Oxide Nanoplates Research Articles

High-Throughput Preparation of Metal Oxide Nanocrystals by Cathodic Corrosion and Their Use as Active Photocatalysts.

Nanoparticle metal oxide photocatalysts are attractive because of their increased reactivity and ease of processing into versatile electrode formats; however, their preparation is cumbersome. We report on the rapid bulk synthesis of photocatalytic nanoparticles with homogeneous shape and size via the cathodic corrosion method, a simple electrochemical approach applied for the first time to the versatile preparation of complex metal oxides. Nanoparticles consisting of tungsten oxide (H2WO4) nanoplates, titanium oxide (TiO2) nanowires, and symmetric star-shaped bismuth vanadate (BiVO4) were prepared conveniently using tungsten, titanium, and vanadium wires as a starting material. Each of the particles were extremely rapid to produce, taking only 2-3 min to etch 2.5 mm of metal wire into a colloidal dispersion of photoactive materials. All crystalline H2WO4 and BiVO4 particles and amorphous TiO2 were photoelectrochemically active toward the water oxidation reaction. Additionally, the BiVO4 particles showed enhanced photocurrent in the visible region toward the oxidation of a sacrificial sulfite reagent. This synthetic method provides an inexpensive alternative to conventional fabrication techniques and is potentially applicable to a wide variety of metal oxides, making the rapid fabrication of active photocatalysts with controlled crystallinity more efficient.

Highly Active Tungsten Oxide Nanoplate Electrocatalysts for the Hydrogen Evolution Reaction in Acidic and Near Neutral Electrolytes.

An efficient, cost-effective, and earth-abundant catalyst that could drive the production of hydrogen from water without or with little external energy is the ultimate goal toward hydrogen economy. Herein, nanoplates of tungsten oxide and its hydrates (WO3·H2O) as promising electrocatalysts for the hydrogen evolution reaction (HER) are reported. The square-shaped and stacked WO3·H2O nanoplates are synthesized at room temperature under air in ethanol only, making it as a promising green synthesis strategy. The repeated electrochemical cyclic voltammetry cycles modified the surface of WO3·H2O nanoplates to WO3 as confirmed by X-ray photoelectron and Auger spectroscopy, which leads to an improved HER activity. Hydrogen evolution is further achieved from distilled water (pH 5.67) producing 1 mA cm–2 at an overpotential of 15 mV versus the reversible hydrogen electrode. Moreover, WO3·H2O and WO3 nanoplates demonstrate excellent durability in acidic and neutral media, which is highly desirable for practical application. Improved hydrogen evolution by WO3(200) when compared to that by Pt(111) is further substantiated by the density functional theory calculations.

Pervaporation of toluene and iso‐octane through poly(vinyl alcohol)/graphene oxide nanoplate mixed matrix membranes: Comparison of crosslinked and noncrosslinked membranes

ABSTRACTRemoval of aromatic compounds from fuel is an essential requirement in new environmental policies. In the present study, poly(vinyl alcohol)/graphene oxide (GO) mixed matrix membranes were prepared and applied to the separation of toluene from iso‐octane by pervaporation, considering the similarity and interaction between graphene and aromatics. The effects of crosslinking and GO content on separation efficiency have been investigated in detail. Owing to the high affinity of GO with toluene through s and π bonds, the selectivity of the membranes was increased by incorporating a low amount of GO. The results also indicated that noncrosslinked membranes have higher selectivity and permeation flux due to higher crystallinity and also have lower mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45853.

Photocatalytic degradation of roxarsone by using synthesized ZnO nanoplates

Abstract An efficient photodegradation of roxarsone (ROX) was achieved by using synthesized zinc oxide (ZnO) nanoplates under UV light irradiation. ZnO nanoplates were synthesized by facile wet chemical method. Characterization of ZnO nanoparticles was done by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, diffuse reflectance (DRS) UV–Visible absorption spectroscopy, BET analyzer, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained results reveal that the synthesized sample is ZnO which has hexagonal structure and plate-like morphology. The band gap and specific surface area of ZnO was found to be 3.02 eV and 7 m2 g−1 respectively. ROX’s degradation by-products such as As(III), As(V) were analyzed by high performance liquid chromatography-hydride generation coupled with atomic absorption spectrometry (HPLC-HG-AAS). The photogenerated hydroxyl ( ) and carbon-centered radicals were detected by electron paramagnetic resonance (EPR) spectroscopy. According to experimental evidences a possible photocatalytic mechanism has also been proposed. Photocatalytic degradation of ROX leads to mineralization as CO2 and As(V). This can be considered as a promising method for removing ROX from contaminated waters.

Creep behaviour of graphite oxide nanoplates embedded glass fiber/epoxy composites: Emphasizing the role of temperature and stress

Graphene based nano-reinforcements have emerged as promising fillers in polymeric materials. The objective of the present article is to elucidate the reinforcement effect of graphite oxide nanoplates (GONP) on the thermal, flexural and creep performance of glass fiber/epoxy (GE) composites. Thermal analyses by DSC, DMA and TGA showed reduced glass transition temperature of GE composite due to GONP incorporation, whereas no significant impact has been observed on the decomposition temperature. GONP addition has been found to be beneficial on the flexural properties of GE composite. To understand the effect of temperature on long-term mechanical durability, creep tests have been performed at various temperatures (50, 80 and 110°C). Further, elevated temperature creep behaviour has been assessed at various stresses (10, 20 and 40MPa) to comprehend the combined effect of temperature and stress. Improved creep resistance has been observed in GONP modified GE composites at relatively lower temperature and stress.

Self-assembled NiCo2O4-anchored reduced graphene oxide nanoplates as high performance anode materials for lithium ion batteries

The NiCo2O4-anchored reduced graphene oxide (NiCo2O4@rGO) nanoplates have been synthesized by a facile self-assembly process. The morphology, crystalline structure and electrochemical performance of the materials have been investigated comprehensively. The results of SEM manifest that NiCo2O4 particles have been densely anchored on the surface of rGO with a mesoporous structure, and the morphology is tunable via altering concentration of urea during the preparation process. Due to the high ratio of NiCo2O4 in the composite and the plate structure, the electrochemical performance of as-prepared material has been greatly improved. When evaluated as anode materials in lithium ion batteries (LIBs), the as-prepared NiCo2O4@rGO nanocomposite delivers a reversible capacity of 994mAhg−1 at a current density of 200mAg−1 with outstanding rate capability, revealing that it could be a promising anode for LIBs.

Evaluating the ion transport characteristics of novel graphene oxide nanoplates entrapped mixed matrix cation exchange membranes in water deionization

Graphene oxide nanoplates (GONs) embedded mixed matrix polyvinylchloride based heterogeneous cation exchange membranes were prepared by solution casting. The effect of the concentration of GONs on the physico-chemical properties of the membrane was studied. Scanning electron microscopy (SEM) and scanning optical microscopy (SOM) images showed a uniform particle distribution and a uniform surface for the modified membranes. Moreover, the cross-sectional SEM images showed a specific direction for GO nanoplates, perpendicular to the membrane surface. XRD patterns showed that the average particle size of was enhanced by increasing the GONs dosage. The surface hydrophilicity of the membranes was improved, and the water content was lower by increasing the GON content. The IEC of the membranes was enhanced from 1.15 to 1.40meq/g by an increase of the GON concentration up to 0.5wt% in the casting solution, and decreased by a further increase of the content of GONs. The membrane potential, transport number, selectivity and conductivity were improved by utilizing GONs. The ion permeability and flux decreased initially by using GONs up to 0.5wt%, followed by a sharp increasing trend at higher concentrations of GONs.

Tailoring the electrochemical properties of ED ion exchange membranes based on the synergism of TiO2 nanoparticles-co-GO nanoplates

In this paper, the synergetic influence of various weight ratios of TiO2 nanoparticles (NPs)/graphene oxide nanoplates (GONs) in the matrix of ion exchange membranes was examined in order to adapt their electrokinetic properties based on the combination of the high specific surface area of GONs and the antifouling ability of TiO2 nanoparticles. The morphology, physico-chemical features and ionic transport behavior of prepared membranes was studied. Scanning optical microscopy (SOM) and scanning electron microscopy (SEM) images showed a uniform surface for the lab-made membranes relatively. It was found that surface hydrophilicity of the membrane was increased in the presence of GONs and TiO2 NPs. All modified membranes showed a higher water uptake than unmodified membranes. Furthermore, a higher ion exchange capacity, fixed ionic concentration, ionic permeability and flux were observed for all modified membranes in comparison with unmodified membranes. The membrane potential, transport number and selectivity improved in NaCl solutions by using GONs and TiO2 nanoparticles. Furthermore, the membrane ionic conductivity showed an increasing trend by utilizing TiO2-co-GONs NPs. As an overall conclusion, the modified membrane containing 3wt% GONs and 1wt% TiO2 NPs with superior transport number and permselectivity (∼99%), highest current density and cation flux and the lowest areal electrical resistance (∼4–5Ωcm2) showed the best performance.

Syntheses of iron oxide nanoplates by hydrothermal treatment of iron-oleate precursor and their magnetization reversal

Magnetic iron oxide (Fe3−xO4) nanoplates with a high aspect ratio (lateral size/thickness ratio of>50) were synthesized via a facile hydrothermal treatment of an iron-oleate precursor. The magnetic domain configuration of the Fe3−xO4 nanoplates was observed by magnetic force microscopy (MFM). Single domain magnetic polarity was observed in the remnant state of isolated Fe3−xO4 nanoplates, with a lateral size of ca. 300nm and thickness of 7.6nm. The magnetization orientation of isolated Fe3−xO4 nanoplates was mainly determined by the magnetic shape anisotropy originating from their high aspect ratio. Magnetization reversal occurred via coherent rotation upon switching the external magnetic field, rather than by domain wall nucleation. Micro-magnetic simulations based on the Landau-Lifshitz Gilbert equation supported the conclusions drawn from the experimental results.

RGO@APTES/hybrid sol-gel nanocomposite for corrosion protection of 2024 aluminum alloy

Abstract In this work, Graphene Oxide (GO) nanoplates were silanized using 3-aminopropyltriethoxysilane (APTES) and dicyclohexylcarbodiimide (DCC) through carboxylic and epoxide groups to obtain reduced GO (rGO)@APTES nanoplates. The rGO@APTES nanoplates were characterized by SEM, FTIR, and XRD techniques. Much better dispersion of the functionalized nanoplates in the hybrid silane mixture (prepared by equimolar mixing of TEOS and GPTMS) was revealed by visual and TEM images. Afterward, the hybrid sol-gel nanocomposites containing different concentrations of the rGO@APTES nanoplates were applied on Al 2024 substrate. Uniform, dense, defect-free and adherent sol-gel films were obtained in all cases. Decreasing of the water contact angle on the surface was much lower than expected due to removal of the oxygen-containing polar groups in the GO structure. Also, the corrosion behavior of the nanocomposites was evaluated after different immersion times in 3.5 wt.% NaCl solution by EIS measurements. The corrosion resistance of the sol-gel coating was significantly improved after incorporation of the rGO@APTES nanoplates. The sol-gel nanocomposite with 100 ppm rGO@APTES content showed the highest polarization resistance which this concentration was much lower than that reported in similar works. The results obtained by the EIS measurements were confirmed by the visual and microscopic observations after the corrosion tests.

Tailoring Anisotropic Li-Ion Transport Tunnels on Orthogonally Arranged Li-Rich Layered Oxide Nanoplates Toward High-Performance Li-Ion Batteries.

High-performance Li-rich layered oxide (LRLO) cathode material is appealing for next-generation Li-ion batteries owing to its high specific capacity (>300 mAh g-1). Despite intense studies in the past decade, the low initial Coulombic efficiency and unsatisfactory cycling stability of LRLO still remain as great challenges for its practical applications. Here, we report a rational design of the orthogonally arranged {010}-oriented LRLO nanoplates with built-in anisotropic Li+ ion transport tunnels. Such a novel structure enables fast Li+ ion intercalation and deintercalation kinetics and enhances structural stability of LRLO. Theoretical calculations and experimental characterizations demonstrate the successful synthesis of target cathode material that delivers an initial discharge capacity as high as 303 mAh g-1 with an initial Coulombic efficiency of 93%. After 200 cycles at 1.0 C rate, an excellent capacity retention of 92% can be attained. Our method reported here opens a door to the development of high-performance Ni-Co-Mn-based cathode materials for high-energy density Li-ion batteries.

Solution-processed n-ZnO nanorod/p-Co3O4 nanoplate heterojunction light-emitting diode

A heterojunction light-emitting diode (LED) based on p-type cobalt oxide (Co3O4) nanoplates (NPs)/n-type zinc oxide (ZnO) nanorods (NRs) is demonstrated. Using a low-temperature aqueous solution process, the n-type ZnO NRs were epitaxially grown on Co3O4 NPs which were two-dimensionally assembled by a modified Langmuir-Blodgett process. The heterojunction LEDs exhibited a typical rectifying behavior with a turn-on voltage of about 2V and emitted not only reddish-orange light at 610nm but also violet light at about 400nm. From the comparative analyses of electroluminescence and photoluminescence, it was determined that the reddish-orange light emission was related to the electronic transitions from zinc interstitials (Zni) to oxygen interstitials (Oi) or conduction-band minimum (CBM) to oxygen vacancies (VO), and the violet light emission was attribute to the transition from CBM to valence-band maximum (VBM) or Zni to zinc vacancies (VZn).

Well-Ordered Oxygen-Deficient CoMoO4 and Fe2O3 Nanoplate Arrays on 3D Graphene Foam: Toward Flexible Asymmetric Supercapacitors with Enhanced Capacitive Properties.

In this work, we report the development of well-ordered hydrogenated CoMoO4 (H-CoMoO4) and hydrogenated Fe2O3 (H-Fe2O3) nanoplate arrays on 3D graphene foam (GF) and explore their practice application as binder-free electrodes in assembling flexible all-solid-state asymmetric supercapacitor (ASC) devices. Our results show that the monolithic 3D porous GF prepared by solution casting method using Ni foam template possesses large surface area, superior electrical conductivity, and sufficient surface functional groups, which not only facilitate in situ growth of CoMoO4 and Fe2O3 nanoplates but also contribute the double-layer capacitance of the resultant supercapacitor. The well-ordered pseudocapacitive metal oxide nanoplate arrays standing up on 3D GF scaffold can provide efficient space and shorten the length for electrolyte diffusion from the outer to the inner region of the electrode material for Faradaic energy storage. Furthermore, one of our major findings is that the introduction of oxygen vacancies in CoMoO4 and Fe2O3 nanoplates by hydrogenation treatment can increase their electronic conductivity as well as improve their donor density and surface properties, which gives rise to a substantially improved electrochemical performance. Benefiting from the synergistic contributions of different components in the nanohybrid electrode, the resultant flexible ASC device with GF/H-CoMoO4 as the positive electrode and GF/H-Fe2O3 as the negative electrode achieves a wide operation voltage of 1.5 V and a maximum volumetric specific capacitance of 3.6 F cm-3, which is two times larger than that of the Ni/GF/CoMoO4//Ni/GF/Fe2O3 device (1.8 F cm-3), and the rate capability is up to 70% as the current density increases from 2 to 200 mA cm-3. Moreover, the Ni/GF/H-CoMoO4//Ni/GF/H-Fe2O3 device also exhibits a high energy density of 1.13 mWh cm-3 and a high power density of 150 mW cm-3, good mechanical flexibility with the decrease in capacitance of less than 4% after being bent inward to different angles and inward to 90° 200 times, and good cycling stability of 93.1% capacitance retention after 5000 cycles.

Poly(Vinyl Alcohol)/Graphene Oxide Mixed Matrix Membranes for Pervaporation of Toluene and Isooctane

ABSTRACTPoly(vinyl alcohol)/graphene oxide mixed matrix membranes have been prepared and applied for the pervaporation of isooctane (aliphatic) and toluene (aromatic) mixtures. Characteristics of the membranes such as crystallinity, morphology, and swelling have been investigated, and the results have been used to describe pervaporation performance. Experimental tests evidenced that incorporation of low content of graphene oxide nanoplates (0.5 wt%) in poly(vinyl alcohol) increases affinity of the membrane to aromatics by S and π bonds and selectivity increase to about four times. Moreover, interaction of graphene oxide with toluene results in increasing of swelling and decreasing of permeation flux.

Self-sacrificed two-dimensional REO(CH3COO) template-assisted synthesis of ultrathin rare earth oxide nanoplates

Ultrathin RE2O3nanoplates are synthesized by a hot-injection methodviathein situformed REO(CH3COO) template.

Pseudocapacitive behaviors of mesoporous nickel–cobalt oxide nanoplate electrodes in different electrolyte systems

A freestanding mesoporous NiCo2O4 nanoplate electrode exhibits superior pseudocapacitive performance and long-life stability.

Facile synthesis of 2-D Cu doped WO3 nanoplates with structural, optical and differential anti cancer characteristics

Simple chemical co-precipitation method has been employed to synthesize two dimensional copper (Cu) doped tungsten oxide (WO3) nanoplates. A numbers of characterization techniques have been used to investigate their structural, optical and biocompatible anti cancer properties. The XRD results have confirmed the monoclinic crystal structure of WO3 nanoplates, and also successful doping of Cu ions into the WO3 crystal lattice. The presence of functional groups and chemical bonding have been verified through FTIR and Raman spectroscopy. The SEM images demonstrate that both undoped and Cu doped WO3 samples have squares plate like morphology. The EDX spectra confirm the presence of Cu, W and O ions. Diffuse reflectance spectroscopy (DRS) analysis has revealed a substantial red-shift in the absorption edge and a decrease in the band gap energy of nanoplates with Cu doping. Photoluminescence spectroscopy has been used to study the presence of defects like oxygen vacancies. Furthermore, the differential cytotoxic properties of Cu doped WO3 samples have been evaluated against human breast (MCF-7) and liver (Hep-2) cancer cells with ectocervical epithelial (HECE) healthy cells. The present findings confirm that the Cu doped WO3 nanoplates can be used as an efficient biocompatible anti cancer agent.

Development of polysulfone-nanohybrid membranes using ZnO-GO composite for enhanced antifouling and antibacterial control

Zinc oxide nanoparticles were well-known for the enhanced antifouling and antibacterial properties which could be beneficial for membrane processes in desalination. The functionalization of ZnO onto graphene oxide nanoplates was targeted for better distribution. Both ZnO and ZnO-GO NPs were synthesized using sol-gel method. The nanoparticles characteristics were checked with XRD, TEM, and FESEM. The nanohybrid membranes were fabricated via wet phase inversion technique and embedded with various percentage of ZnO (1, 2, 3wt%) and ZnO-GO (0.1, 0.3, 0.6wt%) nanoparticles. All the membranes with nanoparticles incorporation exhibited improved membrane properties in comparison with the pristine PSF membrane. The best membrane performance was shown in membrane with 2wt% of ZnO and 0.6wt% of ZnO-GO. These two membranes presented significantly improved performance such as enhanced hydrophilicity, high permeability and porosity, improved humic acid rejection rate as well as good antifouling and antibacterial control. To an extent, the excellent antimicrobial ability of these nanohybrid membranes appeared as appropriate candidate to contribute or overcome bio-fouling issues in applications such as brackish water or seawater desalination. Hence, ZnO and ZnO-GO NPs were superb nanomaterials in the fabrication of PSF-nanohybrid membranes. The use of GO nanoplates allowed reduction of ZnO composition by up to 5 times while showing similar performances.

Application of quercetin and its bio-inspired nanoparticles as anti-adhesive agents against Bacillus subtilis attachment to surface

The aim of this study was directed to reveal the repulsive effect of coated glass slides by quercetin and its bio-inspired titanium oxide and tungsten oxide nanoparticles on physical surface attachment of Bacillus subtilis as an ab-initio step of biofilm formation. Nanoparticles were successfully synthesized using sol–gel and acid precipitation methods for titanium oxide and tungsten oxide, respectively (in the absence or presence of quercetin). The anti-adhesive impact of the coated-slides was tested through the physical attachment of B. subtilis after 24h using Confocal Laser Scanning Microscopy (CLSM). Here, quercetin was presented as a bio-route for the synthesis of tungsten mixed oxides nano-plates at room temperature. In addition, quercetin had an impact on zeta potential and adsorption capacity of both bio-inspired amorphous titanium oxide and tungsten oxide nano-plates. Interestingly, our experiments indicated a contrary effect of quercetin as an anti-adhesive agent than previously reported. However, its bio-inspired metal oxide proved their repulsive efficiency. In addition, quercetin-mediated nano-tungsten and quercetin-mediated amorphous titanium showed anti-adhesive activity against B. subtilis biofilm.

Structural and optical characterization and efficacy of hydrothermal synthesized Cu and Ag doped zinc oxide nanoplate bactericides

This study reports on a novel synthesis of pure zinc oxide and both Cu and Ag doped ZnO nanoplates using a simple and low-cost hydrothermal method. The structural and optical properties of the nanoplates were quantified and the materials were tested for antibacterial activity. X-ray diffraction revealed the formation of the wurtzite phase of ZnO and scanning and transmission electron microscopy showed the formation of randomly oriented ZnO nanoplates, having a thickness less than 80 nm and diameter less than 350 nm. The elemental analyses of both the pure and doped samples were evaluated by energy dispersive X-ray spectrometry. The FTIR spectra of ZnO nanomaterials showed the predictable bands at 3385 cm−1 (OH stretching), 1637 cm−1 (stretching vibration of H2O), 400 cm−1–570 cm−1 (MO stretching). The as synthesized samples showed a strong absorption peak in the UV region (∼376 nm) and a near band edge emission at 392 nm with some defect peaks in the visible region. From the XPS spectra the oxidation states of Zn, Cu and Ag were found to be +2, +2 and 0 respectively. Escherichia coli, Staphylococcus aureus and Salmonella typhi bacteria were used to evaluate the antibacterial activity of undoped and doped ZnO. Ag doped ZnO exhibited low minimum inhibitory concentration (MIC) values as 40 μg/ml for E. coli and S. aureus and 20 μg/ml for S. typhi, which are comparable to commercial antibiotics without optimization. Further, these chemically modified nanoparticles will be applicable in the development of medicine to control the spread and infection of a variety of bacterial strains.