Cr-induced modifications in the structural, photoluminescence and acetone-sensing behaviour of hydrothermally synthesised SnO₂nanoparticles

Cr-doped SnO2 nanoparticles have been synthesised by the hydrothermal route, using SnCl4·5H2O as the host precursor and C15H21CrO6 as the source of dopant. The structural and morphological studies have been carried out by X-ray diffraction, transmission electron microscopy and scanning electron spectroscopy, which reveal a tetragonal rutile structure of SnO2 nanoparticles and improvement in the crystallinity upon Cr doping. Compositional analyses by energy-dispersive X-ray confirm the incorporation of Cr ions into the SnO2 lattice. The existence of defect levels in the visible region has been studied by photoluminescence. The room-temperature electrical conductivity decreases with Cr doping due to the replacement of Sn4+ ions by Cr3+ ions. The response to acetone has been found to improve with the increase of Cr-doping concentration relative to the undoped SnO2, except in the case of 0.5 at% Cr-doped sample where it decreases at low concentrations (up to 30 ppm) and operating temperatures (up to 200 °C). The response time decreases with the increasing Cr-doping concentration and is found to be minimum for the 1.5 at% Cr-doped SnO2. A possible reaction mechanism of acetone sensing has been explained.