Anita Hastir

Deposition, characterization and gas sensors application of RF magnetron-sputtered terbium-doped ZnO films

Influence of terbium (Tb) doping on structural, optical and morphological properties of radio frequency magnetron-sputtered ZnO films has been investigated using various characterization techniques. Investigations revealed the formation of hexagonal wurtzite structure of ZnO with preferential c-axis orientation, presence of oxygen vacancies, modification of surface morphology and surface roughness, and confirmation of oxidation states of elements present in ZnO and Tb-doped ZnO films. Subsequently, films deposited with varied Tb concentrations have been tested for ethanol vapor sensing. Doped films exhibited reduction in optimum operable temperature, enhancement in ethanol sensing response and improvement in response/recovery time in comparison with pristine ZnO. The observed improvement in doped samples has been attributed to modifications in surface properties such as morphology, surface roughness, basicity, structural disorder and oxygen vacancies introduced due to dopant incorporation.

Gas sensing behaviour of Cr2O3 and W6+: Cr2O3 nanoparticles towards acetone

This paper reports the acetone gas sensing properties of Cr2O3 and 2% W6+ doped Cr2O3 nanoparticles. The simple cost-effective hydrolysis assisted co-precipitation method was adopted. Synthesized samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. XRD revealed that synthesized nanoparticles have corundum structure. The lattice parameters have been calculated by Rietveld refinement; and strain and crystallite size have been calculated by using the Williamson-Hall plots. For acetone gas sensing properties, the nanoparticles were applied as thick film onto alumina substrate and tested at different operating temperatures. The results showed that the optimum operating temperature of both the gas sensors is 250°C. At optimum operating temperature, the response of Cr2O3 and 2% W6+ doped Cr2O3 gas sensor towards 100 ppm acetone was found to be 25.5 and 35.6 respectively. The investigations revealed that the addition of W6+ as a dopant enhanced ...

Optical studies of reduced graphene oxide thin films

We report here a simple and efficient method for fabrication of reduced graphene oxide (rGO) thin films. Graphite oxide can be completely exfoliated to produce aqueous colloidal suspensions of graphene oxide (GO) sheets by simple ultra-sonication. Graphene oxide thin films were reduced towards graphene by exposure to hydrazine vapor, ammonia vapor and microwaves. The samples were characterized using X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis).

Hydrogen adsorption properties based on holey graphene sheets

In the present work, holey reduced graphene oxide (rGO) sheets have been synthesized by using hydrothermal method. The structural characteristics of synthesized graphene sheets were analyzed by using X-ray diffraction (XRD), Raman microscopy and transmission electron microscopy (TEM). Textural properties of holey sheets were investigated using N2 adsorption /desorption isotherm at 77 K and 1 bar. Further, hydrogen adsorption properties of graphene sheets were studied and it has been found that holey graphene sheets exhibit a noticeable hydrogen uptake of 0.5 wt % at low pressure (0 −1 bar) and 77 K. This hydrogen uptake of holey graphene sheets have been attributed to their high specific surface area, formation of surface nano holes and hole-edge functionalities.In the present work, holey reduced graphene oxide (rGO) sheets have been synthesized by using hydrothermal method. The structural characteristics of synthesized graphene sheets were analyzed by using X-ray diffraction (XRD), Raman microscopy and transmission electron microscopy (TEM). Textural properties of holey sheets were investigated using N2 adsorption /desorption isotherm at 77 K and 1 bar. Further, hydrogen adsorption properties of graphene sheets were studied and it has been found that holey graphene sheets exhibit a noticeable hydrogen uptake of 0.5 wt % at low pressure (0 −1 bar) and 77 K. This hydrogen uptake of holey graphene sheets have been attributed to their high specific surface area, formation of surface nano holes and hole-edge functionalities.

Influence of Dy doping on structural, morphological and gas sensing properties of ZnO

Effect of dysprosium (Dy) as a dopant on structural, morphological and gas sensing properties of zinc oxide has been studied in the present work. A chemical route was adopted for synthesis of pure and Dy doped zinc oxide. Synthesized samples were characterized using X-ray diffraction, field emission scanning electron microscope, Branneur Emmet Teller and X-ray photoelectron spectroscopy. XRD studies confirmed the hexagonal wurtzite structure of pure and doped samples and the lattice constants and unit cell volume were calculated using Rietveld refinement. Gas sensors were fabricated from synthesized samples and it has been found that Dy doping has significantly improved sensor response towards ethanol. In addition, reduction in optimum operating temperature has been achieved from 400 to 300°C because of doping. The improved sensor properties in doped sensor have been attributed to reduction in particle size, increase in surface area and high surface basicity.

Hydrogen sensor based on Sm-doped SnO2 nanostructures

In this paper the effect of samarium doping on the structural and hydrogen gas sensing properties of SnO2 nanoparticles has been reported. X-ray Diffraction (XRD) results revealed tetragonal rutile structure of both undoped and Sm-doped SnO2 nanoparticles. It has been observed that doping with samarium led to reduction in crystallite size of SnO2 nanoparticles which was confirmed from XRD analysis. Shifting and broadening of Raman peaks in case of doped nanoparticles has been explained by well-known phonon confinement model. The optimum operable temperature of both the sensors was found to 400 °C and the sensor response towards hydrogen gas has been improved after doping with samarium which was attributed to increase in sensing sites for the gas adsorption.

Photoluminescence study of ZnS and ZnS:Pb nanoparticles

Photoluminescence (PL) study of pure and 5wt. % lead doped ZnS prepared by co-precipitation method was conducted at room temperature. The prepared nanoparticles were characterized by X-ray Diffraction (XRD), UV-Visible (UV-Vis) spectrophotometer, Photoluminescence (PL) and Raman spectroscopy. XRD patterns confirm cubic structure of ZnS and PbS in doped sample. The band gap energy value increased in case of Pb doped ZnS nanoparticles. The PL spectrum of pure ZnS was de-convoluted into two peaks centered at 399nm and 441nm which were attributed to defect states of ZnS. In doped sample, a shoulder peak at 389nm and a broad peak centered at 505nm were observed. This broad green emission peak originated due to Pb activated ZnS states.

Improvement in LPG sensing response by surface activation of ZnO thick films with Cr2O3

Liquefied Petroleum Gas (LPG) sensing response of pure and Cr2O3 activated ZnO has been investigated in this study. Zinc oxide was synthesized by co-precipitation route and deposited as a thick film on an alumina substrate. The surface of ZnO sensor was activated by chromium oxide on surface oxidation by chromium chloride. The concentration of chromium chloride solution used to activate the ZnO sensor surface has been varied from 0 to 5 %. It is observed that response to LPG has improved as compared to pure ZnO.

Reduced graphene oxide/CeO2 nanocomposite with enhanced photocatalytic performance

In this work, reduced graphene oxide /cerium oxide (RGO/CeO2) nanocomposite was synthesized by in situ reduction of cerium nitrate Ce(NO3)3·6H2O in the presence of graphene oxide by hydrazine hydrate (N2H4.H2O). The intrinsic characteristics of as-prepared nanocomposite were studied using powder x-ray diffraction (XRD), Raman spectroscopy and field-emission scanning electron microscopy (FESEM). The photocatalytic degradation of methylene blue (MB) was employed as a model reaction to evaluate the photocatalytic activity of the RGO/CeO2 nanocomposite. The as-obtained RGO/CeO2 nanocomposite displays a significantly enhanced photocatalytic degradation of MB dye in comparison with bare CeO2 nanoparticles under sunlight irradiation, which can be attributed to the improved separation of electron-hole pairs and enhanced adsorption performance due to presence of RGO.

Acetone sensor based on zinc oxide hexagonal tubes

In this work hexagonal tubes of zinc oxide have been synthesized by co-precipitation method. For structural, morphological, elemental and optical analysis synthesized powders were characterized by using x-ray diffraction, field emission scanning microscope, EDX, UV-visible and FTIR techniques. For acetone sensing thick films of zinc oxide have been deposited on alumina substrate. The fabricated sensors exhibited maximum sensing response towards acetone vapour at an optimum operating temperature of 400°C.