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Nanomaterials, Volume 7, Issue 3 (March 2017)

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Cover Story Despite being banned in several countries due to its high toxicity, the herbicide paraquat is still [...] Read more.
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Open AccessArticle Influence of Plasma Jet Temperature Profiles in Arc Discharge Methods of Carbon Nanotubes Synthesis
Nanomaterials 2017, 7(3), 50; doi:10.3390/nano7030050
Received: 30 December 2016 / Revised: 14 February 2017 / Accepted: 16 February 2017 / Published: 23 February 2017
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Abstract
One of the most common methods of carbon nanotubes (CNTs) synthesis is application of an electric-arc plasma. However, the final product in the form of cathode deposit is composed of carbon nanotubes and a variety of carbon impurities. An assay of carbon nanotubes
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One of the most common methods of carbon nanotubes (CNTs) synthesis is application of an electric-arc plasma. However, the final product in the form of cathode deposit is composed of carbon nanotubes and a variety of carbon impurities. An assay of carbon nanotubes produced in arc discharge systems available on the market shows that commercial cathode deposits contain about 10% CNTs. Given that the quality of the final product depends on carbon–plasma jet parameters, it is possible to increase the yield of the synthesis by plasma jet control. Most of the carbon nanotubes are multiwall carbon nanotubes (MWCNTs). It was observed that the addition of catalysts significantly changes the plasma composition, effective ionization potential, the arc channel conductance, and in effect temperature of the arc and carbon elements flux. This paper focuses on the influence of metal components on plasma-jet forming containing carbon nanotubes cathode deposit. The plasma jet temperature control system is presented. Full article
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Open AccessArticle Preparation and Characterization of Cellulose Nanocrystals from the Bio-ethanol Residuals
Nanomaterials 2017, 7(3), 51; doi:10.3390/nano7030051
Received: 10 January 2017 / Revised: 15 February 2017 / Accepted: 16 February 2017 / Published: 23 February 2017
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Abstract
This study was to explore the conversion of low-cost bio-residuals into high value-added cellulose nanocrystals. Two enzymatic hydrolyzed residuals (i.e., HRMMW and HRSPW) were collected from two different bio-ethanol producing processes—hydrolyzing medium-milled wood (MMW) and hydrolyzing acid sulfite pretreated wood
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This study was to explore the conversion of low-cost bio-residuals into high value-added cellulose nanocrystals. Two enzymatic hydrolyzed residuals (i.e., HRMMW and HRSPW) were collected from two different bio-ethanol producing processes—hydrolyzing medium-milled wood (MMW) and hydrolyzing acid sulfite pretreated wood (SPW), respectively. The results showed that both residuals contained over 20 wt % glucan with a crystallinity of about 30%, confirming the existence of cellulose in a well-organized structure in two bio-residuals. The cellulose nanocrystals (CNCs) were successfully extracted by first bleaching the hydrolyzed residuals to remove lignin and then hydrolyzing them with sulfuric acid. The resulting CNCs displayed the flow birefringence under two crossed polarizers. Compared with CNCs from microfibrillated cellulose (CNCMCC), HRMMW and its resulted CNC present the smallest particle size and aspect ratio. CNCMCC had the larger particle size, aspect ratio, and higher z-potential value, CNCSPW presented a similar morphology to CNCMCC, and had the largest aspect ratio. The CNCMCC enhanced its high crystallinity to 85.5%. However, CNCMMW and CNCSPW had a better thermal stability and higher activation energy as well as onset temperature and maximum decomposition temperature. As a result, the CNCs from bio-ethanol residuals are valued and promising cellulose nanoparticle resources. Full article
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Open AccessArticle Preparation and Electrochemical Properties of Li3V2(PO4)3−xBrx/Carbon Composites as Cathode Materials for Lithium-Ion Batteries
Nanomaterials 2017, 7(3), 52; doi:10.3390/nano7030052
Received: 25 January 2017 / Revised: 16 February 2017 / Accepted: 21 February 2017 / Published: 24 February 2017
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Abstract
Li3V2(PO4)3−xBrx/carbon (x = 0.08, 0.14, 0.20, and 0.26) composites as cathode materials for lithium-ion batteries were prepared through partially substituting PO43− with Br, via a rheological phase
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Li3V2(PO4)3−xBrx/carbon (x = 0.08, 0.14, 0.20, and 0.26) composites as cathode materials for lithium-ion batteries were prepared through partially substituting PO43− with Br, via a rheological phase reaction method. The crystal structure and morphology of the as-prepared composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and electrochemical properties were evaluated by charge/discharge cycling and electrochemical impedance spectroscopy (EIS). XRD results reveal that the Li3V2(PO4)3−xBrx/carbon composites with solid solution phase are well crystallized and have the same monoclinic structure as the pristine Li3V2(PO4)3/carbon composite. It is indicated by SEM images that the Li3V2(PO4)3−xBrx/carbon composites possess large and irregular particles, with an increasing Br content. Among the Li3V2(PO4)3−xBrx/carbon composites, the Li3V2(PO4)2.86Br0.14/carbon composite shows the highest initial discharge capacity of 178.33 mAh·g−1 at the current rate of 30 mA·g−1 in the voltage range of 4.8–3.0 V, and the discharge capacity of 139.66 mAh·g−1 remains after 100 charge/discharge cycles. Even if operated at the current rate of 90 mA·g−1, Li3V2(PO4)2.86Br0.14/carbon composite still releases the initial discharge capacity of 156.57 mAh·g−1, and the discharge capacity of 123.3 mAh·g−1 can be maintained after the same number of cycles, which is beyond the discharge capacity and cycleability of the pristine Li3V2(PO4)3/carbon composite. EIS results imply that the Li3V2(PO4)2.86Br0.14/carbon composite demonstrates a decreased charge transfer resistance and preserves a good interfacial compatibility between solid electrode and electrolyte solution, compared with the pristine Li3V2(PO4)3/carbon composite upon cycling. Full article
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Open AccessArticle SiO2/ZnO Composite Hollow Sub-Micron Fibers: Fabrication from Facile Single Capillary Electrospinning and Their Photoluminescence Properties
Nanomaterials 2017, 7(3), 53; doi:10.3390/nano7030053
Received: 30 November 2016 / Accepted: 3 February 2017 / Published: 24 February 2017
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Abstract
In this work, SiO2/ZnO composite hollow sub-micron fibers were fabricated by a facile single capillary electrospinning technique followed by calcination, using tetraethyl orthosilicate (TEOS), polyvinylpyrrolidone (PVP) and ZnO nanoparticles as raw materials. The characterization results of the scanning electron microscopy (SEM), transmission electron
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In this work, SiO2/ZnO composite hollow sub-micron fibers were fabricated by a facile single capillary electrospinning technique followed by calcination, using tetraethyl orthosilicate (TEOS), polyvinylpyrrolidone (PVP) and ZnO nanoparticles as raw materials. The characterization results of the scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) spectra indicated that the asprepared composite hollow fibers consisted of amorphous SiO2 and hexagonal wurtzite ZnO. The products revealed uniform tubular structure with outer diameters of 400–500 nm and wall thickness of 50–60 nm. The gases generated and the directional escaped mechanism was proposed to illustrate the formation of SiO2/ZnO composite hollow sub-micron fibers. Furthermore, a broad blue emission band was observed in the photoluminescence (PL) of SiO2/ZnO composite hollow sub-micron fibers, exhibiting great potential applications as blue light-emitting candidate materials. Full article
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Open AccessArticle Microwave-Hydrothermal Synthesis of SnO2-CNTs Hybrid Nanocomposites with Visible Light Photocatalytic Activity
Nanomaterials 2017, 7(3), 54; doi:10.3390/nano7030054
Received: 11 October 2016 / Accepted: 29 November 2016 / Published: 3 March 2017
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Abstract
SnO2 nanoparticles coated on carbon nanotubes (CNTs) were prepared via a simple microwave-hydrothermal route. The as-obtained SnO2-CNTs composites were characterized using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The photocatalytic activity of as-prepared SnO2-CNTs for degradation of Rhodamine B under visible
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SnO2 nanoparticles coated on carbon nanotubes (CNTs) were prepared via a simple microwave-hydrothermal route. The as-obtained SnO2-CNTs composites were characterized using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The photocatalytic activity of as-prepared SnO2-CNTs for degradation of Rhodamine B under visible light irradiation was investigated. The results show that SnO2-CNTs nanocomposites have a higher photocatalytic activity than pure SnO2 due to the rapid transferring of electrons and the effective separation of holes and electrons on SnO2-CNTs. Full article
(This article belongs to the Special Issue Nanomaterials for Water Treatment)
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Open AccessArticle Self‐propagating Combustion Triggered Synthesis of  3D Lamellar Graphene/BaFe12O19 Composite and Its  Electromagnetic Wave Absorption Properties
Nanomaterials 2017, 7(3), 55; doi:10.3390/nano7030055
Received: 13 February 2017 / Accepted: 2 March 2017 / Published: 3 March 2017
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Abstract
The synthesis of 3D lamellar graphene/BaFe12O19 composites was performed by oxidizing graphite and sequentially self‐propagating combustion triggered process. The 3D lamellar graphene structures were formed due to the synergistic effect of the tremendous heat induced gasification as well as huge volume expansion. The
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The synthesis of 3D lamellar graphene/BaFe12O19 composites was performed by oxidizing graphite and sequentially self‐propagating combustion triggered process. The 3D lamellar graphene structures were formed due to the synergistic effect of the tremendous heat induced gasification as well as huge volume expansion. The 3D lamellar graphene/BaFe12O19 composites bearing 30 wt % graphene present the reflection loss peak at −27.23 dB as well as the frequency bandwidth at 2.28 GHz (< −10 dB). The 3D lamellar graphene structures could consume the incident waves through multiple Reflection and scattering within the layered structures, Prolonging the propagation path of electromagnetic waves in the absorbers. Full article
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Open AccessArticle In Vitro Comparative Skin Irritation Induced by Nano and Non-Nano Zinc Oxide
Nanomaterials 2017, 7(3), 56; doi:10.3390/nano7030056
Received: 26 October 2016 / Revised: 25 January 2017 / Accepted: 28 February 2017 / Published: 4 March 2017
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Abstract
This study was designed to determine whether nano-sized ZnO has the potential to cause acute cutaneous irritation using cultured HaCaT keratinocytes and a human skin equivalent as in vitro models, compared to non-nanomaterials. Commercial nano ZnO with different sizes (50 nm and 100
[...] Read more.
This study was designed to determine whether nano-sized ZnO has the potential to cause acute cutaneous irritation using cultured HaCaT keratinocytes and a human skin equivalent as in vitro models, compared to non-nanomaterials. Commercial nano ZnO with different sizes (50 nm and 100 nm) was characterized by dynamic light scattering (DLS) and microscopy (SEM) in different media. Nano ZnO reduced the cell viability of HaCaT in a dose-dependent and time-dependent manner, in a similar way to macro ZnO. However, the 3D-epidermis model revealed no irritation at 1 mg/mL after 24 h of exposure. In conclusion, nano-sized ZnO does not irritate skin, in a similar manner to non-nano ZnO. Full article
(This article belongs to the Special Issue Cytotoxicity of Nanoparticles)
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Open AccessArticle Effect of the Polymeric Stabilizer in the Aqueous Phase Fischer-Tropsch Synthesis Catalyzed by Colloidal Cobalt Nanocatalysts
Nanomaterials 2017, 7(3), 58; doi:10.3390/nano7030058
Received: 22 December 2016 / Accepted: 21 February 2017 / Published: 6 March 2017
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Abstract
A series of small and well defined cobalt nanoparticles were synthesized by the chemical reduction of cobalt salts in water using NaBH4 as a reducing agent and using various polymeric stabilizers. The obtained nanocatalysts of similar mean diameters (ca. 2.6 nm) were fully
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A series of small and well defined cobalt nanoparticles were synthesized by the chemical reduction of cobalt salts in water using NaBH4 as a reducing agent and using various polymeric stabilizers. The obtained nanocatalysts of similar mean diameters (ca. 2.6 nm) were fully characterized and tested in the aqueous phase Fischer-Tropsch Synthesis (AFTS). Interestingly, the nature and structure of the stabilizers used during the synthesis of the CoNPs affected the reduction degree of cobalt and the B-doping of these NPs and consequently, influenced the performance of these nanocatalysts in AFTS. Full article
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Open AccessArticle Chitosan-Functionalized Graphene Oxide as a Potential Immunoadjuvant
Nanomaterials 2017, 7(3), 59; doi:10.3390/nano7030059
Received: 16 January 2017 / Accepted: 5 March 2017 / Published: 8 March 2017
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Abstract
The application of graphene oxide (GO) as a potential vaccine adjuvant has recently attracted considerable attention. However, appropriate surface functionalization of GO is crucial to improve its biocompatibility and enhance its adjuvant activity. In this study, we developed a simple method to prepare
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The application of graphene oxide (GO) as a potential vaccine adjuvant has recently attracted considerable attention. However, appropriate surface functionalization of GO is crucial to improve its biocompatibility and enhance its adjuvant activity. In this study, we developed a simple method to prepare chitosan (CS)-functionalized GO (GO-CS) and further investigated its potential as a nanoadjuvant. Compared with GO, GO-CS possessed considerably smaller size, positive surface charge, and better thermal stability. The functionalization of GO with CS was effective in decreasing the non-specific protein adsorption and improving its biocompatibility. Furthermore, GO-CS significantly activated RAW264.7 cells and stimulated more cytokines for mediating cellular immune response, which was mainly due to the synergistic immunostimulatory effect of both GO and CS. GO-CS exhibits strong potential as a safe nanoadjuvant for vaccines and immunotherapy. Full article
(This article belongs to the Special Issue Nanoparticle-Mediated Cell and Tissue Stimulation)
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Open AccessArticle Fabrication of Functional Polyurethane/Rare Earth Nanocomposite Membranes by Electrospinning and Its VOCs Absorption Capacity from Air
Nanomaterials 2017, 7(3), 60; doi:10.3390/nano7030060
Received: 30 December 2016 / Revised: 8 February 2017 / Accepted: 7 March 2017 / Published: 11 March 2017
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Abstract
Volatile organic compounds (VOCs) are a source of air pollution and are harmful to both human health and the environment. In this study, we fabricated polyurethane/rare earth (PU/RE) composite nanofibrous membranes via electrospinning with the aim of removing VOCs from air. The morphological
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Volatile organic compounds (VOCs) are a source of air pollution and are harmful to both human health and the environment. In this study, we fabricated polyurethane/rare earth (PU/RE) composite nanofibrous membranes via electrospinning with the aim of removing VOCs from air. The morphological structure of PU/RE nanofibrous mats was investigated using field emission scanning electron microscopy (FE-SEM), fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) experimental analyses. A certain amount of RE (up to 50 wt. % compared to PU pellets) nanoparticles (NPs) could be loaded on/into PU fibers. The tensile strength of PU/RE nanofibrous membranes decreased slightly with the increasing RE powder content. The PU nanofiber containing 50 wt. % RE powder had the smallest fiber diameter of 356 nm; it also showed the highest VOC absorption capacity compared with other composite membranes, having an absorption capacity about three times greater than pure PU nanofibers. In addition, all of the PU/RE nanofibrous membranes readily absorbed styrene the most, followed by xylene, toluene, benzene and chloroform. Therefore, the PU/RE nanofibrous membrane can play an important role in removing VOCs from the air, and its development prospects are impressive because they are emerging materials. Full article
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Open AccessArticle Exchange Bias Optimization by Controlled Oxidation of Cobalt Nanoparticle Films Prepared by Sputter Gas Aggregation
Nanomaterials 2017, 7(3), 61; doi:10.3390/nano7030061
Received: 31 January 2017 / Revised: 6 March 2017 / Accepted: 7 March 2017 / Published: 11 March 2017
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Abstract
Porous films of cobalt nanoparticles have been obtained by sputter gas aggregation and controllably oxidized by air annealing at 100 °C for progressively longer times (up to more than 1400 h). The magnetic properties of the samples were monitored during the process, with
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Porous films of cobalt nanoparticles have been obtained by sputter gas aggregation and controllably oxidized by air annealing at 100 °C for progressively longer times (up to more than 1400 h). The magnetic properties of the samples were monitored during the process, with a focus on the exchange bias field. Air annealing proves to be a convenient way to control the Co/CoO ratio in the samples, allowing the optimization of the exchange bias field to a value above 6 kOe at 5 K. The occurrence of the maximum in the exchange bias field is understood in terms of the density of CoO uncompensated spins and their degree of pinning, with the former reducing and the latter increasing upon the growth of a progressively thicker CoO shell. Vertical shifts exhibited in the magnetization loops are found to correlate qualitatively with the peak in the exchange bias field, while an increase in vertical shift observed for longer oxidation times may be explained by a growing fraction of almost completely oxidized particles. The presence of a hummingbird-like form in magnetization loops can be understood in terms of a combination of hard (biased) and soft (unbiased) components; however, the precise origin of the soft phase is as yet unresolved. Full article
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Open AccessArticle Nanofibrous Silver-Coated Polymeric Scaffolds with Tunable Electrical Properties
Nanomaterials 2017, 7(3), 63; doi:10.3390/nano7030063
Received: 2 January 2017 / Revised: 4 March 2017 / Accepted: 9 March 2017 / Published: 13 March 2017
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Abstract
Electrospun micro- and nanofibrous poly(glycerol sebacate)-poly(ε-caprolactone) (PGS-PCL) substrates have been extensively used as scaffolds for engineered tissues due to their desirable mechanical properties and their tunable degradability. In this study, we fabricated micro/nanofibrous scaffolds from a PGS-PCL composite using a standard electrospinning approach
[...] Read more.
Electrospun micro- and nanofibrous poly(glycerol sebacate)-poly(ε-caprolactone) (PGS-PCL) substrates have been extensively used as scaffolds for engineered tissues due to their desirable mechanical properties and their tunable degradability. In this study, we fabricated micro/nanofibrous scaffolds from a PGS-PCL composite using a standard electrospinning approach and then coated them with silver (Ag) using a custom radio frequency (RF) sputtering method. The Ag coating formed an electrically conductive layer around the fibers and decreased the pore size. The thickness of the Ag coating could be controlled, thereby tailoring the conductivity of the substrate. The flexible, stretchable patches formed excellent conformal contact with surrounding tissues and possessed excellent pattern-substrate fidelity. In vitro studies confirmed the platform’s biocompatibility and biodegradability. Finally, the potential controlled release of the Ag coating from the composite fibrous scaffolds could be beneficial for many clinical applications. Full article
(This article belongs to the Special Issue Nanofibrous Scaffolds for Biomedical Application)
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Open AccessFeature PaperArticle Three-Dimensional BiOI/BiOX (X = Cl or Br) Nanohybrids for Enhanced Visible-Light Photocatalytic Activity
Nanomaterials 2017, 7(3), 64; doi:10.3390/nano7030064
Received: 24 January 2017 / Revised: 24 February 2017 / Accepted: 7 March 2017 / Published: 14 March 2017
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Abstract
Three-dimensional flower-like BiOI/BiOX (X = Br or Cl) hybrids were synthesized via a facile one-pot solvothermal approach. With systematic characterizations by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), the Brunauer-Emmett-Teller (BET)specific surface area, X-ray photoelectron spectroscopy (XPS), and the
[...] Read more.
Three-dimensional flower-like BiOI/BiOX (X = Br or Cl) hybrids were synthesized via a facile one-pot solvothermal approach. With systematic characterizations by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), the Brunauer-Emmett-Teller (BET)specific surface area, X-ray photoelectron spectroscopy (XPS), and the UV-Vis diffuse reflectance spectra (DRS), the BiOI/BiOCl composites showed a fluffy and porous 3-D architecture with a large specific surface area (SSA) and high capability for light absorption. Among all the BiOX (X = Cl, Br, I) and BiOI/BiOX (X = Cl or Br) composites, BiOI/BiOCl stands out as the most efficient photocatalyst under both visible and UV light irradiations for methyl orange (MO) oxidation. The reaction rate of MO degradation on BiOI/BiOCl was 2.1 times higher than that on pure BiOI under visible light. Moreover, BiOI/BiOCl exhibited enhanced water oxidation efficiency for O2 evolution which was 1.5 times higher than BiOI. The enhancement of photocatalytic activity could be attributed to the formation of a heterojunction between BiOI and BiOCl, with a nanoporous structure, a larger SSA, and a stronger light absorbance capacity especially in the visible-light region. The in situ electron paramagnetic resonance (EPR) revealed that BiOI/BiOCl composites could effectively evolve superoxide radicals and hydroxyl radicals for photodegradation, and the superoxide radicals are the dominant reactive species. The superb photocatalytic activity of BiOI/BiOCl could be utilized for the degradation of various industrial dyes under natural sunlight irradiation which is of high significance for the remediation of industrial wastewater in the future. Full article
(This article belongs to the Special Issue Nanoscale in Photocatalysis)
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Open AccessArticle Nanoemulsified D-Limonene Reduces the Heat Resistance of Salmonella Senftenberg over 50 Times
Nanomaterials 2017, 7(3), 65; doi:10.3390/nano7030065
Received: 24 January 2017 / Revised: 28 February 2017 / Accepted: 7 March 2017 / Published: 15 March 2017
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Abstract
Salmonella Senftenberg is a pathogen agent causative of foodborne disease and it is considered the most heat-resistant serovar within this genus. Food industries use heat treatment and chemical antimicrobials in order to eliminate this microorganism in food, but consumers prefer natural antimicrobials as
[...] Read more.
Salmonella Senftenberg is a pathogen agent causative of foodborne disease and it is considered the most heat-resistant serovar within this genus. Food industries use heat treatment and chemical antimicrobials in order to eliminate this microorganism in food, but consumers prefer natural antimicrobials as essential oils and their components. This study evaluates the combined effect of thermal treatments and different concentrations of D-limonene nanoemulsion on the inactivation of Salmonella (S.) Senftenberg. The results showed an important effect of the nanoemulsified D-limonene on the heat resistance of S. Senftenberg. The δ50 °C value was reduced by 85%, 96% and 98% when 0.1, 0.5 and 1 mM of nanoemulsified D-limonene was added to the heating medium. The effect was kept along all the heating temperatures researched and the shape of the survival curves did not change with the addition of the antimicrobial. The results obtained in this research could be very useful for food industries for optimizing or improving heat treatments applied to food. Full article
(This article belongs to the Special Issue Nanomaterials in Food Safety)
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Open AccessArticle Improvement of Scratch and Wear Resistance of Polymers by Fillers Including Nanofillers
Nanomaterials 2017, 7(3), 66; doi:10.3390/nano7030066
Received: 24 October 2016 / Revised: 10 February 2017 / Accepted: 6 March 2017 / Published: 16 March 2017
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Abstract
Polymers have lower resistance to scratching and wear than metals. Liquid lubricants work well for metals but not for polymers nor for polymer-based composites (PBCs). We review approaches for improvement of tribological properties of polymers based on inclusion of fillers. The fillers can
[...] Read more.
Polymers have lower resistance to scratching and wear than metals. Liquid lubricants work well for metals but not for polymers nor for polymer-based composites (PBCs). We review approaches for improvement of tribological properties of polymers based on inclusion of fillers. The fillers can be metallic or ceramic—with obvious consequences for electrical resistivity of the composites. Distinctions between effectiveness of micro- versus nano-particles are analyzed. For example, aluminum nanoparticles as filler are more effective for property improvement than microparticles at the same overall volumetric concentration. Prevention of local agglomeration of filler particles is discussed along with a technique to verify the prevention. Full article
(This article belongs to the Special Issue Multifunctional Polymer-Based Nanocomposites)
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Open AccessArticle An Optical Sensor with Polyaniline-Gold Hybrid Nanostructures for Monitoring pH in Saliva
Nanomaterials 2017, 7(3), 67; doi:10.3390/nano7030067
Received: 3 August 2016 / Revised: 10 December 2016 / Accepted: 16 February 2017 / Published: 17 March 2017
Cited by 1 | PDF Full-text (3409 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Saliva contains important personal physiological information that is related to some diseases, and it is a valuable source of biochemical information that can be collected rapidly, frequently, and without stress. In this article, we reported a new and simple localized surface plasmon resonance
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Saliva contains important personal physiological information that is related to some diseases, and it is a valuable source of biochemical information that can be collected rapidly, frequently, and without stress. In this article, we reported a new and simple localized surface plasmon resonance (LSPR) substrate composed of polyaniline (PANI)-gold hybrid nanostructures as an optical sensor for monitoring the pH of saliva samples. The overall appearance and topography of the substrates, the composition, and the wettability of the LSPR surfaces were characterized by optical and scanning electron microscope (SEM) images, infrared spectra, and contact angles measurement, respectively. The PANI-gold hybrid substrate readily responded to the pH. The response time was very short, which was 3.5 s when the pH switched from 2 to 7, and 4.5 s from 7 to 2. The changes of visible-near-infrared (NIR) spectra of this sensor upon varying pH in solution showed that—for the absorption at given wavelengths of 665 nm and 785 nm—the sensitivities were 0.0299 a.u./pH (a.u. = arbitrary unit) with a linear range of pH = 5–8 and 0.0234 a.u./pH with linear range of pH = 2–8, respectively. By using this new sensor, the pH of a real saliva sample was monitored and was consistent with the parallel measurements with a standard laboratory method. The results suggest that this novel LSPR sensor shows great potential in the field of mobile healthcare and home medical devices, and could also be modified by different sensitive materials to detect various molecules or ions in the future. Full article
(This article belongs to the Special Issue Nanostructured Biosensors 2016)
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Open AccessArticle Magnetic Hybrid Nanosorbents for the Uptake of Paraquat from Water
Nanomaterials 2017, 7(3), 68; doi:10.3390/nano7030068
Received: 12 February 2017 / Revised: 12 March 2017 / Accepted: 13 March 2017 / Published: 18 March 2017
Cited by 3 | PDF Full-text (3824 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Although paraquat has been banned in European countries, this herbicide is still used all over the world, thanks to its low-cost, high-efficiency, and fast action. Because paraquat is highly toxic to humans and animals, there is interest in mitigating the consequences of its
[...] Read more.
Although paraquat has been banned in European countries, this herbicide is still used all over the world, thanks to its low-cost, high-efficiency, and fast action. Because paraquat is highly toxic to humans and animals, there is interest in mitigating the consequences of its use, namely by implementing removal procedures capable of curbing its environmental and health risks. This research describes new magnetic nanosorbents composed of magnetite cores functionalized with bio-hybrid siliceous shells, that can be used to uptake paraquat from water using magnetically-assisted procedures. The biopolymers κ-carrageenan and starch were introduced into the siliceous shells, resulting in two hybrid materials, Fe3O4@SiO2/SiCRG and Fe3O4@SiO2/SiStarch, respectively, that exhibit a distinct surface chemistry. The Fe3O4@SiO2/SiCRG biosorbents displayed a superior paraquat removal performance, with a good fitting to the Langmuir and Toth isotherm models. The maximum adsorption capacity of paraquat for Fe3O4@SiO2/SiCRG biosorbents was 257 mg·g−1, which places this sorbent among the best systems for the removal of this herbicide from water. The interesting performance of the κ-carrageenan hybrid, along with its magnetic properties and good regeneration capacity, presents a very efficient way for the remediation of water contaminated with paraquat. Full article
(This article belongs to the Special Issue Nanomaterials for Water Treatment)
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Open AccessArticle Optoelectronic Properties of Van Der Waals Hybrid Structures: Fullerenes on Graphene Nanoribbons
Nanomaterials 2017, 7(3), 69; doi:10.3390/nano7030069
Received: 18 November 2016 / Revised: 16 February 2017 / Accepted: 1 March 2017 / Published: 20 March 2017
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Abstract
The search for new optical materials capable of absorbing light in the frequency range from visible to near infrared is of great importance for applications in optoelectronic devices. In this paper, we report a theoretical study of the electronic and optical properties of
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The search for new optical materials capable of absorbing light in the frequency range from visible to near infrared is of great importance for applications in optoelectronic devices. In this paper, we report a theoretical study of the electronic and optical properties of hybrid structures composed of fullerenes adsorbed on graphene and on graphene nanoribbons. The calculations are performed in the framework of the density functional theory including the van der Waals dispersive interactions. We found that the adsorption of the C 60 fullerenes on a graphene layer does not modify its low energy states, but it has strong consequences for its optical spectrum, introducing new absorption peaks in the visible energy region. The optical absorption of fullerenes and graphene nanoribbon composites shows a strong dependence on photon polarization and geometrical characteristics of the hybrid systems, covering a broad range of energies. We show that an external electric field across the nanoribbon edges can be used to tune different optical transitions coming from nanoribbon–fullerene hybridized states, which yields a very rich electro-absorption spectrum for longitudinally polarized photons. We have carried out a qualitative analysis on the potential of these hybrids as possible donor-acceptor systems in photovoltaic cells. Full article
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Open AccessArticle Melanin-Associated Synthesis of SERS-Active Nanostructures and the Application for Monitoring of Intracellular Melanogenesis
Nanomaterials 2017, 7(3), 70; doi:10.3390/nano7030070
Received: 23 December 2016 / Revised: 11 March 2017 / Accepted: 14 March 2017 / Published: 20 March 2017
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Abstract
Melanin plays an indispensable role in the human body. It serves as a biological reducer for the green synthesis of precious metal nanoparticles. Melanin–Ag nanocomposites were successfully produced which exhibited very strong surface-enhanced Raman scattering (SERS) effect because of the reducibility property of
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Melanin plays an indispensable role in the human body. It serves as a biological reducer for the green synthesis of precious metal nanoparticles. Melanin–Ag nanocomposites were successfully produced which exhibited very strong surface-enhanced Raman scattering (SERS) effect because of the reducibility property of melanin. A melanin–Ag composite structure was synthesized in situ in melanin cells, and SERS technique was performed for the rapid imaging and quantitative assay of intracellular melanin. This imaging technique was also used to successfully trace the formation and secretion of intracellular melanin after stimulation with melanin-stimulating hormones. Based on the self-reducing property of melanin, the proposed SERS imaging method can provide potentially powerful analytical detection tools to study the biological functions of melanin and to prevent and cure melanin-related diseases. Full article
(This article belongs to the Special Issue Nanomaterials for SERS Applications)
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Open AccessArticle A Nanostructured Matrices Assessment to Study Drug Distribution in Solid Tumor Tissues by Mass Spectrometry Imaging
Nanomaterials 2017, 7(3), 71; doi:10.3390/nano7030071
Received: 6 February 2017 / Revised: 13 March 2017 / Accepted: 16 March 2017 / Published: 21 March 2017
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Abstract
The imaging of drugs inside tissues is pivotal in oncology to assess whether a drug reaches all cells in an adequate enough concentration to eradicate the tumor. Matrix-Assisted Laser Desorption Ionization Mass Spectrometry Imaging (MALDI-MSI) is one of the most promising imaging techniques
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The imaging of drugs inside tissues is pivotal in oncology to assess whether a drug reaches all cells in an adequate enough concentration to eradicate the tumor. Matrix-Assisted Laser Desorption Ionization Mass Spectrometry Imaging (MALDI-MSI) is one of the most promising imaging techniques that enables the simultaneous visualization of multiple compounds inside tissues. The choice of a suitable matrix constitutes a critical aspect during the development of a MALDI-MSI protocol since the matrix ionization efficiency changes depending on the analyte structure and its physico-chemical properties. The objective of this study is the improvement of the MALDI-MSI technique in the field of pharmacology; developing specifically designed nanostructured surfaces that allow the imaging of different drugs with high sensitivity and reproducibility. Among several nanomaterials, we tested the behavior of gold and titanium nanoparticles, and halloysites and carbon nanotubes as possible matrices. All nanomaterials were firstly screened by co-spotting them with drugs on a MALDI plate, evaluating the drug signal intensity and the signal-to-noise ratio. The best performing matrices were tested on control tumor slices, and were spotted with drugs to check the ion suppression effect of the biological matrix. Finally; the best nanomaterials were employed in a preliminary drug distribution study inside tumors from treated mice. Full article
(This article belongs to the Special Issue Nanomaterials for Mass Spectrometry Applications)
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Review

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Open AccessReview Nanocellulose-Based Materials for Water Purification
Nanomaterials 2017, 7(3), 57; doi:10.3390/nano7030057
Received: 7 December 2016 / Revised: 21 February 2017 / Accepted: 1 March 2017 / Published: 5 March 2017
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Abstract
Nanocellulose is a renewable material that combines a high surface area with high strength, chemical inertness, and versatile surface chemistry. In this review, we will briefly describe how nanocellulose is produced, and present—in particular, how nanocellulose and its surface modified versions affects the
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Nanocellulose is a renewable material that combines a high surface area with high strength, chemical inertness, and versatile surface chemistry. In this review, we will briefly describe how nanocellulose is produced, and present—in particular, how nanocellulose and its surface modified versions affects the adsorption behavior of important water pollutants, e.g., heavy metal species, dyes, microbes, and organic molecules. The processing of nanocellulose-based membranes and filters for water purification will be described in detail, and the uptake capacity, selectivity, and removal efficiency will also be discussed. The processing and performance of nanocellulose-based membranes, which combine a high removal efficiency with anti-fouling properties, will be highlighted. Full article
(This article belongs to the Special Issue Emerging Applications of Cellulose Nanocrystal and Its Composites)
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Open AccessReview 2D Transition Metal Dichalcogenides and Graphene-Based Ternary Composites for Photocatalytic Hydrogen Evolution and Pollutants Degradation
Nanomaterials 2017, 7(3), 62; doi:10.3390/nano7030062
Received: 26 January 2017 / Revised: 6 March 2017 / Accepted: 8 March 2017 / Published: 15 March 2017
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Abstract
Photocatalysis have attracted great attention due to their useful applications for sustainable hydrogen evolution and pollutants degradation. Transition metal dichalcogenides (TMDs) such as MoS2 and WS2 have exhibited great potential as cocatalysts to increase the photo-activity of some semiconductors. By combination
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Photocatalysis have attracted great attention due to their useful applications for sustainable hydrogen evolution and pollutants degradation. Transition metal dichalcogenides (TMDs) such as MoS2 and WS2 have exhibited great potential as cocatalysts to increase the photo-activity of some semiconductors. By combination with graphene (GR), enhanced cocatalysts of TMD/GR hybrids could be synthesized. GR here can act as a conductive electron channel for the transport of the photogenerated electrons, while the TMDs nanosheets in the hybrids can collect electrons and act as active sites for photocatalytic reactions. This mini review will focus on the application of TMD/GR hybrids as cocatalysts for semiconductors in photocatalytic reactions, by which we hope to provide enriched information of TMD/GR as a platform to develop more efficient photocatalysts for solar energy utilization. Full article
(This article belongs to the Special Issue Nanoscale in Photocatalysis)
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