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Highlights • Hybrid WO 3 –V 2 O 5 nanocomposites were prepared. • Supercapacitor performance was analysed in two electrolytes such as KOH and H 2 SO 4. • The capacitance was enhanced in KOH electrolyte from 44 F/g to 173 F/g. • The capacitance was declined from 246 F/g to 12 F/g in the H 2 SO 4 electrolyte. • WO 3 –V 2 O 5 composites showed capacitance retention of ∼126% up to 5000 cycles. Abstract The rod shape WO 3 –V 2 O 5 hybrid nanocomposites were prepared by microwave assisted wet chemical route. The electrochemical investigations of as-prepared composites were carried in two electrolytes such as KOH and H 2 SO 4 for comparison. Their maximum capacitance was calculated as 44 F/g for WO 3 and 173 F/g for WO 3 –V 2 O 5 composites in KOH electrolyte and its efficiency is 100% up to 5000 cycles and its capacitance retention is ∼126% in KOH electrolyte. In H 2 SO 4 electrolyte, the specific capacitance of WO 3 was recorded as 246 F/g and WO 3 –V 2 O 5 showed poor performance such as less than 12 F/g. [ABSTRACT FROM AUTHOR]

Tungsten oxide (WO3) nanostructures were synthesised using the microwave-assisted wet chemical method without any addition of surfactant for three different microwave irradiation times (10, 20 and 30 min). Then as-prepared nanostructures were characterised using various characterization techniques to know their structural, morphology and optical properties. The monoclinic and orthorhombic (WO3) crystal structure was obtained from the as-prepared nanostructures by using X-ray diffraction analysis and its calculated crystalline size were found to be increased from 14 to 18 nm on increasing microwave irradiation time. The functional groups were investigated by using Fourier transform infrared spectroscopy analysis and the W-O chemical bonding nature was confirmed. The surface morphology was unclear using scanning electron microscope analysis, and a careful observation in high resolution transmission electron microscope studies shows that rod shaped structure. A blue-shifted optical absorption spectrum was observed by ultraviolet-visible spectroscopy analysis analysis and the bandgap energy value of WO3 was calculated as approximately 3.62 eV. The emission behaviours were investigated by using photoluminescence spectrofluorometer analysis and an enhanced defect reduced emission was obtained. Finally, the electrochemical properties were analyzed by using cyclic voltammogram and galvanostatic charge-discharge analysis analyses. The maximum capacitance was recorded at 264 F/g which was declined to 149 F/g with the growth of WO3 nanostructures size. Hence, the effect of microwave on structure and morphology, and consequent supercapacitor performances of WO3 were discussed in details. [ABSTRACT FROM AUTHOR]

Abstract: CdO hexagonal sheets were prepared by a simple chemical route assisted by microwave irradiation. Two different preparation procedures were adopted and characterized in the presence of urea as a directing agent and poly-vinyl-pyrrolidone (PVP) as a surfactant. The morphological and microstructural characteristics were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) analysis, diffuse reflectance infrared spectroscopy (DRIFT) and X-ray powder diffraction (XRD). Characterization results have demonstrated that, after annealing at 300°C, the formation of CdO hexagonal sheets with different thickness. Thicker sheets were obtained when urea and PVP were used. Chemoresistive devices consisting of a thick layer of CdO hexagonal sheets on interdigitated alumina substrates had been fabricated and their electrical and sensing characteristics were investigated. The sensor performances of the CdO sheets for carbon monoxide were reported. The results indicated that both the sensors exhibited high response and quick response-recovery dynamics. The sensing properties were explained in terms of rapid gas diffusion onto the sensing layer surface. [Copyright &y& Elsevier]

Zinc oxide nanostructures were prepared by microwave-irradiation technique in the presence of polyvinyl pyrrolidone as a shape modifier. The synthesized nanostructures were analyzed using scanning and transmission electron microscopy, selected-area electron diffraction, X-ray diffraction, and Fourier transform infrared spectroscopy (FT-IR). Characterization techniques revealed the formation of crystalline ZnO with a star-like shaped morphology, having the crystal structure of wurtzite. The microwave irradiated samples were further investigated to exploit their electrical and sensing properties. The good sensitivity and relatively short response and recovery times of chemoresistive sensors based on star-like ZnO thick films in the monitoring of low concentration of ammonia gas in air were related to the peculiar nanostructure of the sensing layer. [ABSTRACT FROM AUTHOR]

Abstract: A simple wet chemical process assisted by microwave has been investigated for the synthesis of ZnO nanostructures for sensing applications. Characterization results have shown that microwave irradiation is able to quickly convert the reaction product zinc hydroxide into single phase crystalline ZnO. Different ZnO nanostructures (spherical-, flower- and star-like) have been prepared by adapting the experimental conditions. These ZnO nanostructures have been tested for CO gas monitoring by depositing them as thick films on an interdigitated alumina substrate and evaluating the surface resistance of the deposited layer as a function of operating temperature and CO concentrations. The gas sensitivity tests have demonstrated that the ZnO nanostructures, especially flower-like morphology, exhibit high sensitivity to CO proving their applicability in gas sensors. The role of the nanostructure on the sensing properties of ZnO is also discussed. [Copyright &y& Elsevier]

Abstract: A microwave-assisted solution-phase approach has been applied for the synthesis of zinc oxide nanostructures. The synthesis procedure was carried out by using two reagents: hydrazine hydrate and ammonia. Flower shaped particles were obtained with hydrazine hydrate whereas mainly spherical agglomerated particles were observed with ammonia. The nanostructures were influenced by microwave irradiation time, reagent concentration and molar ratio of the precursors. High crystalline materials were found without the need of a post-synthesis treatment. The average crystalline size of ZnO nanostructures has been analyzed by X-ray Diffraction (XRD) pattern and estimated to be 18 nm. The presence of flower shaped zinc oxide with nanorods arranged has been confirmed from Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) micrographs. The samples were further analyzed by Fourier Transform InfraRed (FT-IR), Thermogravimetric Analysis (TGA) and photoluminescence spectroscopic techniques. [Copyright &y& Elsevier]

Abstract: Microwave technique was adopted for preparation of tin dioxide nanoparticles with particles size ranging from 10 to 11 nm within 10 min. The formation of monocrystalline SnO2 nanoparticles was confirmed by the XRD (X-Ray Diffraction) and TEM (Transmission Electron Microscopy) as well as with SAED (Selected Area Electron Diffraction) analysis. The structure of the SnO2 crystal was found to be Cassiterite type tetragonal structure. The FT-IR results further supported the formation of tin dioxide from tin hydroxyl group without any post annealing. The samples were further characterized by thermo gravimetric analysis (TGA), electrical resistance measurements and photoluminescence spectrum. [Copyright &y& Elsevier]

Tungsten oxide (WO x ) nanoparticles were synthesized by a facile and eco-friendly microwave-assisted hydrothermal method without need for using any surfactant. A thorough investigation was performed in order to elucidate the effects of microwave irradiation time (10, 20 and 30 min) on the structural, morphological and optical properties of the as-prepared WO x . Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) of the samples revealed the presence of irregular nanosized particles containing some well-structured rod shape particles. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that these nanoparticles are crystallines with mean crystalline size of about 16 nm exhibiting both monoclinic and orthorhombic WO x crystal structures. The optical properties were investigated by using ultraviolet visible spectroscopy (UV-VIS) and photoluminescence (PL). A blue-shifted optical absorption spectrum with an enhanced defects emission was observed when it was compared to bulk spectrum of WO 3 . Thermal-aged WO x nanoparticles at mild temperature (350 °C) were also used to fabricate conductometric gas sensors Gas sensing tests showed excellent performance towards ethanol monitoring for each synthesized material. In particular, the highest sensitivity was obtained for the sensor based on WO x synthesized by 10 min irradiation time (S10). At the optimal operating temperature of 300 °C, the S10 sensor showed a response R a /R g  = 8.5 towards 100 ppm ethanol with fast response time of 10 s, in addition to an excellent selectivity against common interfering gases. [ABSTRACT FROM AUTHOR]

Abstract: Cadmium oxide nanostructures were prepared with simple and cost-effective chemical route assisted by microwave irradiation. The synthesized samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Selected Area Electron Diffraction (SAED), Energy Dispersive X-ray (EDX) analysis and Fourier Transform Infrared spectroscopy (FT-IR) techniques. Highly crystalline CdO nanostructures with different morphology (spherical and rod-like) have been obtained by the microwave-assisted procedure adopted without any post-synthesis annealing treatment. Furthermore, the formation of these CdO nanostructures can be easily addressed within short times (5–15min) by a fine tuning of the microwave irradiation. The CdO nanostructures have been investigated as sensing layer in resistive sensors and tested for NO2 sensing at mild temperature. The sensors have shown high response to NO2 down to 0.5ppm at low operating temperature of 100°C and high selectivity against CO. [Copyright &y& Elsevier]

Abstract: A microwave-assisted combustion route for the preparation of cadmium oxide (CdO) nanowire is carried and its characterization results are discussed. This method resembles a supportive way in the formation of CdO nanowire which is confirmed with the structure and morphological analysis carried for the prepared sample. Microwave combustion method is a cost effective and less time consumption to achieve CdO nanowires. The controlled shapes and size are attained due to microwave irradiation. Yielded sample is investigated with Fourier transformation infra-red (FTIR) spectra, X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDX) spectra and transmission electron microscopy (TEM) with SAED pattern. The formation of CdO phase with a face centered cubic structure is confirmed from XRD spectra and the presence of Cdc bond is also confirmed with FTIR spectra. The formation of CdO nanowires is visualized through the TEM images and presence of elements is also recorded from EDX spectra. [Copyright &y& Elsevier]