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Ag2Te and Pd doped Ag2Te nanowires are synthesized using chemical route. Field Emission Scanning Electron Microscopy (FESEM) shows the presence of nanowires of nearly few micron length and ~ 200 nm diameter. The composition analysis performed using Electron Dispersive Spectroscopy (EDS) shows the presence of almost 1.98 at% palladium. Reitveld refinement of X-ray diffraction (XRD) shows the presence of 0.3% of PdTe phase in addition to Ag2Te in Pd doped Ag2Te sample. [ABSTRACT FROM AUTHOR]

Pure and Cu doped SnO2 nanowires and nanobelts were grown in a tubular furnace under argon atmosphere at ambient pressure. X-ray diffraction showed that Cu gets incorporated into the SnO2 lattice. Isolated single nanowire sensors have been fabricated for detection of H2S gas at room temperature. Cu doping was found to reduce the sensitivity of these sensors in contrast to results reported for Cu doped SnO2 thin films. Photoluminescence studies indicate that the reduction is sensitivity may be due to reduced defect density. [ABSTRACT FROM AUTHOR]

The gas sensing characteristics of ZnO nanowires (NWs) coated with different thickness of CuO film have been investigated. ZnO NWs were grown on Si/SiO2 by hydrothermal method and CuO films were deposited by thermal evaporation. It has been found that ZnO NWs exhibit characteristic n-type behavior upto a CuO thickness of 50 nm; whereas at higher thickness the samples show p-type behavior (typical of CuO). At a CuO thickness of 10 nm the sensitivity towards H2S was 500% more as compared to pure ZnO NWs films. In addition, the operating temperature was reduced to 200°C. [ABSTRACT FROM AUTHOR]

Hydrothermal growth of ZnO nanowires were performed using ZnO nanoparticles as a seed layer. The growth was found to depend strongly on the reaction duration. These nanowires detected H2S with faster response and recovery time of 13 and 78 s, respectively towards 20 ppm at 350° C. The lowest detection limit was improved to 0.6 ppm upon annealing in O2 flow of 50 sccm. The response time was further improved to just 6 s towards 20 ppm of H2S at 350° C. The enhanced response characteristics have been attributed to the high surface area to volume ratio of nanowires. Photoluminescence (PL) studies showed increase in the green emission related to defect states in ZnO. This is also expected to contribute for the improved sensing characteristics. [ABSTRACT FROM AUTHOR]

Hierarchical heterostructures consisting of W18O49 nanowires grown on CuO nanowires have been prepared and studied for their gas sensing properties. SEM images show that W18O49 initially grow as an shell over core CuO nanowire with protusion like branches whose thickness depends on oxygen partial pressure. These CuO:W18O49 structures were dielectrophoretically isolated and studied for their gas sensing properties. The results show potential of use of tailored hierarchical heterostructures for the fabrication of gas sensors. [ABSTRACT FROM AUTHOR]

Work function of the material is a strong indicator of the state of a surface and its surrounding. Au being an excellent promoter for H2S, work function changes of pure and Au modified ZnO network films upon exposure to gas have been investigated using Kelvin probe method. Au modified ZnO sample exhibited a work function of 5.42 eV which is ∼320 meV higher than that of pure ZnO sample (5.10 eV). This increase could be attributed to the nano-Schottky type of barrier junction formed between Au and ZnO nanowires. Exposure to H2S resulted in decrease of work function for both pure and Au modified ZnO NWs network films. H2S being reducing in nature, this decrease can be accounted on the basis of Fermi level shift due to large number of electrons that the gas donates to the matrix upon interaction with adsorbed oxygen species. [ABSTRACT FROM AUTHOR]

The Kelvin Probe (KP) studies have been carried out on CuO:ZnO nanowires random networks before and after H2S exposure. The results show that on exposure to H2S, the work function of the CuO:ZnO NWs increases by 200 meV. Using conductance and KP data, both the components of work function i.e. band bending and electron affinity has been obtained. It was observed that the affinity values changed substantially with H2S gas exposure. [ABSTRACT FROM AUTHOR]