Growth of thermally evaporated SnO2 nanostructures for optical and humidity sensing application

Nanoscaled spherical, facetted-spherical and octahedral shapes of high yield and economically viable tin oxide (SnO2) was synthesized using direct sublimation process employing thermal evaporation at 1350 °C without any catalyst. The crystalline structure and morphology of SnO2 nanostructures were characterized using X-ray diffraction and electron microscopy. The morphology reveals that the reaction time, that is evaporation time, is important for successful synthesis of different shape and size of SnO2 nanostructures. High resolution transmission electron microscopy exhibited the particle size of SnO2 between 5 and 6 nm. Nanoscale morphological tuning in size and shape facilitates alteration in optical band gap, absorption and photolumiscence properties. The humidity sensor based on spherical SnO2 nanostructures demonstrates an excellent sensitivity with an increase in relative humidity (RH) at room temperature.