Cr-induced modifications in the structural,photoluminescence and acetone-sensing behaviour of hydrothermally synthesised SnO2 nanoparticles

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.