The photo-electrochemical studies of Eu doped yttrium orthovanadate–zinc oxide–reduced graphene oxide nanohybrid

A new class of nanostructured photo-electrocatalyst Eu³⁺ doped yttrium orthovanadate–zinc oxide–reduced graphene oxide (YVO₄:Eu³⁺–ZnO–RGO) nanohybrid was developed by a simple electrostatic self-assembly at room temperature, using ZnO, YVO₄:Eu³⁺ and RGO as building blocks. Interaction among YVO₄:Eu³⁺, ZnO and RGO is indicated by variation in hydrodynamic diameter (H_D) and zeta potentials of the products as compared to their individual components, thus suggesting that YVO₄:Eu³⁺–ZnO–RGO is a nanohybrid and not a physical mixture. Electrochemical response of this nanohybrid towards the redox couple of Fe(CN)₆^3−/4− was investigated before and after UV irradiation. Apart from quenching of the green emission of ZnO in photoluminescence spectrum, which serves as a probe to monitor the interfacial electron transfer from excited ZnO to RGO, degradation in electrochemical redox process provides an additional path to monitor interfacial electron transfer.     

Fast and facile preparation of reduced graphene oxide supported Pt–Co electrocatalyst for methanol oxidation

In this study, we report a scalable, fast, and facile method for preparation of reduced graphene oxide (RGO) sheets supported Pt–Co electrocatalyst for methanol oxidation. Mixed reducing agents were used and the activity of the catalysts was studied. It was found that the presence of RGO leads to higher activity, which might be due to the increasing of electrochemically accessible surface areas and easier charge–transfer at the interfaces. Co can greatly enhance the electrocatalytic activity and moderate the poisoning of Pt catalyst. Under same Pt loading mass and experimental conditions, the RGO-Pt-Co catalyst shows the highest electro catalytic activity and improved resistance to carbon monoxide poisoning among the prepared catalysts.     

One-step synthesis of mesoporous silica–graphene composites by simultaneous hydrothermal coupling and reduction of graphene oxide

Silica–graphene oxide composites were synthesized by hydrothermal method with simultaneous functionalization and reduction of graphene oxide (GO) in the presence of mesoporous silica. Two types of silica were used in the study, mesoporous synthetic silica (MSU-F) synthesized by sol-gel method and mesoporous mineral silica (meso-celite) from pseudomorphic synthesis. The infrared spectra of the composites showed the disappearance of the carboxyl peak at 1735 cm^-1 which could be due to the reduction of the –COOH group. The enhancement of the band at 1385 cm^–1 is attributed to the vibration of the Si–O–C=O moiety formed by reaction of the –COOH group of GO and the silanol (Si–OH) of silica. The Raman spectra of the composites show a diminished intensity ratio of D to G band indicating that GO was reduced to graphene sheets. The TEM images demonstrate the coupling of silica to GO surface revealing dense loading of silica on GO in planar structure.     

Bioactive magnetic nanoparticles of Fe–Ga synthesized by sol–gel for their potential use in hyperthermia treatment

Hyperthermia is one of the most recents therapies for cancer treatment using particles with nanometric size and appropriate magnetic properties for destroying cancer cells. Magnetic nanoparticles (MNP’s) of Fe–Ga and synthesized using a polycondensation reaction by sol–gel method were obtained. MNP’s of Fe_1.4Ga_1.6O₄ that posses an inverse spinel structure were identified by X-Ray Diffraction, Transmission Electron Microscopy, Scanning Electron Microscopy and Energy Dispersive Spectroscopy. The results showed that the MNP’s are composed only by Fe, Ga and O and their size is between 15 and 20 nm. The magnetic properties measured by Vibration Sample Magnetometry demonstrated a saturation magnetization value of 37.5 emu/g. To induce the MNP’s bioactivity, a biomimetic method was used which consisted in the immersion of MNP’s in a Simulated Body Fluid (SBF) for different periods of time (7, 14 and 21d) along with a wollastonite disk. The formation of a bioactive layer, which closely resembles that formed on the existing bioactive systems and with a Ca/P atomic ratio within a range of 1.37–1.73 was observed on the MNP’s. Cytotoxicity of MNP’s was evaluated by in vitro hemolysis testing using human red blood cells at concentrations between 0.25 and 6.0 mg/mL. It was found that the MNP’s were not cytotoxic at none of the concentrations used. The results indicate that Fe–Ga MNP’s are potential materials for cancer treatment of both hard and soft tissue by hyperthermia and drug carriers, among other applications.     

The sensitive electrical response of reduced graphene oxide–polymer nanocomposites to large deformation

In this paper, the reduced graphene oxide (rGO)–polymer nanocomposite films were prepared by two comparable methods, and their electrical performances at large deformation were measured and analyzed. It is concluded that the gauge factor (GF) value of strain-sensing composite strongly depends on rGO’s content and preparing process. The composites with rGO’s content between percolation threshold and the content which rGO conducting as a complete network show better sensitive electrical response. What’s more, strong interface interaction between conducting filler and matrix benefits the improvement of GF value. The composites we prepared display significant and consistent changes in their GF values when subjected to large deformation, which are suitable for large structural deformation monitoring in advanced civil engineering.     

Fabrication of reduced graphene oxide nanosheets reinforced Sn–Bi nanocomposites by electro-chemical deposition

Novel Sn–Bi/reduced graphene oxide nanosheets (RGOS) nanocomposites were fabricated using electro-chemical deposition process at room temperature. The RGOS dispersed and distributed in Sn–Bi alloy. Nano-sized Sn–Bi grain clusters grew on the surface of RGOS and the Sn–Bi grains became finer after the incorporation of RGOS. The mechanical properties including micro-hardness and shear strength were enhanced by the incorporation of RGOS. The enhance mechanism of RGOS in Sn–Bi/RGOS nanocomposites was proposed by finite element method simulation. The graphene with extra-thin thickness and huge aspect ratio lead to an effective stress transfer and stress concentration occurs near the edge of graphene. The Sn–Bi/RGOS nanocomposites are promising in application as TIM of high power electronics, integrated circuits.     

In situ controllable synthesis of Ag@AgCl core–shell nanoparticles on graphene oxide sheets

Graphene oxide-supported uniform Ag@AgCl core–shell nanoparticle composites have been successfully prepared by a facile two-step synthetic process. First, graphene oxide sheets were used as carriers to anchor and disperse Ag nanoparticles on their surface. Then these fixed Ag nanoparticles on carbon sheets are utilized as precursors, around which AgCl nanocrystals form in situ using FeCl₃ as oxidant, forming graphene oxide-supported Ag@AgCl core–shell nanoparticle composites. The composition of these attached Ag@AgCl core–shell nanoparticles can be easily controlled by adjusting the usage of FeCl₃, resulting in the formation of controllable core–shell nanostructures. Furthermore, these as-prepared graphene oxide–Ag@AgCl nanoparticle composites display effective photodegradation of methylene orange dye under visible light irradiation, which indicates their potential applications in environmental areas.     

Mesoporous titanium dioxide@ zinc oxide–graphene oxide nanocarriers for colon-specific drug delivery

In this project, TiO₂@ZnO nanoparticles core–shell nanostructured and titanium dioxide@ mesoporous zinc oxide–graphene oxide (TiO₂@ZnO–GO) hybrid nanocomposites as controlled targeted drug delivery systems were synthesized by a facile sono-chemical method. We prepared a novel mesoporous and core–shell structure as a drug nanocarrier (NCs) for the loading and pH-responsive characteristics of the chemotherapeutic curcumin. The structure, surface charge, and surface morphology of NCs were studied using with X-ray diffraction, Fourier transform infrared spectroscopy, dynamic light scattering, brunauer–emmett–teller, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The SEM and TEM images of NCs show the uniform hexagonal mesoporous morphology with average grain size of about ～ 190 nm. The drug loading was very high about 16 and 19 for TiO₂@ZnO and TiO₂@ZnO–GO, respectively. The NCs showed pH-dependent drug release behavior. Drug release from TiO₂@ZnO–GO in neutral pH were higher than in acidic medium, due to anionic charge of GO nanosheet. MTT assay results showed that the curcumin-loaded NCs showed significant toxicity due to which cell viability reduced to below 50% at 140 μg/mL concentration, thereby confirming its anticancer effects. The goal of this study is the application of water-dispersed TiO₂@ZnO–GO with pH-dependent release properties for design a new drug delivery carrier.     

Ascorbic acid-mediated synthesis and characterisation of iron oxide/gold core–shell nanoparticles.

The current article reports on providing surface modification of magnetic nanoparticles with gold to provide stability against aggregation. Gold-coated magnetite nanoparticles were synthesised to combine both magnetic as well as surface plasma resonance (SPR) properties in a single moiety. The nanocomposites were produced by reduction (using ascorbic acid) of gold chloride on to the surface of iron oxide nanoparticles. Ascorbic acid not only acts as a reducing agent, but also the oxidised form of ascorbic acid i.e. Dehydro-ascorbic acid acts as a capping agent to impart stability to as synthesised gold-coated iron oxide nanocomposites. The synthesised nanocomposite was monodispersed with a mean particle size of around 16 nm and polydispersity index of 0.190. X-ray diffraction analysis confirms presence of gold on the surface of magnetite nanoparticles. The synthesised nanocomposites had a total organic content of around 3.2% w/w and also showed a shifted SPR peak at 546 nm as compared to gold nanoparticles (528 nm). Both uncoated and gold-coated magnetite exhibited superparamagnetic behaviour at room temperature. Upon coating with gold shell, saturation magnetisation of iron oxide nanoparticles decreases from 42.806 to 3.54 emu/gram.     

In situ synthesis of gold–polyaniline composite in nanopores of polycarbonate membrane

In situ one-step chemical synthesis route for the preparation of a gold–polyaniline composite in nanopores of polycarbonate (PC) membrane is reported. PC membrane, which was placed in a specially designed two-compartment cell, separated the aqueous solution of aniline from HAuCl₄ solution. Concentration gradient across the membrane caused movement of AuCl₄ ⁻ and anilinium ions in the pores of polycarbonate membrane. Nanopores in PC membrane acted as reaction vessels where aniline and HAuCl₄ were allowed to mix together, and the redox reaction between aniline and HAuCl₄ led to the formation of gold–polyaniline composite. The gold–polyaniline composite in PC membrane was characterised by EDXRF, XRD, UV–Vis spectroscopy, FTIR and TEM. Peak broadening in XRD suggests that Au particles formed in the membrane are nanocrystallites and average crystallite size is (24 ± 4) nm. TEM studies show that gold nanoparticles are randomly dispersed in polyaniline clusters formed in the nanopores of PC membrane. Characterisation results show that the surfaces of the PC membrane exposed to HAuCl₄ and aniline have significantly higher concentrations of Au nanoparticles and polyaniline, respectively.     

Facile synthesis of FeCo@NC core–shell nanospheres supported on graphene as an efficient bifunctional oxygen electrocatalyst

Electrocatalytic conversion of oxygen holds great potential for clean energy technologies,including water electrolysis,regenerative fuel cells,and rechargeable metal-air batteries.The development of highly efficient and inexpensive oxygen electrocatalysts as replacements for precious metal-based catalysts is vitally important for large-scale practical application in the future.A bifunctional oxygen electrocatalyst based on FeCo nanoparticles/N-doped carbon core-shell spheres supported on N-doped graphene sheets was prepared via one-step pyrolysis of graphitic carbon nitride and acetylacetonates.The optimized product exhibited an oxygen electrode activity of 0.87 V and excellent durability.The remarkable performance is mainly attributed to the synergetic effect arising from the FeCo nanoparticles and N-doped carbon shell.This study introduces an inexpensive and simple way to develop highly active bifunctional oxygen electrocatalysts.     

Exploration of photoreduction ability of reduced graphene oxide–cadmium sulphide hetero-nanostructures and their intensified activities against harmful microbes

Journal of Materials Science - Fabrication of effective photocatalyst using semiconductors and graphene or reduced graphene oxide has been regarded as one of the most promising task to attenuate...     

Field effect in a graphene oxide transistor for proton and electron–hole conductivities

Proton (wet atmosphere) and electron (reduced graphene oxide) conductivities can be observed in graphene oxide films. The field effect in a graphene oxide transistor for different conductivity types has been discovered and investigated.     

One step synthesis of β-FeOOH nanowire bundles/graphene oxide nanocomposites

A nanocomposite of graphene oxide (GO) and β-ferric oxyhydroxide (β-FeOOH) nanowire bundles is synthesized by in situ hydrolysis of the precursor ferric chloride and GO nanosheets. Characterization by X-ray diffraction, transmission electron microscopy, and thermogravimetric analysis established the composite structure of the synthesized sample. The results revealed that the surface of GO nanosheets was uniformly assembled by numerous nanowire bundles with diameters in the range of 30–50 nm and lengths of 100–150 nm. Furthermore, β-FeOOH/GO nanocomposites showed a very high adsorption capacity of Congo red and thus these nanocomposites can be used as good adsorbents and can be used for the removal of organic dye from the waste water system.     

Novel and simple route for the synthesis of core–shell chitosan–gold nanocomposites

This work presents a novel and simple route for the synthesis of water-soluble core–shell chitosan–gold nanocomposites. The experimental procedure can be summarized by the following steps: (i) chitosan deacetylation, (ii) chitosan depolymerization, (iii) chitosan nanoparticles’ formation and (iv) chitosan–gold nanocomposite formation. FT-IR spectroscopic results indicate that the formation of chitosan nanoparticles (ChtNPs) occurs via NH₃⁺ and PO⁻ groups electrostatic interactions, while UV–vis spectra points to a possible embedding of gold nanoparticles into the ChtNPs. This feature was confirmed by electronic transmission microscopy measurements. Chitosan and gold are biocompatible materials. Added to this, the obtained chitosan–gold nanocomposites presented thermal and absorbance properties which strongly point to their potential use in phototherapeutic processes.     

Facile synthesis of heterostructure NiO–SnO2 nanocomposite for selective electrochemical determination of l-cysteine

Journal of Materials Science: Materials in Electronics - In this present research, heterostructure NiO–SnO2 nanocomposite modified electrode was developed to determine l-cysteine molecule....