Carbothermal Evaporation Method Research Articles

Effects of persistence time and Au catalyst on the morphology and optical properties of ZnO micro/nanostructures

Zinc oxide (ZnO) micro and nanostructures were synthesised on a quartz substrate by the carbothermal evaporation method. The thin layers of gold were used as a catalyst and syntheses were carried out at different persistence time. Characterisation of the layer was conducted in order to study the effect of persistence time on morphology and crystal structure and optical properties of the fabricated ZnO nanostructures. The samples were characterised by scanning electron microscopy, X-ray diffraction (XRD) and UV–vis spectrophotometry which were performed to investigate the optical properties of the fabricated ZnO layer. The XRD spectrum clearly shows that the structure is in a hexagonal wurtzite phase. Optical properties of ZnO micro and nanostructures were evaluated from transmittance data using the method proposed by Swanepoel (in the regions λ = 200–900 nm). The study’s results indicate that increasing the persistence time as well as decreasing the size of ZnO nanostructures enhances the optical bandgap to about 3.‏46 eV. To the best of this work's knowledge, this is the first report on the study of the correlation of optical properties obtained by Swanepoel method and morphology of ZnO nanostructures.

Effects of swift heavy ion irradiation on structural, optical and photocatalytic properties of ZnO-CuO nanocomposites prepared by carbothermal evaporation method.

ZnO–CuO nanocomposite thin films were prepared by carbothermal evaporation of ZnO and Cu, combined with annealing. The effects of 90 MeV Ni7+ ion irradiation on the structural and optical properties of ZnO–CuO nanocomposites were studied by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–visible absorption spectroscopy and Raman spectroscopy. XRD studies showed the presence of ZnO and CuO nanostructures in the nanocomposites. FESEM images revealed the presence of nanosheets and nanorods in the nanocomposites. The photocatalytic activity of ZnO–CuO nanocomposites was evaluated on the basis of degradation of methylene blue (MB) and methyl orange (MO) dyes under sun light irradiation and it was observed that swift heavy ion irradiation results in significant enhancement in the photocatalytic efficiency of ZnO–CuO nanocomposites towards degradation of MB and MO dyes. The possible mechanism for the enhanced photocatalytic activity of ZnO–CuO nanocomposites is proposed. We attribute the observed enhanced photocatalytic activity of ZnO–CuO nanocomposites to the combined effects of improved sun light utilization and suppression of the recombination of photogenerated charge carriers in ZnO–CuO nanocomposites.

MeV ion irradiation induced evolution of morphological, structural and optical properties of nanostructured SnO2 thin films

Nanostructured SnO2 thin films were prepared by carbothermal evaporation method. Morphological, structural and optical properties of the SnO2 thin films, before and after 8 MeV Si ion irradiation to fluences varying from 1 × 1013 to 1 × 1015 ions cm−2, were well characterized using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), Raman spectroscopy and photoluminescence spectroscopy (PL). XRD studies revealed the presence of SnO2 and Sn nanoparticles in the as-deposited samples. AFM and FESEM studies on the irradiated samples revealed formation of nanoring-like structures, at a fluence of 1 × 1015 ions cm−2, with a central hole and circular rim consisting of nearly monodisperse SnO2 nanoparticles. PL studies revealed strong enhancement in UV emissions upon 8 MeV Si ion irradiation. A growth mechanism underlying the formation of SnO2 nanorings involving self-assembly of SnO2 nanoparticles around nanoholes is tentatively proposed.

Fabrication of Microfibre-Nanowire Junction Arrays of ZnO/SnO2 Composite by the Carbothermal Evaporation Method

A cotton-like ZnO/SnO2 nanocomposite was grown by the carbothermal evaporation of a mixture of ZnO and SnO2 powders at 1100°C by the vapour-liquid-solid process, in which the Sn particles produced by the reduction of SnO2 act as the catalyst. Field-emission scanning electron microscope images suggest that the composites are made of microfibre-nanowire junction arrays. The structure is formed due to the fast growth of the ZnO microfibre and the subsequent epitaxial radial growth of the ZnO nanowires with Sn particles at the tips. The photovoltaic performance of the ZnO/SnO2 nanocomposite sensitized with a D35-cpdt dye was investigated. A dye-sensitized solar cell (DSSC) with a ZnO/SnO2 nanocomposite photoanode based on a cobalt electrolyte achieved a solar-to-electricity conversion efficiency of ~0.34% with a short circuit current (JSC) of 0.66 mA/cm2, an open circuit voltage (VOC) of 870 mV, and a fill factor (FF) of 59. The results show the potential of this one dimensional structure in cobalt electrolyte-based DSSCs; the further optimization which is needed to achieve higher efficiencies is also discussed.

The correlation between the substrate temperature and morphological ZnO nanostructures for H2S gas sensors

In this work, different ZnO nanostructures are prepared by carbothermal evaporation method on quartz substrates at various deposition temperatures. The mixture powders ZnO/C with 1:1 ratio as a source of materials inserted in the center of furnace tube. The effect of temperature, by keeping constant other parameters, on growth and morphological surface are investigated which is an important parameter for gas sensing. The crystalline structure of Zn is verified by X-ray diffraction and the surface morphology is analyzed by scanning electron microscopy. The results showed that the sensitivity of sensor synthesized at temperature of 500°C and operated at 300°C for 20ppm H2S gas, is 80% with 35s and 390s for recovery and response time, respectively.

Influence of Sb in synthesize of ZnO nanowire using sandwich type substrate in carbothermal evaporation method

The paper deals with synthesis of Sb doped ZnO nanowire by considering Si coated with Sb and Au as substrate using carbothermal evaporation method. The horizontally oriented Sb doped ZnO nanowires with a diameter of 1μm synthesized at 900°C, which is quite high as compared to the Pure ZnO nanowires generated without the influence of Sb at 900°C. The nanowire synthesized at 900°C showed a measurable lower angle of about 0.06° from XRD and suppression of A1T and E1(L0) modes in Raman spectroscopic, this confirms the incorporation of Sb in ZnO lattice. The strong exciton emission and weak deep-level emission from room temperature PL and Strong emission attributed to the radiant recombination from neutral–acceptor–bound exciton (A0X) peak accompanied by two strong and broad emission of donor acceptor pair (DAP) from low temperature PL, this confirms the use of Sb as an acceptor for ZnO.

Stimulated Optical Emission from ZnO Nanobelts Grown with a Simple Carbothermal Evaporation Method

This work reports on the stimulated optical emission characteristics of ZnO nanobelts that were grown with a simple carbothermal evaporation method without using any catalyst or dopant. Such nanobelts grew along the a-axis enclosed by {0001} and {01−10} base planes through a vapor-solid mechanism. Room temperature and temperature-dependent photoluminescence results indicated that such nanobelts were of high optical qualityand were better than those nanobelts grown from dopant-assisted thermal evaporation or oxidation methods. Amplified spontaneous emission was observed from ZnO nanobelts with low-growth density while random laser was observed for high-density samples with increasing optical pumping density.

Effect of catalyst layer on morphology and optical properties of zinc-oxide nanostructures fabricated by carbothermal evaporation method

Zinc-oxide nanostructures were synthesised by carbothermal evaporation of ZnO+C at elevated temperatures. Substrates were silicon wafers, and different materials such as SiO2, Al2O3, Au and silica-gel were used as the catalyst layer. Characterisation of morphology by scanning electron microscopy showed that the catalyst layer has a major role in controlling of geometrical shape and dimensions of the resultant nanostructures. The long and narrow nanowires with a regular cross-section were formed on the substrate coated by Au particles. On the substrate coated by silica-gel, the authors achieved the capillary microtubes with the hexagonal cross-section, nanometre-thick walls and also radial sheets inside them. Such nanostructures are believed to be reported for the first time. The electro-optical specifications of the samples were investigated by measurement of their optical absorption spectra using ultraviolet/visible (UV/VIS) spectrophotometry. Determination of the optical band gap from Tauc's plot showed that, in contrary to different shapes, the samples have identical band gap energy. This phenomenon revealed that the optical behaviour of the nanostructures grown by the proposed method does not depend to their morphology.

The influence of substrate location and deposition time on ZnO nanostructures

A study on the formation of ZnO nanostructures using the carbothermal evaporation method without catalyst and at atmospheric argon pressure has been conducted. The effects of the position of the substrates to the source and deposition time were investigated. The results of these parametric studies based on field-emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX) spectrum and X-ray diffraction (XRD) analyses support the reduction-evaporation model for ZnO nanostructures formation using carbothermal evaporation.

Glucose Oxidase-Coated ZnO Nanowires for Glucose Sensor Applications

)Abstract Well-aligned Zinc oxide (ZnO) nanowires were synthesized on silicon substrates by a carbothermalevaporation method using a mixture of ZnO and graphite powder with Au thin film was used as a catalyst.The XRD results showed that as-prepared product is the hexagonal wurzite ZnO nanostructure and SEMimages demonstrated that ZnO nanowires had been grown along the [0001] direction with hexagonal crosssection. As-grown ZnO nanowires were coated with glucose oxidase (GOx) for glucose sensing. Glucoseconverted into gluconic acid by reaction with GOx and two electrons are generated. They transfer into ZnOnanowires due to the electric force between electrons and the positively charged ZnO nanostructures in PBS.Photoluminescence (PL) spectroscopy was employed for investigating the movements of electrons, and the peakPL intensity increased with the glucose concentration and became saturated when the glucose concentrationis above 10 mM. These results demonstrate that ZnO nanostructures have potential applications in biosensors.Keywords ZnO nanowires, glucose sensor, glucose oxidase (GOx), photoluminescense (PL)

Oxide-assisted growth of silicon nanowires by carbothermal evaporation

Silicon nanowires (SiNWs) have successfully been synthesized by carbothermal evaporation method. By ramping-up the furnace system at 20 °C min −1 to 1100 °C for 6 h, the vertically aligned coexist with crooked SiNWs were achieved on the silicon substrate located at 12 cm from source material. The processing parameters such as temperature, heating rate, duration, substrate position and location are very important to produce SiNWs. Morphology and chemical composition of deposited products were investigated by field-emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray analysis (EDX). The existence of small sphere silicon oxide capped nanowires suggested that the formation of SiNWs was governed by oxide-assisted growth (OAG) mechanism.