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Nanomaterials
Volume 7
Issue 1
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Nanomaterials, Volume 7, Issue 1 (January 2017) – 22 articles

Cover Story (view full-size image): We developed a novel heterostructure of multiwalled carbon nanotubes (MWCNTs) coated with BiOI nanosheets via a facile one-pot solvothermal method as an efficient visible-light-driven (VLD) photocatalyst. The MWCNTs/BiOI composite can efficiently degrade diverse organic pollutants (RhB/MO/4-CP) with good stability due to the strong coupling interface between MWCNTs and BiOI. Therefore, MWCNTs/BiOI has great potential as an efficient and stable VLD photocatalyst for wastewater treatment. View the paper
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6336 KiB  
Article
A Novel Heterostructure of BiOI Nanosheets Anchored onto MWCNTs with Excellent Visible-Light Photocatalytic Activity
by Shijie Li, Shiwei Hu, Kaibing Xu, Wei Jiang, Jianshe Liu and Zhaohui Wang
Nanomaterials 2017, 7(1), 22; https://doi.org/10.3390/nano7010022 - 23 Jan 2017
Cited by 48 | Viewed by 6743
Abstract
Developing efficient visible-light-driven (VLD) photocatalysts for environmental decontamination has drawn significant attention in recent years. Herein, we have reported a novel heterostructure of multiwalled carbon nanotubes (MWCNTs) coated with BiOI nanosheets as an efficient VLD photocatalyst, which was prepared via a simple solvothermal [...] Read more.
Developing efficient visible-light-driven (VLD) photocatalysts for environmental decontamination has drawn significant attention in recent years. Herein, we have reported a novel heterostructure of multiwalled carbon nanotubes (MWCNTs) coated with BiOI nanosheets as an efficient VLD photocatalyst, which was prepared via a simple solvothermal method. The morphology and structure were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and specific surface area measurements. The results showed that BiOI nanosheets were well deposited on MWCNTs. The MWCNTs/BiOI composites exhibited remarkably enhanced photocatalytic activity for the degradation of rhodamine B (RhB), methyl orange (MO), and para-chlorophenol (4-CP) under visible-light, compared with pure BiOI. When the MWCNTs content is 3 wt %, the MWCNTs/BiOI composite (3%M-Bi) achieves the highest activity, which is even higher than that of a mechanical mixture (3 wt % MWCNTs + 97 wt % BiOI). The superior photocatalytic activity is predominantly due to the strong coupling interface between MWCNTs and BiOI, which significantly promotes the efficient electron-hole separation. The photo-induced holes (h+) and superoxide radicals (O2−) mainly contribute to the photocatalytic degradation of RhB over 3%M-Bi. Therefore, the MWCNTs/BiOI composite is expected to be an efficient VLD photocatalyst for environmental purification. Full article
(This article belongs to the Special Issue Nanoscale in Photocatalysis)
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Full article ">Figure 1
<p>X-ray diffraction (XRD) patterns of as-prepared multiwalled carbon nanotubes (MWCNTs)/BiOI composites, BiOI, and MWCNTs.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) images of (<b>a</b>) BiOI, and (<b>b</b>–<b>d</b>) 3%M-Bi.</p> Full article ">Figure 3
<p>(<b>a</b>–<b>d</b>) Transmission electron microscopy (TEM) images of 3%M-Bi.</p> Full article ">Figure 4
<p>(<b>a</b>) N<sub>2</sub> adsorption/desorption isotherms of BiOI and 3%M-Bi; the inset is the corresponding pore size distributions; (<b>b</b>) UV-Vis reflectance spectra of BiOI, MWCNTs, and MWCNTs/BiOI composites.</p> Full article ">Figure 5
<p>(<b>a</b>) UV-Vis absorption spectra of rhodamine B (RhB) dye versus reaction time over 3%M-Bi; (<b>b</b>) Photocatalytic degradation of RhB under visible light (λ &gt; 400 nm), in the absence of catalysts and in the presence of as-prepared catalysts (10 mg).</p> Full article ">Figure 6
<p>The effect of the initial concentrations of RhB (<b>a</b>) and methyl orange (MO) (<b>b</b>) on the photocatalytic activity of 3%M-Bi (10 mg).</p> Full article ">Figure 7
<p>The degradation efficiencies (<b>a</b>) and rate constants (<b>b</b>) of <span class="html-italic">para</span>-chlorophenol (4-CP) in aqueous solution (1 mg·L<sup>−1</sup>, 50 mL) versus the exposure time under visible light (λ &gt; 400 nm), in the absence of catalysts and in the presence of as-prepared catalysts (10 mg).</p> Full article ">Figure 8
<p>Total organic carbon (TOC) removal during RhB degradation (40 mg·L<sup>−1</sup>, 100 mL) over 3%M-Bi (100 mg) under visible light (λ &gt; 400 nm).</p> Full article ">Figure 9
<p>(<b>a</b>) Cycling runs in photocatalytic degradation of RhB (5 mg·L<sup>−1</sup>, 50 mL) over 3%M-Bi (10 mg) under visible light (λ &gt; 400 nm); (<b>b</b>) XRD patterns of 3%M-Bi before and after the reaction.</p> Full article ">Figure 10
<p>Effect of different scavengers on the degradation efficiencies (<b>a</b>) and rate constants (<b>b</b>) of RhB over 3%M-Bi under visible light (λ &gt; 400 nm).</p> Full article ">Figure 11
<p>The proposed photocatalytic mechanism for the high activity of MWCNTs/BiOI.</p> Full article ">
2569 KiB  
Review
Behavior and Potential Impacts of Metal-Based Engineered Nanoparticles in Aquatic Environments
by Cheng Peng, Wen Zhang, Haiping Gao, Yang Li, Xin Tong, Kungang Li, Xiaoshan Zhu, Yixiang Wang and Yongsheng Chen
Nanomaterials 2017, 7(1), 21; https://doi.org/10.3390/nano7010021 - 22 Jan 2017
Cited by 126 | Viewed by 10116
Abstract
The specific properties of metal-based nanoparticles (NPs) have not only led to rapidly increasing applications in various industrial and commercial products, but also caused environmental concerns due to the inevitable release of NPs and their unpredictable biological/ecological impacts. This review discusses the environmental [...] Read more.
The specific properties of metal-based nanoparticles (NPs) have not only led to rapidly increasing applications in various industrial and commercial products, but also caused environmental concerns due to the inevitable release of NPs and their unpredictable biological/ecological impacts. This review discusses the environmental behavior of metal-based NPs with an in-depth analysis of the mechanisms and kinetics. The focus is on knowledge gaps in the interaction of NPs with aquatic organisms, which can influence the fate, transport and toxicity of NPs in the aquatic environment. Aggregation transforms NPs into micrometer-sized clusters in the aqueous environment, whereas dissolution also alters the size distribution and surface reactivity of metal-based NPs. A unique toxicity mechanism of metal-based NPs is related to the generation of reactive oxygen species (ROS) and the subsequent ROS-induced oxidative stress. Furthermore, aggregation, dissolution and ROS generation could influence each other and also be influenced by many factors, including the sizes, shapes and surface charge of NPs, as well as the pH, ionic strength, natural organic matter and experimental conditions. Bioaccumulation of NPs in single organism species, such as aquatic plants, zooplankton, fish and benthos, is summarized and compared. Moreover, the trophic transfer and/or biomagnification of metal-based NPs in an aquatic ecosystem are discussed. In addition, genetic effects could result from direct or indirect interactions between DNA and NPs. Finally, several challenges facing us are put forward in the review. Full article
(This article belongs to the Special Issue Environmental Applications and Implications of Nanotechnology)
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Figure 1
<p>Potential physiochemical processes and biological impacts of metal-based NPs (e.g., Ag NPs) in natural waters (reprinted with major modification from [<a href="#B44-nanomaterials-07-00021" class="html-bibr">44</a>] with permission, Copyright Elsevier, 2011).</p> Full article ">Figure 2
<p>Mechanism of photogenerated ROS (<b>a</b>); and correlation with the antibacterial properties of metal-based NPs (<b>b</b>) (reproduced with permission from [<a href="#B29-nanomaterials-07-00021" class="html-bibr">29</a>], Copyright American Chemical Society, 2012).</p> Full article ">Figure 3
<p>Surface interactions affect the toxicity of metal oxide NPs toward <span class="html-italic">Paramecium</span>: (<b>a</b>) survival ratios of <span class="html-italic">P. multimicronucleatum</span> after 48 h of exposure to NPs; (<b>b</b>) net interaction energy profiles between NPs and <span class="html-italic">P. multimicronucleatum</span>; (<b>c</b>) relationship of the magnitude of energy barrier and the 48-h <span class="html-italic">LC</span><sub>50</sub> of metal oxide NPs to <span class="html-italic">P. multimicronucleatum</span> (reproduced with permission from [<a href="#B213-nanomaterials-07-00021" class="html-bibr">213</a>], Copyright American Chemical Society, 2012)</p> Full article ">Figure 4
<p>Relationship between the tested concentration of NPs significantly inhibiting DNA replication in vitro and the determined energy barrier between NPs and DNA (reprinted with permission from [<a href="#B258-nanomaterials-07-00021" class="html-bibr">258</a>], Copyright American Chemical Society, 2013).</p> Full article ">
3778 KiB  
Article
Enhanced Visible Light Photocatalytic Activity of ZnO Nanowires Doped with Mn2+ and Co2+ Ions
by Wei Li, Guojing Wang, Chienhua Chen, Jiecui Liao and Zhengcao Li
Nanomaterials 2017, 7(1), 20; https://doi.org/10.3390/nano7010020 - 19 Jan 2017
Cited by 149 | Viewed by 8627
Abstract
In this research, ZnO nanowires doped with Mn2+ and Co2+ ions were synthesized through a facile and inexpensive hydrothermal approach, in which Mn2+ and Co2+ ions successfully substituted Zn2+ in the ZnO crystal lattice without changing the morphology [...] Read more.
In this research, ZnO nanowires doped with Mn2+ and Co2+ ions were synthesized through a facile and inexpensive hydrothermal approach, in which Mn2+ and Co2+ ions successfully substituted Zn2+ in the ZnO crystal lattice without changing the morphology and crystalline structure of ZnO. The atomic percentages of Mn and Co were 6.29% and 1.68%, respectively, in the doped ZnO nanowires. The photocatalytic results showed that Mn-doped and Co-doped ZnO nanowires both exhibited higher photocatalytic activities than undoped ZnO nanowires. Among the doped ZnO nanowires, Co-doped ZnO, which owns a twice active visible-light photocatalytic performance compared to pure ZnO, is considered a more efficient photocatalyst material. The enhancement of its photocatalytic performance originates from the doped metal ions, which enhance the light absorption ability and inhibit the recombination of photo-generated electron-hole pairs as well. The effect of the doped ion types on the morphology, crystal lattice and other properties of ZnO was also investigated. Full article
(This article belongs to the Special Issue Nanoscale in Photocatalysis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>X-ray diffraction (XRD) pattern of ZnO, Mn-doped ZnO and Co-doped ZnO.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) images of the top and side view of (<b>a</b>,<b>b</b>) ZnO; (<b>c</b>,<b>d</b>) Mn-doped ZnO; (<b>d</b>,<b>e</b>) Co-doped ZnO. Energy dispersive X-ray spectroscopy (EDS) pattern of (<b>g</b>) Mn-doped ZnO; (<b>h</b>) Co-doped ZnO.</p> Full article ">Figure 3
<p>X-ray photoelectron (XPS) spectra of Mn-doped ZnO (<b>a</b>) Zn 2p; (<b>c</b>) O 1s; (<b>e</b>) Mn 2p and Co-doped ZnO (<b>b</b>) Zn 2p; (<b>d</b>) O 1 s; (<b>f</b>) Co 2p.</p> Full article ">Figure 4
<p>(<b>a</b>) UV-Vis spectra of ZnO, Mn-doped ZnO and Co-doped ZnO; (<b>b</b>) bandgap calculation figure.</p> Full article ">Figure 5
<p>Photoluminescence (PL) spectrum of ZnO, Mn-doped ZnO and Co-doped ZnO.</p> Full article ">Figure 6
<p>The absorption spectra of MO degraded by (<b>a</b>) ZnO; (<b>b</b>) Mn-doped ZnO; (<b>c</b>) Co-doped ZnO; (<b>d</b>) ln(<span class="html-italic">c<sub>t</sub></span>/<span class="html-italic">c</span><sub>0</sub>)-<span class="html-italic">t</span> figure. Cycling performance of (<b>e</b>) Mn-doped ZnO; (<b>f</b>) Co-doped ZnO.</p> Full article ">Figure 7
<p>The photocatalytic mechanism of Mn-doped ZnO and Co-doped ZnO nanowires.</p> Full article ">
3496 KiB  
Article
Enhanced Photocatalytic Performance under Visible and Near-Infrared Irradiation of Cu1.8Se/Cu3Se2 Composite via a Phase Junction
by Li-Na Qiao, Huan-Chun Wang, Yang Shen, Yuan-Hua Lin and Ce-Wen Nan
Nanomaterials 2017, 7(1), 19; https://doi.org/10.3390/nano7010019 - 18 Jan 2017
Cited by 31 | Viewed by 6159
Abstract
A novel Cu1.8Se/Cu3Se2 composite photocatalyst was prepared by the simple precipitation method. This composite possesses a wide photoabsorption until the range of near-infrared light, and exhibits significantly enhanced photocatalytic activity for methyl orange degradation under visible and near-infrared [...] Read more.
A novel Cu1.8Se/Cu3Se2 composite photocatalyst was prepared by the simple precipitation method. This composite possesses a wide photoabsorption until the range of near-infrared light, and exhibits significantly enhanced photocatalytic activity for methyl orange degradation under visible and near-infrared light irradiation compared with bare Cu1.8Se and Cu3Se2. The mechanism of this outstanding photocatalytic behavior can be explained by the calculated energy band positions. The efficient charge separation via a phase junction of Cu1.8Se/Cu3Se2 composite would make a great contribution to its much-enhanced photocatalytic efficiency. Full article
(This article belongs to the Special Issue Nanoscale in Photocatalysis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>X-ray diffraction profiles of as-prepared copper selenides, (<b>a</b>) Cu<sub>3</sub>Se<sub>2</sub>, (<b>b</b>) Cu<sub>1.8</sub>Se/Cu<sub>3</sub>Se<sub>2</sub> composite, (<b>c</b>) Cu<sub>1.8</sub>Se.</p> Full article ">Figure 2
<p>TEM (transmission electron microscopy) images of (<b>a</b>) Cu<sub>1.8</sub>Se; (<b>b</b>) Cu<sub>3</sub>Se<sub>2</sub>; (<b>c</b>) Cu<sub>1.8</sub>Se/Cu<sub>3</sub>Se<sub>2</sub> composite; (<b>d</b>) HRTEM (high resolution transmission electron microscopy) of Cu<sub>1.8</sub>Se/Cu<sub>3</sub>Se<sub>2</sub> composite.</p> Full article ">Figure 3
<p>(<b>a</b>) UV-visible-near-infrared (UV-Vis-NIR) diffuse reflectance absorption (DRS) spectrum of copper selenides; (<b>b</b>) A plot transformed according to the Kubelka–Munk function versus energy of light.</p> Full article ">Figure 4
<p>Photocatalytic degradation of methyl orange (MO) solution with copper selenides as catalysts under (<b>a</b>) visible light; (<b>b</b>) NIR light; (<b>c</b>) full solar light; (<b>d</b>) the degradation kinetics by means of plotting ln(<span class="html-italic">C</span><sub>0</sub>/<span class="html-italic">C<sub>t</sub></span>) versus time.</p> Full article ">Figure 5
<p>Cycling runs for the photocatalytic degradation of MO under full solar light in the presence of (<b>a</b>) Cu<sub>1.8</sub>Se/Cu<sub>3</sub>Se<sub>2</sub> composite; (<b>b</b>) Cu<sub>1.8</sub>Se; (<b>c</b>) Cu<sub>3</sub>Se.</p> Full article ">Figure 6
<p>High-resolution X-ray photoelectron spectroscopy (XPS) scan of Cu 2p (<b>a</b>) Cu<sub>3</sub>Se<sub>2</sub>; (<b>b</b>) Cu<sub>1.8</sub>Se/Cu<sub>3</sub>Se<sub>2</sub> composite; (<b>c</b>) Cu<sub>1.8</sub>Se.</p> Full article ">Figure 7
<p>Diagram of energy band levels of Cu<sub>1.8</sub>Se/Cu<sub>3</sub>Se<sub>2</sub> composites vs. NHE (normal hydrogen electrode) and the possible charge separation process.</p> Full article ">Figure 8
<p>The photocurrent responses of copper selenides in 0.5 M Na<sub>2</sub>SO<sub>4</sub> electrolyte under visible light.</p> Full article ">
4533 KiB  
Article
Amorphous Silica Particles Relevant in Food Industry Influence Cellular Growth and Associated Signaling Pathways in Human Gastric Carcinoma Cells
by Anja Wittig, Helge Gehrke, Giorgia Del Favero, Eva-Maria Fritz, Marco Al-Rawi, Silvia Diabaté, Carsten Weiss, Haider Sami, Manfred Ogris and Doris Marko
Nanomaterials 2017, 7(1), 18; https://doi.org/10.3390/nano7010018 - 13 Jan 2017
Cited by 15 | Viewed by 8229
Abstract
Nanostructured silica particles are commonly used in biomedical and biotechnical fields, as well as, in cosmetics and food industry. Thus, their environmental and health impacts are of great interest and effects after oral uptake are only rarely investigated. In the present study, the [...] Read more.
Nanostructured silica particles are commonly used in biomedical and biotechnical fields, as well as, in cosmetics and food industry. Thus, their environmental and health impacts are of great interest and effects after oral uptake are only rarely investigated. In the present study, the toxicological effects of commercially available nano-scaled silica with a nominal primary diameter of 12 nm were investigated on the human gastric carcinoma cell line GXF251L. Besides the analysis of cytotoxic and proliferative effects and the comparison with effects of particles with a nominal primary diameter of 200 nm, emphasis was also given to their influence on the cellular epidermal growth factor receptor (EGFR) and mitogen-activated protein kinases (MAPK) signaling pathways—both of them deeply involved in the regulation of cellular processes like cell cycle progression, differentiation or proliferation. The investigated silica nanoparticles (NPs) were found to stimulate cell proliferation as measured by microscopy and the sulforhodamine B assay. In accordance, the nuclear level of the proliferation marker Ki-67 was enhanced in a concentration-dependent manner. At high particle concentrations also necrosis was induced. Finally, silica NPs affected the EGFR and MAPK pathways at various levels dependent on concentration and time. However, classical activation of the EGFR, to be reflected by enhanced levels of phosphorylation, could be excluded as major trigger of the proliferative stimulus. After 45 min of incubation the level of phosphorylated EGFR did not increase, whereas enhanced levels of total EGFR protein were observed. These results indicate interference with the complex homeostasis of the EGFR protein, whereby up to 24 h no impact on the transcription level was detected. In addition, downstream on the level of the MAP kinases ERK1/2 short term incubation appeared to affect total protein levels without clear increase in phosphorylation. Depending on the concentration range, enhanced levels of ERK1/2 phosphorylation were only observed after 24 h of incubation. Taken together, the present study demonstrates the potential of the tested silica particles to enhance the growth of gastric carcinoma cells. Although interference with the EGFR/MAPK cascade is observed, additional mechanisms are likely to be involved in the onset of the proliferative stimulus. Full article
(This article belongs to the Special Issue Cytotoxicity of Nanoparticles)
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Graphical abstract

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Full article ">Figure 1
<p>Influence of the suspension medium and the fetal bovine serum (FBS) amount on size distribution of 12 nm SiO<sub>2</sub> NPs analyzed by nanoparticle tracking analysis after 0 h and 24 h of incubation. Depicted are exemplary particle size distribution profiles (mean ± SEM of five measurements) of 1 mg/mL particle stock suspensions in (<b>A</b>) double-distilled water (FBS-free) or (<b>B</b>) 9% FBS-containing RPMI 1640 cell culture medium. Please mind the varying ordinate scaling; (<b>C</b>) Represented are D10, D50 and D90 values of the particle stock suspensions (1 mg/mL) suspended in either double-distilled water or RPMI 1640 cell culture medium, as well as, the medium incubation suspensions with area concentrations of 31.3 and 93.8 µg/cm<sup>2</sup>. The final FBS amount varied. The D values indicate percentage undersize distribution, for example D10 indicates 10% particles are smaller than the D10 value. This gives indication of the distribution of particle sizes and their corresponding merged particle diameter in [nm] (<span class="html-italic">n</span> ≥ 2).</p> Full article ">Figure 2
<p>Influence of 12 nm SiO<sub>2</sub> NPs on cell proliferation and cell death of GXF251L cells monitored microscopically after an incubation period of 4 h, 24 h and 72 h. Staurosporine (800 nM) was applied as a positive control (+Cntrl) resulting in apoptotic and necrotic cell death. (<b>A</b>) Viable (Via), early apoptotic (EA) and late apoptotic (LA), as well as, necrotic cells (N) are plotted in relation to the total cell count; (<b>B</b>) The depicted bars represent the total cell counts and the respective amount of viable cells. Total cell count was quantified in relation to the negative control (−Cntrl). Cell viability was quantified in relation to the viability of the negative control, as well as, the total cell count of the negative control (T/C [%]). The solid line represents the negative control set to 100%; (<b>C</b>) Represented are microscopic bright field (bf) images of the negative and positive control and the incubation sample with 31.3 µg/cm<sup>2</sup> of 12 nm SiO<sub>2</sub> NPs after an incubation time of 24 h. Furthermore, the software analysis after detection in the Hoechst-channel is shown distinguishing between viable cells (green), early (blue) and late (violet) apoptotic cells, as well as, necrotic cells (red). Scale bars are equivalent to 50 µm. Statistical analysis was performed by One-way ANOVA followed by Fisher’s LSD test. Significances indicated as * refer to a comparison to the respective negative control (* ≡ <span class="html-italic">p</span> ≤ 0.05; ** ≡ <span class="html-italic">p</span> ≤ 0.01 and *** ≡ <span class="html-italic">p</span> ≤ 0.001; <span class="html-italic">n</span> ≥ 3). The same letters indicate a significant difference of these data (in (A): refers to necrotic cells only) with a statistical level of at least <span class="html-italic">p</span> ≤ 0.05.</p> Full article ">Figure 3
<p>Influence of 200 nm SiO<sub>2</sub> particles on cell proliferation and cell death of GXF251L cells monitored microscopically after an incubation period of 4 h, 24 h and 72 h. Staurosporine (800 nM) was applied as a positive control (+Cntrl) resulting in apoptotic and necrotic cell death. (<b>A</b>) Viable (Via), early apoptotic (EA) and late apoptotic (LA), as well as, necrotic cells (N) are plotted in relation to the total cell count; (<b>B</b>) The depicted bars represent the total cell counts and the respective amount of viable cells. Total cell count was quantified in relation to the negative control (−Cntrl). Cell viability was quantified in relation to the viability of the negative control, as well as, the total cell count of the negative control (T/C [%]). The solid line represents the negative control set to 100%. Statistical analysis was performed by One-way ANOVA followed by Fisher’s LSD test. Significances indicated as * refer to a comparison to the respective negative control (* ≡ <span class="html-italic">p</span> ≤ 0.05; ** ≡ <span class="html-italic">p</span> ≤ 0.01 and *** ≡ <span class="html-italic">p</span> ≤ 0.001; <span class="html-italic">n</span> ≥ 3). The same letters indicate a significant difference of these data (in (<b>A</b>): refers to necrotic cells only) with a statistical level of at least <span class="html-italic">p</span> ≤ 0.05.</p> Full article ">Figure 4
<p>Analysis of the cytotoxic effects of 12 nm SiO<sub>2</sub> NPs on GXF251L cells. (<b>A</b>) Influences on the mitochondrial activity determined by WST-1 assay and (<b>B</b>) on the membrane integrity determined by LDH leakage assay after 45 min and 24 h of incubation; (<b>C</b>) Growth effects after 24 h, 48 h and 72 h of incubation determined by SRB assay. For WST-1 and SRB assay all effects were quantified in relation to the negative assay control (T/C [%]). For the LDH leakage assay effects were quantified in relation to the positive assay control (T/C [%]). The solid lines represent the respective control set to 100%. Triton X-100 (1% <span class="html-italic">v</span>/<span class="html-italic">v</span>) was used as positive control. Statistical analysis was performed by One-way ANOVA followed by Fisher’s LSD test. Significances indicated as * refer to a comparison to the respective negative control (* ≡ <span class="html-italic">p</span> ≤ 0.05; ** ≡ <span class="html-italic">p</span> ≤ 0.01 and *** ≡ <span class="html-italic">p</span> ≤ 0.001; <span class="html-italic">n</span> ≥ 3).</p> Full article ">Figure 5
<p>Intracellular levels and localization of Ki-67. Representative images of GXF251L cells treated with 12 nm SiO<sub>2</sub> NPs for 24 h after immunofluorescence staining of Ki-67 (<b>red</b>), α-Tubulin (<b>green</b>) and Lamin B (<b>blue</b>). White arrows indicate enhanced presence of Ki-67 in the nucleus. Scale bars are equivalent to 5 µm.</p> Full article ">Figure 6
<p>(<b>A</b>) Representative appearance of Ki-67 and Lamin B in GXF251L cells treated with 12 nm SiO<sub>2</sub> NPs for 24 h after the application of the co-localization tool on the images. White fields represent the co-localization of Ki-67 (red) and Lamin B (blue). α-Tubulin is presented in green. Scale bars are equivalent to 5 µm; (<b>B</b>) Quantification of the red fluorescence associated with Ki-67 nuclear staining. [%]). The solid line represents the negative control set to 100%. Statistical analysis was performed by Student’s t-test. Significances indicated as * refer to a comparison to the samples treated with SiO<sub>2</sub> NP concentration of 31.3 µg/cm<sup>2</sup>. (** ≡ <span class="html-italic">p</span> ≤ 0.01 and *** ≡ <span class="html-italic">p</span> ≤ 0.001; 31.3 µg/cm<sup>2</sup> <span class="html-italic">n</span> = 66 nuclei; 93.8 µg/cm<sup>2</sup> <span class="html-italic">n</span> = 72 nuclei; EGF <span class="html-italic">n</span> = 67 nuclei).</p> Full article ">Figure 7
<p>Endogenous epidermal growth factor (EGF) receptor levels and their activation status (pEGFR) in GXF251L cells after 45 min and 24 h of incubation with 12 nm SiO<sub>2</sub> NPs. EGF was applied as a positive control for phosphorylation of EGFR. (<b>A</b>) The relative amount was quantified as arbitrary light units in relation to the negative control (T/C [%]). The solid line represents the negative control set to 100%; (<b>B</b>) Representative images of a Western blot experiment. α-Tubulin was used as loading control and detected on the same membrane. Statistical analysis was obtained by one-way ANOVA followed by Fisher’s LSD test. Significances indicated as * refer to a comparison to the respective negative control (* ≡ <span class="html-italic">p</span> ≤ 0.05; ** ≡ <span class="html-italic">p</span> ≤ 0.01 and *** ≡ <span class="html-italic">p</span> ≤ 0.001; <span class="html-italic">n</span> ≥ 3). The same letters indicate a significant difference of these data with a statistical level of at least <span class="html-italic">p</span> ≤ 0.05.</p> Full article ">Figure 8
<p>Endogenous ERK1/2 protein levels and their activation status (pERK1/2) in GXF251L cells after 45 min and 24 h of incubation with 12 nm SiO<sub>2</sub> NPs. EGF was applied as a positive control for phosphorylation of ERK1/2. (<b>A</b>) The relative amounts were quantified as arbitrary light units in relation to the negative control (T/C [%]). The solid line represents the negative control set to 100%; (<b>B</b>) Representative images of a Western blot experiment. α-Tubulin was used as loading control and detected on the same membrane. Statistical analysis was performed by One-way ANOVA followed by Fisher’s LSD test. Significances indicated as * refer to a comparison to the respective negative control (* ≡ <span class="html-italic">p</span> ≤ 0.05; ** ≡ <span class="html-italic">p</span> ≤ 0.01 and *** ≡ <span class="html-italic">p</span> ≤ 0.001; <span class="html-italic">n</span> ≥ 3). The same letters indicate a significant difference of these data with a statistical level of at least <span class="html-italic">p</span> ≤ 0.05.</p> Full article ">Figure 9
<p>Investigation of the molecular mechanisms influencing the EGF receptor at the cellular level by analysis of its relative mRNA transcription rates and its localization in GXF251L cells. (<b>A</b>) Relative gene transcription rates of the EGFR after incubation with 12 nm SiO<sub>2</sub> NPs for 2 h, 6 h, 16 h and 24 h. The depicted bars represent the relative transcription rates in relation to the negative control (solid line) after normalization to β-actin and GAPDH expression (T/C [%]) (<span class="html-italic">n</span> ≥ 3); (<b>B</b>) 3D reconstruction of the appearance of the EGFR localization (red) and tubulin cytoskeleton (green) after immunocytochemical analysis. Represented are the results of the negative control, the incubation with 31.3 µg/cm<sup>2</sup> and with 93.8 µg/cm<sup>2</sup> of 12 nm SiO<sub>2</sub> NPs after 45 min of incubation and EGF stimulation as positive control. Scale bar distances are expressed in 10 µm.</p> Full article ">
3966 KiB  
Article
Nano-Photonic Structures for Light Trapping in Ultra-Thin Crystalline Silicon Solar Cells
by Prathap Pathi, Akshit Peer and Rana Biswas
Nanomaterials 2017, 7(1), 17; https://doi.org/10.3390/nano7010017 - 13 Jan 2017
Cited by 45 | Viewed by 10258
Abstract
Thick wafer-silicon is the dominant solar cell technology. It is of great interest to develop ultra-thin solar cells that can reduce materials usage, but still achieve acceptable performance and high solar absorption. Accordingly, we developed a highly absorbing ultra-thin crystalline Si based solar [...] Read more.
Thick wafer-silicon is the dominant solar cell technology. It is of great interest to develop ultra-thin solar cells that can reduce materials usage, but still achieve acceptable performance and high solar absorption. Accordingly, we developed a highly absorbing ultra-thin crystalline Si based solar cell architecture using periodically patterned front and rear dielectric nanocone arrays which provide enhanced light trapping. The rear nanocones are embedded in a silver back reflector. In contrast to previous approaches, we utilize dielectric photonic crystals with a completely flat silicon absorber layer, providing expected high electronic quality and low carrier recombination. This architecture creates a dense mesh of wave-guided modes at near-infrared wavelengths in the absorber layer, generating enhanced absorption. For thin silicon (<2 μm) and 750 nm pitch arrays, scattering matrix simulations predict enhancements exceeding 90%. Absorption approaches the Lambertian limit at small thicknesses (<10 μm) and is slightly lower (by ~5%) at wafer-scale thicknesses. Parasitic losses are ~25% for ultra-thin (2 μm) silicon and just 1%–2% for thicker (>100 μm) cells. There is potential for 20 μm thick cells to provide 30 mA/cm2 photo-current and >20% efficiency. This architecture has great promise for ultra-thin silicon solar panels with reduced material utilization and enhanced light-trapping. Full article
(This article belongs to the Special Issue Nanostructured Solar Cells)
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<p>Photon absorption length as a function of wavelength for crystalline silicon (c-Si) and nano- crystalline silicon (nc-Si) (using the complex refractive index (<span class="html-italic">n</span>, <span class="html-italic">k</span>) parameters of Reference [<a href="#B26-nanomaterials-07-00017" class="html-bibr">26</a>]).</p> Full article ">Figure 2
<p>Proposed solar architecture consists of thin flat spacer titanium dioxide (TiO<sub>2</sub>) layers on the front and rear surfaces of silicon, nanocone gratings on both sides with optimized pitch and height, and rear cones are surrounded by Ag metal reflector.</p> Full article ">Figure 3
<p>(<b>a</b>) Cell structure used for optimization of texture parameter using simulations. The structure consists of thin flat TiO<sub>2</sub> layers on the front and rear surfaces of flat silicon (1 μm). The cones are only on the front surface without rear cones and Ag metal reflector; (<b>b</b>) Weighted absorption, &lt;<span class="html-italic">A<sub>w</sub></span>&gt; and (<b>c</b>) Short-circuit current density, <span class="html-italic">J<sub>SC</sub></span>, as a function of cone height for different pitch values. Figure shows optimum pitch &gt;750 nm and cone height &gt;500 nm with an increasing trend of tolerance of optimum cone height at larger pitch.</p> Full article ">Figure 4
<p>Sequence of light trapping structures on flat silicon. (<b>a</b>) Grating-free cell with thin layers of 60 and 50 nm on front and rear surface, respectively, and flat Ag back-reflector; (<b>b</b>) Front-grating cell with only front cones of height of 600 nm and a pitch of 750 nm and flat Ag back-reflector; (<b>c</b>) <span class="html-italic">Rear-grating cell</span> with only rear cones of height of 200 nm and a pitch of 750 nm and corrugated Ag back-reflector; (<b>d</b>) <span class="html-italic">Dual-grating cell</span> with a combination of front and rear cones with optimized parameters used in ‘b’ and ‘c’ with corrugated Ag back-reflector.</p> Full article ">Figure 5
<p>Comparison of absorption spectra of planar silicon with 4<span class="html-italic">n</span><sup>2</sup> absorption limit for different light trapping configurations shown in <a href="#nanomaterials-07-00017-f002" class="html-fig">Figure 2</a> such as (<b>a</b>) <span class="html-italic">grating-free</span> <span class="html-italic">cell</span>, (<b>b</b>) <span class="html-italic">front-grating cell</span>, (<b>c</b>) <span class="html-italic">rear-grating cell</span>, and (<b>d</b>) <span class="html-italic">dual-grating cell</span> using the optimized grating parameter for 2 μm silicon; (<b>e</b>) Comparison of <span class="html-italic">J<sub>SC</sub></span> of planar cell for different light trapping configurations shown in <a href="#nanomaterials-07-00017-f002" class="html-fig">Figure 2</a> with respect to silicon thickness using optimized grating parameters for 2 μm silicon; (<b>f</b>) <span class="html-italic">J<sub>SC</sub></span> of the cell for a particular thickness of 2 μm for four different configurations.</p> Full article ">Figure 6
<p>(<b>a</b>) Absorption spectra of the dual-grating cell (c-Si thickness = 2 μm) and (<b>b</b>) corresponding <span class="html-italic">J<sub>SC</sub></span> of the cell as a function of angle of incidence (AoI) in the range 0°–85° in steps of 5° (inset shows the <span class="html-italic">J<sub>SC</sub></span> of grating-free cell for p- and s-polarization and its average). The average absorption is more than 80% over a wide wavelength band. <span class="html-italic">J<sub>SC</sub></span> is independent of polarization and is less influenced until the AoI reaches 70°, showing the omni-directionality of the nanocone grating structures.</p> Full article ">Figure 7
<p>Electric field intensity distribution across the silicon absorber layer at an incident wavelength of (<b>a</b>) 500 nm and (<b>b</b>) 700 nm for the dual-grating cell with optimized parameters for the front and rear nano-cone arrays. The incident electric field intensity is normalized to 1.</p> Full article ">Figure 8
<p>Comparison of the simulated short-circuit photo-current <span class="html-italic">J<sub>SC</sub></span> as a function of the thickness of the Si absorber layer in the real-space method utilizing only the absorption in the Si layer, compared to the Fourier space method which includes the absorption in all layers. The difference between the real-space and Fourier space results is the parasitic absorption. The Lambertian limit is shown for comparison.</p> Full article ">Figure 9
<p>Schematic of the TiO<sub>2</sub> nanoimprinting process. (<b>1</b>) TiO<sub>2</sub> film is spin-coated on silicon substrate using a precursor titanium diisopropoxide bis(acetylacetonate); (<b>2</b>) The polydimethylsiloxane (PDMS) stamp having nanocups is placed on the spin-coated film with patterned side facing the film. The whole assembly is sandwiched between two glass slides and held together with binder clips (not shown here); (<b>3</b>) After keeping at ~170 °C for 15 min, the binder clips are released to reveal the inverse of PDMS nanocups on the TiO<sub>2</sub> film.</p> Full article ">Figure 10
<p>(<b>a</b>) Atomic force microscopy (AFM) image of the periodic array of nanocones imprinted on TiO<sub>2</sub> film. The AFM line scan shows the periodicity at ~750 nm and the average height of nanocones at ~35 nm; (<b>b</b>) Three-dimensional view of the structure showing titania nanocone arrays.</p> Full article ">
2703 KiB  
Article
Influence of Solution Properties and Process Parameters on the Formation and Morphology of YSZ and NiO Ceramic Nanofibers by Electrospinning
by Gerard Cadafalch Gazquez, Vera Smulders, Sjoerd A. Veldhuis, Paul Wieringa, Lorenzo Moroni, Bernard A. Boukamp and Johan E. Ten Elshof
Nanomaterials 2017, 7(1), 16; https://doi.org/10.3390/nano7010016 - 13 Jan 2017
Cited by 44 | Viewed by 5928
Abstract
The fabrication process of ceramic yttria-stabilized zirconia (YSZ) and nickel oxide nanofibers by electrospinning is reported. The preparation of hollow YSZ nanofibers and aligned nanofiber arrays is also demonstrated. The influence of the process parameters of the electrospinning process, the physicochemical properties of [...] Read more.
The fabrication process of ceramic yttria-stabilized zirconia (YSZ) and nickel oxide nanofibers by electrospinning is reported. The preparation of hollow YSZ nanofibers and aligned nanofiber arrays is also demonstrated. The influence of the process parameters of the electrospinning process, the physicochemical properties of the spinning solutions, and the thermal treatment procedure on spinnability and final microstructure of the ceramic fibers was determined. The fiber diameter can be varied from hundreds of nanometers to more than a micrometer by controlling the solution properties of the electrospinning process, while the grain size and surface roughness of the resulting fibers are mainly controlled via the final thermal annealing process. Although most observed phenomena are in qualitative agreement with previous studies on the electrospinning of polymeric nanofibers, one of the main differences is the high ionic strength of ceramic precursor solutions, which may hamper the spinnability. A strategy to control the effective ionic strength of precursor solutions is also presented. Full article
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<p>Schematic representation of the electrospinning process.</p> Full article ">Figure 2
<p>(<b>A</b>) Scanning electron microscopy (SEM) picture of three percent yttria partially-stabilized zirconia (3YSZ) fibers. Precursor concentration 0.65 M, polymer concentration 10 mg/mL polyvinylpyrrolidone (PVP). Influence of precursor concentration on (<b>B</b>) fiber diameter (nm) and (<b>C</b>) solution conductivity (μS/m; black squares), static viscosity (mPa·s; red triangles) and surface tension (mN/m; blue circles). Polymer concentration 10 mg/mL. Influence of polymer concentration on (<b>D</b>) fiber diameter (nm) and (<b>E</b>) solution conductivity (μS/m; black squares), static viscosity (mPa·s; red triangles) and surface tension (mN/m; blue circles). Precursor concentration 0.65 M.</p> Full article ">Figure 3
<p>Dynamic viscosity data of the standard solution. Precursor concentration, 0.65 M; PVP concentration, 10 mg/mL.</p> Full article ">Figure 4
<p>(<b>A</b>) Conductivity of a 0.21 M Ni(NO<sub>3</sub>)<sub>2</sub> solution in various solvents; (<b>B</b>) conductivity of a 0.21 M Ni(NO<sub>3</sub>)<sub>2</sub> solution in 2-ME at different molar ratios citric acid (CA):Ni; (<b>C</b>) conductivity of a 0.21 M Ni(NO<sub>3</sub>)<sub>2</sub> solution in 2-ME with different polymer concentrations; (<b>D</b>) viscosity of a 0.21 M Ni(NO<sub>3</sub>)<sub>2</sub> solution in 2-ME with different polymer concentrations. The conductivity of the final 0.21 M Ni(NO<sub>3</sub>)<sub>2</sub> solution and the standard 3YSZ are also plotted as reference; and (<b>E</b>) electrospun NiO microfibers from a 0.21 M Ni(NO<sub>3</sub>)<sub>2</sub> solution in 2-ME with 70 mg/mL of PVP at a molar ratio CA:Ni of 6:1.</p> Full article ">Figure 5
<p>(<b>A</b>) Influence of flow rate on electrospinning process. Flow rate 0.05–1 mL/h. Fiber diameter (black squares) and rectilinear jet length (blue circles) at different flow rates are shown; (<b>B</b>) rectilinear jet length at flow rates of 0.05–1 mL/h; (<b>C</b>) influence of potential between spinneret and collector plate. Fiber diameter at voltages between 5 and 25 kV are shown; (<b>D</b>) electrospinning jet at voltages of 5–25 kV; (<b>E</b>) thermogravimetic analysis and differential scanning calorimetry (5 °C/min in air); (<b>F</b>) surface morphology of ceramic fibers after different annealing procedures; (<b>G</b>) fiber diameters after different annealing procedures; and (<b>H</b>) crystallite size of ceramic fibers after different annealing procedures.</p> Full article ">Figure 6
<p>(<b>a</b>) Coaxial spinneret; (<b>b</b>) coaxial spinning of porous fibers. Inner flow rate is 0.2 mL/h PolyActive solution; Outer flow rate is 1 mL/h of 3YSZ precursor solution; no hollow fibers are formed; (<b>c</b>) hollow fiber made by coaxial electrospinning. Inner flow rate is 0.6 mL/h of the PolyActive solution; the outer flow rate rete is 1 mL/h of 3YSZ solution; (<b>d</b>) frequency distribution of the inner hollow fiber diameter at inner flow rates of 0.4 and 0.6 mL/h of the PolyActive solution. The outer flow rate is 1 mL/h of 3YSZ precursor solution; and (<b>e</b>) frequency distribution of the outer hollow fiber diameter under the same conditions. The fibers shown were thermally treated at 850 °C.</p> Full article ">Figure 7
<p>(<b>A</b>) Electrically-driven alignment: two ground electrodes with an insulating gap; (<b>B</b>) mechanically-driven alignment: rotating mandrel as the ground electrode. (<b>C</b>,<b>D</b>) Influence of gap distance on the degree of alignment of thermally-annealed fibers after 15 s of deposition. The flow rate is 0.25 mL/h; (<b>C</b>) degree of alignment versus gap distance; (<b>D</b>) SEM pictures of the samples spun with gap distances of 1.0 and 7.5 cm. (<b>E</b>,<b>F</b>) Influence of the flow rate of the 3YSZ precursor solution on the degree of alignment of fibers after 15 s of deposition. Gap distance is 2.0 cm; (<b>E</b>) degree of alignment and voltage versus ground at the gap center versus flow rate; (<b>F</b>) SEM pictures of the samples spun with flow rates of 0.05 mL/h and 1 mL/h. (<b>G</b>,<b>H</b>). Influence of deposition time on directionality of a sample spun at 0.25 mL/h of the 3YSZ precursor solution and a gap of 2.0 cm; (<b>G</b>) degree of alignment and voltage at the gap center versus time; (<b>H</b>) SEM image of a samples spun for 90 s. (<b>I</b>,<b>J</b>) Mechanical alignment of nanofibers with a rotating mandrel; (<b>I</b>) degree of alignment vs linear speed of the mandrel; (<b>J</b>) Sample spun for 30 min. All samples were spun at a flow rate of 1 mL/h of 3YSZ solution and thermally treated.</p> Full article ">
6157 KiB  
Article
Modification of the Surface Topography and Composition of Ultrafine and Coarse Grained Titanium by Chemical Etching
by Denis V. Nazarov, Elena G. Zemtsova, Alexandr Yu. Solokhin, Ruslan Z. Valiev and Vladimir M. Smirnov
Nanomaterials 2017, 7(1), 15; https://doi.org/10.3390/nano7010015 - 13 Jan 2017
Cited by 46 | Viewed by 8406
Abstract
In this study, we present the detailed investigation of the influence of the etching medium (acidic or basic Piranha solutions) and the etching time on the morphology and surface relief of ultrafine grained (UFG) and coarse grained (CG) titanium. The surface relief and [...] Read more.
In this study, we present the detailed investigation of the influence of the etching medium (acidic or basic Piranha solutions) and the etching time on the morphology and surface relief of ultrafine grained (UFG) and coarse grained (CG) titanium. The surface relief and morphology have been studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), and the spectral ellipsometry. The composition of the samples has been determined by X-ray fluorescence analysis (XRF) and X-ray Photoelectron Spectroscopy (XPS). Significant difference in the etching behavior of UFG and CG titanium has been found. UFG titanium exhibits higher etching activity independently of the etching medium. Formed structures possess higher homogeneity. The variation of the etching medium and time leads to micro-, nano-, or hierarchical micro/nanostructures on the surface. Significant difference has been found between surface composition for UFG titanium etched in basic and acidic Piranha solution. Based on the experimental data, the possible reasons and mechanisms are considered for the formation of nano- and microstructures. The prospects of etched UFG titanium as the material for implants are discussed. Full article
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<p>Characteristic scanning electron microscopy (SEM) images of ultrafine grained-ultrafine grained (UFG) (<b>a</b>) and coarse grained-coarse grained (CG) (<b>b</b>) titanium etched in H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O<sub>2</sub> solutions during 2 h (magnification—400,000×). Red lines mark inhomogeneous areas.</p> Full article ">Figure 2
<p>Characteristic SEM images of UFG titanium etched in H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O<sub>2</sub> solutions during 5 (<b>a</b>), 15 min (<b>b</b>); and 1 (<b>c</b>), 2 (<b>d</b>), 6 (<b>e</b>) and 24 h (<b>f</b>) (magnification 200,000×—main picture, 10,000×—insets).</p> Full article ">Figure 3
<p>Characteristic SEM images of СG titanium etched in H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O<sub>2</sub> solutions during 5 (<b>a</b>), 15 min (<b>b</b>); and 1 (<b>c</b>), 2 (<b>d</b>), 6 (<b>e</b>) and 24 h (<b>f</b>) (magnification 200,000×—main picture, 10,000×—insets). Orange lines mark various etching areas.</p> Full article ">Figure 4
<p>Characteristic SEM images of UFG and СG titanium etched in H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O<sub>2</sub> solutions during 5 (<b>a</b>), 15 min (<b>b</b>); and 1 (<b>c</b>), 2 (<b>d</b>), 6 (<b>e</b>) and 24 h (<b>f</b>) (magnifications 200,000× and 10,000×).</p> Full article ">Figure 5
<p>Atomic force microscopy (AFM) surface topographies of the UFG and CG titanium etched in H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O<sub>2</sub>. Nonetched UFG-Ti (<b>a</b>), UFG-Ti etched 15 min (<b>b</b>), 1 h (<b>c</b>), nonetched CG-Ti (<b>d</b>), CG-Ti etched 15 min (<b>e</b>), 1 h (<b>f</b>), UFG-Ti etched 2 h (<b>g</b>), 6 h (<b>h</b>), 24 h (<b>i</b>), CG-Ti etched 2 h (<b>j</b>), 6 h (<b>k</b>), 24 h (<b>l</b>).</p> Full article ">Figure 6
<p>Roughness values as a function of the etching time for solutions H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O<sub>2</sub>—(<b>a</b>) and NH<sub>4</sub>OH/H<sub>2</sub>O<sub>2</sub>—(<b>b</b>).</p> Full article ">Figure 7
<p>Specific surface area (<b>a</b>) and height amplitudes (<b>b</b>) as a functions of the etching time.</p> Full article ">Figure 8
<p>AFM surface topographies of the UFG and CG titanium etched in NH<sub>4</sub>OH/H<sub>2</sub>O<sub>2</sub>. Nonetched UFG-Ti (<b>a</b>), UFG-Ti etched 15 min (<b>b</b>), 1 h (<b>c</b>), nonetched CG-Ti (<b>d</b>), CG-Ti etched 15 min (<b>e</b>), 1 h (<b>f</b>), UFG-Ti etched 2 h (<b>g</b>), 6 h (<b>h</b>), 24 h (<b>i</b>), CG-Ti etched 2 h (<b>j</b>), 6 h (<b>k</b>), 24 h (<b>l</b>).</p> Full article ">Figure 9
<p>XPS high resolution Ti 2p spectra of nanotitanium etched in (<b>a</b>) acidic Piranha and (<b>b</b>) basic Piranha.</p> Full article ">Figure 10
<p>XPS high resolution O 1s spectra of nanotitanium etched in (<b>a</b>) acidic Piranha and (<b>b</b>) basic Piranha.</p> Full article ">Figure 11
<p>Characteristic SEM images of CG titanium (<b>a</b>) and UFG titanium (<b>b</b>) etched in H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O<sub>2</sub> solution during 24 h (magnification—3000×).</p> Full article ">
3011 KiB  
Article
Effects of Iodine Doping on Optoelectronic and Chemical Properties of Polyterpenol Thin Films
by Kateryna Bazaka and Mohan V. Jacob
Nanomaterials 2017, 7(1), 11; https://doi.org/10.3390/nano7010011 - 13 Jan 2017
Cited by 38 | Viewed by 5745
Abstract
Owing to their amorphous, highly cross-liked nature, most plasma polymers display dielectric properties. This study investigates iodine doping as the means to tune optoelectronic properties of plasma polymer derived from a low-cost, renewable resource, i.e., Melaleuca alternifolia oil. In situ exposure of polyterpenol [...] Read more.
Owing to their amorphous, highly cross-liked nature, most plasma polymers display dielectric properties. This study investigates iodine doping as the means to tune optoelectronic properties of plasma polymer derived from a low-cost, renewable resource, i.e., Melaleuca alternifolia oil. In situ exposure of polyterpenol to vapors of electron-accepting dopant reduced the optical band gap to 1.5 eV and increased the conductivity from 5.05 × 10−8 S/cm to 1.20 × 10−6 S/cm. The increased conductivity may, in part, be attributed to the formation of charge-transfer complexes between the polymer chain and halogen, which act as a cation and anion, respectively. Higher levels of doping notably increased the refractive index, from 1.54 to 1.70 (at 500 nm), and significantly reduced the transparency of films. Full article
(This article belongs to the Special Issue Nanoengineered Interfaces, Coatings and Structures by Plasma Techniques)
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<p>Chemical properties of pristine and iodine-doped polyterpenol samples: XPS spectra for pristine (<b>a</b>) and doped (<b>b</b>) samples; and (<b>c</b>) FTIR spectra.</p> Full article ">Figure 2
<p>Optical properties of pristine and iodine-doped polyterpenol samples obtained using ellipsometry: (<b>a</b>) refractive index; (<b>b</b>) extinction coefficient; (<b>c</b>) real and (<b>d</b>) imaginary parts of permittivity as a function of frequency; (<b>e</b>) direct and (<b>f</b>) indirect allowed transition energies of pristine and iodine-doped polyterpenol films.</p> Full article ">Figure 3
<p>(<b>a</b>) Film thickness and (<b>b</b>) dynamic refractive index of pristine and iodine-doped polyterpenol film as a function of annealing temperature; (<b>c</b>) band gap and (<b>d</b>) direct allowed and indirect allowed transition energies of iodine doped polyterpenol thin films heat treated at 100 °C for 5 h.</p> Full article ">Figure 4
<p>Current density, <span class="html-italic">J</span>, of devices containing pristine and iodine-doped polyterpenol with an applied voltage between 0 V and 20 V.</p> Full article ">Figure 5
<p>(<b>a</b>) Schottky/Poole–Frenkel and (<b>b</b>) space charge limited conduction mechanism fits to <span class="html-italic">J–V</span> curves in the high-field region for pristine and iodine-doped polyterpenol.</p> Full article ">Figure 6
<p>Representative atomic force microscope (AFM) images of (<b>a</b>) pristine and (<b>b</b>) iodine-doped polyterpenol thin films deposited on glass substrates. Evolution of average surface roughness of iodine-doped films as a functions of (<b>c</b>) deposition power when deposition time is fixed at 10 min, and (<b>d</b>) as a function of deposition time when deposition power is fixed at 25 W.</p> Full article ">Figure 7
<p>Schematic of the plasma polymerization system. Inter-electrode distance is 10 cm. Deposition takes place within the plasma glow, with terpinen-4-ol and iodine vapours released into the glass chamber concurrently, in the absence of heating or carrier gas.</p> Full article ">
397 KiB  
Editorial
Acknowledgement to Reviewers of Nanomaterials in 2016
by Nanomaterials Editorial Office
Nanomaterials 2017, 7(1), 14; https://doi.org/10.3390/nano7010014 - 12 Jan 2017
Cited by 2 | Viewed by 4269
Abstract
The editors of Nanomaterials would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article
1864 KiB  
Article
Parametrically Optimized Carbon Nanotube-Coated Cold Cathode Spindt Arrays
by Xuesong Yuan, Matthew T. Cole, Yu Zhang, Jianqiang Wu, William I. Milne and Yang Yan
Nanomaterials 2017, 7(1), 13; https://doi.org/10.3390/nano7010013 - 12 Jan 2017
Cited by 20 | Viewed by 6303
Abstract
Here, we investigate, through parametrically optimized macroscale simulations, the field electron emission from arrays of carbon nanotube (CNT)-coated Spindts towards the development of an emerging class of novel vacuum electron devices. The present study builds on empirical data gleaned from our recent experimental [...] Read more.
Here, we investigate, through parametrically optimized macroscale simulations, the field electron emission from arrays of carbon nanotube (CNT)-coated Spindts towards the development of an emerging class of novel vacuum electron devices. The present study builds on empirical data gleaned from our recent experimental findings on the room temperature electron emission from large area CNT electron sources. We determine the field emission current of the present microstructures directly using particle in cell (PIC) software and present a new CNT cold cathode array variant which has been geometrically optimized to provide maximal emission current density, with current densities of up to 11.5 A/cm2 at low operational electric fields of 5.0 V/μm. Full article
(This article belongs to the Special Issue Computational Modeling and Simulations of Carbon Nanomaterials)
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<p>Fitting, simulation, and experimental results. (<b>a</b>) Fitting and experimental current density as a function of global electric field. Inset: Scheme depicting the truncated-Spindt carbon nanotube cold cathode electron source; (<b>b</b>) Simulation and experimental for a generalized square emitter confirming the commutability of the Fowler–Nordheim (FN) coefficient extraction processed outlined. Inset: simulation geometry.</p> Full article ">Figure 2
<p>Single carbon nanotube (CNT)-coated Spindt field emission. (<b>a</b>) Surface electric field as a function of Spindt height. Inset: single Spindt geometry. (<b>b</b>) The maximum field enhancement factor β<sub>max</sub>, extracted from the geometry terms, as a function of <span class="html-italic">h</span> and <span class="html-italic">r</span><sub>1</sub>. (<b>c</b>) Simulated emission from a single Spindt CNT cold cathode. Inset: beam trajectories.</p> Full article ">Figure 2 Cont.
<p>Single carbon nanotube (CNT)-coated Spindt field emission. (<b>a</b>) Surface electric field as a function of Spindt height. Inset: single Spindt geometry. (<b>b</b>) The maximum field enhancement factor β<sub>max</sub>, extracted from the geometry terms, as a function of <span class="html-italic">h</span> and <span class="html-italic">r</span><sub>1</sub>. (<b>c</b>) Simulated emission from a single Spindt CNT cold cathode. Inset: beam trajectories.</p> Full article ">Figure 3
<p>Simulated CNT-coated Spindt cold cathode array.</p> Full article ">Figure 4
<p>Field emission current density as a function of <span class="html-italic">h</span> and <span class="html-italic">D</span>. Under low-bias (35 V), (<b>a</b>) <span class="html-italic">r</span><sub>1</sub> = 0.50 μm and (<b>b</b>) <span class="html-italic">r</span><sub>1</sub> = 0.75 μm; under high-bias (50 V), (<b>c</b>) <span class="html-italic">r</span><sub>1</sub> = 1.00 μm and (<b>d</b>) <span class="html-italic">r</span><sub>1</sub> = 1.25 μm.</p> Full article ">
4195 KiB  
Article
Preparation of g-C3N4/Graphene Composite for Detecting NO2 at Room Temperature
by Shaolin Zhang, Nguyen Thuy Hang, Zhijun Zhang, Hongyan Yue and Woochul Yang
Nanomaterials 2017, 7(1), 12; https://doi.org/10.3390/nano7010012 - 12 Jan 2017
Cited by 63 | Viewed by 9283
Abstract
Graphitic carbon nitride (g-C3N4) nanosheets were exfoliated from bulk g-C3N4 and utilized to improve the sensing performance of a pure graphene sensor for the first time. The role of hydrochloric acid treatment on the exfoliation result [...] Read more.
Graphitic carbon nitride (g-C3N4) nanosheets were exfoliated from bulk g-C3N4 and utilized to improve the sensing performance of a pure graphene sensor for the first time. The role of hydrochloric acid treatment on the exfoliation result was carefully examined. The exfoliated products were characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis spectroscopy. The exfoliated g-C3N4 nanosheets exhibited a uniform thickness of about 3–5 nm and a lateral size of about 1–2 µm. A g-C3N4/graphene nanocomposite was prepared via a self-assembly process and was demonstrated to be a promising sensing material for detecting nitrogen dioxide gas at room temperature. The nanocomposite sensor exhibited better recovery as well as two-times the response compared to pure graphene sensor. The detailed sensing mechanism was then proposed. Full article
(This article belongs to the Special Issue Nanocomposite Coatings)
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<p>Schematic of the acid treatment enhanced liquid-phase exfoliation process from bulk g-C<sub>3</sub>N<sub>4</sub> to ultrathin nanosheets.</p> Full article ">Figure 2
<p>X-ray diffraction (XRD) patterns of bulk g-C<sub>3</sub>N<sub>4</sub> and g-C<sub>3</sub>N<sub>4</sub> nanosheets exfoliated at different acid treatment times.</p> Full article ">Figure 3
<p>UV-Vis absorption spectra of diluted bulk g-C<sub>3</sub>N<sub>4</sub> and as prepared g-C<sub>3</sub>N<sub>4</sub> nanosheets exfoliated at different acid treatment times.</p> Full article ">Figure 4
<p>(<b>a</b>) Typical atomic force microscopy (AFM) image; (<b>b</b>) corresponding thickness profile along the yellow dashed line in (<b>a</b>), and (<b>c</b>) thickness distribution of the exfoliated g-C<sub>3</sub>N<sub>4</sub> with 1 h acid treatment.</p> Full article ">Figure 5
<p>Field emission scanning electron microscopy (FE-SEM) images of exfoliated (<b>a</b>) graphene; (<b>b</b>) g-C<sub>3</sub>N<sub>4</sub>; and (<b>c</b>) g-C<sub>3</sub>N<sub>4</sub>/graphene composite. The insets in (<b>a</b>,<b>b</b>) are SEM images of their bulk counterparts.</p> Full article ">Figure 6
<p>(<b>a</b>) Low-magnification SEM image of g-C<sub>3</sub>N<sub>4</sub>/graphene nanocomposite; (<b>b</b>) Carbon and (<b>c</b>) nitrogen elemental mapping captured in (<b>a</b>); (<b>d</b>) Energy-dispersive X-ray spectroscopy (EDS) pattern and elemental composition of nanocomposite.</p> Full article ">Figure 7
<p>(<b>a</b>) Typical response of pure graphene and g-C<sub>3</sub>N<sub>4</sub>/graphene composite sensors toward 5 ppm of NO<sub>2</sub> gas at room temperature; (<b>b</b>) Dynamic response of pure graphene and g-C<sub>3</sub>N<sub>4</sub>/graphene composite sensors toward various concentrations of NO<sub>2</sub> gas at room temperature.</p> Full article ">Figure 8
<p>(<b>a</b>) Cyclic response of g-C<sub>3</sub>N<sub>4</sub>/graphene composite sensor toward 20 ppm of NO<sub>2</sub>; (<b>b</b>) Proposed sensing mechanism of g-C<sub>3</sub>N<sub>4</sub>/graphene composite sensor.</p> Full article ">
805 KiB  
Article
Synthesis of Vertically-Aligned Zinc Oxide Nanowires and Their Application as a Photocatalyst
by Qiong Zhou, John Z. Wen, Pei Zhao and William A. Anderson
Nanomaterials 2017, 7(1), 9; https://doi.org/10.3390/nano7010009 - 11 Jan 2017
Cited by 64 | Viewed by 8643
Abstract
Vertically aligned zinc oxide (ZnO) nanowires were hydrothermally synthesized on a glass substrate with the assistance of a pre-coated ZnO seeding layer. The crystalline structure, morphology and transmission spectrum of the as-synthesized sample were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy [...] Read more.
Vertically aligned zinc oxide (ZnO) nanowires were hydrothermally synthesized on a glass substrate with the assistance of a pre-coated ZnO seeding layer. The crystalline structure, morphology and transmission spectrum of the as-synthesized sample were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and ultraviolet-visible (UV-Vis) spectrophotometry, respectively, indicating a wurzite ZnO material of approximately 100 nm wire diameter and absorbance at 425 nm and lower wavelengths. The photocatalytic activity of the sample was tested via the degradation of methyl orange in aqueous solution under UV-A irradiation. The synthesized nanowires showed a high photocatalytic activity, which increased up to 90% degradation in 2 h as pH was increased to 12. It was shown that the photocatalytic activity of the nanowires was proportional to the length to diameter ratio of the nanowires, which was in turn controlled by the growth time and grain size of the seed layer. Estimates suggest that diffusion into the regions between nanowires may be significantly hindered. Finally, the reusability of the prepared ZnO nanowire samples was also investigated, with results showing that the nanowires still showed 97% of its original photoactivity after ten cycles of use. Full article
(This article belongs to the Special Issue Nanomaterials for Water Treatment)
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<p>X-ray diffraction (XRD) patterns of the synthesized ZnO nanowire arrays.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) images of the as-synthesized ZnO nanowire arrays: (<b>A</b>) top view; (<b>B</b>) cross-sectional view.</p> Full article ">Figure 3
<p>Ultraviolet-visible (UV-Vis) transmittance spectra of the prepared ZnO nanowire arrays and the standard glass substrate.</p> Full article ">Figure 4
<p>Photodegradation rates of methyl orange (MO) solutions in the presence of ZnO nanowires, ZnO seed layer, and without both.</p> Full article ">Figure 5
<p>Photodegradation rates of MO solutions with different pH values catalyzed by ZnO nanowires prepared at the same conditions.</p> Full article ">Figure 6
<p>Photodegradation rates of MO solutions with different initial dye concentrations catalyzed by ZnO nanowires prepared at the same conditions.</p> Full article ">Figure 7
<p>UV-Vis transmission spectra of MO solutions with different concentrations.</p> Full article ">Figure 8
<p>Photodegradation rates of MO solutions catalyzed by ZnO nanowires prepared for different growth durations (6, 12, and 18 h) in the precursor solutions at the same conditions.</p> Full article ">Figure 9
<p>Percentage degradation values of MO solutions after 2 h of irradiation using the same ZnO nanowire sample after multiple cycles.</p> Full article ">
1038 KiB  
Article
Gold Nanobeacons for Tracking Gene Silencing in Zebrafish
by Milton Cordeiro, Lara Carvalho, Joana Silva, Leonor Saúde, Alexandra R. Fernandes and Pedro V. Baptista
Nanomaterials 2017, 7(1), 10; https://doi.org/10.3390/nano7010010 - 11 Jan 2017
Cited by 19 | Viewed by 5483
Abstract
The use of gold nanoparticles for effective gene silencing has demonstrated its potential as a tool for gene expression experiments and for the treatment of several diseases. Here, we used a gold nanobeacon designed to specifically silence the enhanced green fluorescence protein (EGFP) [...] Read more.
The use of gold nanoparticles for effective gene silencing has demonstrated its potential as a tool for gene expression experiments and for the treatment of several diseases. Here, we used a gold nanobeacon designed to specifically silence the enhanced green fluorescence protein (EGFP) mRNA in embryos of a fli-EGFP transgenic zebrafish line, while simultaneously allowing the tracking and localization of the silencing events via the beacon’s emission. Fluorescence imaging measurements demonstrated a decrease of the EGFP emission with a concomitant increase in the fluorescence of the Au-nanobeacon. Furthermore, microinjection of the Au-nanobeacon led to a negligible difference in mortality and malformations in comparison to the free oligonucleotide, indicating that this system is a biocompatible platform for the administration of gene silencing moieties. Together, these data illustrate the potential of Au-nanobeacons as tools for in vivo zebrafish gene modulation with low toxicity which may be used towards any gene of interest. Full article
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<p>Characterization of the synthesized AuNP@citrate and Au-nanobeacon; (<b>a</b>) Size distribution of the synthesized AuNP@citrate, Inset: Transmission electron microscopy (TEM) image of the AuNP@citrate (scale bar: 100 nm); (<b>b</b>) Ultra-violet (UV)-Vis spectra of the AuNP@citrate (solid black line) and Au-nanobeacon (solid grey line); (<b>c</b>) Hydrodynamic diameter of AuNP@citrate and Au-nanobeacon; (<b>d</b>) Calibration curve for the quantification of the number of hairpins per PEGylated AuNPs; (<b>e</b>) Zeta potential of AuNP@citrate and Au-nanobeacon.</p> Full article ">Figure 2
<p>Au-nanobeacon silencing efficiency of the enhanced green fluorescence protein (EGFP) and acute toxicity assessment. Fluorescence imaging of whole embryos after injection (amplification 8.1×); (<b>a</b>) Green channel of control embryos; (<b>b</b>) Red channel of control embryos; (<b>c</b>) Merged channels for control embryos; (<b>d</b>) Green channel of injected embryos; (<b>e</b>) Red channel of injected embryos; (<b>f</b>) Merged channels for injected embryos (8.1× amplification); (<b>g</b>) Quantification of fluorescence in whole embryos using Image J. The results were normalized to the respective channel of the control. The data are expressed as mean ± standard deviation of five embryos (sample <span class="html-italic">t</span> test—*** for <span class="html-italic">p</span> &lt; 0.05); (<b>h</b>) Zoom of 32.4× of the injected embryos’ merged channels (400% of 8.1×); (<b>i</b>) Quantification of death, survival and morphological malformations upon microinjection of AuNP@citrate, AuNP@PEG, Oligo anti-EGFP and Au-nanobeacon; Error bars corresponds to standard deviation of at least 50 embryos; (<b>j</b>) Example of embryos observed after microinjection of AuNP@citrate, AuNP@PEG, Oligo anti-EGFP and Au-nanobeacon: (<b>j1</b>) Normal embryo; (<b>j2</b>) Head and tail malformation; (<b>j3</b>) Pericardial edema; (<b>j4</b>) Underdeveloped embryo.</p> Full article ">
2539 KiB  
Article
SERS-Based Flavonoid Detection Using Ethylenediamine-β-Cyclodextrin as a Capturing Ligand
by Jae Min Choi, Eunil Hahm, Kyeonghui Park, Daham Jeong, Won-Yeop Rho, Jaehi Kim, Dae Hong Jeong, Yoon-Sik Lee, Sung Ho Jhang, Hyun Jong Chung, Eunae Cho, Jae-Hyuk Yu, Bong-Hyun Jun and Seunho Jung
Nanomaterials 2017, 7(1), 8; https://doi.org/10.3390/nano7010008 - 6 Jan 2017
Cited by 17 | Viewed by 7607
Abstract
Ethylenediamine-modified β-cyclodextrin (Et-β-CD) was immobilized on aggregated silver nanoparticle (NP)-embedded silica NPs (SiO2@Ag@Et-β-CD NPs) for the effective detection of flavonoids. Silica NPs were used as the template for embedding silver NPs to create hot spots and enhance surface-enhanced Raman scattering (SERS) [...] Read more.
Ethylenediamine-modified β-cyclodextrin (Et-β-CD) was immobilized on aggregated silver nanoparticle (NP)-embedded silica NPs (SiO2@Ag@Et-β-CD NPs) for the effective detection of flavonoids. Silica NPs were used as the template for embedding silver NPs to create hot spots and enhance surface-enhanced Raman scattering (SERS) signals. Et-β-CD was immobilized on Ag NPs to capture flavonoids via host-guest inclusion complex formation, as indicated by enhanced ultraviolet absorption spectra. The resulting SiO2@Ag@Et-β-CD NPs were used as the SERS substrate for detecting flavonoids, such as hesperetin, naringenin, quercetin, and luteolin. In particular, luteolin was detected more strongly in the linear range 10−7 to 10−3 M than various organic molecules, namely ethylene glycol, β-estradiol, isopropyl alcohol, naphthalene, and toluene. In addition, the SERS signal for luteolin captured by the SiO2@Ag@Et-β-CD NPs remained even after repeated washing. These results indicated that the SiO2@Ag@Et-β-CD NPs can be used as a rapid, sensitive, and selective sensor for flavonoids. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Chemical structures of the flavonoids: (<b>a</b>) hesperetin; (<b>b</b>) naringenin; (<b>c</b>) quercetin; and (<b>d</b>) luteolin.</p> Full article ">Figure 1 Cont.
<p>Chemical structures of the flavonoids: (<b>a</b>) hesperetin; (<b>b</b>) naringenin; (<b>c</b>) quercetin; and (<b>d</b>) luteolin.</p> Full article ">Figure 2
<p>Ultraviolet-visible (UV-Vis) absorption spectra of the flavonoids and their complexes: (<b>a</b>) Hesperetin (Hes); (<b>b</b>) Naringenin (Nar); (<b>c</b>) Quercetin (Que); and (<b>d</b>) Luteolin (Lut) in the absence (orange) and presence of β-cyclodextrin (β-CD, purple), dimethyl-β-CD (DM-β-CD, red), 2-hydroxypropyl-β-CD (HP-β-CD, green), and ethylenediamine-modified β-CD (Et-β-CD, blue).</p> Full article ">Figure 3
<p>Surface enhanced Raman scattering (SERS) spectra. (<b>a</b>) SERS spectra of (i) silver nanoparticle (NP)-embedded silica NPs (SiO<sub>2</sub>@Ag NPs), (ii) SiO<sub>2</sub>@Ag@Et-β-CD NPs, (iii) SiO<sub>2</sub>@Ag@Et-β-CD NPs with Nar, (iv) SiO<sub>2</sub>@Ag@Et-β-CD NPs with Hes, (v) SiO<sub>2</sub>@Ag@Et-β-CD NPs with Que, and (vi) SiO<sub>2</sub>@Ag@Et-β-CD NPs with Lut; (<b>b</b>) SERS spectra of (i) SiO<sub>2</sub>@Ag NPs, (ii) SiO<sub>2</sub>@Ag@Et-β-CD NPs, (iii) Lut in ethanol (10<sup>−2</sup> M), (iv) SiO<sub>2</sub>@Ag NPs mixing with Lut (10<sup>−4</sup> M), and (v) SiO<sub>2</sub>@Ag@Et-β-CD NPs mixing with Lut (10<sup>−4</sup> M).</p> Full article ">Figure 4
<p>SERS spectra and normalized SERS intensity. (<b>a</b>) SERS spectra of SiO<sub>2</sub>@Ag@Et-β-CD NPs mixed with Lut at concentrations from 1 × 10<sup>−3</sup> M to 1 × 10<sup>−7</sup> M; (<b>b</b>) Normalized SERS intensities at 742 cm<sup>−1</sup> ((i) 10<sup>−3</sup> M, (ii) 10<sup>−4</sup> M, (iii) 10<sup>−5</sup> M, (iv) 10<sup>−6</sup> M, (v) 10<sup>−7</sup> M, and (vi) 0 M).</p> Full article ">Figure 5
<p>(<b>a</b>) Raman spectra and (<b>b</b>) normalized intensities of Lut captured by SiO<sub>2</sub>@Ag@Et-β-CD NPs at 742 cm<sup>−1</sup> after washing with ethanol (Lut concentration, 10<sup>−4</sup> M).</p> Full article ">
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Article
Bulk Surfaces Coated with Triangular Silver Nanoplates: Antibacterial Action Based on Silver Release and Photo-Thermal Effect
by Agnese D’Agostino, Angelo Taglietti, Roberto Desando, Marcella Bini, Maddalena Patrini, Giacomo Dacarro, Lucia Cucca, Piersandro Pallavicini and Pietro Grisoli
Nanomaterials 2017, 7(1), 7; https://doi.org/10.3390/nano7010007 - 6 Jan 2017
Cited by 92 | Viewed by 8207
Abstract
A layer of silver nanoplates, specifically synthesized with the desired localized surface plasmon resonance (LSPR) features, was grafted on amino-functionalized bulk glass surfaces to impart a double antibacterial action: (i) the well-known, long-term antibacterial effect based on the release of Ag+; [...] Read more.
A layer of silver nanoplates, specifically synthesized with the desired localized surface plasmon resonance (LSPR) features, was grafted on amino-functionalized bulk glass surfaces to impart a double antibacterial action: (i) the well-known, long-term antibacterial effect based on the release of Ag+; (ii) an “on demand” action which can be switched on by the use of photo-thermal properties of silver nano-objects. Irradiation of these samples with a laser having a wavelength falling into the so called “therapeutic window” of the near infrared region allows the reinforcement, in the timescale of minutes, of the classical antibacterial effect of silver nanoparticles. We demonstrate how using the two actions allows for almost complete elimination of the population of two bacterial strains of representative Gram-positive and Gram-negative bacteria. Full article
(This article belongs to the Special Issue Antimicrobial Nanomaterials and Nanotechnology)
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<p>(<b>a</b>) UV–vis spectra of colloidal suspension of silver nanoplates obtained with the standard preparation; (<b>b</b>,<b>c</b>) Transmission electron microscope (TEM) images of silver nanoplates obtained with the standard preparation.</p> Full article ">Figure 2
<p>(<b>a</b>) UV–vis spectra of a GLASS-PEI-TRI sample; (<b>b</b>) Scanning electron microscope (SEM) image of a GLASS-PEI-TRI sample; (<b>c</b>) detail of a high magnification SEM image showing the presence of triangular nanoplates on the GLASS-PEI-TRI samples.</p> Full article ">Figure 3
<p>Temperature increase as a function of irradiation time, measured under NIR laser irradiation (808 nm, 0.26 W/cm<sup>2</sup>) for a freshly prepared GLASS-PEI-TRI sample (black solid line) and for a GLASS-PEI-TRI sample after an immersion of 48 h in water (black dashed line). The red solid line represents the thermogram obtained for an uncoated glass in the same conditions.</p> Full article ">Scheme 1
<p>A schematic representation of the synthetic route to polyethylenimine (PEI)-functionalized glass with citrate-capped Ag nanoplates (GLASS-PEI-TRI) samples.</p> Full article ">
2489 KiB  
Article
Spectroscopic Characterization of Copper-Chitosan Nanoantimicrobials Prepared by Laser Ablation Synthesis in Aqueous Solutions
by Maria Chiara Sportelli, Annalisa Volpe, Rosaria Anna Picca, Adriana Trapani, Claudio Palazzo, Antonio Ancona, Pietro Mario Lugarà, Giuseppe Trapani and Nicola Cioffi
Nanomaterials 2017, 7(1), 6; https://doi.org/10.3390/nano7010006 - 30 Dec 2016
Cited by 25 | Viewed by 6299
Abstract
Copper-chitosan (Cu-CS) nanoantimicrobials are a novel class of bioactive agents, providing enhanced and synergistic efficiency in the prevention of biocontamination in several application fields, from food packaging to biomedical. Femtosecond laser pulses were here exploited to disrupt a Cu solid target immersed into [...] Read more.
Copper-chitosan (Cu-CS) nanoantimicrobials are a novel class of bioactive agents, providing enhanced and synergistic efficiency in the prevention of biocontamination in several application fields, from food packaging to biomedical. Femtosecond laser pulses were here exploited to disrupt a Cu solid target immersed into aqueous acidic solutions containing different CS concentrations. After preparation, Cu-CS colloids were obtained by tuning both Cu/CS molar ratios and laser operating conditions. As prepared Cu-CS colloids were characterized by Fourier transform infrared spectroscopy (FTIR), to study copper complexation with the biopolymer. X-ray photoelectron spectroscopy (XPS) was used to elucidate the nanomaterials’ surface chemical composition and chemical speciation of the most representative elements. Transmission electron microscopy was used to characterize nanocolloids morphology. For all samples, ξ-potential measurements showed highly positive potentials, which could be correlated with the XPS information. The spectroscopic and morphological characterization herein presented outlines the characteristics of a technologically-relevant nanomaterial and provides evidence about the optimal synthesis parameters to produce almost monodisperse and properly-capped Cu nanophases, which combine in the same core-shell structure two renowned antibacterial agents. Full article
(This article belongs to the Special Issue New Developments in Nanomaterial Analysis)
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<p>Transmission electron microscopy (TEM) images of laser-generated Cu nanoparticles (CuNPs) in the presence of different chitosan (CS) concentrations and corresponding size distribution histograms. Sizing could not be performed on 3 g/L CuNPs-CS nanocomposite, because of the massive presence of organic matrix.</p> Full article ">Figure 2
<p>C1s high-resolution regions of freshly-prepared CuNPs-CS nanocomposites synthetized at a CS concentration of: (<b>a</b>) no CS; (<b>b</b>) 0.01 g/L; (<b>c</b>) 0.1 g/L; (<b>d</b>) 1 g/L; (<b>e</b>) 3 g/L; (<b>f</b>) pure CS.</p> Full article ">Figure 3
<p>N1s high-resolution regions of freshly-prepared CuNPs-CS nanocomposites synthetized at CS concentration of: (<b>a</b>) 0.01 g/L; (<b>b</b>) 0.1 g/L; (<b>c</b>) 1 g/L; (<b>d</b>) 3 g/L; (<b>e</b>) pure CS.</p> Full article ">Figure 4
<p>Cu2p<sub>3/2</sub> high-resolution regions of freshly-prepared CuNPs-CS nanocomposites synthetized at CS concentrations of: (<b>a</b>) no CS; (<b>b</b>) 0.01 g/L; (<b>c</b>) 0.1 g/L; (<b>d</b>) 1 g/L; (<b>e</b>) 3 g/L.</p> Full article ">Figure 5
<p>Fourier transform infrared (FTIR) spectra of freshly-prepared CuNPs stabilized by CS (CuNPs@CS nanocomposites, “@” stands for “stabilized by”), synthetized at CS concentrations of: (<b>a</b>) 0.01 g/L; (<b>b</b>) 0.1 g/L; (<b>c</b>) 1 g/L; (<b>d</b>) 3 g/L.</p> Full article ">
5980 KiB  
Article
Synthesis of Polyhydroxybutyrate Particles with Micro-to-Nanosized Structures and Application as Protective Coating for Packaging Papers
by Vibhore Kumar Rastogi and Pieter Samyn
Nanomaterials 2017, 7(1), 5; https://doi.org/10.3390/nano7010005 - 30 Dec 2016
Cited by 21 | Viewed by 7285
Abstract
This study reports on the development of bio-based hydrophobic coatings for packaging papers through deposition of polyhydroxybutyrate (PHB) particles in combination with nanofibrillated cellulose (NFC) and plant wax. In the first approach, PHB particles in the micrometer range (PHB-MP) were prepared through a [...] Read more.
This study reports on the development of bio-based hydrophobic coatings for packaging papers through deposition of polyhydroxybutyrate (PHB) particles in combination with nanofibrillated cellulose (NFC) and plant wax. In the first approach, PHB particles in the micrometer range (PHB-MP) were prepared through a phase-separation technique providing internally-nanosized structures. The particles were transferred as a coating by dip-coating filter papers in the particle suspension, followed by sizing with a carnauba wax solution. This approach allowed partial to almost full surface coverage of PHB-MP over the paper surface, resulting in static water contact angles of 105°–122° and 129°–144° after additional wax coating. In the second approach, PHB particles with submicron sizes (PHB-SP) were synthesized by an oil-in-water emulsion (o/w) solvent evaporation method and mixed in aqueous suspensions with 0–7 wt % NFC. After dip-coating filter papers in PHB-SP/NFC suspensions and sizing with a carnauba wax solution, static water contact angles of 112°–152° were obtained. The intrinsic properties of the particles were analyzed by scanning electron microscopy, thermal analysis and infrared spectroscopy, indicating higher crystallinity for PHB-SP than PHB-MP. The chemical interactions between the more amorphous PHB-MP particles and paper fibers were identified as an esterification reaction, while the morphology of the NFC fibrillar network was playing a key role as the binding agent in the retention of more crystalline PHB-SP at the paper surface, hence contributing to higher hydrophobicity. Full article
(This article belongs to the Special Issue Nanomaterials in Food Safety)
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<p>Scanning electron microscopy of (<b>a</b>,<b>b</b>) internally-structured polyhydroxyalkanoate microparticles (PHB-MP), and (<b>c</b>,<b>d</b>) non-structured polyhydroxyalkanoate submicron particles (PHB-SP), (note the different scales of magnification for the best representation of the particle morphology).</p> Full article ">Figure 2
<p>Thermogravimetric analysis (TGA) representing weight loss and differential weight loss (inset) curves of (i) neat PHB, (ii) PHB-MP and (iii) PHB-SP.</p> Full article ">Figure 3
<p>Differential scanning calorimetry (DSC) thermographs of (i) neat PHB, (ii) PHB-MP and (iii) PHB-SP.</p> Full article ">Figure 4
<p>Fourier-transform infrared (FTIR) spectra showing (<b>a</b>) complete wavenumber range 4000–400 cm<sup>−1</sup>; (<b>b</b>) detailed spectra in wavenumber range 1500–1100 cm<sup>−1</sup> for (i) neat PHB, (ii) PHB-MP and (iii) PHB-SP.</p> Full article ">Figure 5
<p>Scanning electron microscopy for PHB-MP-coated papers from suspensions with different concentrations: (<b>a</b>,<b>b</b>) PHB-MP, with 8.5 <span class="html-italic">w</span>/<span class="html-italic">v</span> % of PHB and 7.4 <span class="html-italic">v</span>/<span class="html-italic">v</span> % non-solvent; (<b>c</b>,<b>d</b>) PHB-MP, with 17.0 <span class="html-italic">w</span>/<span class="html-italic">v</span> % of PHB and 7.4 <span class="html-italic">v</span>/<span class="html-italic">v</span> % non-solvent; (<b>e</b>,<b>f</b>) PHB-MP, with 17.0 <span class="html-italic">w</span>/<span class="html-italic">v</span> % of PHB and 14.8 <span class="html-italic">v</span>/<span class="html-italic">v</span> % non-solvent; (<b>g</b>,<b>h</b>) PHB-MP, with 17.0 <span class="html-italic">w</span>/<span class="html-italic">v</span> % of PHB and 23.1 <span class="html-italic">v</span>/<span class="html-italic">v</span> % non-solvent; (<b>i</b>,<b>j</b>) neat PHB, with 8.5 <span class="html-italic">w</span>/<span class="html-italic">v</span> % of PHB without non-solvent. The figures (<b>a</b>,<b>c</b>,<b>e</b>,<b>g</b>,<b>i</b>) are magnified images with a scale of 50 µm; insets are water contact angles on coated papers without additional wax coating. The figures in (<b>b</b>,<b>d</b>,<b>f</b>,<b>h</b>,<b>j</b>) are images of a larger area with a scale of 1 mm; insets are water contact angles after the application of an additional wax layer over the coated papers.</p> Full article ">Figure 6
<p>FTIR spectra showing the interactions between PHB-MP and cellulose fibers of the paper substrate: (<b>a</b>) spectra normalized over non-overlapped region, 730–645 cm<sup>−1</sup>; (<b>b</b>) spectra normalized over the PHB insensitive crystalline band, 1453 cm<sup>−1</sup>, for (i) uncoated filter paper, (ii) PHB-MP coated paper and (iii) PHB-MP powder.</p> Full article ">Figure 7
<p>Scanning electron microscopy for PHB-SP- or PHB-SP/NFC-coated papers from suspensions with different concentrations PHB-SP and NFC: (<b>a</b>) non-coated reference filter paper, no PHB-SP and no NFC; (<b>b</b>) 5 <span class="html-italic">w</span>/<span class="html-italic">v</span> % PHB-SP, no NFC; (<b>c</b>) 20 <span class="html-italic">w</span>/<span class="html-italic">v</span> % PHB-SP, no NFC; (<b>d</b>) detail of 20 <span class="html-italic">w</span>/<span class="html-italic">v</span> % PHB-SP, no NFC; (<b>e</b>) 5 <span class="html-italic">w</span>/<span class="html-italic">v</span> % PHB-SP, 1 wt % NFC; (<b>f</b>) 5 <span class="html-italic">w</span>/<span class="html-italic">v</span> % PHB-SP, 2 wt % NFC; (<b>g</b>) 5 <span class="html-italic">w</span>/<span class="html-italic">v</span> % PHB-SP, 7 wt % NFC; insets are water contact angles after the application of an additional wax layer over the coated papers.</p> Full article ">Figure 8
<p>Scanning electron micrographs of filter paper dip-coated with the PHB-SP/NFC suspension having 7 wt % NFC, showing: (<b>a</b>) a dense NFC network retaining PHB-SP, when placed under strong X-rays for 5 min; and (<b>b</b>) retention of PHB-SP over the single fiber of paper after diluting the coating suspension (added 4 mL distilled water).</p> Full article ">Figure 9
<p>Scheme for preparing PHB-SP/NFC coating slurry used for paper coatings.</p> Full article ">
3593 KiB  
Article
On the Use of the Electrospinning Coating Technique to Produce Antimicrobial Polyhydroxyalkanoate Materials Containing In Situ-Stabilized Silver Nanoparticles
by Jinneth Lorena Castro-Mayorga, Maria Jose Fabra, Luis Cabedo and Jose Maria Lagaron
Nanomaterials 2017, 7(1), 4; https://doi.org/10.3390/nano7010004 - 29 Dec 2016
Cited by 57 | Viewed by 6048
Abstract
Electro-hydrodynamic processing, comprising electrospraying and electrospinning techniques, has emerged as a versatile technology to produce nanostructured fiber-based and particle-based materials. In this work, an antimicrobial active multilayer system comprising a commercial polyhydroxyalkanoate substrate (PHA) and an electrospun PHA coating containing in situ-stabilized silver [...] Read more.
Electro-hydrodynamic processing, comprising electrospraying and electrospinning techniques, has emerged as a versatile technology to produce nanostructured fiber-based and particle-based materials. In this work, an antimicrobial active multilayer system comprising a commercial polyhydroxyalkanoate substrate (PHA) and an electrospun PHA coating containing in situ-stabilized silver nanoparticles (AgNPs) was successfully developed and characterized in terms of morphology, thermal, mechanical, and barrier properties. The obtained materials reduced the bacterial population of Salmonella enterica below the detection limits at very low silver loading of 0.002 ± 0.0005 wt %. As a result, this study provides an innovative route to generate fully renewable and biodegradable materials that could prevent microbial outbreaks in food packages and food contact surfaces. Full article
(This article belongs to the Special Issue Multifunctional Polymer-Based Nanocomposites)
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Figure 1
<p>Scanning electron microscopy (SEM) images of the electrospun fibers: (<b>a</b>) PHBVs (PHBVs corresponds to a mixture between PHBV3 and PHBV18 (without silver nanoparticles), PHBV3, poly(3-hydroxybutyrate-co-3 mol %-3-hydroxyvalerate), PHBV18, poly(3-hydroxybutyrate-co-18 mol %-3-hydroxyvalerate)); (<b>b</b>) PHBVs/ silver nanoparticles (AgNPs); (<b>c</b>) size distribution of fibers.</p> Full article ">Figure 2
<p>Transmission electron microscopy (TEM) micrographs of ultramicrotomed silver-containing materials: (<b>a</b>) in PHBVs/AgNPs; (<b>b</b>) in the active multilayer film. The dashed line in the <a href="#nanomaterials-07-00004-f002" class="html-fig">Figure 2</a>a shows a group of AgNPs whose diameter matches with the fiber’s diameter of 0.46 µm.</p> Full article ">Figure 3
<p>SEM micrographs of the active multilayer; (<b>a</b>) top view of the film; (<b>b</b>) side view of the cryo-fractured film section.</p> Full article ">Figure 4
<p>Contact transparency pictures of films. (<b>A</b>) poly(3-hydroxybutyrate-co-3 mol %-3-hydroxyvalerate) (PHBV3); (<b>B</b>) multilayer; (<b>C</b>) active multilayer.</p> Full article ">Figure 5
<p>Differential scanning calorimetry (DSC) thermograms of first heating run of the neat electrospun fibers and films and their silver-based coating system.</p> Full article ">Figure 6
<p>Antimicrobial activity of PHBV and PHBV/AgNP films against <span class="html-italic">Listeria monocytogenes</span> and <span class="html-italic">Salmonella enterica</span> after 24 h of exposure. The initial inoculum size was ~5 log CFU/mL and the detection limit was 20 CFU/mL.</p> Full article ">
3073 KiB  
Article
Pnma-BN: Another Boron Nitride Polymorph with Interesting Physical Properties
by Zhenyang Ma, Zheng Han, Xuhong Liu, Xinhai Yu, Dayun Wang and Yi Tian
Nanomaterials 2017, 7(1), 3; https://doi.org/10.3390/nano7010003 - 28 Dec 2016
Cited by 42 | Viewed by 5500
Abstract
Structural, mechanical, electronic properties, and stability of boron nitride (BN) in Pnma structure were studied using first-principles calculations by Cambridge Serial Total Energy Package (CASTEP) plane-wave code, and the calculations were performed with the local density approximation and generalized gradient approximation in the [...] Read more.
Structural, mechanical, electronic properties, and stability of boron nitride (BN) in Pnma structure were studied using first-principles calculations by Cambridge Serial Total Energy Package (CASTEP) plane-wave code, and the calculations were performed with the local density approximation and generalized gradient approximation in the form of Perdew–Burke–Ernzerhof. This BN, called Pnma-BN, contains four boron atoms and four nitrogen atoms buckled through sp3-hybridized bonds in an orthorhombic symmetry unit cell with Space group of Pnma. Pnma-BN is energetically stable, mechanically stable, and dynamically stable at ambient pressure and high pressure. The calculated Pugh ratio and Poisson’s ratio revealed that Pnma-BN is brittle, and Pnma-BN is found to turn brittle to ductile (~94 GPa) in this pressure range. It shows a higher mechanical anisotropy in Poisson’s ratio, shear modulus, Young’s modulus, and the universal elastic anisotropy index AU. Band structure calculations indicate that Pnma-BN is an insulator with indirect band gap of 7.18 eV. The most extraordinary thing is that the band gap increases first and then decreases with the increase of pressure from 0 to 60 GPa, and from 60 to 100 GPa, the band gap increases first and then decreases again. Full article
(This article belongs to the Special Issue Computational Modeling and Simulations of Carbon Nanomaterials)
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Figure 1

Figure 1
<p>Unit cell crystal structures of BN in <span class="html-italic">Pnma</span> structure.</p> Full article ">Figure 2
<p>The lattice constants <span class="html-italic">a</span>/<span class="html-italic">a</span><sub>0</sub>, <span class="html-italic">b</span>/<span class="html-italic">b</span><sub>0</sub>, <span class="html-italic">c</span>/<span class="html-italic">c</span><sub>0</sub> compression as functions of pressure for <span class="html-italic">Pnma</span>-BN (<b>a</b>), and primitive cell volume <span class="html-italic">V</span>/<span class="html-italic">V</span><sub>0</sub> for <span class="html-italic">Pbca</span>-BN, <span class="html-italic">Pnma</span>-BN, c-BN, and diamond (<b>b</b>).</p> Full article ">Figure 3
<p>The phonon spectra of <span class="html-italic">Pnma</span>-BN at 0 GPa (<b>a</b>) and 100 GPa (<b>b</b>); Mixing enthalpy Δ<span class="html-italic">H</span> of BN alltropes calculated using PBE (<b>c</b>).</p> Full article ">Figure 4
<p>Elastic constants and elastic modulus (<b>a</b>) and <span class="html-italic">B</span>/<span class="html-italic">G</span> ratio (<b>b</b>); Poissons’ ratio <span class="html-italic">v</span> (<b>c</b>) of <span class="html-italic">Pnma</span>-BN as a function of pressure.</p> Full article ">Figure 5
<p>The surface construction of Poisson’s ratio (<b>a</b>); shear modulus (<b>b</b>); and Young’s modulus (<b>c</b>) for the <span class="html-italic">Pnma</span>-BN.</p> Full article ">Figure 6
<p>2D representation of Poisson’s ratio (<b>a</b>); shear modulus (<b>b</b>) and Young’s modulus (<b>c</b>) in the main plane for <span class="html-italic">Pnma</span>-BN, respectively.</p> Full article ">Figure 7
<p>The band structures under pressure of <span class="html-italic">Pnma</span>-BN, (<b>a</b>) 0 GPa, (<b>b</b>) 30 GPa, (<b>c</b>) 60 GPa, (<b>d</b>) 100 GPa.</p> Full article ">Figure 8
<p>The band gap under pressure of <span class="html-italic">Pnma</span>-BN (<b>a</b>), the Fermi level and the energy of <span class="html-italic">G</span> high-symmetry points along valence band maximum (VBM) (<b>b</b>); the energy of <span class="html-italic">T</span> and <span class="html-italic">Y</span> high-symmetry points along conduction band minimum (CBM) (<b>c</b>).</p> Full article ">
2583 KiB  
Article
Visible Light-Responsive Platinum-Containing Titania Nanoparticle-Mediated Photocatalysis Induces Nucleotide Insertion, Deletion and Substitution Mutations
by Der-Shan Sun, Yao-Hsuan Tseng, Wen-Shiang Wu, Ming-Show Wong and Hsin-Hou Chang
Nanomaterials 2017, 7(1), 2; https://doi.org/10.3390/nano7010002 - 28 Dec 2016
Cited by 8 | Viewed by 4716
Abstract
Conventional photocatalysts are primarily stimulated using ultraviolet (UV) light to elicit reactive oxygen species and have wide applications in environmental and energy fields, including self-cleaning surfaces and sterilization. Because UV illumination is hazardous to humans, visible light-responsive photocatalysts (VLRPs) were discovered and are [...] Read more.
Conventional photocatalysts are primarily stimulated using ultraviolet (UV) light to elicit reactive oxygen species and have wide applications in environmental and energy fields, including self-cleaning surfaces and sterilization. Because UV illumination is hazardous to humans, visible light-responsive photocatalysts (VLRPs) were discovered and are now applied to increase photocatalysis. However, fundamental questions regarding the ability of VLRPs to trigger DNA mutations and the mutation types it elicits remain elusive. Here, through plasmid transformation and β-galactosidase α-complementation analyses, we observed that visible light-responsive platinum-containing titania (TiO2) nanoparticle (NP)-mediated photocatalysis considerably reduces the number of Escherichia coli transformants. This suggests that such photocatalytic reactions cause DNA damage. DNA sequencing results demonstrated that the DNA damage comprises three mutation types, namely nucleotide insertion, deletion and substitution; this is the first study to report the types of mutations occurring after photocatalysis by TiO2-VLRPs. Our results may facilitate the development and appropriate use of new-generation TiO2 NPs for biomedical applications. Full article
(This article belongs to the Special Issue Antimicrobial Nanomaterials and Nanotechnology)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Influence of heat on photocatalyst-induced DNA damage. Plasmid pBlueScript II SK<sup>+</sup> DNA was transformed to <span class="html-italic">Escherichia coli</span> (<span class="html-italic">E. coli</span>) competent cells after photocatalysis environments set to 4 °C and 25 °C. The level of DNA damage involving ultraviolet (UV)- and heat-induced nanoscale-TiO<sub>2</sub> film-mediated photocatalysis was indicated by the reduction of transformants. * <span class="html-italic">p</span> &lt; 0.05 vs. 4 °C group. <span class="html-italic">n</span> = 6, three experiments with two replicates.</p> Full article ">Figure 2
<p>(<b>A</b>) Dose-dependent and (<b>B</b>) kinetic responses, with increasing illumination density and with increasing time, respectively. The visible light stimulated TiO<sub>2</sub>-Pt photocatalysis-mediated DNA damage was determined by the reduction of transformants. The DNA samples of those dark groups were covered with aluminum foil to prevent the photocatalysis. UV-responsive TiO<sub>2</sub> NPs were used as control materials. ** <span class="html-italic">p</span> &lt; 0.01 vs. respective TiO<sub>2</sub>-Pt dark groups. <span class="html-italic">n</span> = 6, three experiments with two replicates.</p> Full article ">Figure 3
<p>Significant visible light stimulated TiO<sub>2</sub>-Pt-mediated photocatalysis-induced DNA damage occurred in the pGEX-2KS, pET16 and pBlueScript II SK<sup>+</sup> plasmids. Notably, these plasmids all displayed similar reductions after the photocatalysis. ** <span class="html-italic">p</span> &lt; 0.01; * <span class="html-italic">p</span> &lt; 0.05 vs. respective dark groups. <span class="html-italic">n</span> = 6, three experiments with two replicates.</p> Full article ">Figure 4
<p>Detection of mutated clones using <span class="html-italic">lac</span>Z α-peptide complementation. (<b>A</b>,<b>B</b>) After being complemented with <span class="html-italic">lac</span>Z α-peptide expression, the transformants are displayed as blue colonies on the agar plates with 5-bromo-4-chloro-3-indolyl-β-<span class="html-small-caps">d</span>-galactopyranoside. The VLRP TiO<sub>2</sub>-Pt NP-mediated photocatalysis markedly reduces the number of transformants, compared with the control groups using UV-responsive TiO<sub>2</sub> NPs, under visible light illumination. (<b>C</b>) Quantified results show that TiO<sub>2</sub>-Pt photocatalysis can induce the formation of white colonies. This indicates that mutations hit the <span class="html-italic">lac</span>Zα region because of a loss-of-function (loss-of-complementation) phenotype, compared with the wild-type plasmid-transformed blue colonies. ND: no detected colony. * <span class="html-italic">p</span> &lt; 0.05 vs. both blue groups of TiO<sub>2</sub>-visible light and TiO<sub>2</sub>-Pt-dark; ** <span class="html-italic">p</span> &lt; 0.01 vs. respective blue groups. <span class="html-italic">n</span> = 6, three experiments with two replicates.</p> Full article ">Figure 5
<p>Mutation sites in the <span class="html-italic">lac</span>Z α-peptide coding (<span class="html-italic">lac</span>Zα) region. Examples of DNA sequences in the <span class="html-italic">lac</span>Zα region of the white colonies are provided, in which insertion (Clones 1, 6, 7, 9 and 10) deletion (Clones 2–4, 8) and nucleotide substitution (Clones 2, 4, 5, 7, 8 and 10) mutation types are involved. The nucleotides at the mutation sites are labeled in red.</p> Full article ">Figure 6
<p><span class="html-italic">lac</span>Z α-peptide amino acid sequence aliment of one wild-type and 10 mutated clones. The amino acid sequences encoded by multiple cloning sites are labeled in red; the sequences encoded by <span class="html-italic">lac</span>Zα are labeled in green; and the mutation-caused reading frame shifts are labeled in blue. The * indicates the translation termination by the stop codon.</p> Full article ">
3623 KiB  
Article
Improving Powder Magnetic Core Properties via Application of Thin, Insulating Silica-Nanosheet Layers on Iron Powder Particles
by Toshitaka Ishizaki, Hideyuki Nakano, Shin Tajima and Naoko Takahashi
Nanomaterials 2017, 7(1), 1; https://doi.org/10.3390/nano7010001 - 23 Dec 2016
Cited by 15 | Viewed by 5721
Abstract
A thin, insulating layer with high electrical resistivity is vital to achieving high performance of powder magnetic cores. Using layer-by-layer deposition of silica nanosheets or colloidal silica over insulating layers composed of strontium phosphate and boron oxide, we succeeded in fabricating insulating layers [...] Read more.
A thin, insulating layer with high electrical resistivity is vital to achieving high performance of powder magnetic cores. Using layer-by-layer deposition of silica nanosheets or colloidal silica over insulating layers composed of strontium phosphate and boron oxide, we succeeded in fabricating insulating layers with high electrical resistivity on iron powder particles, which were subsequently used to prepare toroidal cores. The compact density of these cores decreased after coating with colloidal silica due to the substantial increase in the volume, causing the magnetic flux density to deteriorate. Coating with silica nanosheets, on the other hand, resulted in a higher electrical resistivity and a good balance between high magnetic flux density and low iron loss due to the thinner silica layers. Transmission electron microscopy images showed that the thickness of the colloidal silica coating was about 700 nm, while that of the silica nanosheet coating was 30 nm. There was one drawback to using silica nanosheets, namely a deterioration in the core mechanical strength. Nevertheless, the silica nanosheet coating resulted in nanoscale-thick silica layers that are favorable for enhancing the electrical resistivity. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Electrical resistivities; and (<b>b</b>) compact densities of the annealed toroidal cores fabricated from iron powder particles coated with colloidal silica with and without Sr-B-P-O insulating layers increasing number of silica coatings from 1–5.</p> Full article ">Figure 2
<p>(<b>a</b>) Iron losses, magnetic flux densities; (<b>b</b>) coercivities; and (<b>c</b>) maximum permeabilities of the annealed toroidal cores fabricated from iron powder particles coated with colloidal silica with and without Sr-B-P-O insulating layers increasing number of silica coatings from 1 to 5.</p> Full article ">Figure 3
<p>X-ray photoelectron spectroscopy (XPS) (<b>a</b>) Si2p; and (<b>b</b>) Fe2p3/2 core level spectra of uncoated iron powder particles and iron power particles coated five times with colloidal silica with and without Sr-B-P-O insulating layers.</p> Full article ">Figure 4
<p>Schematic models for the silica coating of iron powder particles by the lbl method (<b>a</b>) without; and (<b>b</b>) with Sr-B-P-O insulating layers.</p> Full article ">Figure 5
<p>TEM images of silica layers on iron powder particles with Sr-B-P-O insulating layers coated five times by (<b>a</b>) colloidal silica; and (<b>b</b>) silica nanosheets.</p> Full article ">Figure 6
<p>(<b>a</b>) Electrical resistivities; and (<b>b</b>) compact densities of annealed toroidal cores fabricated from iron powder particles coated only with Sr-B-P-O insulating layers, and with five coatings of colloidal silica or silica nanosheets over Sr-B-P-O insulating layers.</p> Full article ">Figure 7
<p>(<b>a</b>) Iron losses, magnetic flux densities; (<b>b</b>) coercivities; and (<b>c</b>) maximum permeabilities of annealed toroidal cores fabricated from iron powder particles coated only with Sr-B-P-O insulating layers, and with five coatings of colloidal silica or silica nanosheets over Sr-B-P-O insulating layers.</p> Full article ">Figure 7 Cont.
<p>(<b>a</b>) Iron losses, magnetic flux densities; (<b>b</b>) coercivities; and (<b>c</b>) maximum permeabilities of annealed toroidal cores fabricated from iron powder particles coated only with Sr-B-P-O insulating layers, and with five coatings of colloidal silica or silica nanosheets over Sr-B-P-O insulating layers.</p> Full article ">Figure 8
<p>XPS (<b>a</b>) Si2p; and (<b>b</b>) Fe2p3/2 core level spectra of iron powder particles coated five times with colloidal silica or silica nanosheets over Sr-B-P-O insulating layers.</p> Full article ">Figure 9
<p>Radial crushing strengths of annealed toroidal cores fabricated from uncoated iron powder particles, particles with only Sr-B-P-O insulating layers, and particles with five coatings of colloidal silica or silica nanosheets over Sr-B-P-O insulating layers.</p> Full article ">
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