AP1.4 - In2O3 and NiO/In2O3 Hybrid Nanoicicles for Enhanced NO2 Gas Sensing at Room Temperature and High Humidity

17th International Meeting on Chemical Sensors - IMCS 2018
2018-07-15 - 2018-07-19
Vienna, Austria
Applications 1 - Sensing NO2
W. Tseng, O. Lee, C. Chen - Department of Materials Science and Engineering, National Chung Hsing University, Taichung (Taiwan)
163 - 164


Single-crystalline In2O3 nanoicicles have been synthesized via a thermal vapor-transport route. Growth of the In2O3 nanoicicles depends critically on temperature at which oxygen was introduced as well as the indium vapor pressure involved in the synthesis. An aggregated assembly of In2O3 nanorods with pyramids at one end first forms, which then evolves into a tapered needle-like geometry as the isothermal time lengthens. Gas-sensing properties of the nanoicicles have been examined against oxidizing NO2 and reducing H2S gases, respectively, over a range of aspect ratios of the nanoicicles, working temperatures and humidity levels. The In2O3 nanoicicles are then functionalized with NiO nanoparticles. A pronouncedly enhanced sensing response toward NO2 gas has been found for the NiO/In2O3 hybrid nanoicicles at a relatively low working temperature (100° C) and even at room temperature of high relative humidity (80% RH). For the first time, the NiO/In2O3 hybrid nanoicicles present a virtually identical room-temperature sensing response of 1.8 against 3 ppm NO2 over a wide humidity range (4-80% RH); more importantly, the hybrids also show a sensing response of 25 times higher for the oxidizing NO2 gas than for the reducing H2S gas. This is attributable to a) the energyband bending at the p-n heterojunction and b) the augmented effect on electron-depletion width at bridging junctions of neighboring nanoicicles across the sensor electrodes, due exclusively to the narrowing In2O3 diameter toward the tip.