Vithoba L. Patil

Ultrasensitive Gold Nanostar–Polyaniline Composite for Ammonia Gas Sensing

Gold in the form of bulk metal mostly does not react with gases or liquids at room temperature. On the other hand, nanoparticles of gold are very reactive and useful as catalysts. The reactivity of nanoparticles depends on the size and the morphology of the nanoparticles. Gold nanostars containing copper have rough surfaces and large numbers of active sites due to tips, sides, corners, and large surface area-to-volume ratios due to their branched morphology. Here the sensitivity of the gold nanostar-polyaniline composite (average size of nanostars ∼170 nm) toward ammonia gas has been investigated. For 100 ppm ammonia, the sensitivity of the composite increased to 52% from a mere 7% value for pure polyaniline. The gold nanostar-polyaniline composite even showed a response time as short as 15 s at room temperature. The gold nanostars act as a catalyst in the nanocomposite. The stability and sensitivity at different concentrations and the selectivity for ammonia gas were also investigated.

Rapid synthesis of CdS nanowire mesh via a simplistic wet chemical route and its NO2 gas sensing properties

In this report, 1-D interconnected CdS nanowires were prepared rapidly via a wet chemical route at relatively low temperature, using cadmium sulphate, thiourea and ammonia as raw materials. The formation of a CdS nanowire mesh (CdS NW mesh) and its structural, optical, surface morphological properties and elemental composition were studied by various characterization techniques. The cubic crystal structure of the CdS interconnected nanowire mesh was confirmed via X-ray diffraction and field emission scanning electron microscopy analysis. The photoluminescence spectroscopy measurements reveal the presence of defects in the as synthesized CdS NW mesh. However, the defect states are beneficial for the gas sensing behavior. Therefore, the gas sensing properties of the CdS NW mesh were studied using NO2 as an analyte gas at moderate operating temperature. The nanowire mesh and inter-wire space were observed to play a crucial role in determining the gas sensing performance of the devices. The as synthesized CdS NW mesh shows a gas response of about 1850% to 100 ppm NO2 gas. In particular, our CdS based gas sensor showed a fifty fold better gas response towards NO2 gas than the earlier reports in the literature. Due to the high value of gas sensitivity, the reported CdS NW mesh could be a suitable candidate for NO2 sensing.

Chemically synthesized PbS Nano particulate thin films for a rapid NO2 gas sensor

Abstract Rapid NO2 gas sensor has been developed based on PbS nanoparticulate thin films synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method at different precursor concentrations. The structural and morphological properties were investigated by means of X-ray diffraction and field emission scanning electron microscope. NO2 gas sensing properties of PbS thin films deposited at different concentrations were tested. PbS film with 0.25 M precursor concentration showed the highest sensitivity. In order to optimize the operating temperature, the sensitivity of the sensor to 50 ppm NO2 gas was measured at different operating temperatures, from 50 to 200 °C. The gas sensitivity increased with an increase in operating temperature and achieved the maximum value at 150 °C, followed by a decrease in sensitivity with further increase of the operating temperature. The sensitivity was about 35 % for 50 ppm NO2 at 150 °C with rapid response time of 6 s. T90 and T10 recovery time was 97 s at this gas concentration.

Gas sensing properties of 3D mesoporous nanostructured ZnO thin films

Advancing the properties of selective and sensitive metal oxide based gas sensors is a challenging research topic for the detection of toxic, and pollutant gases. In the present research, we successfully deposited a three dimensional (3D) mesoporous ZnO nanostructure on a glass substrate by using a hydrothermal method, and tested the material for its gas sensing performance. These 3D mesoporous ZnO nanostructures were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and photoluminescence techniques. Gas sensing performance analysis was carried out for nitrogen dioxide (NO2) gas at different temperatures and concentrations. The 3D mesoporous ZnO nanostructure revealed excellent gas sensing performance for NO2 gas because of its large surface area. The larger surface area led to an increase in the gas sensitivity. In addition, the sensor based on the 3D mesoporous ZnO nanostructure could be used at a low operating temperature of 150 °C. This work suggests that the 3D mesoporous ZnO nanostructure is a versatile material for NO2 gas sensing applications.

Facile green synthesis of In2O3 bricks and its NO2 gas sensing properties

Recently, metal oxide semiconductor based gas sensors have been used to monitor and maintain amount of toxic gases in environment. Use of In2O3 nano/microstructures have been increased as a heterogeneous catalyst for gas sensing due to its high response, good selectivity, short response and recovery time. In the present work, synthesis of In2O3 bricks was carried by a hydrothermal method using biomolecule as green product. The effect of precursor concentrations of In2O3 thin film was studied in this particular work. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Photoluminescence (PL), scanning electron microscope (SEM), Field emission scanning electron microscope (FE-SEM) and Brunauer–Emmett–Teller (BET) analyses were used for structural, optical, morphological and surface analysis characterizations. The In2O3 thin film displays high sensitivity and selectivity due to its active sites present on sensing layer. The results assures that optimized In2O3 thin films exhibit a high response with very low response and recovery time about 600 for NO2 gas.

Synthesis and characterization of chemically deposited ZnO nanorods for NO 2 gas sensing applications

Zinc oxide (ZnO) nanorod arrays were deposited on to the soda-lime glass substrates by wet chemical route using zinc acetate as precursor. The structural and surface morphological properties of the ZnO nanorod arrays (ZNAs) were investigated by X-ray diffraction (XRD), and scanning electron microscopy (SEM) respectively. The XRD pattern revealed wurtzite crystal structures of ZNAs, preferentially orienting in the (002) direction. Depending on the length of nanorod, the intensity of the (002) plane was found to be varied. SEM micrographs show the vertical alignment of ZNAs perpendicular to the substrate and increase in rod length with increase in deposition time. The Gas sensing device was prepared by using ZNAs and tested for NO2 gas at different temperatures, concentrations and size of nanorods. Response increased with gas concentration as well as temperature. It was revealed that ZNAs gas sensor operating at 150 0C temperature could detect NO2 at low concentration (100ppm) with very high sensitivity (90 %).