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Nanomaterials, Volume 9, Issue 8 (August 2019)

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Cover Story (view full-size image) We report on the β-Na(Gd,Lu)F4:Tb3+ nanodosimeter which has a particle size of only 85 nm but [...] Read more.
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Open AccessArticle
Catalytic Reduction of Hexavalent Chromium Using Iron/Palladium Bimetallic Nanoparticle-Assembled Filter Paper
Nanomaterials 2019, 9(8), 1183; https://doi.org/10.3390/nano9081183 - 20 Aug 2019
Viewed by 537
Abstract
Iron/palladium bimetallic nanoparticles (Fe/Pd NPs) are important catalytic materials for the field of environmental remediation. In the present study, filter paper was employed as a substrate for the assembly of Fe/Pd NPs and further applied for the catalytic conversion of hexavalent chromium Cr(VI) [...] Read more.
Iron/palladium bimetallic nanoparticles (Fe/Pd NPs) are important catalytic materials for the field of environmental remediation. In the present study, filter paper was employed as a substrate for the assembly of Fe/Pd NPs and further applied for the catalytic conversion of hexavalent chromium Cr(VI) toward trivalent Cr(III). First, a filter paper with negative charge was assembled with a layer of positively charged polyethylenimine (PEI) through electrostatic interaction; then, the abundant amine groups of PEI were used to complex Fe(III) ions, followed by reduction via sodium borohydride to produce an Fe NP-assembled filter paper. Thereafter, the Fe/Pd NPs were produced by the reduction of PdCl42− through Fe NPs. The prepared filter paper assembled with Fe/Pd NPs with a mean diameter of 10.1 nm was characterized by various techniques. The Fe/Pd NP-assembled filter paper possesses powerful catalytic activity and can be used to transform Cr(VI) to Cr(III). With its low cost, high sustainability, and convenient industrialization potential, the developed approach may be extended to produce other bimetallic NP-immobilized filter paper for different environmental remediation applications. Full article
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Open AccessArticle
Fabrication, Characterization, and Properties of Poly (Ethylene-Co-Vinyl Acetate) Composite Thin Films Doped with Piezoelectric Nanofillers
Nanomaterials 2019, 9(8), 1182; https://doi.org/10.3390/nano9081182 - 20 Aug 2019
Viewed by 563
Abstract
Ethylene vinyl acetate (EVA) is a copolymer comprehending the semi-crystalline polyethylene and amorphous vinyl acetate phases, which potentially allow the fabrication of tunable materials. This paper aims at describing the fabrication and characterization of nanocomposite thin films made of polyethylene vinyl acetate, at [...] Read more.
Ethylene vinyl acetate (EVA) is a copolymer comprehending the semi-crystalline polyethylene and amorphous vinyl acetate phases, which potentially allow the fabrication of tunable materials. This paper aims at describing the fabrication and characterization of nanocomposite thin films made of polyethylene vinyl acetate, at different polymer concentration and vinyl acetate content, doped with piezoelectric nanomaterials, namely zinc oxide and barium titanate. These membranes are prepared by solvent casting, achieving a thickness in the order of 100–200 µm. The nanocomposites are characterized in terms of morphological, mechanical, and chemical properties. Analysis of the nanocomposites shows the nanofillers to be homogeneously dispersed in EVA matrix at different vinyl acetate content. Their influence is also noted in the mechanical behavior of thin films, which elastic modulus ranged from about 2 to 25 MPa, while keeping an elongation break from 600% to 1500% and tensile strength from 2 up to 13 MPa. At the same time, doped nanocomposite materials increase their crystallinity degree than the bare ones. The radiopacity provided by the addition of the dopant agents is proven. Finally, the direct piezoelectricity of nanocomposites membranes is demonstrated, showing higher voltage outputs (up to 2.5 V) for stiffer doped matrices. These results show the potentialities provided by the addition of piezoelectric nanomaterials towards mechanical reinforcement of EVA-based matrices while introducing radiopaque properties and responsiveness to mechanical stimuli. Full article
(This article belongs to the Special Issue Synthesis and Modification of Nanostructured Thin Films)
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Open AccessArticle
The Role of Fluorinated IL as an Interfacial Agent in P(VDF-CTFE)/Graphene Composite Films
Nanomaterials 2019, 9(8), 1181; https://doi.org/10.3390/nano9081181 - 19 Aug 2019
Viewed by 524
Abstract
The incorporation of graphene into a polymer matrix can endow composites with extended functions. However, it is difficult to well disperse pristine graphene into a polymer matrix in order to obtain polymer nanocomposites due to the lack of functional groups on the surface [...] Read more.
The incorporation of graphene into a polymer matrix can endow composites with extended functions. However, it is difficult to well disperse pristine graphene into a polymer matrix in order to obtain polymer nanocomposites due to the lack of functional groups on the surface for bonding with a polymer matrix. Herein, we investigated the role of fluorinated ionic liquid (IL) as a new interfacial agent in poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-CTFE))/graphene composite films. First, a task-specific IL, perfluorooctyltriphenylphosphonium iodide (IL-C8F13), was synthesized and adsorbed on the surface of graphene oxide (GO) and reduced graphene oxide (rGO) for making functional nanofillers which were capable of being incorporated into the P(VDF-CTFE) matrix. The cation structure of IL combined three phenyls (potential π–π interactions with graphene) and a short fluorinated chain (enhanced miscibility with fluorinated matrix via dipolar interactions) to make a compatible graphene filler and P(VDF-CTFE) matrix at the interface among them. Second, two series of P(VDF-CTFE)/GO-IL and P(VDF-CTFE)/rGO-IL composites with different loading contents were prepared with the goal of providing an understanding of the mechanism of interfacial interactions. This paper investigated the difference in the interaction model between GO with IL and rGO with IL. Subsequently, the interfacial effect of IL on the properties of P(VDF-CTFE)/graphene composites, such as crystallization, chain segmental relaxation behavior, dispersion, and the final dielectric properties will be further studied. Full article
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Open AccessArticle
Structural Characterization of Graphene Oxide: Surface Functional Groups and Fractionated Oxidative Debris
Nanomaterials 2019, 9(8), 1180; https://doi.org/10.3390/nano9081180 - 18 Aug 2019
Viewed by 713
Abstract
The purpose of this work is the structural analysis of graphene oxide (GO) and by means of a new structural model to answer the questions arising from the Lerf–Klinowski and the Lee structural models. Surface functional groups of GO layers and the oxidative [...] Read more.
The purpose of this work is the structural analysis of graphene oxide (GO) and by means of a new structural model to answer the questions arising from the Lerf–Klinowski and the Lee structural models. Surface functional groups of GO layers and the oxidative debris (OD) stacked on them were investigated after OD was extracted. Analysis was performed successfully using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), X-ray photoemission spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, solid-state nuclear magnetic resonance spectroscopy (SSNMR), standardized Boehm potentiometric titration analysis, elemental analysis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The analysis showed that graphene oxide layers, as well as oxidative debris contain different functional groups such as phenolic –OH, ketone, lactone, carboxyl, quinone and epoxy. Based on these results, a new structural model for GO layers is proposed, which covers all spectroscopic data and explains the presence of the other oxygen functionalities besides carboxyl, phenolic –OH and epoxy groups. Full article
(This article belongs to the Special Issue Characterization, Synthesis and Applications of 2D Nanomaterials)
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Open AccessArticle
The Effect of Acceptor Structure on Emission Color Tuning in Organic Semiconductors with D–π–A–π–D Structures
Nanomaterials 2019, 9(8), 1179; https://doi.org/10.3390/nano9081179 - 17 Aug 2019
Viewed by 647
Abstract
A series of novel donor–acceptor D–π–A–π–D compounds were synthesized and characterized in order to determine the influence of different acceptor units on their properties. The introduction of acceptor moieties had a direct impact on the HOMO and LUMO energy levels. Fluorescence spectra of [...] Read more.
A series of novel donor–acceptor D–π–A–π–D compounds were synthesized and characterized in order to determine the influence of different acceptor units on their properties. The introduction of acceptor moieties had a direct impact on the HOMO and LUMO energy levels. Fluorescence spectra of compounds can be changed by the choice of an appropriate acceptor and were shifted from the green to the near-infrared part of spectra. Due to observed concentration induced emission quenching, the green exciplex type host was used to evaluate the potential of synthesized molecules as emitters in organic light emitting diodes (OLEDs). Full article
(This article belongs to the Special Issue Low-Dimensional Nanomaterials for Photonics and Optoelectronics)
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Open AccessArticle
High-Power GaN-Based Vertical Light-Emitting Diodes on 4-Inch Silicon Substrate
Nanomaterials 2019, 9(8), 1178; https://doi.org/10.3390/nano9081178 - 17 Aug 2019
Viewed by 564
Abstract
We demonstrate high-power GaN-based vertical light-emitting diodes (LEDs) (VLEDs) on a 4-inch silicon substrate and flip-chip LEDs on a sapphire substrate. The GaN-based VLEDs were transferred onto the silicon substrate by using the Au–In eutectic bonding technique in combination with the laser lift-off [...] Read more.
We demonstrate high-power GaN-based vertical light-emitting diodes (LEDs) (VLEDs) on a 4-inch silicon substrate and flip-chip LEDs on a sapphire substrate. The GaN-based VLEDs were transferred onto the silicon substrate by using the Au–In eutectic bonding technique in combination with the laser lift-off (LLO) process. The silicon substrate with high thermal conductivity can provide a satisfactory path for heat dissipation of VLEDs. The nitrogen polar n-GaN surface was textured by KOH solution, which not only improved light extract efficiency (LEE) but also broke down Fabry–Pérot interference in VLEDs. As a result, a near Lambertian emission pattern was obtained in a VLED. To improve current spreading, the ring-shaped n-electrode was uniformly distributed over the entire VLED. Our combined numerical and experimental results revealed that the VLED exhibited superior heat dissipation and current spreading performance over a flip-chip LED (FCLED). As a result, under 350 mA injection current, the forward voltage of the VLED was 0.36 V lower than that of the FCLED, while the light output power (LOP) of the VLED was 3.7% higher than that of the FCLED. The LOP of the FCLED saturated at 1280 mA, but the light output saturation did not appear in the VLED. Full article
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Open AccessArticle
Hydrophilic Silver Nanoparticles Loaded into Niosomes: Physical–Chemical Characterization in View of Biological Applications
Nanomaterials 2019, 9(8), 1177; https://doi.org/10.3390/nano9081177 - 17 Aug 2019
Viewed by 528
Abstract
Silver nanoparticles (AgNPs) are widely used as antibacterial agents and anticancer drugs, but often their low stability limits their mass production and broad applications. The use of niosomes as a carrier to protect and envelop AgNPs gives a new perspective to solve these [...] Read more.
Silver nanoparticles (AgNPs) are widely used as antibacterial agents and anticancer drugs, but often their low stability limits their mass production and broad applications. The use of niosomes as a carrier to protect and envelop AgNPs gives a new perspective to solve these problems. In this study, AgNPs were functionalized with sodium 3-mercapto-1-propanesulfonate (3MPS) to induce hydrophilic behavior, improving loading in Tween 20 and Span 20 niosomes (NioTw20 and NioSp20, respectively). Entrapment efficiency was evaluated by UV analyses and is around 1–4%. Dimensions were investigated by means of dynamic light scattering (DLS) (<2RH> = 140 ± 4 nm and <2RH> = 251 ± 1 nm respectively for NioTw20 + AgNPs and NioSp20 + AgNPs) and were compared with those by atomic force microscopy (AFM) and small angle X ray scattering (SAXS) analyses. Stability was assessed in water up to 90 days, and both in bovine serum and human serum for up to 8 h. In order to characterize the local structure of niosomes, SAXS measurements have been performed on Tween 20 and Span 20 empty niosomes and loaded with AgNPs. The release profiles of hydrophilic probe calcein and lipophilic probe Nile Red were performed in HEPES buffer and in human serum. All these features contribute to conclude that the two systems, NioTw20 + AgNPs and NioSp20 + AgNPs, are suitable and promising in the field of biological applications. Full article
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Open AccessArticle
Synthesis of Magnetic Ferrite Nanoparticles with High Hyperthermia Performance via a Controlled Co-Precipitation Method
Nanomaterials 2019, 9(8), 1176; https://doi.org/10.3390/nano9081176 - 16 Aug 2019
Viewed by 612
Abstract
Magnetic nanoparticles (MNPs) that exhibit high specific loss power (SLP) at lower metal content are highly desirable for hyperthermia applications. The conventional co-precipitation process has been widely employed for the synthesis of magnetic nanoparticles. However, their hyperthermia performance is often insufficient, which is [...] Read more.
Magnetic nanoparticles (MNPs) that exhibit high specific loss power (SLP) at lower metal content are highly desirable for hyperthermia applications. The conventional co-precipitation process has been widely employed for the synthesis of magnetic nanoparticles. However, their hyperthermia performance is often insufficient, which is considered as the main challenge to the development of practicable cancer treatments. In particular, ferrite MNPs have unique properties, such as a strong magnetocrystalline anisotropy, high coercivity, and moderate saturation magnetization, however their hyperthermia performance needs to be further improved. In this study, cobalt ferrite (CoFe2O4) and zinc cobalt ferrite nanoparticles (ZnCoFe2O4) were prepared to achieve high SLP values by modifying the conventional co-precipitation method. Our modified method, which allows for precursor material compositions (molar ratio of Fe+3:Fe+2:Co+2/Zn+2 of 3:2:1), is a simple, environmentally friendly, and low temperature process carried out in air at a maximum temperature of 60 °C, without the need for oxidizing or coating agents. The particles produced were characterized using multiple techniques, such as X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV–Vis spectroscopy), and a vibrating sample magnetometer (VSM). SLP values of the prepared nanoparticles were carefully evaluated as a function of time, magnetic field strength (30, 40, and 50 kA m−1), and the viscosity of the medium (water and glycerol), and compared to commercial magnetic nanoparticle materials under the same conditions. The cytotoxicity of the prepared nanoparticles by in vitro culture with NIH-3T3 fibroblasts exhibited good cytocompatibility up to 0.5 mg/mL. The safety limit of magnetic field parameters for SLP was tested. It did not exceed the 5 × 109 Am−1 s−1 threshold. A saturation temperature of 45 °C could be achieved. These nanoparticles, with minimal metal content, can ideally be used for in vivo hyperthermia applications, such as cancer treatments. Full article
(This article belongs to the Special Issue Applications and Properties of Magnetic Nanoparticles)
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Open AccessArticle
Food Additive Titanium Dioxide and Its Fate in Commercial Foods
Nanomaterials 2019, 9(8), 1175; https://doi.org/10.3390/nano9081175 - 16 Aug 2019
Viewed by 630
Abstract
Titanium dioxide (TiO2) is one of the most extensively utilized food additives (E171) in the food industry. Along with nanotechnology development, the concern about the presence of nanostructured particles in E171 TiO2 and commercial food products is growing. In the [...] Read more.
Titanium dioxide (TiO2) is one of the most extensively utilized food additives (E171) in the food industry. Along with nanotechnology development, the concern about the presence of nanostructured particles in E171 TiO2 and commercial food products is growing. In the present study, the physicochemical properties of commercially available E171 TiO2 particles, including particle size distribution, were investigated, followed by their cytotoxicity and intestinal transport evaluation. The fate determination and quantification of E171 TiO2 in commercial foods were carried out based on the analytical procedure developed using simulated foods. The results demonstrated that TiO2 is a material mainly composed of particles larger than 100 nm, but present as an agglomerated or aggregated particle in commercial foods with amounts of less than 1% (wt/wt). Titanium dioxide particles generated reactive oxygen species and inhibited long-term colony formation, but the cytotoxicity was not related to particle size distribution or particle type (food- or general-grade). All TiO2 particles were mainly transported by microfold (M) cells, but also by intestinal tight junction. These findings will be useful for TiO2 application in the food industry and predicting its potential toxicity. Full article
(This article belongs to the Special Issue Nanostructured Materials and Natural Extract)
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Open AccessEditorial
Layered Double Hydroxide-Based Nanomaterials-From Fundamentals to Applications
Nanomaterials 2019, 9(8), 1174; https://doi.org/10.3390/nano9081174 - 16 Aug 2019
Viewed by 635
Abstract
Layered double hydroxides (LDHs) and their composites with various substances represent an important class of materials suitable for several existing and future applications in biological, chemical, and environmental processes [...] Full article
Open AccessArticle
Preparation of TiO2 and Fe-TiO2 with an Impinging Stream-Rotating Packed Bed by the Precipitation Method for the Photodegradation of Gaseous Toluene
Nanomaterials 2019, 9(8), 1173; https://doi.org/10.3390/nano9081173 - 16 Aug 2019
Viewed by 559
Abstract
Nano-TiO2 has always been one of the most important topics in the research of photocatalysts due to its special activity and stability. However, it has always been difficult to obtain nano-TiO2 with high dispersion, a small particle size and high photocatalytic [...] Read more.
Nano-TiO2 has always been one of the most important topics in the research of photocatalysts due to its special activity and stability. However, it has always been difficult to obtain nano-TiO2 with high dispersion, a small particle size and high photocatalytic activity. In this paper, nano-TiO2 powder was prepared by combining the high-gravity technique and direct precipitation method in an impinging stream-rotating packed bed (IS-RPB) reactor followed by Fe3+ in-situ doping. TiOSO4 and NH3·H2O solutions were cut into very small liquid microelements by high-speed rotating packing, and the mass transfer and microscopic mixing of the nucleation and growth processes of nano-TiO2 were strengthened in IS-RPB, which was beneficial to the continuous production of high quality nano-TiO2. Pure TiO2 and iron-doped nano-TiO2 (Fe-TiO2) were obtained in IS-RPB and were investigated by means of X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) and Brunauer–Emmett–Teller (BET) analysis, which found that pure TiO2 had a particle size of about 12.5 nm, good dispersibility and a complete anatase crystal at the rotating speed of packing of 800 rpm and calcination temperature of 500 °C. The addition of Fe3+ did not change the crystalline structure of TiO2. Iron was highly dispersed in TiO2 without the detection of aggregates and was found to exist in a positive trivalent form by XPS. With the increase of iron doping, the photoresponse range of TiO2 to visible light was broadened from 3.06 eV to 2.26 eV. The degradation efficiency of gaseous toluene by Fe-TiO2 under ultraviolet light was higher than that of pure TiO2 and commercial P25 due to Fe3+ effectively suppressing the recombination of TiO2 electrons and holes; the highest efficiency produced by 1.0% Fe-TiO2 was 95.7%. Full article
(This article belongs to the Special Issue Photocatalytic Nanomaterials)
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Open AccessArticle
Silica Nanoparticles Provoke Cell Death Independent of p53 and BAX in Human Colon Cancer Cells
Nanomaterials 2019, 9(8), 1172; https://doi.org/10.3390/nano9081172 - 16 Aug 2019
Viewed by 650
Abstract
Several in vitro studies have suggested that silica nanoparticles (NPs) might induce adverse effects in gut cells. Here, we used the human colon cancer epithelial cell line HCT116 to study the potential cytotoxic effects of ingested silica NPs in the presence or absence [...] Read more.
Several in vitro studies have suggested that silica nanoparticles (NPs) might induce adverse effects in gut cells. Here, we used the human colon cancer epithelial cell line HCT116 to study the potential cytotoxic effects of ingested silica NPs in the presence or absence of serum. Furthermore, we evaluated different physico-chemical parameters important for the assessment of nanoparticle safety, including primary particle size (12, 70, 200, and 500 nm) and surface modification (–NH2 and –COOH). Silica NPs triggered cytotoxicity, as evidenced by reduced metabolism and enhanced membrane leakage. Automated microscopy revealed that the silica NPs promoted apoptosis and necrosis proportional to the administered specific surface area dose. Cytotoxicity of silica NPs was suppressed by increasing amount of serum and surface modification. Furthermore, inhibition of caspases partially prevented silica NP-induced cytotoxicity. In order to investigate the role of specific cell death pathways in more detail, we used isogenic derivatives of HCT116 cells which lack the pro-apoptotic proteins p53 or BAX. In contrast to the anticancer drug cisplatin, silica NPs induced cell death independent of the p53–BAX axis. In conclusion, silica NPs initiated cell death in colon cancer cells dependent on the specific surface area and presence of serum. Further studies in vivo are warranted to address potential cytotoxic actions in the gut epithelium. The unintended toxicity of silica NPs as observed here could also be beneficial. As loss of p53 in colon cancer cells contributes to resistance against anticancer drugs, and thus to reoccurrence of colon cancer, targeted delivery of silica NPs could be envisioned to also deplete p53 deficient tumor cells. Full article
(This article belongs to the Special Issue Toxicology and Biocompatibility of Nanomaterials)
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Open AccessArticle
Green Bio-Assisted Synthesis, Characterization and Biological Evaluation of Biocompatible ZnO NPs Synthesized from Different Tissues of Milk Thistle (Silybum marianum)
Nanomaterials 2019, 9(8), 1171; https://doi.org/10.3390/nano9081171 - 16 Aug 2019
Viewed by 511
Abstract
The purpose of the current study was green synthesis of ZnO-nanoparticles (NPs) from different tissues of Silybum marianum (L.) Gaernt. (i.e., seeds, wild plant, in vitro derived plantlets and callus cultures) followed by extensive characterization and evaluation of their biological potency. ZnO-NPs thus [...] Read more.
The purpose of the current study was green synthesis of ZnO-nanoparticles (NPs) from different tissues of Silybum marianum (L.) Gaernt. (i.e., seeds, wild plant, in vitro derived plantlets and callus cultures) followed by extensive characterization and evaluation of their biological potency. ZnO-NPs thus synthesized were subjected to characterization using standard techniques such as XRD, FTIR and SEM. Thermal stability of synthesized NPs was also evaluated using thermo-gravimetric analysis. Highly stable crystalline NPs with size ranging between 30.8 and 46.0 nm were obtained from different tissues of S. marianum. These NPs have revealed a wide range of biological applications showing antioxidant, moderate α-amylase inhibitor, antibacterial and cytotoxic potencies. The highest antibacterial activity (20 ± 0.98 mm) was shown by seed extract-mediated ZnO NPs against Staphylococcus aureus (ATCC-6538). Seed extract-mediated ZnO NPs also showed the most potent antioxidant activity (27.7 ± 0.9 µgAAE/mg, 23.8 ± 0.7 µgAAE/mg and 12.7 ± 1.9% total antioxidant capacity (TAC), total reducing power (TRP) and DPPH-free radical scavenging assay (FRSA), respectively). All of the synthesized ZnO NPs also showed cytotoxic activity against the hepato-cellular carcinoma (HepG2) human cells. Interestingly, these ZnO NPs were also highly biocompatible, as evidenced by the brine shrimp lethality and human red blood cells hemolytic assays. Among all of the NPs synthesized and used, the effect of seed extract-mediated NPs was found to be most promising for future applications. Full article
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Open AccessArticle
Formation of 3-Dimensional Gold, Copper and Palladium Microelectrode Arrays for Enhanced Electrochemical Sensing Applications
Nanomaterials 2019, 9(8), 1170; https://doi.org/10.3390/nano9081170 - 15 Aug 2019
Viewed by 739
Abstract
Microelectrodes offer higher current density and lower ohmic drop due to increased radial diffusion. They are beneficial for electroanalytical applications, particularly for the detection of analytes at trace concentrations. Microelectrodes can be fabricated as arrays to improve the current response, but are presently [...] Read more.
Microelectrodes offer higher current density and lower ohmic drop due to increased radial diffusion. They are beneficial for electroanalytical applications, particularly for the detection of analytes at trace concentrations. Microelectrodes can be fabricated as arrays to improve the current response, but are presently only commercially available with gold or platinum electrode surfaces, thus limiting the sensing of analytes that are more electroactive on other surfaces. In this work, gold (Au), copper (Cu), and palladium (Pd) are electrodeposited at two different potentials into the recessed holes of commercial microelectrode arrays to produce 3-dimensional (3D) spiky, dendritic or coral-like structures. The rough fractal structures that are produced afford enhanced electroactive surface area and increased radial diffusion due to the 3D nature, which drastically improves the sensitivity. 2,4,6-trinitrotoluene (TNT), carbon dioxide gas (CO2), and hydrogen gas (H2) were chosen as model analytes in room temperature ionic liquid solvents, to demonstrate improvements in the sensitivity of the modified microelectrode arrays, and, in some cases (e.g., for CO2 and H2), enhancements in the electrocatalytic ability. With the deposition of different materials, we have demonstrated enhanced sensitivity and electrocatalytic behaviour towards the chosen analytes. Full article
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Open AccessArticle
Functionalized Multiwalled CNTs in Classical and Nonclassical CaCO3 Crystallization
Nanomaterials 2019, 9(8), 1169; https://doi.org/10.3390/nano9081169 - 15 Aug 2019
Viewed by 591
Abstract
Multiwalled carbon nanotubes (MWCNTs) are interesting high-tech nanomaterials. MWCNTs oxidized and functionalized with itaconic acid and monomethylitaconate were demonstrated to be efficient additives for controlling nucleation of calcium carbonate (CaCO3) via gas diffusion (GD) in classical as well as nonclassical crystallization, [...] Read more.
Multiwalled carbon nanotubes (MWCNTs) are interesting high-tech nanomaterials. MWCNTs oxidized and functionalized with itaconic acid and monomethylitaconate were demonstrated to be efficient additives for controlling nucleation of calcium carbonate (CaCO3) via gas diffusion (GD) in classical as well as nonclassical crystallization, yielding aragonite and truncated calcite. For the first time, all amorphous calcium carbonate (ACC) proto-structures, such as proto calcite-ACC, proto vaterite-ACC and proto aragonite-ACC, were synthesized via prenucleation cluster (PNC) intermediates and stabilized at room temperature. The MWCNTs also showed concentration-dependent nucleation promotion and inhibition similar to biomolecules in nature. Incorporation of fluorescein-5-thiosemicarbazide (5-FTSC) dye-labeled MWCNTs into the CaCO3 lattice resulted in fluorescent hybrid nanosized CaCO3. We demonstrate that functionalized MWCNTs offer a good alternative for controlled selective crystallization and for understanding an inorganic mineralization process. Full article
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Open AccessArticle
The Conductivity and Dielectric Properties of Neobium Substituted Sr-Hexaferrites
Nanomaterials 2019, 9(8), 1168; https://doi.org/10.3390/nano9081168 - 15 Aug 2019
Viewed by 547
Abstract
The Nb3+ ion substituted Sr hexaferrites (SrNbxFe12−xO19 (x = 0.00–0.08) hexaferrites (HFs)) were fabricated via a citrate-assisted sol-gel approach. X-ray powder diffractometer analysis affirmed the pureness of all products. The crystallite sizes of the products which were estimated from [...] Read more.
The Nb3+ ion substituted Sr hexaferrites (SrNbxFe12−xO19 (x = 0.00–0.08) hexaferrites (HFs)) were fabricated via a citrate-assisted sol-gel approach. X-ray powder diffractometer analysis affirmed the pureness of all products. The crystallite sizes of the products which were estimated from Scherrer equation were in the 36–40 nm range. The chemical component of the samples was proved by Energy-dispersive X-ray spectroscopy (EDX) and Elemental mapping. The hexagonal morphology of all products was confirmed by Field Emission Scanning Electron Microscopy (FE-SEM). The electrical conduction mechanisms and dielectric properties of a variety of Nb3+ions-substituted SrNbxFe12−xO19 HFs were investigated by a complex impedance system. Dielectric parameters such as conductivity, dielectric constant, dielectric loss, dielectric tangent loss and complex modulus, were studied at temperatures up to 120 °C in a frequency range varying from 1.0 Hz to 3.0 MHz for several Nb ratios. The frequency dependence of the conductivity was found to comply with the power law with diverse exponents at all frequencies studied here. Subsequently, incremental tendencies in dc conductivity with temperature indicate that the substituted Sr-HFs leads to a semiconductor-semimetal like behavior. This could be attributable to a feature of conduction mechanism which is based on the tunneling processes. Additionally, the dielectric dispersion pattern was also explained by Maxwell–Wagner polarization in accordance with the Koop’s phenomenological theory. Full article
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Open AccessArticle
Spray-Dried, Nanoencapsulated, Multi-Drug Anti-Tuberculosis Therapy Aimed at Once Weekly Administration for the Duration of Treatment
Nanomaterials 2019, 9(8), 1167; https://doi.org/10.3390/nano9081167 - 15 Aug 2019
Viewed by 590
Abstract
Aiming to improve the treatment outcomes of current daily tuberculosis (TB) chemotherapy over several months, we investigated whether nanoencapsulation of existing drugs would allow decreasing the treatment frequency to weekly, thereby ultimately improving patient compliance. Nanoencapsulation of three first-line anti-TB drugs was achieved [...] Read more.
Aiming to improve the treatment outcomes of current daily tuberculosis (TB) chemotherapy over several months, we investigated whether nanoencapsulation of existing drugs would allow decreasing the treatment frequency to weekly, thereby ultimately improving patient compliance. Nanoencapsulation of three first-line anti-TB drugs was achieved by a unique, scalable spray-drying technology forming free-flowing powders in the nanometer range with encapsulation efficiencies of 82, 75, and 62% respectively for rifampicin, pyrazinamide, and isoniazid. In a pre-clinical study on TB infected mice, we demonstrate that the encapsulated drugs, administered once weekly for nine weeks, showed comparable efficacy to daily treatment with free drugs over the same experimental period. Both treatment approaches had equivalent outcomes for resolution of inflammation associated with the infection of lungs and spleens. These results demonstrate how scalable technology could be used to manufacture nanoencapsulated drugs. The formulations may be used to reduce the oral dose frequency from daily to once weekly in order to treat uncomplicated TB. Full article
(This article belongs to the Special Issue Applications of Nano-Designed Systems in Biomedical Research)
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Open AccessArticle
Enzymatic Conversion of Oleuropein to Hydroxytyrosol Using Immobilized β-Glucosidase on Porous Carbon Cuboids
Nanomaterials 2019, 9(8), 1166; https://doi.org/10.3390/nano9081166 - 14 Aug 2019
Viewed by 633
Abstract
In the present study, we developed novel β-glucosidase-based nano-biocatalysts for the bioconversion of oleuropein to hydroxytyrosol. Using non-covalent or covalent immobilization approaches, β-glucosidases from almonds and Thermotoga maritima were attached for the first time on oxidized and non-oxidized porous carbon cuboids [...] Read more.
In the present study, we developed novel β-glucosidase-based nano-biocatalysts for the bioconversion of oleuropein to hydroxytyrosol. Using non-covalent or covalent immobilization approaches, β-glucosidases from almonds and Thermotoga maritima were attached for the first time on oxidized and non-oxidized porous carbon cuboids (PCC). Various methods were used for the characterization of the bio-nanoconjugates, such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and fluorescence spectroscopy. The oxidation state of the nanο-support and the immobilization procedure play a key role for the immobilization efficiency or the catalytic activity of the immobilized β-glucosidases. The nano-biocatalysts were successfully used for the hydrolysis of oleuropein, which leads to the formation of its bioactive derivative, hydroxytyrosol (up to 2.4 g L−1), which is a phenolic compound with numerous health benefits. The bio-nanoconjugates exhibited high thermal and operational stability (up to 240 h of repeated use), which indicated that they are efficient tools for various bio-transformations. Full article
(This article belongs to the Special Issue Advances in Heterocatalysis by Nanomaterials)
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Open AccessArticle
L-Aspartic Acid Capped CdS Quantum Dots as a High Performance Fluorescence Assay for Sliver Ions (I) Detection
Nanomaterials 2019, 9(8), 1165; https://doi.org/10.3390/nano9081165 - 14 Aug 2019
Viewed by 557
Abstract
A new high performance fluorescence assay for detection of Ag+ based on CdS quantum dots (QDs) using L-Aspartic acid (L-Asp) as a stabilizer was proposed in this work. The CdS quantum dots conjugation with L-Aspartic acid ([email protected] QDs) were successfully synthesized via [...] Read more.
A new high performance fluorescence assay for detection of Ag+ based on CdS quantum dots (QDs) using L-Aspartic acid (L-Asp) as a stabilizer was proposed in this work. The CdS quantum dots conjugation with L-Aspartic acid ([email protected] QDs) were successfully synthesized via a simple hydrothermal process. The QDs have a fluorescence emission band maximum at 595 nm with a quantum yield of 11%. The obtained CdS QDs exhibit a particle size of 1.63 ± 0.28 nm and look like quantum dot flowers. Basically, the fluorescence intensity of [email protected] QDs can be enhanced only upon addition of Ag+ and a redshift in the fluorescence spectrum was observed. Under optimum conditions, the fluorescence enhancement of [email protected] QDs appeared to exhibit a good linear relationship in between 100–7000 nM (R2 = 0.9945) with the Ag+ concentration, with a detection limit of 39 nM. The results indicated that the [email protected] QDs were well used in detection for Ag+ as fluorescence probe in aqueous solution with high sensitivity and selectivity. Moreover, the sensing system has been applied in detection Ag+ in real water samples. The recovery test results were 98.6%~113%, and relative standard deviation (n = 5) is less than 3.6%, which was satisfactory. Full article
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Open AccessCommunication
Continuous Flow Removal of Anionic Dyes in Water by Chitosan-Functionalized Iron Oxide Nanoparticles Incorporated in a Dextran Gel Column
Nanomaterials 2019, 9(8), 1164; https://doi.org/10.3390/nano9081164 - 14 Aug 2019
Viewed by 603
Abstract
This paper describes a novel chromatographic method for efficient removal of anionic dyes from aqueous solutions. Chitosan-coated Fe3O4 nanoparticles can easily be immobilized on a dextran gel column. Single elution of Evans Blue (EB) solution to the nanoadsorbent-incorporated columns provides [...] Read more.
This paper describes a novel chromatographic method for efficient removal of anionic dyes from aqueous solutions. Chitosan-coated Fe3O4 nanoparticles can easily be immobilized on a dextran gel column. Single elution of Evans Blue (EB) solution to the nanoadsorbent-incorporated columns provides high removal efficiency with a maximum adsorption capacity of 243.9 mg/g. We also investigated the influence of initial concentration and solution pH on the removal efficiency of EB. The electrostatic interaction between the adsorbent surface and negatively charged sulfate groups on EB molecules promotes the efficient adsorption of dyes. The equilibrium data matched well with the Langmuir isotherm model, which indicated monolayer dye adsorption onto the adsorbent surface. To extend the application of the current method, we performed further adsorption experiments using other anionic dyes of different colors (Cy5.5, Acid Yellow 25, Acid Green 25, and Acid Red 1). All of these molecules can efficiently be captured under continuous flow conditions, with higher removal efficiency obtained with more negatively charged dyes. These findings clearly demonstrate that the present approach is a useful method for the removal of anionic dye contaminants in aqueous media by adsorption. Full article
(This article belongs to the Special Issue Nanomaterials and Nanotechnology in Wastewater Treatment)
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Open AccessArticle
Facile Synthesis of SnO2/LaFeO3−XNX Composite: Photocatalytic Activity and Gas Sensing Performance
Nanomaterials 2019, 9(8), 1163; https://doi.org/10.3390/nano9081163 - 14 Aug 2019
Viewed by 1338
Abstract
Here SnO2/LaFeO3−XNX composite was fabricated using a wet chemical method and was applied to pollutants degradation and gas sensing for the first time. The composite exhibits high performance for photocatalytic degradation of Rhodamine B (RhB) dye and selectivity [...] Read more.
Here SnO2/LaFeO3−XNX composite was fabricated using a wet chemical method and was applied to pollutants degradation and gas sensing for the first time. The composite exhibits high performance for photocatalytic degradation of Rhodamine B (RhB) dye and selectivity sensing of various gases. On the basis of the completed experiments, the improved RhB degradation and selective gas sensing performance resulted from the extended optical absorption via N2 incorporated surface states and enhanced charge separation via coupling SnO2. Using the scavengers trapping experiments, the superoxide radical (O2•−) was investigated as the major scavenger involved in the degradation of RhB over SnO2/LaFeO3−XNX composite. In this paper, the probable reaction steps involved in the RhB dye degradation over SnO2/LaFeO3−XNX composite are proposed. This work will provide reasonable strategies to fabricate LaFeO3-based proficient and stable catalysts for environmental purification. In addition, the result of the selectivity of gas performance is also presented. Full article
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Open AccessArticle
Carvacrol Loaded Solid Lipid Nanoparticles of Propylene Glycol Monopalmitate and Glyceryl Monostearate: Preparation, Characterization, and Synergistic Antimicrobial Activity
Nanomaterials 2019, 9(8), 1162; https://doi.org/10.3390/nano9081162 - 14 Aug 2019
Viewed by 591
Abstract
To develop solid lipid nanoparticles (SLNs) with stable lipid matrix structures for the delivery of bioactive compounds, a new class of SLNs was studied using propylene glycol monopalmitate (PGMP) and glyceryl monostearate (GMS) mixtures and carvacrol as a model lipophilic antimicrobial. Stable SLNs [...] Read more.
To develop solid lipid nanoparticles (SLNs) with stable lipid matrix structures for the delivery of bioactive compounds, a new class of SLNs was studied using propylene glycol monopalmitate (PGMP) and glyceryl monostearate (GMS) mixtures and carvacrol as a model lipophilic antimicrobial. Stable SLNs were fabricated at PGMP:GMS mass ratios of 2:1 and 1:1, and the carvacrol loading was up to 30% of lipids with >98% encapsulation efficiency and absence of visual instability. Fluorescence spectra and release profiles indicated the carvacrol was successfully encapsulated and homogeneously distributed within the SLNs. SLNs fabricated with equal masses of PGMP and GMS had better stability of carvacrol during storage and higher sphericity than those with a ratio of 2:1 and were much more effective than free carvacrol against Escherichia coli O157:H7 and Staphylococcus aureus. These findings demonstrated the potential applications of the studied SLNs in delivering lipophilic bioactive compounds in food and other products. Full article
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Open AccessReview
Recent Advances in Oxygen Electrocatalysts Based on Perovskite Oxides
Nanomaterials 2019, 9(8), 1161; https://doi.org/10.3390/nano9081161 - 14 Aug 2019
Viewed by 623
Abstract
Electrochemical oxygen reduction and oxygen evolution are two key processes that limit the efficiency of important energy conversion devices such as metal–air battery and electrolysis. Perovskite oxides are receiving discernable attention as potential bifunctional oxygen electrocatalysts to replace precious metals because of their [...] Read more.
Electrochemical oxygen reduction and oxygen evolution are two key processes that limit the efficiency of important energy conversion devices such as metal–air battery and electrolysis. Perovskite oxides are receiving discernable attention as potential bifunctional oxygen electrocatalysts to replace precious metals because of their low cost, good activity, and versatility. In this review, we provide a brief summary on the fundamentals of perovskite oxygen electrocatalysts and a detailed discussion on emerging high-performance oxygen electrocatalysts based on perovskite, which include perovskite with a controlled composition, perovskite with high surface area, and perovskite composites. Challenges and outlooks in the further development of perovskite oxygen electrocatalysts are also presented. Full article
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Open AccessArticle
Gold Plate Electrodes Functionalized by Multiwall Carbon Nanotube Film for Potentiometric Thallium(I) Detection
Nanomaterials 2019, 9(8), 1160; https://doi.org/10.3390/nano9081160 - 14 Aug 2019
Viewed by 671
Abstract
Solid-contact potentiometric ion-selective electrodes (SC-ISEs) for thallium determination have been designed using multiwall carbon nanotubes (MWCNTs) as the ion-to-electron transducer. Dispersed MWCNTs were drop-casted over a gold plate electrode. Two different crown ethers were used in the sensing membrane for the recognition of [...] Read more.
Solid-contact potentiometric ion-selective electrodes (SC-ISEs) for thallium determination have been designed using multiwall carbon nanotubes (MWCNTs) as the ion-to-electron transducer. Dispersed MWCNTs were drop-casted over a gold plate electrode. Two different crown ethers were used in the sensing membrane for the recognition of thallium (I). Sensorsbased on dibenzo-18-crown-6 (DB18C6) as a neutral carrier and NaTPB as an anionic additive exhibited a near Nernstian response of 57.3 mV/decade towards Tl+ ions over the activity range 4.5 × 10−6–7.0 × 10−4 M, with a limit of detection of 3.2 × 10−7 M. The time required to achieve 95% of the steadyequilibrium potential was <10 s. The complex formation constant (log βML) between dibenzo-18-crown-6 and thallium (I) (i.e., 5.99) was measured using the sandwich membrane technique. The potential response was pH independent over the range 3.0–9.5. The introduction of MWCNTs as an electron-ion-transducer layer between gold plate and the sensing membrane lead to a smaller membrane resistance and a large double layer capacitance, which was proven using impedance spectra and chronopotentiometry (i.e., 114.9 ± 12 kΩ, 52.1 ± 3.3 pF, 200 ± 13.2 kΩ, and 50 ± 4.2 µF). Additionally, reduction ofthe water layer between the sensing membrane and the underlying conductor wastested. Thus, it is clear that MWCNTs can be used as a transducing layer in SC-ISEs. The proposed sensor was introduced as an indicator electrode for potentiometric titration of single and ternary mixtures of I, Br, and S2− anions. Full article
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Open AccessArticle
Fabrication and Surface Interactions of Super-Hydrophobic Silicon Carbide for Membrane Distillation
Nanomaterials 2019, 9(8), 1159; https://doi.org/10.3390/nano9081159 - 13 Aug 2019
Viewed by 608
Abstract
Hydrophilic silicon carbide was modified by surface deposition of a super-hydrophobic coating that is based on perfluorosilanes. The modification was proven to yield membrane surfaces with contact angles that were higher than 145° and to be stable under hydrothermal conditions. The measurement of [...] Read more.
Hydrophilic silicon carbide was modified by surface deposition of a super-hydrophobic coating that is based on perfluorosilanes. The modification was proven to yield membrane surfaces with contact angles that were higher than 145° and to be stable under hydrothermal conditions. The measurement of the isosteric heat of adsorption of water and toluene by microgravimetry showed that, after modification, the membrane material was fully covered by a low-energy surface, which is consistent with the fluorocarbon moieties that were introduced by the modification. The same modification method was applied to a commercial multichannel SiC membrane tube (nominal pore size = 0.04 µm), which was tested in a direct contact membrane distillation apparatus. The membrane was permeable to water vapour and volatiles, but it showed full rejection for salt ions and organic pollutants with low vapour pressure (such as ibuprofen and caffeine). Moreover, the membrane was reusable, and its performances were stable with no sign of pore wetting over 8 h of filtration. Full article
(This article belongs to the Special Issue Sustainable and Safe Nano-Enabled Water Treatment Applications)
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Open AccessArticle
Stability of Hybrid Organic-Inorganic Perovskite CH3NH3PbBr3 Nanocrystals under Co-Stresses of UV Light Illumination and Temperature
Nanomaterials 2019, 9(8), 1158; https://doi.org/10.3390/nano9081158 - 13 Aug 2019
Viewed by 658
Abstract
Hybrid organic–inorganic metal halide perovskite nanocrystals (NCs) are among the candidates for color conversion materials in displays, especially in NC-based micro-light-emitting diode (micro-LED) displays. However, these NCs are still lacking long-term stability, which has hindered their large-scale applications. We mimic the working conditions, [...] Read more.
Hybrid organic–inorganic metal halide perovskite nanocrystals (NCs) are among the candidates for color conversion materials in displays, especially in NC-based micro-light-emitting diode (micro-LED) displays. However, these NCs are still lacking long-term stability, which has hindered their large-scale applications. We mimic the working conditions, which include ultraviolet light illumination at 323 K and three different types of atmosphere (N2, vacuum, and air), respectively, to investigate the stability of CH3NH3PbBr3 NCs embedded in the polyvinylidene fluoride matrix. X-ray diffraction results indicate the generation of NH4Pb2Br5, which is produced from the encapsulated CH3NH3PbBr3 NCs in all three atmospheres, and the decomposition generates a large amount of accompanying interface defects at the surface area of NCs, resulting in the significant decrease of the photoluminescence (PL) intensity. This work highlights the stability-related mechanism of CH3NH3PbBr3 NCs under combined external stresses that mimic operating conditions. In addition, this work also suggests a new method for conducting aging tests and contributes to developing effective routes towards higher stability of perovskite NCs. Full article
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Open AccessArticle
Photo-Fenton Degradation of Pentachlorophenol: Competition between Additives and Photolysis
Nanomaterials 2019, 9(8), 1157; https://doi.org/10.3390/nano9081157 - 13 Aug 2019
Viewed by 629
Abstract
In the present work, the photo-Fenton degradation of pentachlorophenol (PCP, 1 mg/L) has been studied under simulated and natural solar irradiation; moreover, the effect on the process efficiency of urban waste-derived soluble bio-based substances (SBO), structurally comparable to humic acids, has been investigated. [...] Read more.
In the present work, the photo-Fenton degradation of pentachlorophenol (PCP, 1 mg/L) has been studied under simulated and natural solar irradiation; moreover, the effect on the process efficiency of urban waste-derived soluble bio-based substances (SBO), structurally comparable to humic acids, has been investigated. Experiments showed a crucial role of PCP photolysis, present in the solar pilot plant and hindered by the Pyrex® filter present in the solar simulator. Indeed, the SBO screen negatively affects PCP degradation when working under natural solar light, where the photolysis of PCP is relevant. In contrast, in the absence of PCP photolysis, a significant improvement of the photo-Fenton process was observed when added to SBO. Furthermore, SBO were able to extend the application of the photo-Fenton process at circumneutral pH values, due to their ability to complex iron, avoiding its precipitation as oxides or hydroxides. This positive effect has been observed at higher concentration of Fe(II) (4 mg/L), whereas at 1 mg/L, the degradation rates of PCP were comparable in the presence and absence of SBO. Full article
(This article belongs to the Special Issue Sustainable and Safe Nano-Enabled Water Treatment Applications)
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Open AccessArticle
Structural and Electrical Studies for Birnessite-Type Materials Synthesized by Solid-State Reactions
Nanomaterials 2019, 9(8), 1156; https://doi.org/10.3390/nano9081156 - 12 Aug 2019
Viewed by 601
Abstract
The focus of this paper is centered on the thermal reduction of KMnO4 at controlled temperatures of 400 and 800 °C. The materials under study were characterized by atomic absorption spectroscopy, thermogravimetric analysis, average oxidation state of manganese, nitrogen adsorption–desorption, and impedance [...] Read more.
The focus of this paper is centered on the thermal reduction of KMnO4 at controlled temperatures of 400 and 800 °C. The materials under study were characterized by atomic absorption spectroscopy, thermogravimetric analysis, average oxidation state of manganese, nitrogen adsorption–desorption, and impedance spectroscopy. The structural formulas, found as a result of these analyses, were K 0.29 + ( M n 0.84 4 + M n 0.16 3 + ) O 2.07 · 0.61 H 2 O and K 0.48 + ( M n 0.64 4 + M n 0.36 3 + ) O 2.06 · 0.50 H 2 O . The N2 adsorption–desorption isotherms show the microporous and mesoporous nature of the structure. Structural analysis showed that synthesis temperature affects the crystal size and symmetry, varying their electrical properties. Impedance spectroscopy (IS) was used to measure the electrical properties of these materials. The measurements attained, as a result of IS, show that these materials have both electronic and ionic conductivity. The conductivity values obtained at 10 Hz were 4.1250 × 10−6 and 1.6870 × 10−4−1cm−1 for Mn4 at 298 and 423 K respectively. For Mn8, the conductivity values at this frequency were 3.7074 × 10−7 (298) and 3.9866 × 10−5−1cm−1 (423 K). The electrical behavior was associated with electron hopping at high frequencies, and protonic conduction and ionic movement of the K+ species, in the interlayer region at low frequencies. Full article
(This article belongs to the Special Issue Functional Nanoporous Materials)
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Open AccessArticle
Improvement of the Bias Stress Stability in 2D MoS2 and WS2 Transistors with a TiO2 Interfacial Layer
Nanomaterials 2019, 9(8), 1155; https://doi.org/10.3390/nano9081155 - 12 Aug 2019
Viewed by 629
Abstract
The fermi-level pinning phenomenon, which occurs at the metal–semiconductor interface, not only obstructs the achievement of high-performance field effect transistors (FETs) but also results in poor long-term stability. This paper reports on the improvement in gate-bias stress stability in two-dimensional (2D) transition metal [...] Read more.
The fermi-level pinning phenomenon, which occurs at the metal–semiconductor interface, not only obstructs the achievement of high-performance field effect transistors (FETs) but also results in poor long-term stability. This paper reports on the improvement in gate-bias stress stability in two-dimensional (2D) transition metal dichalcogenide (TMD) FETs with a titanium dioxide (TiO2) interfacial layer inserted between the 2D TMDs (MoS2 or WS2) and metal electrodes. Compared to the control MoS2, the device without the TiO2 layer, the TiO2 interfacial layer deposited on 2D TMDs could lead to more effective carrier modulation by simply changing the contact metal, thereby improving the performance of the Schottky-barrier-modulated FET device. The TiO2 layer could also suppress the Fermi-level pinning phenomenon usually fixed to the metal–semiconductor interface, resulting in an improvement in transistor performance. Especially, the introduction of the TiO2 layer contributed to achieving stable device performance. Threshold voltage variation of MoS2 and WS2 FETs with the TiO2 interfacial layer was ~2 V and ~3.6 V, respectively. The theoretical result of the density function theory validated that mid-gap energy states created within the bandgap of 2D MoS2 can cause a doping effect. The simple approach of introducing a thin interfacial oxide layer offers a promising way toward the implementation of high-performance 2D TMD-based logic circuits. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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Open AccessArticle
Preparation of Graphene/ITO Nanorod Metamaterial/U-Bent-Annealing Fiber Sensor and DNA Biomolecule Detection
Nanomaterials 2019, 9(8), 1154; https://doi.org/10.3390/nano9081154 - 12 Aug 2019
Viewed by 659
Abstract
In this paper, a graphene/ITO nanorod metamaterial/U-bent-annealing (Gr/ITO-NM/U-bent-A)-based U-bent optical fiber local surface plasmon resonance (LSPR) sensor is presented and demonstrated for DNA detection. The proposed sensor, compared with other conventional sensors, exhibits higher sensitivity, lower cost, as well as better biological affinity [...] Read more.
In this paper, a graphene/ITO nanorod metamaterial/U-bent-annealing (Gr/ITO-NM/U-bent-A)-based U-bent optical fiber local surface plasmon resonance (LSPR) sensor is presented and demonstrated for DNA detection. The proposed sensor, compared with other conventional sensors, exhibits higher sensitivity, lower cost, as well as better biological affinity and oxidize resistance. Besides, it has a structure of an original Indium Tin Oxides (ITO) nanocolumn array coated with graphene, allowing the sensor to exert significant bulk plasmon resonance effect. Moreover, for its discontinuous structure, a larger specific surface area is created to accommodate more biomolecules, thus maximizing the biological properties. The fabricated sensors exhibit great performance (690.7 nm/RIU) in alcohol solution testing. Furthermore, it also exhibits an excellent linear response (R2 = 0.998) to the target DNA with respective concentrations from 0.1 to 100 nM suggesting the promising medical applications of such sensors. Full article
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