LCP shows higher working potential (4.8 V vs. 3.6 V) compared to LFP and similar theoretical capacity (167 mAh·g−1). Our goal is to show the effect of the synthesis condition of the ability of LCP to reversibly cycle lithium in electrochemical cells. LCP samples have been prepared through a solvo-thermal method in aqueous-non aqueous solvent blends. Different Co2+ salts have been used to study the effect of the anion on the crystal growth as well as the effect of solution acidity, temperature and reaction time. Materials properties have been characterized by Fast-Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopies. The correlation between structure/morphology and electrochemical performances has been investigated by galvanostatic charge-discharge cycles. Full article
(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)
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<p>Schematic diagram of the synthesis route of LiCoPO<sub>4</sub> (LCP).</p> Full article ">Figure 2
<p>X-ray diffraction (XRD) patterns of all the samples obtained starting from the reagent ratios LiOH:LiH<sub>2</sub>PO<sub>4</sub>:CoSO<sub>4</sub> ranging from 0:1:1 to 4:1:1. The red patterns correspond to the LCP reference diffractograms ((*) indicate peaks from impurities) whereas black patterns correspond to other reaction products. All materials have been obtained at 240 °C with solvo-thermal treatments of 5 h.</p> Full article ">Figure 3
<p>XRD patterns of the samples obtained starting from the reagent ratio LiOH:LiH<sub>2</sub>PO<sub>4</sub>:CoSO<sub>4</sub> = 2:1:1 at 240 °C for different reaction time. The red patterns correspond to the LCP reference diffractograms whereas black patterns correspond to other reaction products.</p> Full article ">Figure 4
<p>Fast-Fourier Transform infrared spectroscopy (FTIR) spectra of the samples obtained starting from the reagent ratios LiOH:LiH<sub>2</sub>PO<sub>4</sub>:CoSO<sub>4</sub> = 2:1:1 at 240 °C for different reaction time. The red spectra correspond to the LCP reference one from reference [<a href="#B6-nanomaterials-05-02212" class="html-bibr">6</a>] whereas black patterns correspond to other reaction intermediates.</p> Full article ">Figure 5
<p>Scanning electron microscopy (SEM) micrographs of the LCP phase-pure samples obtained at 240 °C from the reagent ratio LiOH:LiH<sub>2</sub>PO<sub>4</sub>:CoSO<sub>4</sub> = 2:1:1 after a reaction time of 5 h ((<b>a</b>) panel) and 10 h ((<b>b</b>)panel).</p> Full article ">Figure 5 Cont.
<p>Scanning electron microscopy (SEM) micrographs of the LCP phase-pure samples obtained at 240 °C from the reagent ratio LiOH:LiH<sub>2</sub>PO<sub>4</sub>:CoSO<sub>4</sub> = 2:1:1 after a reaction time of 5 h ((<b>a</b>) panel) and 10 h ((<b>b</b>)panel).</p> Full article ">Figure 6
<p>Evolution of the surface area of the LCP samples prepared at 240 °C from the reagent ratio LiOH:LiH<sub>2</sub>PO<sub>4</sub>:CoSO<sub>4</sub> = 2:1:1. Data from samples crystallized in a LCP olivine lattice falls into the red rectangle.</p> Full article ">Figure 7
<p>SEM micrographs of the materials prepared at (<b>a</b>) 200, (<b>b</b>) 220, and (<b>c</b>) 240 °C in acidic pH conditions.</p> Full article ">Figure 7 Cont.
<p>SEM micrographs of the materials prepared at (<b>a</b>) 200, (<b>b</b>) 220, and (<b>c</b>) 240 °C in acidic pH conditions.</p> Full article ">Figure 8
<p>SEM micrographs of the prepared LiCoPO<sub>4</sub> powders: (<b>a</b>) nitrate; (<b>b</b>) sulfate; (<b>c</b>) acetate; and (<b>d</b>) carbonate.</p> Full article ">Figure 9
<p>Lithium de-insertion/insertion curves from galvanostatic cycling of the LCP materials.</p> Full article ">Figure 10
<p>Cycling performance (charge capacities) of the LCP-07 material prepared at 220 °C under moderately-acidic conditions for 15 h.</p> Full article ">
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Article
Hydrothermal Synthesis of Ultrasmall Pt Nanoparticles as Highly Active Electrocatalysts for Methanol Oxidation
by Wenhai Ji, Weihong Qi, Shasha Tang, Hongcheng Peng and Siqi Li
Nanomaterials 2015, 5(4), 2203-2211; https://doi.org/10.3390/nano5042203 - 8 Dec 2015
Cited by 37 | Viewed by 7484
Abstract
Ultrasmall nanoparticles, with sizes in the 1–3 nm range, exhibit unique properties distinct from those of free molecules and larger-sized nanoparticles. Demonstrating that the hydrothermal method can serve as a facile method for the synthesis of platinum nanoparticles, we successfully synthesized ultrasmall Pt [...] Read more.
Ultrasmall nanoparticles, with sizes in the 1–3 nm range, exhibit unique properties distinct from those of free molecules and larger-sized nanoparticles. Demonstrating that the hydrothermal method can serve as a facile method for the synthesis of platinum nanoparticles, we successfully synthesized ultrasmall Pt nanoparticles with an average size of 2.45 nm, with the aid of poly(vinyl pyrrolidone) (PVP) as reducing agents and capping agents. Because of the size effect, these ultrasmall Pt nanoparticles exhibit a high activity toward the methanol oxidation reaction. Full article
(This article belongs to the Special Issue Nanoparticles for Catalysis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>,<b>b</b>) Typical transmission electron microscope (TEM) images of ultrasmall Pt nanoparticles at different magnification and (<b>c</b>,<b>d</b>) high-resolution TEM image and the corresponding size distributions of the samples.</p> Full article ">Figure 2
<p>Powder X-Ray diffraction (XRD) pattern of ultrasmall Pt nanoparticles.</p> Full article ">Figure 3
<p>(<b>a</b>) TEM images of Pt ultrasmall nanoparticles (USNPs) supported on Vulcan XC-72 carbon; (<b>b</b>) Cyclic voltammetry (CV) curves of Pt electrocatalysts in N<sub>2</sub>-saturated 0.5 M H<sub>2</sub>SO<sub>4</sub> with a scan rate of 50 mV·s<sup>−1</sup>; (<b>c</b>) CV curves at a scan rate of 50 mV·s<sup>−1</sup> with different Pt electrocatalysts in 0.5 M H<sub>2</sub>SO<sub>4</sub> + 0.5 M CH<sub>3</sub>OH; (<b>d</b>) Amperometric <span class="html-italic">i</span>-<span class="html-italic">t</span> curves of Pt electrocatalysts in 0.5 M H<sub>2</sub>SO<sub>4</sub> + 0.5 M CH<sub>3</sub>OH solution at 0.6 V (<span class="html-italic">vs.</span> saturated calomel electrode (SCE)).</p> Full article ">Figure 4
<p>Formulas of OH-terminated poly(vinyl pyrrolidone) (PVP) and the structural variation in the effect of PtCl<sub>6</sub><sup>2−</sup> ions.</p> Full article ">
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Article
Morphological, Chemical Surface, and Diffusive Transport Characterizations of a Nanoporous Alumina Membrane
by María I. Vázquez, Virgina Romero, Victor Vega, Javier García, Victor M. Prida, Blanca Hernando and Juana Benavente
Nanomaterials 2015, 5(4), 2192-2202; https://doi.org/10.3390/nano5042192 - 5 Dec 2015
Cited by 15 | Viewed by 4771
Abstract
Synthesis of a nanoporous alumina membrane (NPAM) by the two-step anodization method and its morphological and chemical surface characterization by analyzing Scanning Electron Microscopy (SEM) micrographs and X-Ray Photoelectron Spectroscopy (XPS) spectra is reported. Influence of electrical and diffusive effects on the NaCl [...] Read more.
Synthesis of a nanoporous alumina membrane (NPAM) by the two-step anodization method and its morphological and chemical surface characterization by analyzing Scanning Electron Microscopy (SEM) micrographs and X-Ray Photoelectron Spectroscopy (XPS) spectra is reported. Influence of electrical and diffusive effects on the NaCl transport across the membrane nanopores is determined from salt diffusion measurements performed with a wide range of NaCl concentrations, which allows the estimation of characteristic electrochemical membrane parameters such as the NaCl diffusion coefficient and the concentration of fixed charges in the membrane, by using an appropriated model and the membrane geometrical parameters (porosity and pore length). These results indicate a reduction of ~70% in the value of the NaCl diffusion coefficient through the membrane pores with respect to solution. The transport number of ions in the membrane pores (Na+ and Cl−, respectively) were determined from concentration potential measurements, and the effect of concentration-polarization at the membrane surfaces was also considered by comparing concentration potential values obtained with stirred solutions (550 rpm) and without stirring. From both kinds of results, a value higher than 0.05 M NaCl for the feed solution seems to be necessary to neglect the contribution of electrical interactions in the diffusive transport. Full article
(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)
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<p>Scanning Electron Microscopy (SEM) micrographs of both membrane surfaces, (<b>a</b>) and (<b>b</b>), and cross-section (<b>c</b>) of the Al-O<span class="html-italic">x</span> nanoporous alumina membrane (NPAM).</p> Full article ">Figure 2
<p>(<b>a</b>) Time evolution of solutions concentrations for <span class="html-italic">C<sub>f</sub></span> = 0.01 M (o) and <span class="html-italic">C<sub>f</sub></span> = 0.1 M (◊); (<b>b</b>) Variation of diffusive permeability in the membrane with NaCl feed concentration.</p> Full article ">Figure 3
<p>(<b>a</b>) Concentration potentials <span class="html-italic">versus</span> C<sub>2</sub> solution concentration for the studied Al-O<span class="html-italic">x</span> NPAM for both opposite external and solution stirring conditions; (<b>b</b>) Cation (<span class="html-italic">t</span><sub>+</sub> = <span class="html-italic">t</span><sub>Na+</sub>) transport number as a function of the average concentration C<sub>avg</sub>. Dense symbols: stirred solutions; open symbols: non-stirred solutions. Solution cation transport number: dot-dashed line.</p> Full article ">
2586 KiB  
Article
Utilization of Enzyme-Immobilized Mesoporous Silica Nanocontainers (IBN-4) in Prodrug-Activated Cancer Theranostics
by Bau-Yen Hung, Yaswanth Kuthati, Ranjith Kumar Kankala, Shravankumar Kankala, Jin-Pei Deng, Chen-Lun Liu and Chia-Hung Lee
Nanomaterials 2015, 5(4), 2169-2191; https://doi.org/10.3390/nano5042169 - 4 Dec 2015
Cited by 40 | Viewed by 8623
Abstract
To develop a carrier for use in enzyme prodrug therapy, Horseradish peroxidase (HRP) was immobilized onto mesoporous silica nanoparticles (IBN-4: Institute of Bioengineering and Nanotechnology), where the nanoparticle surfaces were functionalized with 3-aminopropyltrimethoxysilane and further conjugated with glutaraldehyde. Consequently, the enzymes could be [...] Read more.
To develop a carrier for use in enzyme prodrug therapy, Horseradish peroxidase (HRP) was immobilized onto mesoporous silica nanoparticles (IBN-4: Institute of Bioengineering and Nanotechnology), where the nanoparticle surfaces were functionalized with 3-aminopropyltrimethoxysilane and further conjugated with glutaraldehyde. Consequently, the enzymes could be stabilized in nanochannels through the formation of covalent imine bonds. This strategy was used to protect HRP from immune exclusion, degradation and denaturation under biological conditions. Furthermore, immobilization of HRP in the nanochannels of IBN-4 nanomaterials exhibited good functional stability upon repetitive use and long-term storage (60 days) at 4 °C. The generation of functionalized and HRP-immobilized nanomaterials was further verified using various characterization techniques. The possibility of using HRP-encapsulated IBN-4 materials in prodrug cancer therapy was also demonstrated by evaluating their ability to convert a prodrug (indole-3- acetic acid (IAA)) into cytotoxic radicals, which triggered tumor cell apoptosis in human colon carcinoma (HT-29 cell line) cells. A lactate dehydrogenase (LDH) assay revealed that cells could be exposed to the IBN-4 nanocomposites without damaging their membranes, confirming apoptotic cell death. In summary, we demonstrated the potential of utilizing large porous mesoporous silica nanomaterials (IBN-4) as enzyme carriers for prodrug therapy. Full article
(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)
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<p>Schematic representation of enzyme prodrug therapy using IBN-4-HRP nanocomposites in the presence of indole-3-acetic acid and the resultant cell apoptosis (<b>1</b>. Skatolyl radical and <b>2</b>. Peroxyl radical).</p> Full article ">Figure 2
<p>Transmission electron microscopic images of IBN-4 nanoparticles: (<b>a</b>) As-synthesized IBN-4, (<b>b</b>) IBN-4-extracted, (<b>c</b>) IBN-4-NH<sub>2</sub>, and (<b>d</b>) IBN-4-HRP.</p> Full article ">Figure 3
<p>(<b>A</b>) Nitrogen adsorption–desorption isotherms of (<b>a</b>) as-synthesized IBN-4, (<b>b</b>) IBN-4 extracted, (<b>c</b>) IBN-4-NH<sub>2</sub> and (<b>d</b>) IBN-4-HRP. Corresponding pore size distribution plots are shown in the inset figure. (<b>B</b>) Thermogravimetric analysis curves of (<b>a</b>) as-synthesized IBN-4; (<b>b</b>) IBN-4 extracted, (<b>c</b>) IBN-4-NH<sub>2</sub>, (<b>d</b>) IBN-4-NH-GA and (<b>e</b>) IBN-4-HRP.</p> Full article ">Figure 4
<p>Fourier transform infrared spectroscopy (FT-IR) spectra of the (<b>a</b>) as-synthesized IBN-4 nanoparticles, (<b>b</b>) IBN-4 nanoparticles after surfactant removal (IBN-4-extracted), (<b>c</b>) IBN-4 nanoparticles modified with APTS groups (IBN-4-NH<sub>2</sub>), (<b>d</b>) IBN-4-NH<sub>2</sub> nanoparticles modified with glutaraldehyde groups (IBN-4-NH-GA) and (<b>e</b>) IBN-4-NH-GA nanoparticles immobilized with HRP (IBN-4-HRP).</p> Full article ">Figure 5
<p>Ultraviolet–visible (UV-Vis) spectra and white-light sample images (inset) of (<b>a</b>) ninhydrin alone, (<b>b</b>) IBN-4 nanoparticles after surfactant removal, (<b>c</b>) IBN-4 nanoparticles modified with APTS groups (IBN-4-NH<sub>2</sub>) and (<b>d</b>) IBN-4 nanoparticles modified with glutaraldehyde groups (IBN-4-NH-GA).</p> Full article ">Figure 6
<p>The viability of Human colon carcinoma (HT-29) cells: (<b>A</b>) treatment with IBN-4 loaded with Horseradish peroxidase (HRP) prepared via two synthetic routes; (<b>B</b>) treatment of IBN-4-HRP synthesized using two different routes in the presence or absence of indole-3-acetic acid (IAA) (IAA expressed in µM); and (<b>C</b>) treatment of various concentrations (200 and 500 μg/mL) of IBN-4-HRP synthesized in the presence or absence of IAA (IAA expressed in µM).</p> Full article ">Figure 6 Cont.
<p>The viability of Human colon carcinoma (HT-29) cells: (<b>A</b>) treatment with IBN-4 loaded with Horseradish peroxidase (HRP) prepared via two synthetic routes; (<b>B</b>) treatment of IBN-4-HRP synthesized using two different routes in the presence or absence of indole-3-acetic acid (IAA) (IAA expressed in µM); and (<b>C</b>) treatment of various concentrations (200 and 500 μg/mL) of IBN-4-HRP synthesized in the presence or absence of IAA (IAA expressed in µM).</p> Full article ">Figure 7
<p>Bright field images of HT-29 cells without or with treatment of HRP-loaded IBN-4 nanoparticles and IAA: (<b>a</b>) Control (cells without treatment), (<b>b</b>) treatment with IAA (500 μM), (<b>c</b>) treatment with IAA (500 μM) and IBN-4-HRP (one-pot) (100 μg/mL) and (<b>d</b>) treatment with IAA (500 μM) and IBN-4-HRP (100 μg/mL).</p> Full article ">Figure 8
<p>Cytotoxic estimates of IBN-4 nanocomposites using an lactate dehydrogenase (LDH) leakage assay. Control experiment (CTL), P represents positive control (treated with Triton x-100) with various treatments using combinations of IAA and IBN-4-HRP.</p> Full article ">Figure 9
<p>Bright field images of HT-29 cells with or without treatment of IBN-4-HRP and IAA: (<b>a</b>) HT-29 cells without treatment; (<b>b</b>) treatment with IAA (1.6 mM); (<b>c</b>) treatment with IBN-4-HRP alone; and (<b>d</b>) treatment with IBN-4-HRP and IAA (1.6 mM).</p> Full article ">Figure 10
<p>Microphotographs of bright field and fluorescent microscopic views of HT-29 cells: (<b>a</b>) Bright field view of untreated control cells (undamaged cells); (<b>b</b>) fluorescent microscopic view of untreated control cells (undamaged cells); (<b>c</b>) bright field view of cells treated with IAA (1 mM) and IBN-4-HRP (100 μg/mL) (shrunken morphologies); and (<b>d</b>) fluorescent microscopic view of cells IAA (1 mM) and IBN-4-HRP (100 μg/mL) (damaged cells with elongated tails).</p> Full article ">
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Review
Upconverting NIR Photons for Bioimaging
by Zhanjun Li, Yuanwei Zhang, Hieu La, Richard Zhu, Ghida El-Banna, Yuzou Wei and Gang Han
Nanomaterials 2015, 5(4), 2148-2168; https://doi.org/10.3390/nano5042148 - 4 Dec 2015
Cited by 61 | Viewed by 10652
Abstract
Lanthanide-doped upconverting nanoparticles (UCNPs) possess uniqueanti-Stokes optical properties, in which low energy near-infrared (NIR) photons can beconverted into high energy UV, visible, shorter NIR emission via multiphoton upconversionprocesses. Due to the rapid development of synthesis chemistry, lanthanide-doped UCNPscan be fabricated with narrow distribution [...] Read more.
Lanthanide-doped upconverting nanoparticles (UCNPs) possess uniqueanti-Stokes optical properties, in which low energy near-infrared (NIR) photons can beconverted into high energy UV, visible, shorter NIR emission via multiphoton upconversionprocesses. Due to the rapid development of synthesis chemistry, lanthanide-doped UCNPscan be fabricated with narrow distribution and tunable multi-color optical properties. Theseunique attributes grant them unique NIR-driven imaging/drug delivery/therapeuticapplications, especially in the cases of deep tissue environments. In this brief review, weintroduce both the basic concepts of and recent progress with UCNPs in material engineeringand theranostic applications in imaging, molecular delivery, and tumor therapeutics. The aimof this brief review is to address the most typical progress in basic mechanism, materialdesign as bioimaging tools. Full article
(This article belongs to the Special Issue Nanoparticles in Bioimaging)
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<p>Typical upconversion spectra of β-NaYF<sub>4</sub>:20%Yb, 2%Er (dark green) and β-NaYF<sub>4</sub>:20%Yb, 0.5%Tm (blue).</p> Full article ">Figure 2
<p>Upconversion process of Nd/Yb/Er(Tm) tri-dopants system with 800 nm excitation. Reproduced with permission from [<a href="#B12-nanomaterials-05-02148" class="html-bibr">12</a>]. Copyright John Wiley &amp; Sons, 2013.</p> Full article ">Figure 3
<p>Upconversion emission spetra of (<b>a</b>) NaGdF<sub>4</sub>:25%Yb/0.3%Tm (15 nm) and (<b>b</b>) corresponding core-shell nanoparticles (20 nm) in nonylphenylether/ethanol/water solutions with different water ratio. Reproduced with permission from [<a href="#B23-nanomaterials-05-02148" class="html-bibr">23</a>]. Copyright John Wiley &amp; Sons, 2010.</p> Full article ">Figure 4
<p>Heteroshell structure of α-NaYbF<sub>4</sub>:Tm@CaF<sub>2</sub>. (<b>a</b>)TEM, (<b>b</b>) high-angle annular dark-field STEM, (<b>c</b>) linear EDX scanning of a single UCNP and (<b>d</b>) corresponding elemental ratio analysis. Reproduced with permission from [<a href="#B24-nanomaterials-05-02148" class="html-bibr">24</a>]. Copyright John Wiley &amp; Sons, 2013.</p> Full article ">Figure 5
<p>Bright upconversion under 800 nm excitation by engineering core@shell@shell structure. (<b>a</b>) Simplied energy-level diagrams depicting the energy transfer between Nd, Yb, and Er ions upon 800 nm excitation. (<b>b</b>) Schematic illustration of the proposed energy transfer mechanisms in the quenching-shield sandwich-structured UCNPs, (<b>c</b>) upconversion emission spectra of the as-synthesized UCNPs. Reproduced with permission from [<a href="#B25-nanomaterials-05-02148" class="html-bibr">25</a>]. Copyright John Wiley &amp; Sons, 2014.</p> Full article ">Figure 6
<p>(<b>a</b>) Schematic design of tuning the Nd-sensitized upconversion process through nanostructural engineering. (<b>b</b>) Emisssion spectra of the multishelled nanoparticles under excitation at 808 and 976 nm, respectively. Inset: digital camera photograph of corresponding solution sample. Reproduced with permission from [<a href="#B27-nanomaterials-05-02148" class="html-bibr">27</a>]. Copyright John Wiley &amp; Sons, 2013.</p> Full article ">Figure 7
<p>(<b>a</b>) Illustration of two-way photoswitching of spiropyran by using UCNPs with dual NIR excitations. (<b>b</b>) Tm<sup>3+</sup> and Er<sup>3+</sup> emissions from the UCNPs under 808 nm and 980 nm excitations and the evolution of the UV-vis absorption spectrum of the photoisomerization. (<b>c</b>) Kinetic monitoring of the photoswitching reaction. The red line shows the kinetics of the reaction of merocyanine to spiropyran. (<b>d</b>) Dual NIR-driven photoswitching of spiropyran over many cycles in THF/methanol (9/1, <span class="html-italic">v</span>/<span class="html-italic">v</span>) solution by monitoring the absorbance of merocyanine at 560 nm. Reproduced with permission from [<a href="#B28-nanomaterials-05-02148" class="html-bibr">28</a>]. Copyright John Wiley &amp; Sons, 2014.</p> Full article ">Figure 8
<p>Scheme of the phase transition and ligand exchange procedure by using NOBF<sub>4</sub>. Reprinted with the permission with permission from [<a href="#B32-nanomaterials-05-02148" class="html-bibr">32</a>]. Copyright American Chemical Society, 2011.</p> Full article ">Figure 9
<p>Upconverted luminescence of individual water-soluble upconverting nanoparticles (UCNPs). (<b>A</b>) Confocal upconverted luminescent image of individual amphiphilic polymer-coated UCNPs (schematically shown in the <span class="html-italic">Inset</span>) sparsely dispersed on a clean coverglass. The laser power is approximately 10 mW, equivalent to approximately 5 × 10<sup>6</sup> W/cm<sup>2</sup>. Some of the bright luminescent spots represent multiple UCNPs within the diffraction limited area, generating saturated “white” spots in the image. (<b>B</b>) A histogram of integrated emission intensity from over 200 upconverted luminescent spots, suggesting that most of the luminescent spots are from single polymer-coated UCNPs. The data were analyzed from confocal upconverted luminescent images over a 75 × 75 μm area, and the number of saturated “white” spots was shown in the histogram as a blue bar. Such single water-soluble UCNPs also exhibit exceptional photostability (<b>C</b>) and non-blinking behavior (<b>D</b>) Reprinted with the permission from [<a href="#B3-nanomaterials-05-02148" class="html-bibr">3</a>]. Copyright American Chemical Society, 2009.</p> Full article ">Figure 10
<p>Example of lanthanide-doped UCNPs of core-shell structures with NIR-to-NIR optical transitions and their application for small animal imaging studies plus illustration showing the better penetration of NIR light in contrast with visible light. Reprinted with permission from [<a href="#B5-nanomaterials-05-02148" class="html-bibr">5</a>]. Copyright American Chemical Society, 2012.</p> Full article ">Figure 11
<p>Illustration scheme for UCNP-RGD and <span class="html-italic">in vivo</span> upconversion luminescence imaging of subcutaneous U87MG tumor (left hind leg) and MCF-7 tumor (right hind leg) after intravenous injection of UCNP-RGD conjugate over 24-hour period. (<b>a</b>,<b>d</b>,<b>g</b>) bright field, (<b>b</b>,<b>e</b>,<b>h</b>) upconversion images, (<b>c</b>,<b>f</b>,<b>i</b>) overlay of the corresponding bright field images with the upconversion ones. (<b>a</b>–<b>c</b>), (<b>d</b>–<b>f</b>), and (<b>g</b>–<b>i</b>) are taken at 1, 4 and 24 h postinjection, respectively. Reprinted with permission from [<a href="#B35-nanomaterials-05-02148" class="html-bibr">35</a>]. Copyright American Chemical Society, 2009.</p> Full article ">Figure 12
<p>Schematic illustration of antigen-loaded UCNPs for dendritic cell stimulation, tracking, and vaccination in immunotherapy. Reprinted with permission from [<a href="#B39-nanomaterials-05-02148" class="html-bibr">39</a>]. Copyright American Chemical Society, 2015.</p> Full article ">Figure 13
<p>Scheme of real-time monitoring of ATP-responsive drug release using mesoporous-silica-coated multicolor upconversion nanoparticles. Reprinted with permission from [<a href="#B41-nanomaterials-05-02148" class="html-bibr">41</a>]. Copyright American Chemical Society, 2015.</p> Full article ">Figure 14
<p>Schematic drawing of FRET-based UCNPs/siRNA-BOBO-3 complex system. siRNA are stained with BOBO-3 dyes, and the stained siRNA are attached to the surface of NaYF<sub>4</sub>:Yb,Er nanoparticles. Upon excitation of the nanoparticles at 980 nm, energy is transferred from the donor (UCNPs) to the acceptor (BOBO-3). Reprinted with permission from [<a href="#B42-nanomaterials-05-02148" class="html-bibr">42</a>]. Copyright American Chemical Society, 2010.</p> Full article ">Figure 15
<p>(<b>a</b>) <span class="html-italic">In vivo</span> volume of tumors exposed to various controls and ALA-UCNPs with red and near-infrared irradiation (0.5 W/cm<sup>2</sup>) in simulated deep tumors, (<b>b</b>) scheme of the simulated deep tumor PDT process. Reprinted with permission from [<a href="#B51-nanomaterials-05-02148" class="html-bibr">51</a>]. Copyright American Chemical Society, 2014.</p> Full article ">Figure 16
<p>Schematic illustration of the NIR-driven reactive oxygen species generation by the use of UCNP/TiO<sub>2</sub>. Reprinted with permission from [<a href="#B55-nanomaterials-05-02148" class="html-bibr">55</a>]. Copyright American Chemical Society, 2015.</p> Full article ">Figure 17
<p>(<b>a</b>) Illustration of nano-carriers for enhanced photothermal ablation and radiotherapy synergistic therapy; (<b>b</b>) photographs of mice in 30, 60, 90 and 120 days of treatment, showing complete eradication of the tumor and no visible recurrences of the tumors in at least 120 days. Reprinted with permission from [<a href="#B59-nanomaterials-05-02148" class="html-bibr">59</a>]. Copyright American Chemical Society, 2013.</p> Full article ">
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Article
Performance Evaluation of a Nanofluid-Based Direct Absorption Solar Collector with Parabolic Trough Concentrator
by Guoying Xu, Wei Chen, Shiming Deng, Xiaosong Zhang and Sainan Zhao
Nanomaterials 2015, 5(4), 2131-2147; https://doi.org/10.3390/nano5042131 - 4 Dec 2015
Cited by 62 | Viewed by 7943
Abstract
Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors’ tube/plate wall. The poor durability of the [...] Read more.
Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors’ tube/plate wall. The poor durability of the coating can lead to an increased manufacturing cost and unreliability for a solar collector operated at a higher temperature. Therefore, a novel nanofluid-based direct absorption solar collector (NDASC) employing uncoated collector tubes has been proposed, and its operating characteristics for medium-temperature solar collection were theoretically and experimentally studied in this paper. CuO/oil nanofluid was prepared and used as working fluid of the NDASC. The heat-transfer mechanism of the NDASC with parabolic trough concentrator was theoretically evaluated and compared with a conventional indirect absorption solar collector (IASC). The theoretical analysis results suggested that the fluid’s temperature distribution in the NDASC was much more uniform than that in the IASC, and an enhanced collection efficiency could be achieved for the NDASC operated within a preferred working temperature range. To demonstrate the feasibility of the proposed NDASC, experimental performances of an NDASC and an IASC with the same parabolic trough concentrator were furthermore evaluated and comparatively discussed. Full article
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<p>Schematic diagram of the cross section of a parabolic trough concentrating solar collector.</p> Full article ">Figure 2
<p>Schematics of solar collection principles. (<b>a</b>) A conventional indirect absorption solar collector (IASC); (<b>b</b>) The proposed novel nanofluid-based direct absorption solar collector (NDASC); (<b>c</b>) The heat transfer around nanoparticles inside the tube of NDASC.</p> Full article ">Figure 3
<p>The solar radiation transfer inside the tube of the NDASC.</p> Full article ">Figure 4
<p>(<b>a</b>) Scanning Electron Microscope (SEM) image of CuO nanoparticles; (<b>b</b>) Photos prepared CuO/oil nanofluid used in the NDASC.</p> Full article ">Figure 5
<p>Extinction and absorption spectra of CuO/oil nanofluid and pure synthetic oil. (<b>a</b>) Variations of extinction coefficient with wavelength; (<b>b</b>) Variations of absorption coefficient with wavelength.</p> Full article ">Figure 6
<p>Solar radiation intensity along the circumference of collector tubes.</p> Full article ">Figure 7
<p>Fluid’s temperature distributions of cross sections at different length points (<span class="html-italic">t</span><sub>f,i</sub> = 100 °C).</p> Full article ">Figure 8
<p>Fluid’s temperature distribution at <span class="html-italic">z</span> = 1.7 m in the NDASC and IASC (<span class="html-italic">t</span><sub>f,i</sub> = 130 °C).</p> Full article ">Figure 9
<p>Variations of solar collection efficiencies with <span class="html-italic">t</span><sub>f,i</sub> for both the NDASC and the IASC.</p> Full article ">Figure 10
<p>Photos of the experimental setups of the NDASC and the IASC.</p> Full article ">Figure 11
<p>Variation of solar radiation with time during the experiment.</p> Full article ">Figure 12
<p>Variations of working fluid’s temperatures with time for two collectors.</p> Full article ">Figure 13
<p>Comparison of the experimental and theoretical solar collection efficiencies for two collectors.</p> Full article ">
6363 KiB  
Review
Composites of Polymer Hydrogels and Nanoparticulate Systems for Biomedical and Pharmaceutical Applications
by Fuli Zhao, Dan Yao, Ruiwei Guo, Liandong Deng, Anjie Dong and Jianhua Zhang
Nanomaterials 2015, 5(4), 2054-2130; https://doi.org/10.3390/nano5042054 - 3 Dec 2015
Cited by 299 | Viewed by 25900
Abstract
Due to their unique structures and properties, three-dimensional hydrogels and nanostructured particles have been widely studied and shown a very high potential for medical, therapeutic and diagnostic applications. However, hydrogels and nanoparticulate systems have respective disadvantages that limit their widespread applications. Recently, the [...] Read more.
Due to their unique structures and properties, three-dimensional hydrogels and nanostructured particles have been widely studied and shown a very high potential for medical, therapeutic and diagnostic applications. However, hydrogels and nanoparticulate systems have respective disadvantages that limit their widespread applications. Recently, the incorporation of nanostructured fillers into hydrogels has been developed as an innovative means for the creation of novel materials with diverse functionality in order to meet new challenges. In this review, the fundamentals of hydrogels and nanoparticles (NPs) were briefly discussed, and then we comprehensively summarized recent advances in the design, synthesis, functionalization and application of nanocomposite hydrogels with enhanced mechanical, biological and physicochemical properties. Moreover, the current challenges and future opportunities for the use of these promising materials in the biomedical sector, especially the nanocomposite hydrogels produced from hydrogels and polymeric NPs, are discussed. Full article
(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic illustration of methods for formation of physically crosslinked hydrogels.</p> Full article ">Figure 2
<p>Examples of typical nanoparticles and their applications in biomedical fields.</p> Full article ">Figure 3
<p>Schematic illustration of typical nanocomposite hydrogels from hydrogels and drug-loaded nanoparticles (NPs). NPs were non-covalently or covalently immobilized in a hydrogel matrix.</p> Full article ">Figure 4
<p>Schematic illustration of the concept of gluing swollen polymer networks together using silica NPs, reproduced with permission from [<a href="#B81-nanomaterials-05-02054" class="html-bibr">81</a>]. Copyright Nature Publishing Group, 2014.</p> Full article ">Figure 5
<p>Schematic illustrations of incorporating graphene-based materials into hydrogel matrixes; The formation of graphene-hydrogel composite materials by (<b>A</b>): self-assembly and photo-crosslinking between graphene and peptide, reproduced with permission from [<a href="#B99-nanomaterials-05-02054" class="html-bibr">99</a>]. Copyright Royal Society of Chemistry, 2015; (<b>B</b>): photopolymerization of vinyl moieties present on surface of graphene and polymer chains, reproduced with permission from [<a href="#B91-nanomaterials-05-02054" class="html-bibr">91</a>]. Copyright American Chemical Society, 2015; (<b>C</b>): <span class="html-italic">in situ</span> biosynthesis, reproduced with permission from [<a href="#B103-nanomaterials-05-02054" class="html-bibr">103</a>]. Copyright Royal Society of Chemistry, 2014; (<b>D</b>): surface-grafted polymerization, reproduced with permission from [<a href="#B104-nanomaterials-05-02054" class="html-bibr">104</a>]. Copyright American Chemical Society, 2012; (<b>E</b>): supramolecular self-assembly by hydrogen bonding, reproduced with permission from [<a href="#B102-nanomaterials-05-02054" class="html-bibr">102</a>]. Copyright Royal Society of Chemistry, 2015.</p> Full article ">Figure 6
<p>Illustration of the preparation of PVA-GPTMS-PVP-GLY film-forming gel and the appearance photo and SEM micrograph of the resultant gel, reproduced with permission from [<a href="#B69-nanomaterials-05-02054" class="html-bibr">69</a>]. Copyright Elsevier, 2011.</p> Full article ">Figure 7
<p>Depiction of the enzyme induced chemical-to-physical cross-link transition and subsequent mass loss and blue shift of nanocomposite hydrogels after exposure to chymotrypsin, reproduced with permission from [<a href="#B140-nanomaterials-05-02054" class="html-bibr">140</a>]. Copyright American Chemical Society, 2015.</p> Full article ">Figure 8
<p>Proposed mechanism (<b>a</b>–<b>c</b>), photographs (<b>d</b>–<b>f</b>), and SEM image (<b>g</b>) and TEM image (<b>h</b>), UV-Vis absorbance and images under an ultraviolet lamp of the functional nanocomposite hydrogels prepared by a QDots-initiated polymerization approach under sunlight, reproduced with permission from [<a href="#B146-nanomaterials-05-02054" class="html-bibr">146</a>]. Copyright Nature Publishing Group, 2013.</p> Full article ">Figure 9
<p>Schematic illustration of Doxorubicin (DOX)/Au NPs embedded hybrid hydrogels with the ability of photothermal therapy (PTT) and near infrared (NIR)-triggered thermo-responsive drug release, reproduced with permission from [<a href="#B270-nanomaterials-05-02054" class="html-bibr">270</a>]. Copyright Nature Publishing Group, 2015.</p> Full article ">Figure 10
<p>Schematic illustrations of typical biomedical applications of iron oxide NPs-hydrogel composites. Magnetic field induced hyperthermia, reproduced with permission from [<a href="#B286-nanomaterials-05-02054" class="html-bibr">286</a>] Copyright Ivyspring International Publisher, 2012; Magnet-controlled drug delivery, reproduced with permission from [<a href="#B283-nanomaterials-05-02054" class="html-bibr">283</a>]. Copyright American Chemical Society, 2006; Magnetic resonance imaging, reproduced with permission from [<a href="#B287-nanomaterials-05-02054" class="html-bibr">287</a>]. Copyright American Chemical Society, 2012; Magnet-controlled cell patterning, immobilization and separation, reproduced with permission from [<a href="#B288-nanomaterials-05-02054" class="html-bibr">288</a>]. Copyright American Chemical Society, 2015.</p> Full article ">Figure 11
<p>Schematic illustration of a NIR laser responsive deformation-free hydrogel containing embedded polypyrrole (PPy) NPs: (<b>a</b>) pre-heated agarose solution was mixed with alginate and PPy NPs and injected into patterned mold; (<b>b</b>) cooling to induce gelation of agarose, determining shape of the hydrogel and served as a template for alginate gelation; (<b>c</b>) CaCl<sub>2</sub> was added to form an alginate network, which provided the mechanical support during laser irradiation; (<b>d</b>) periodic switching of NIR laser to digitally control agarose melting for pulsatile drug release, reproduced with permission from [<a href="#B408-nanomaterials-05-02054" class="html-bibr">408</a>]. Copyright Royal Society of Chemistry, 2014.</p> Full article ">Figure 12
<p>Schematic illustration of a hydrogel retaining toxin-absorbing nanosponges (NS-gel) for local treatment of bacterial infection. The toxin nanosponge was constructed with a poly(D,L-lactide-co-glycolide) (PLGA) core wrapped in natural red blood cell (RBC) bilayer membrane and was subsequently embedded into polyacrylamide (PAM) hydrogel, reproduced with permission from [<a href="#B396-nanomaterials-05-02054" class="html-bibr">396</a>]. Copyright John Wiley and Sons, 2015.</p> Full article ">Figure 13
<p>Schematic illustration of agarose hydrogels embedded with pH-responsive diblock copolymer micelles for triggered release of substances, reproduced with permission from [<a href="#B433-nanomaterials-05-02054" class="html-bibr">433</a>]. Copyright American Chemical Society, 2013.</p> Full article ">Figure 14
<p>Schematic illustrations of nanocomposite hydrogels (<b>A</b>): from hydrogel and liposomes, and the formation of hybrid hydrogels by stepwise orthogonal self-assembly, reproduced with permission from [<a href="#B423-nanomaterials-05-02054" class="html-bibr">423</a>]. Copyright American Chemical Society, 2014; (<b>B</b>): from hydrogel and vesicles, the formation of hybrid hydrogels by the sol–gel transition of vesicle-embedded composite hydrogels, reproduced with permission from [<a href="#B452-nanomaterials-05-02054" class="html-bibr">452</a>]. Copyright Royal Society of Chemistry, 2009; (<b>C</b>): from hydrogel and polymer nanogels, and the formation of hybrid hydrogels via an enzymatic reaction, reproduced with permission from [<a href="#B453-nanomaterials-05-02054" class="html-bibr">453</a>]. Copyright American Chemical Society, 2014</p> Full article ">
3176 KiB  
Review
Recent Advance on Mesoporous Silica Nanoparticles-Based Controlled Release System: Intelligent Switches Open up New Horizon
by Ruijuan Sun, Wenqian Wang, Yongqiang Wen and Xueji Zhang
Nanomaterials 2015, 5(4), 2019-2053; https://doi.org/10.3390/nano5042019 - 25 Nov 2015
Cited by 67 | Viewed by 10626
Abstract
Mesoporous silica nanoparticle (MSN)-based intelligent transport systems have attracted many researchers’ attention due to the characteristics of uniform pore and particle size distribution, good biocompatibility, high surface area, and versatile functionalization, which have led to their widespread application in diverse areas. In the [...] Read more.
Mesoporous silica nanoparticle (MSN)-based intelligent transport systems have attracted many researchers’ attention due to the characteristics of uniform pore and particle size distribution, good biocompatibility, high surface area, and versatile functionalization, which have led to their widespread application in diverse areas. In the past two decades, many kinds of smart controlled release systems were prepared with the development of brilliant nano-switches. This article reviews and discusses the advantages of MSN-based controlled release systems. Meanwhile, the switching mechanisms based on different types of stimulus response are systematically analyzed and summarized. Additionally, the application fields of these devices are further discussed. Obviously, the recent evolution of smart nano-switches promoted the upgrading of the controlled release system from the simple “separated” switch to the reversible, multifunctional, complicated logical switches and selective switches. Especially the free-blockage switches, which are based on hydrophobic/hydrophilic conversion, have been proposed and designed in the last two years. The prospects and directions of this research field are also briefly addressed, which could be better used to promote the further development of this field to meet the needs of mankind. Full article
(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)
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<p>Schematic of the stimuli-responsive controlled release system (magnet-MSN) based on MSNs capped with Fe<sub>3</sub>O<sub>4</sub> nanoparticles. Reproduced with permission from [<a href="#B23-nanomaterials-05-02019" class="html-bibr">23</a>]. Copyright John Wiley and Sons, 2005.</p> Full article ">Figure 2
<p>Depiction of the assembly of the components to form nanovalves with the structural formulas of the bistable [<a href="#B2-nanomaterials-05-02019" class="html-bibr">2</a>] rotaxanes 1<sup>4+</sup> and 2<sup>4+</sup>, the three silane linkers <b>a</b>, <b>b</b>, and <b>c</b> used in this study, as well as the graphical representations of luminescent probe molecules and the possible positions (IN and OUT) of the linkers relative to the pore orifice. The pores are loaded when the valves are open and the probe molecules are trapped inside the pores when the valves are closed. The trapped molecules are released when the valves are reopened. The cycle can be repeated over and over again. Reproduced with permission from [<a href="#B28-nanomaterials-05-02019" class="html-bibr">28</a>]. Copyright American Chemical Society, 2007.</p> Full article ">Figure 3
<p>Schematic illustration of pH-responsive nanogated ensemble based on gold-capped MSNs through acid-labile acetal linker. Reproduced with permission from [<a href="#B37-nanomaterials-05-02019" class="html-bibr">37</a>]. Copyright American Chemical Society, 2010.</p> Full article ">Figure 4
<p>(<b>a</b>) Synthetic procedure for up-converting nanoparticles coated with a MSN outer layer. (<b>b</b>) The schematic of NIR light-triggered doxorubicin release by making use of the up-conversion property of UCNPs and <span class="html-italic">trans-cis</span> photoisomerization of azobenzene group molecules grafted on MSNs. Reproduced with permission from [<a href="#B62-nanomaterials-05-02019" class="html-bibr">62</a>]. Copyright John Wiley and Sons, 2013.</p> Full article ">Figure 5
<p>Schematic illustration of the synthesis and operation of a magnet-responsive controlled release system, using ZnNCs encapsulated within MSNs. Reproduced with permission from [<a href="#B72-nanomaterials-05-02019" class="html-bibr">72</a>]. Copyright American Chemical Society, 2010.</p> Full article ">Figure 6
<p>Schematic representation of the glucose-responsive MSN-based delivery system for controlled release of bioactive G-Ins and cAMP. Reproduced with permission from [<a href="#B79-nanomaterials-05-02019" class="html-bibr">79</a>]. Copyright American Chemical Society, 2009.</p> Full article ">Figure 7
<p>Schematic representation of proton-fueled release of a drug from the pores of MSNs capped with <span class="html-italic">i</span>-motif DNA. Reproduced with permission from [<a href="#B84-nanomaterials-05-02019" class="html-bibr">84</a>]. Copyright Oxford University Press, 2011.</p> Full article ">Figure 8
<p>(<b>a</b>) Scheme of preparation of DNA-modified MSNs. (1) 3-Aminopropyltriethoxy silane; (2) succinic anhydride and triethylamine; (3) <span class="html-italic">N</span>-hydroxy-succinimide (NHS), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-HCl (EDC), and NH<sub>2</sub>-ended DNA strand 1; (4) cargo molecules, Rodamine B; (5) DNA 2-functionalized AuNPs. (<b>b</b>) The controlled release was modulated by the motor DNA’s conformation change which was driven by changing the pH value of the solution. (<b>c</b>) A schematic sketch of the hydrogen bonding between the protonated cytosines. Reproduced with permission from [<a href="#B85-nanomaterials-05-02019" class="html-bibr">85</a>]. Copyright The Royal Society of Chemistry, 2011.</p> Full article ">Figure 9
<p>Graphical representation of operating supramolecular nanovalves from DB24C8/dialkylammonium-tethered porous silica particle MSNs. Reproduced with permission from [<a href="#B94-nanomaterials-05-02019" class="html-bibr">94</a>]. Copyright American Chemical Society, 2006.</p> Full article ">Figure 10
<p>The release process of the dual-dye-loaded MSNs. The dual dyes were loaded into the MSNs separately by pH-controlled nanogates and UV-controlled nanovalves. This system can selectively release Eosin Yellowish (EY) upon UV irradiation (at pH 7.0) and Rhodamine B (RhB) at pH 3.5. Reproduced with permission from [<a href="#B98-nanomaterials-05-02019" class="html-bibr">98</a>]. Copyright John Wiley and Sons, 2014.</p> Full article ">Figure 11
<p>Schematic illustration of a multi-responsive Au@MSN@Valve. Reproduced with permission from [<a href="#B105-nanomaterials-05-02019" class="html-bibr">105</a>]. Copyright American Chemical Society, 2012.</p> Full article ">Figure 12
<p>Schematic for the preparation process of M-MSN–PNIPAAm. Reproduced with permission from [<a href="#B108-nanomaterials-05-02019" class="html-bibr">108</a>]. Copyright John Wiley and Sons, 2014.</p> Full article ">
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Article
Nanostructuring of Palladium with Low-Temperature Helium Plasma
by P. Fiflis, M.P. Christenson, N. Connolly and D.N. Ruzic
Nanomaterials 2015, 5(4), 2007-2018; https://doi.org/10.3390/nano5042007 - 25 Nov 2015
Cited by 14 | Viewed by 5041
Abstract
Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly [...] Read more.
Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium. Full article
(This article belongs to the Special Issue Plasma Nanoengineering and Nanofabrication)
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<p>Photo of exposure chamber showing MORI (Trikon Technologies, Newport, UK) automated matching network, exposure volume, load lock gate valve, and transfer arm for introducing samples without breaking vacuum.</p> Full article ">Figure 2
<p>Scanning electron microscope (SEM) micrographs of palladium surface (0.5 mm diameter wire sample) after exposure to helium plasma at elevated temperature. The flux to each area is identical, the only changed variable is temperature (noted in the upper left corner of each micrograph both absolute and as a fraction of the melting point of palladium).</p> Full article ">Figure 3
<p>SEM micrographs of palladium surface (0.5 mm plate sample) after exposure to helium plasma at elevated temperature. The flux to each area is identical, the only changed variable is temperature (noted in the upper left corner of each micrograph both absolute and as a fraction of the melting point of palladium). Secondary electron collection performed at a tilt angle of 0° with respect to the surface normal.</p> Full article ">Figure 4
<p>SEM micrographs of palladium surface (0.5 mm plate sample) after exposure to helium plasma at elevated temperature. The flux to each area is identical, the only changed variable is temperature (noted in the upper left corner of each micrograph both absolute and as a fraction of the melting point of palladium). Secondary electron collection performed at a tilt angle of 40° with respect to the surface normal.</p> Full article ">Figure 5
<p>SEM micrograph of palladium surface (0.5 mm diameter wire sample) after exposure to helium plasma at 900 K, only a couple tendrils are visible as the annealing rate of the tendrils begins to exceed the rate of growth.</p> Full article ">Figure 6
<p>SEM micrograph of palladium surface (300 nm thin film deposited on SiO<sub>2</sub>) after exposure to helium plasma at elevated temperature. (<b>A</b>), (<b>B</b>), and (<b>C</b>) are different resolutions of the same location showing growth of tendrils and voids that appear to penetrate down to the SiO<sub>2</sub> substrate. Tendrils approximately the same diameter as those observed on bulk Pd samples are observed. Pits of similar diameter are also observed. (<b>D</b>) shows an area of the palladium film where the helium plasma has eroded through the palladium film to the substrate with very thin tendrils of Pd stretching across.</p> Full article ">Figure 7
<p>SEM micrograph of palladium surface (30 nm thin film deposited on SiO<sub>2</sub>) after exposure to helium plasma at elevated temperature. <a href="#nanomaterials-05-02007-f005" class="html-fig">Figure 5</a>A–D are different resolutions of the same location showing growth no tendril growth, but a significant amount of voids. These voids are of a diameter greater than the pits observed in the bulk and 300 nm film samples. Large wrinkles appear evident in the film. It appears as though formation and growth of bubbles within the 30 nm thick film rupture the film without being able to build upon each other and grow nanostructures.</p> Full article ">Figure 8
<p>A block diagram of the palladium-catalyzed hydrogenation reaction vessel, including the hydrogen gas inlet, the vacuum cylinder outlet, the magnetic stirrer, and the gas bubbler used to qualitatively determine the flow rate of the hydrogen through the reactant volume.</p> Full article ">Figure 9
<p>A plot of the yield measured as the ratio of the concentration of the cylcohexane to cyclohexene. This ratio is based on the ratios of areas under the curve of the cyclohexane 1.4 ppm peak and the mean of the intensities of the three cyclohexene peaks seen at 1.2 ppm, 1.7 ppm, and 2.0 ppm in the NMR scans, which are characteristic for the respective compounds and are normalized to the deuterated chloroform standard. These ratios were also taken as a function of time to, not only observe the effectiveness of each catalyst type, but also how the kinetics of the reaction compare with each catalyst type.</p> Full article ">
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Article
Electrochemical Characterization of Graphene and MWCNT Screen-Printed Electrodes Modified with AuNPs for Laccase Biosensor Development
by Gabriele Favero, Giovanni Fusco, Franco Mazzei, Federico Tasca and Riccarda Antiochia
Nanomaterials 2015, 5(4), 1995-2006; https://doi.org/10.3390/nano5041995 - 20 Nov 2015
Cited by 48 | Viewed by 6821
Abstract
The aim of this work is to show how the integration of gold nanoparticles (AuNPs) into multi-wall-carbon-nanotubes (MWCNTs) based screen-printed electrodes and into graphene-based screen-printed electrodes (GPHs) could represent a potential way to further enhance the electrochemical properties of those electrodes based on [...] Read more.
The aim of this work is to show how the integration of gold nanoparticles (AuNPs) into multi-wall-carbon-nanotubes (MWCNTs) based screen-printed electrodes and into graphene-based screen-printed electrodes (GPHs) could represent a potential way to further enhance the electrochemical properties of those electrodes based on nanoparticles. Laccase from Trametes versicolor (TvL) was immobilized over MWCNTs and GPH previously modified with AuNPs (of 5 and 10 nm). The characterization of the modified electrode surface has been carried out by cyclic voltammetry. The results showed that the use of AuNPs for modification of both graphene and MWCNTs screen-printed electrode surfaces would increase the electrochemical performances of the electrodes. MWCNTs showed better results than GPH in terms of higher electroactive area formation after modification with AuNPs. The two modified nanostructured electrodes were successively proven to efficiently immobilize the TvL; the electrochemical sensing properties of the GPH- and MWCNT-based AuNPs-TvL biosensors were investigated by choosing 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic-acid diammonium salt (ABTS), catechol and caffeic acid as laccase mediators; and the kinetic parameters of the laccase biosensor were carefully evaluated. Full article
(This article belongs to the Special Issue Nanomaterials for Biosensing Applications)
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<p>Cyclic voltammograms of 0.1 mM potassium ferricyanide solution at unmodified GPH (red curve) and at GPH modified with AuNPs of 5 nm diameter (<b>a</b>) and of 10 nm (<b>b</b>) at the following concentrations: 7 × 10<sup>−4</sup> M (green curve), 1 × 10<sup>−3</sup> M (black curve), 1.4 × 10<sup>−3</sup> mM (blue curve). Experimental conditions: 0.1 M phosphate buffer pH 7; scan rate 5 m·Vs<sup>−1</sup>.</p> Full article ">Figure 2
<p>Cyclic voltammograms of 0.1 mM potassium ferricyanide solution at unmodified multi-wall-carbon-nanotubes (MWCNTs) (red curve) and at MWCNTs modified with AuNPs of 5 nm diameter (<a href="#nanomaterials-05-01995-f002" class="html-fig">Figure 2</a>a) and of 10 nm (<a href="#nanomaterials-05-01995-f002" class="html-fig">Figure 2</a>b) at the following concentrations: 7 × 10<sup>−4</sup> M (green curve), 1 × 10<sup>−3</sup> M (black curve), 1.4 × 10<sup>−3</sup> mM (blue curve). Experimental conditions: 0.1 M phosphate buffer pH 7; scan rate 5 m·Vs<sup>−1</sup>.</p> Full article ">Figure 3
<p>Cyclic voltammograms for 0.5 mM (<b>a</b>) 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic-acid diammonium salt (ABTS) or (<b>b</b>) caffeic acid solution onto a MWCNTs-poly(vinylalcohol) (PVA)-AuNPs before (red curve) and after (blue curve) the immobilization of laccase.</p> Full article ">Figure 4
<p>Chronoamperometric current response under flow injection analysis (FIA) conditions to caffeic acid in the range 0.5 μM–1.5 mM, using MWCNTs-PVA-AuNPs-<span class="html-italic">Trametes versicolor</span> (TvL) screen-printed electrode. Experimental conditions: 0.1 M B-R buffer pH 5; flow rate: 0.716 mL/min; loop 250 μL, <span class="html-italic">E</span> = −0.15 V (<span class="html-italic">vs</span>. Ag/AgCl).</p> Full article ">
3519 KiB  
Article
Lithium-Excess Research of Cathode Material Li2MnTiO4 for Lithium-Ion Batteries
by Xinyi Zhang, Le Yang, Feng Hao, Haosen Chen, Meng Yang and Daining Fang
Nanomaterials 2015, 5(4), 1985-1994; https://doi.org/10.3390/nano5041985 - 20 Nov 2015
Cited by 30 | Viewed by 6964
Abstract
Lithium-excess and nano-sized Li2+xMn1−x/2TiO4 (x = 0, 0.2, 0.4) cathode materials were synthesized via a sol-gel method. The X-ray diffraction (XRD) experiments indicate that the obtained main phases of Li2.0MnTiO4 and [...] Read more.
Lithium-excess and nano-sized Li2+xMn1−x/2TiO4 (x = 0, 0.2, 0.4) cathode materials were synthesized via a sol-gel method. The X-ray diffraction (XRD) experiments indicate that the obtained main phases of Li2.0MnTiO4 and the lithium-excess materials are monoclinic and cubic, respectively. The scanning electron microscope (SEM) images show that the as-prepared particles are well distributed and the primary particles have an average size of about 20–30 nm. The further electrochemical tests reveal that the charge-discharge performance of the material improves remarkably with the lithium content increasing. Particularly, the first discharging capacity at the current of 30 mA g−1 increases from 112.2 mAh g−1 of Li2.0MnTiO4 to 187.5 mAh g−1 of Li2.4Mn0.8TiO4. In addition, the ex situ XRD experiments indicate that the monoclinic Li2MnTiO4 tends to transform to an amorphous state with the extraction of lithium ions, while the cubic Li2MnTiO4 phase shows better structural reversibility and stability. Full article
(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)
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<p>Thermogravimetry and differential scanning calorimetry (TG-DSC) curves of the L2.0 and L2.2 precursors.</p> Full article ">Figure 2
<p>X-ray diffraction (XRD) patterns of L2.0 (<b>a</b>), L2.2 (<b>b</b>), L2.4 (<b>c</b>) and the microstructure of the involved phases. The spheres of red, pink, dark blue, and watchet blue denote the atoms of O, Li, Mn, and Ti, respectively, and the proportions of the colors correspond to the occupations of the elements.</p> Full article ">Figure 3
<p>Typical scanning electron microscope (SEM) images of the as-prepared materials. (<b>a</b>) L2.0; (<b>b</b>) L2.2; (<b>c,d</b>) L2.4.</p> Full article ">Figure 4
<p>The first charge-discharge curves of the Li<sub>2+<span class="html-italic">x</span></sub>Mn<sub>1</sub><sub>−<span class="html-italic">x</span>/2</sub>TiO<sub>4</sub> cathode at a constant current of 30 mAg<sup>−1</sup> (<b>a</b>) and 60 mAg<sup>−1</sup> (<b>b</b>).</p> Full article ">Figure 5
<p>Cycling stability curves of Li<sub>2+<span class="html-italic">x</span></sub>Mn<sub>1</sub><sub>−</sub><span class="html-italic"><sub>x</sub></span><sub>/2</sub>TiO<sub>4</sub> cathodes (<b>a</b>) and charge-discharge curves of L2.4 (<b>b</b>) at a constant current of 30 mA g<sup>−1</sup>.</p> Full article ">Figure 6
<p><span class="html-italic">Ex situ</span> XRD patterns of L2.0 (<b>a</b>,<b>b</b>) and L2.4 (<b>c</b>,<b>d</b>) electrodes during the first charge and discharge. I: initial, II: charge to 4.2 V, III: charge to 4.8 V, IV: discharge to 4.2 V, V: discharge to 1.5 V.</p> Full article ">
1861 KiB  
Article
Synthesis of Ordered Mesoporous CuO/CeO2 Composite Frameworks as Anode Catalysts for Water Oxidation
by Vassiliki Markoulaki Ι, Ioannis T. Papadas, Ioannis Kornarakis and Gerasimos S. Armatas
Nanomaterials 2015, 5(4), 1971-1984; https://doi.org/10.3390/nano5041971 - 17 Nov 2015
Cited by 32 | Viewed by 8236
Abstract
Cerium-rich metal oxide materials have recently emerged as promising candidates for the photocatalytic oxygen evolution reaction (OER). In this article, we report the synthesis of ordered mesoporous CuO/CeO2 composite frameworks with different contents of copper(II) oxide and demonstrate their activity for photocatalytic [...] Read more.
Cerium-rich metal oxide materials have recently emerged as promising candidates for the photocatalytic oxygen evolution reaction (OER). In this article, we report the synthesis of ordered mesoporous CuO/CeO2 composite frameworks with different contents of copper(II) oxide and demonstrate their activity for photocatalytic O2 production via UV-Vis light-driven oxidation of water. Mesoporous CuO/CeO2 materials have been successfully prepared by a nanocasting route, using mesoporous silica as a rigid template. X-ray diffraction, electron transmission microscopy and N2 porosimetry characterization of the as-prepared products reveal a mesoporous structure composed of parallel arranged nanorods, with a large surface area and a narrow pore size distribution. The molecular structure and optical properties of the composite materials were investigated with Raman and UV-Vis/NIR diffuse reflectance spectroscopy. Catalytic results indicated that incorporation of CuO clusters in the CeO2 lattice improved the photochemical properties. As a result, the CuO/CeO2 composite catalyst containing ~38 wt % CuO reaches a high O2 evolution rate of ~19.6 µmol·h−1 (or 392 µmol·h−1·g−1) with an apparent quantum efficiency of 17.6% at λ = 365 ± 10 nm. This OER activity compares favorably with that obtained from the non-porous CuO/CeO2 counterpart (~1.3 µmol·h−1) and pure mesoporous CeO2 (~1 µmol·h−1). Full article
(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)
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Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Typical transmission electron microscopy (TEM) images; (<b>b</b>) High-resolution TEM image (the inset shows the corresponding FFT pattern indexed as the (110) zone axis of cubic CeO<sub>2</sub>) and (<b>c</b>) Selected-area electron diffraction (SAED) pattern of the mesoporous CuO(38)/CeO<sub>2</sub> material. In (<b>b</b>), the white arrowheads indicate the bridge region between neighboring nanorods.</p> Full article ">Figure 2
<p>X-ray diffraction (XRD) patterns of mesoporous (<b>a</b>) <span class="html-italic">mp</span>-CeO<sub>2</sub>; (<b>b</b>) CuO(16)/CeO<sub>2</sub>; (<b>c</b>) CuO(26)/CeO<sub>2</sub>; (<b>d</b>) CuO(38)/CeO<sub>2</sub> and (<b>e</b>) CuO(45)/CeO<sub>2</sub> materials.</p> Full article ">Figure 3
<p>Nitrogen adsorption–desorption isotherms at 77 K and the corresponding nonlocal density functional theory (NLDFT) pore-size distribution plots calculated from the adsorption branch (inset) for mesoporous (<b>a</b>) <span class="html-italic">mp</span>-CeO<sub>2</sub>; (<b>b</b>) CuO(16)/CeO<sub>2</sub>; (<b>c</b>) CuO(26)/CeO<sub>2</sub>; (<b>d</b>) CuO(38)/CeO<sub>2</sub> and (<b>e</b>) CuO(45)/CeO<sub>2</sub> materials (STP: standard temperature and pressure). For clarity, the isotherms of (<b>a</b>), (<b>b</b>) and (<b>c</b>) are offset by 5, 40 and 20 cm<sup>3</sup>·g<sup>−1</sup>, respectively.</p> Full article ">Figure 4
<p>(<b>a</b>) Raman spectra and (<b>b</b>) ultraviolet-visible/near-IR (UV-Vis/NIR) diffuse reflectance spectra for mesoporous <span class="html-italic">mp</span>-CeO<sub>2</sub> and CuO/CeO<sub>2</sub> composite samples. Inset of (<b>b</b>) is the corresponding (α<span class="html-italic">hv</span>)<sup>2</sup> <span class="html-italic">versus</span> energy curves, where α is the absorption coefficient, <span class="html-italic">h</span> is Planck’s constant and <span class="html-italic">v</span> is the light frequency.</p> Full article ">Figure 5
<p>(<b>a</b>) Oxygen evolution curves and (<b>b</b>) time courses of photocatalytic O<sub>2</sub> evolution rates for mesoporous <span class="html-italic">mp</span>-CeO<sub>2</sub> and CuO/CeO<sub>2</sub> composite materials and bulk <span class="html-italic">b</span>-CuO(38)/CeO<sub>2</sub> solid.</p> Full article ">Figure 6
<p>Photocatalytic O<sub>2</sub> production mechanism on the CuO/CeO<sub>2</sub> interface under UV-Vis light irradiation (VB: valence band, CB: conduction band, NHE: normal hydrogen electrode).</p> Full article ">
1033 KiB  
Article
Surface Properties and Photocatalytic Activities of the Colloidal ZnS:Mn Nanocrystals Prepared at Various pH Conditions
by Jungho Heo and Cheong-Soo Hwang
Nanomaterials 2015, 5(4), 1955-1970; https://doi.org/10.3390/nano5041955 - 11 Nov 2015
Cited by 11 | Viewed by 6140
Abstract
Water-dispersible ZnS:Mn nanocrystals (NC) were synthesized by capping the surface with mercaptoacetic acid (MAA) molecules at three different pH conditions. The obtained ZnS:Mn-MAA NC products were physically and optically characterized by corresponding spectroscopic methods. The UV-Visible absorption spectra and PL emission spectra showed [...] Read more.
Water-dispersible ZnS:Mn nanocrystals (NC) were synthesized by capping the surface with mercaptoacetic acid (MAA) molecules at three different pH conditions. The obtained ZnS:Mn-MAA NC products were physically and optically characterized by corresponding spectroscopic methods. The UV-Visible absorption spectra and PL emission spectra showed broad peaks at 310 and 590 nm, respectively. The average particle sizes measured from the HR-TEM images were 5 nm, which were also supported by the Debye-Scherrer calculations using the X-ray diffraction (XRD) data. Moreover, the surface charges and the degrees of aggregation of the ZnS:Mn-MAA NCs were determined by electrophoretic and hydrodynamic light scattering methods, indicating formation of agglomerates in water with various sizes (50–440 nm) and different surface charge values accordingly the preparation conditions of the NCs (−7.59 to −24.98 mV). Finally, the relative photocatalytic activities of the ZnS:Mn-MAA NCs were evaluated by measuring the degradation rate of methylene blue (MB) molecule in a pseudo first-order reaction condition under the UV-visible light irradiation. As a result, the ZnS:Mn-MAA NC prepared at the pH 7 showed the best photo-degradation efficiency of the MB molecule with the first-order rate constant (kobs) of 2.0 × 10−3·min−1. Full article
(This article belongs to the Special Issue Current Trends in Colloidal Nanocrystals)
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<p>High-resolution transmission electron microscopy (HR-TEM) images of the ZnS:Mn-MAA nanocrystals (NCs) prepared at: (<b>a</b>,<b>b</b>) pH 2; (<b>c</b>,<b>d</b>) pH 7; and (<b>e</b>,<b>f</b>) pH 12.</p> Full article ">Figure 2
<p>Ultra violet (UV)-visible absorption spectra of the ZnS:Mn-MAA NCs prepared at pH 2 (blue); pH 7 (green); and pH 12 (black).</p> Full article ">Figure 3
<p>Room temperature solution photoluminescence (PL) emission spectra of the ZnS:Mn-MAA NCs prepared at pH 2 (blue); pH 7 (green); and pH 12 (black).</p> Full article ">Figure 4
<p>X-ray diffraction (XRD) pattern diagrams of the ZnS:Mn-MAA NCs prepared at: (<b>a</b>) pH 2; (<b>b</b>) pH 7; and (<b>c</b>) pH 12. The diagram (<b>d</b>) is a reference ZnS bulk solid pattern in a cubic zinc blend phase (JCPDS 05-0566).</p> Full article ">Figure 5
<p>Fourier transform (FT) -Raman spectra of the: (<b>a</b>) ZnS:Mn-MAA NC (pH 12); and (<b>b</b>) Neat MAA molecule.</p> Full article ">Figure 6
<p>Particle size distribution diagrams of the ZnS:Mn-MAA NCs prepared at pH 2 (blue), pH 7 (green), and pH 12 (black).</p> Full article ">Figure 7
<p>Temporal UV visible absorption spectral changes of methylene blue (MB) in the presence of ZnS:Mn-MAA-pH 7 NC under the UV light irradiation.</p> Full article ">Figure 8
<p>First-order kinetic plots of photo-degradation of MB in the presence of ZnS:Mn-MAA-pH 2 (blue), ZnS:Mn-MAA-pH 7 (green), and ZnS:Mn-MAA-pH 12 (black) NCs under the UV light irradiation.</p> Full article ">
751 KiB  
Article
Cytotoxicity, Uptake Behaviors, and Oral Absorption of Food Grade Calcium Carbonate Nanomaterials
by Mi-Kyung Kim, Jeong-A. Lee, Mi-Rae Jo, Min-Kyu Kim, Hyoung-Mi Kim, Jae-Min Oh, Nam Woong Song and Soo-Jin Choi
Nanomaterials 2015, 5(4), 1938-1954; https://doi.org/10.3390/nano5041938 - 10 Nov 2015
Cited by 42 | Viewed by 7645
Abstract
Calcium is the most abundant mineral in human body and essential for the formation and maintenance of bones and teeth as well as diverse cellular functions. Calcium carbonate (CaCO3) is widely used as a dietary supplement; however, oral absorption efficiency of [...] Read more.
Calcium is the most abundant mineral in human body and essential for the formation and maintenance of bones and teeth as well as diverse cellular functions. Calcium carbonate (CaCO3) is widely used as a dietary supplement; however, oral absorption efficiency of CaCO3 is extremely low, which may be overcome by applying nano-sized materials. In this study, we evaluated the efficacy of food grade nano CaCO3 in comparison with that of bulk- or reagent grade nano CaCO3 in terms of cytotoxicity, cellular uptake, intestinal transport, and oral absorption. Cytotoxicity results demonstrated that nano-sized CaCO3 particles were slightly more toxic than bulk materials in terms of oxidative stress and membrane damage. Cellular uptake behaviors of CaCO3 nanoparticles were different from bulk CaCO3 or Ca2+ ions in human intestinal epithelial cells, showing efficient cellular internalization and elevated intracellular Ca2+ levels. Meanwhile, CaCO3 nanoparticles were efficiently transported by microfold (M) cells in vitro model of human intestinal follicle-associated epithelium, in a similar manner as Ca2+ ions did. Biokinetic study revealed that the biological fate of CaCO3 particles was different from Ca2+ ions; however, in vivo, its oral absorption was not significantly affected by particle size. These findings provide crucial information to understand and predict potential toxicity and oral absorption efficiency of food grade nanoparticles. Full article
(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)
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<p>Scanning electron microscopy (SEM) images, atomic force microscope (AFM) images, height profiles, and 3D images of (<b>A</b>) food bulk CaCO<sub>3</sub>; (<b>B</b>) food nano CaCO<sub>3</sub>; and (<b>C</b>) SS CaCO<sub>3</sub>.</p> Full article ">Figure 2
<p>Hydrodynamic diameter of food bulk CaCO<sub>3</sub> (dashed line), food nano CaCO<sub>3</sub> (solid line) and SS CaCO<sub>3</sub> (dotted line) as a function of differntial intensity. Horizontal line stands for the position of full-width at half-maximum to evaluate peak broadness.</p> Full article ">Figure 3
<p>Effect of three different types of CaCO<sub>3</sub> particles on cell proliferation of human intestinal INT-407 cells, as measured by water-soluble tetrazolium salts (WST-1) assay. (<b>A</b>) Cell proliferation exposed to 250 μg/mL particles or an equivalent amount of CaCl<sub>2</sub> (based on calcium content) for 1–24 h; (<b>B</b>) Cell proliferation treated with different concentrations of CaCO<sub>3</sub> particles or CaCl<sub>2</sub> for 24 h.</p> Full article ">Figure 4
<p>Effect of three different types of CaCO<sub>3</sub> particles or an equivalent amount of CaCl<sub>2</sub> (based on calcium content) on (<b>A</b>) ROS generation and (<b>B</b>) lactate dehydrogenase (LDH) release from human intestinal INT-407 cells after 24 h of incubation. The mean values with different letters (a, a,b, b, c) at the same concentration or time points indicate statistically significant difference (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 5
<p>(<b>A</b>) Cellular internalization of three different types of CaCO<sub>3</sub> particles or an equivalent amount of CaCl<sub>2</sub> (based on calcium content) in human intestinal INT-407 cells after 2 h of incubation, as measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES); (<b>B</b>) intracellular Ca<sup>2+</sup> levels monitored with Calcium Green™<sup>−1</sup> probe (Life Technologies, Carsbad, CA, USA). The mean values with different letters (a, a,b, b) at the same temperature or time points indicate statistically significant difference (<span class="html-italic">p</span> &lt; 0.05). * denotes significant difference in uptake amount between 37 and 4 °C (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 6
<p>Intestinal transport of three different types of CaCO<sub>3</sub> particles or an equivalent amount of CaCl<sub>2</sub> (based on calcium content) by microfold (M) cells using an <span class="html-italic">in vitro</span> model of human FAE after 6 h of incubation, as measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The mean values with different letters (a, a,b, b) in tested groups indicate statistically significant difference (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 7
<p>Plasma concentration-time curves of three different types of CaCO<sub>3</sub> particles (250 μg/mL) or an equivalent amount of CaCl<sub>2</sub> (based on calcium content) after a single-dose oral administration to female rats. Biokinetic data are presented as increase in calcium levels after subtracting the basal plasma calcium levels detected in untreated controls.</p> Full article ">
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Review
Smart Mesoporous Nanomaterials for Antitumor Therapy
by Marina Martínez-Carmona, Montserrat Colilla and Maria Vallet-Regí
Nanomaterials 2015, 5(4), 1906-1937; https://doi.org/10.3390/nano5041906 - 6 Nov 2015
Cited by 79 | Viewed by 10697
Abstract
The use of nanomaterials for the treatment of solid tumours is receiving increasing attention by the scientific community. Among them, mesoporous silica nanoparticles (MSNs) exhibit unique features that make them suitable nanocarriers to host, transport and protect drug molecules until the target is [...] Read more.
The use of nanomaterials for the treatment of solid tumours is receiving increasing attention by the scientific community. Among them, mesoporous silica nanoparticles (MSNs) exhibit unique features that make them suitable nanocarriers to host, transport and protect drug molecules until the target is reached. It is possible to incorporate different targeting ligands to the outermost surface of MSNs to selectively drive the drugs to the tumour tissues. To prevent the premature release of the cargo entrapped in the mesopores, it is feasible to cap the pore entrances using stimuli-responsive nanogates. Therefore, upon exposure to internal (pH, enzymes, glutathione, etc.) or external (temperature, light, magnetic field, etc.) stimuli, the pore opening takes place and the release of the entrapped cargo occurs. These smart MSNs are capable of selectively reaching and accumulating at the target tissue and releasing the entrapped drug in a specific and controlled fashion, constituting a promising alternative to conventional chemotherapy, which is typically associated with undesired side effects. In this review, we overview the recent advances reported by the scientific community in developing MSNs for antitumor therapy. We highlight the possibility to design multifunctional nanosystems using different therapeutic approaches aimed at increasing the efficacy of the antitumor treatment. Full article
(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)
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<p>Schematic depiction of drug administration for cancer therapy: systemic treatments <span class="html-italic">versus</span> targeted therapies using nanomaterials.</p> Full article ">Figure 2
<p><b>Left</b>: Main characteristics of MSNs. <b>Right</b>: transmission electron microscopy (TEM) images of 2D-hexagonal MCM-41 type mesoporous silica nanoparticles (MSNs) taken with the electron beam parallel (<b>up</b>) and perpendicular (<b>down</b>) to the mesoporous channels.</p> Full article ">Figure 3
<p>Schematic illustration of enhanced permeation and retention (EPR) effect.</p> Full article ">Figure 4
<p>Molecular targets for active targeting of cancer by mesoporous silica nanoparticles: (i) tumor cell membrane receptors, such as transferrin receptors (TfR), folic acid receptors (FR-α) and lectin receptors; (ii) tumor vasculature receptors, such metalloproteinases, as αβ-integrins and vascular endothelial growth factor receptor (VEGFR). Molecular targets for active targeting of cancer by mesoporous silica nanoparticles.</p> Full article ">Figure 5
<p>Schematic representation of the performance of stimuli-responsive MSNs.</p> Full article ">Figure 6
<p><b>Up</b>: Schematic illustration of the action mechanism of light-responsive nanosystem based in MSNs decorated with a biocompatible protein shell (transferrin, Tf, grafted to MSNs using a light cleavable photolinker), affording MSN-Tf. <b>Down</b>: Cellular uptake of MSNs and MSN-Tf labeled with fluorescein. Confocal microscopy images show NPs (green) inside tumor cells (actin in red, nucleus in blue). The light irradiation of MSN-Tf provokes the cleaving of the photolinker, which triggers pore uncapping and subsequent drug release [<a href="#B76-nanomaterials-05-01906" class="html-bibr">76</a>].</p> Full article ">Figure 7
<p>Schematic illustration of the <span class="html-italic">in situ</span> cytotoxic generation for antitumor therapy [<a href="#B139-nanomaterials-05-01906" class="html-bibr">139</a>]. (i) Functionalization of MSNs with amino group (MSN-NH<sub>2</sub>); (ii) loading of the pro-drug indol-3-acetic acid (IAA) (MSN-NH<sub>2</sub>-IAA); grafting of an enzyme horseradish peroxidase (HRP)-polymer nanocapsule to the external surface of the nanosystem (MSN-NH<sub>2</sub>-IAA-HRPc). TEM images of the nanosystem and cytotoxicity studies with neuroblastoma cells are also displayed.</p> Full article ">
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Article
Nanoporous Carbon Nanofibers Decorated with Platinum Nanoparticles for Non-Enzymatic Electrochemical Sensing of H2O2
by Yang Li, Mingfa Zhang, Xiaopeng Zhang, Guocheng Xie, Zhiqiang Su and Gang Wei
Nanomaterials 2015, 5(4), 1891-1905; https://doi.org/10.3390/nano5041891 - 6 Nov 2015
Cited by 56 | Viewed by 8098
Abstract
We describe the preparation of nanoporous carbon nanofibers (CNFs) decorated with platinum nanoparticles (PtNPs) in this work by electrospining polyacrylonitrile (PAN) nanofibers and subsequent carbonization and binding of PtNPs. The fabricated nanoporous CNF-PtNP hybrids were further utilized to modify glass carbon electrodes and [...] Read more.
We describe the preparation of nanoporous carbon nanofibers (CNFs) decorated with platinum nanoparticles (PtNPs) in this work by electrospining polyacrylonitrile (PAN) nanofibers and subsequent carbonization and binding of PtNPs. The fabricated nanoporous CNF-PtNP hybrids were further utilized to modify glass carbon electrodes and used for the non-enzymatic amperometric biosensor for the highly sensitive detection of hydrogen peroxide (H2O2). The morphologies of the fabricated nanoporous CNF-PtNP hybrids were observed by scanning electron microscopy, transmission electron microscopy, and their structure was further investigated with Brunauer–Emmett–Teller (BET) surface area analysis, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectrum. The cyclic voltammetry experiments indicate that CNF-PtNP modified electrodes have high electrocatalytic activity toward H2O2 and the chronoamperometry measurements illustrate that the fabricated biosensor has a high sensitivity for detecting H2O2. We anticipate that the strategies utilized in this work will not only guide the further design and fabrication of functional nanofiber-based biomaterials and nanodevices, but also extend the potential applications in energy storage, cytology, and tissue engineering. Full article
(This article belongs to the Special Issue Nanomaterials for Biosensing Applications)
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<p>Schematic presentation on: (<b>a</b>) The electrospinning apparatus for preparing the polyacrylonitrile (PAN)-CaCO<sub>3</sub> nanofibers (NFs); and (<b>b</b>) Preparation of nanoporous carbon nanofibers (CNFs) decorated with platinum nanoparticles (PtNPs) (CNF-PtNP) hybrid.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) images of electrospun PAN-CaCO<sub>3</sub> NFs: (<b>a</b>,<b>b</b>) Different magnification, and (<b>c</b>,<b>d</b>) Longitudinal section.</p> Full article ">Figure 3
<p>Morphology characterization: (<b>a</b>,<b>b</b>) SEM images of electrospun PAN-CaCO<sub>3</sub> hybrid NFs by treating with carbonization and HCl; (<b>c</b>) SEM image for the cross-section of porous CNFs; (<b>d</b>) TEM image of the porous CNFs.</p> Full article ">Figure 4
<p>N<sub>2</sub> adsorption/desorption isotherms of the CNF-PtNP hybrids as well as the pore size distributions.</p> Full article ">Figure 5
<p>(<b>a</b>) Typical SEM image of the fabricated nanoporous CNF-PtNP hybrids; (<b>b</b>) Energy-dispersive X-ray (EDX) spectra of the fabricated nanoporous CNF-PtNP hybrids.</p> Full article ">Figure 6
<p>Characterization of electrospun CNF-PtNP hybrids: (<b>a</b>,<b>b</b>) X-ray photoelectron spectroscopy (XPS) spectra; (<b>c</b>) Power X-ray diffraction (XRD) pattern; and (<b>d</b>) Raman spectrum.</p> Full article ">Figure 7
<p>Electrochemical detection of H<sub>2</sub>O<sub>2</sub>: (<b>a</b>) Cyclic voltammograms (CVs) of glass carbon electrode (GCE) and GCEs modified with CNFs and CNF-PtNP hybrids; (<b>b</b>) I-T response of CNF-PtNP modified GCE; (<b>c</b>) Calibrated line; and (<b>d</b>) Selectivity of biosensor.</p> Full article ">
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Article
T1-MRI Fluorescent Iron Oxide Nanoparticles by Microwave Assisted Synthesis
by Riju Bhavesh, Ana V. Lechuga-Vieco, Jesús Ruiz-Cabello and Fernando Herranz
Nanomaterials 2015, 5(4), 1880-1890; https://doi.org/10.3390/nano5041880 - 4 Nov 2015
Cited by 22 | Viewed by 6872
Abstract
Iron oxide nanoparticles have long been studied as a T2 contrast agent in MRI due to their superparamagnetic behavior. T1-based positive contrast, being much more favorable for clinical application due to brighter and more accurate signaling is, however, still limited [...] Read more.
Iron oxide nanoparticles have long been studied as a T2 contrast agent in MRI due to their superparamagnetic behavior. T1-based positive contrast, being much more favorable for clinical application due to brighter and more accurate signaling is, however, still limited to gadolinium- or manganese-based imaging tools. Though being the only available commercial positive-contrast agents, they lack an efficient argument when it comes to biological toxicity and their circulatory half-life in blood. The need arises to design a biocompatible contrast agent with a scope for easy surface functionalization for long circulation in blood and/or targeted imaging. We hereby propose an extremely fast microwave synthesis for fluorescein-labeled extremely-small iron oxide nanoparticles (fdIONP), in a single step, as a viable tool for cell labeling and T1-MRI. We demonstrate the capabilities of such an approach through high-quality magnetic resonance angiographic images of mice. Full article
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<p>Physicochemical characterization of fdIONP. (<b>a</b>) Hydrodynamic size for fdIONP (<span class="html-italic">N</span> = 6); (<b>b</b>) Transmission electron microscopy (TEM) image of fdIONP; (<b>c</b>) Fourier transform infrared spectroscopy (FTIR) spectrum for fdIONP; (<b>d</b>) Field dependent magnetization of fdIONP and (<b>e</b>) Relaxivities (<span class="html-italic">r</span><sub>1</sub> and <span class="html-italic">r</span><sub>2</sub>) measurements for fdIONP in water at 37 °C and 1.5 T.</p> Full article ">Figure 2
<p>(<b>a</b>) Fluorescent imaging and magnetic resonance imaging (MRI) of labeled MAFs cells with fdIONP; (<b>b</b>) Percentage of signal enhancement in magnetic resonance images of labeled MAFs cells; (<b>c</b>) Percentage of signal enhancement in fluorescence images of labeled MAFs cells; and (<b>d</b>) Fluorescent confocal images of fdIONP-labeled cells at 80 µg/mL Fe concentration after 24 h of incubation, signal from fdIONP (green), phalloidin dye (red), and DAPI (blue).</p> Full article ">Figure 3
<p>Magnetic resonance angiography of a mouse at increasing times after intravenous injection of fdIONP.</p> Full article ">
704 KiB  
Review
Gold Nanotheranostics: Proof-of-Concept or Clinical Tool?
by Pedro Pedrosa, Raquel Vinhas, Alexandra Fernandes and Pedro V Baptista
Nanomaterials 2015, 5(4), 1853-1879; https://doi.org/10.3390/nano5041853 - 3 Nov 2015
Cited by 107 | Viewed by 12242
Abstract
Nanoparticles have been making their way in biomedical applications and personalized medicine, allowing for the coupling of diagnostics and therapeutics into a single nanomaterial—nanotheranostics. Gold nanoparticles, in particular, have unique features that make them excellent nanomaterials for theranostics, enabling the integration of targeting, [...] Read more.
Nanoparticles have been making their way in biomedical applications and personalized medicine, allowing for the coupling of diagnostics and therapeutics into a single nanomaterial—nanotheranostics. Gold nanoparticles, in particular, have unique features that make them excellent nanomaterials for theranostics, enabling the integration of targeting, imaging and therapeutics in a single platform, with proven applicability in the management of heterogeneous diseases, such as cancer. In this review, we focus on gold nanoparticle-based theranostics at the lab bench, through pre-clinical and clinical stages. With few products facing clinical trials, much remains to be done to effectively assess the real benefits of nanotheranostics at the clinical level. Hence, we also discuss the efforts currently being made to translate nanotheranostics into the market, as well as their commercial impact. Full article
(This article belongs to the Special Issue Nanoparticles in Theranostics)
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<p>Different types of nanoparticles and their applications in theranostic. Schematic overview of the possible functionalization and application of gold nanoparticles (AuNPs) as nanocarriers for theranostics.</p> Full article ">Figure 2
<p>Schematics of a multifunctional approach, coupling targeting, chemotherapy, gene therapy, phototherapy and diagnostics by fluorescent imaging.</p> Full article ">
5799 KiB  
Article
Structural Stability of Diffusion Barriers in Cu/Ru/MgO/Ta/Si
by Shu-Huei Hsieh, Wen Jauh Chen and Chu-Mo Chien
Nanomaterials 2015, 5(4), 1840-1852; https://doi.org/10.3390/nano5041840 - 3 Nov 2015
Cited by 6 | Viewed by 5912
Abstract
Various structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si were prepared by sputtering and electroplating techniques, in which the ultra-thin trilayer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is used as the diffusion barrier against the interdiffusion between Cu [...] Read more.
Various structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si were prepared by sputtering and electroplating techniques, in which the ultra-thin trilayer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is used as the diffusion barrier against the interdiffusion between Cu film and Si substrate. The various structures of Cu/Ru/MgO/Ta/Si were characterized by four-point probes for their sheet resistances, by X-ray diffractometers for their crystal structures, by scanning electron microscopes for their surface morphologies, and by transmission electron microscopes for their cross-section and high resolution views. The results showed that the ultra-thin tri-layer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is an effective diffusion barrier against the interdiffusion between Cu film and Si substrate. The MgO, and Ta layers as deposited are amorphous. The mechanism for the failure of the diffusion barrier is that the Ru layer first became discontinuous at a high temperature and the Ta layer sequentially become discontinuous at a higher temperature, the Cu atoms then diffuse through the MgO layer and to the substrate at the discontinuities, and the Cu3Si phases finally form. The maximum temperature at which the structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si are annealed and still have low sheet resistance is from 550 to 750 °C for the annealing time of 5 min and from 500 to 700 °C for the annealing time of 30 min. Full article
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<p>Relation between sheet resistances and annealing temperatures for Cu (50 nm)/Ru (2 nm)/MgO (3 nm)/Ta (2 nm)/Si structure annealed for 5 min.</p> Full article ">Figure 2
<p>X-ray diffraction patterns for the MgO (3 nm) sample annealed for 5 min at temperatures from room temperature to 800 °C.</p> Full article ">Figure 3
<p>Scanning electron microscope (SEM) views for the surface morphologies of MgO (3 nm) sample annealed for 5 min at temperatures of 700 °C (<b>a</b>); 750 °C (<b>b</b>); and 800 °C (<b>c</b>); respectively.</p> Full article ">Figure 4
<p>Transmission electron microscope (TEM) cross section views for the MgO (3 nm) sample as deposited at a relatively low magnification (<b>a</b>); and at a relatively high magnification (500,000×) (<b>b</b>).</p> Full article ">Figure 5
<p>TEM cross section views for the structures of MgO (3 nm) sample annealed for 5 min at 500 °C at a relatively low magnification (<b>a</b>); and at a relatively high magnification (<b>b</b>).</p> Full article ">Figure 6
<p>TEM cross section views for the structures of Cu (50 nm)/Ru (2 nm)/MgO (3 nm)/Ta (2 nm)/Si annealed for 5 min at 750 °C at a relatively low magnification (<b>a</b>); and at a relatively high magnification (<b>b</b>).</p> Full article ">Figure 7
<p>(<b>a</b>) TEM cross section views for the MgO (3 nm) sample annealed for 5 min at 800 °C; (<b>b</b>) Enlarged view of the left part of (<b>a</b>).</p> Full article ">Figure 8
<p>Relation between sheet resistances and annealing temperatures for a Cu (50 nm)/Ru (2 nm)/MgO (2 nm)/Ta (2 nm)/Si structure annealed for 5 min.</p> Full article ">Figure 9
<p>X-ray diffraction patterns for the structures of MgO (2 nm) sample annealed for 5 min at temperatures from room temperature to 800 °C.</p> Full article ">Figure 10
<p>SEM views for the surface morphologies of structures of MgO (2 nm) sample annealed for 5 min at temperatures 700 °C (<b>a</b>); 750 °C (<b>b</b>); and 800 °C (<b>c</b>); respectively.</p> Full article ">Figure 11
<p>Relation between sheet resistance and annealing temperature for Cu (50 nm)/Ru (2 nm)/MgO (1 nm)/Ta (2 nm)/Si structures annealed for 5 min.</p> Full article ">Figure 12
<p>X-ray diffraction patterns for the structures of MgO (1 nm) sample annealed for 5 min at temperatures from room temperature to 800 °C.</p> Full article ">Figure 13
<p>SEM views for the surface morphologies of structures of MgO (1 nm) sample annealed for 5 min at temperatures at 700 °C (<b>a</b>); 750 °C (<b>b</b>); and 800 °C (<b>c</b>); respectively.</p> Full article ">Figure 14
<p>Relation between sheet resistances and annealing temperatures for the Cu (50 nm)/Ru (2 nm)/MgO (0.5 nm)/Ta (2 nm)/Si structures annealed for 5 min.</p> Full article ">Figure 15
<p>X-ray diffraction patterns for the structures of MgO (0.5 nm) sample annealed for 5 min at temperatures from room temperature to 650 °C.</p> Full article ">Figure 16
<p>SEM images for the surface morphologies of structures of MgO (0.5 nm) sample annealed for 5 min at temperature 500 °C (<b>a</b>); 550 °C (<b>b</b>); and 600 °C (<b>c</b>), respectively.</p> Full article ">
2348 KiB  
Article
Effects of Annealing Temperature on Properties of Ti-Ga–Doped ZnO Films Deposited on Flexible Substrates
by Tao-Hsing Chen and Ting-You Chen
Nanomaterials 2015, 5(4), 1831-1839; https://doi.org/10.3390/nano5041831 - 3 Nov 2015
Cited by 24 | Viewed by 5362
Abstract
An investigation is performed into the optical, electrical, and microstructural properties of Ti-Ga–doped ZnO films deposited on polyimide (PI) flexible substrates and then annealed at temperatures of 300 °C, 400 °C, and 450 °C, respectively. The X-ray diffraction (XRD) analysis results show that [...] Read more.
An investigation is performed into the optical, electrical, and microstructural properties of Ti-Ga–doped ZnO films deposited on polyimide (PI) flexible substrates and then annealed at temperatures of 300 °C, 400 °C, and 450 °C, respectively. The X-ray diffraction (XRD) analysis results show that all of the films have a strong (002) Ga doped ZnO (GZO) preferential orientation. As the annealing temperature is increased to 400 °C, the optical transmittance increases and the electrical resistivity decreases. However, as the temperature is further increased to 450 °C, the transmittance reduces and the resistivity increases due to a carbonization of the PI substrate. Finally, the crystallinity of the ZnO film improves with an increasing annealing temperature only up to 400 °C and is accompanied by a smaller crystallite size and a lower surface roughness. Full article
(This article belongs to the Special Issue Nanomaterials for Flexible and Stretchable Devices: Synthesis, Processes, and Applications)
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<p>Energy dispersive X-ray (EDX) analysis results for as-deposited Ti-Ga–doped ZnO film.</p> Full article ">Figure 2
<p>(<b>a</b>) X-ray diffraction (XRD) patterns; (<b>b</b>) Full width at half maximum (FWHM) values of as-deposited and annealed Ti-Ga–doped ZnO thin films as a function of annealing temperature.</p> Full article ">Figure 3
<p>Optical transmittance of as-deposited and annealed Ti-Ga–doped ZnO thin films.</p> Full article ">Figure 4
<p>(<b>a</b>) Resistivity; (<b>b</b>) Carrier concentration; and (<b>c</b>) Hall mobility of as-deposited and annealed Ti-Ga–doped ZnO thin films.</p> Full article ">Figure 5
<p>Three-dimensional (3D) atomic force microscope (AFM) images of Ti-Ga–doped ZnO thin films in (<b>a</b>) as-deposited condition; and following annealing at: (<b>b</b>) 300 °C; (<b>c</b>) 400 °C; and (<b>d</b>) 450 °C.</p> Full article ">Figure 6
<p>Scanning electron microscope (SEM) images of Ti-Ga–doped ZnO films in (<b>a</b>) as-deposited condition; and following annealing at: (<b>b</b>) 300 °C; (<b>c</b>) 400 °C; and (<b>d</b>) 450 °C.</p> Full article ">Figure 6 Cont.
<p>Scanning electron microscope (SEM) images of Ti-Ga–doped ZnO films in (<b>a</b>) as-deposited condition; and following annealing at: (<b>b</b>) 300 °C; (<b>c</b>) 400 °C; and (<b>d</b>) 450 °C.</p> Full article ">
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