Sumangala Thondiyanoor Pisharam

Bio: Sumangala Thondiyanoor Pisharam is an academic researcher from University of Toulouse. The author has contributed to research in topics: Nanocrystalline material & Adsorption. The author has an hindex of 1, co-authored 1 publications receiving 14 citations.

Ethanol and Hydrogen Gas-Sensing Properties of CuO–CuFe 2 O 4 Nanostructured Thin Films

Abstract: Nanocrystalline CuO–CuFe2O4 composite thin films were developed from CuFeO2 ceramic target using a radio-frequency sputtering method followed by a thermal oxidation process. This fabrication process helps to develop porous sensing layers which are highly desirable for solid-state resistive gas sensors. Their sensing properties toward ethanol and hydrogen gas in dry air were examined at the operating temperatures ranging from 250 °C to 500 °C. The electrical transients during adsorption and desorption of the test gases were fitted with the Langmuir single site gas adsorption model. A composite thin film with a total thickness of 25 nm showed highest response (79%) toward hydrogen (500 ppm) at the operating temperature of 400 °C. The shortest response time ( $\tau _{\mathrm {res}}$ ) was found to be ~60 and ~90 s for hydrogen and ethanol, respectively. The dependence of the response of the sensor on gas concentration (10–500 ppm) was also studied.

Ethanol sensing properties and reduced sensor resistance using porous Nb2O5-TiO2 n-n junction nanofibers

Abstract: One-dimensional (1D) and porous Nb2O5-TiO2 n-n junction nanofibers with different Nb molar ratios have been synthesized by a simple electrospinning approach. A decrease in the average grain size and consequently an increase in the specific surface area were observed due to the introduction of Nb2O5 into TiO2 nanofibers. In comparison with pure TiO2 nanofibers, the Nb2O5-TiO2 nanofibers exhibited improved ethanol sensing response and a reduction in electrical resistance. The optimum operation temperature was reduced from 300 °C for pure TiO2 to 250 °C for Nb2O5-TiO2. The best sensing property was found for Nb2O5-TiO2 with 6 mol% Nb2O5, showing the highest response of 21.64–500 ppm ethanol at 250 °C, which was 2.79 times as high as that of pure TiO2 nanofibers at 300 °C. The reduction of Nb2O5-TiO2 based sensor resistance was attributed to the substitution of Ti4+ by Nb5+ ions and the formation of n-n junctions between Nb2O5 nanoparticles and TiO2 nanoparticles. The enhancement sensing mechanism of Nb2O5-TiO2 nanofibers was mainly ascribed to the enhanced resistance modulation owing to the substitution of Ti4+ by Nb5+ ions, formation of n-n junctions, and high surface area as well as small grain size of Nb2O5-TiO2 nanofibers.