Synthesis of TiO₂:Ce nanoparticles for development of ammonia gas sensors

A less time consuming and cost ineffective sol–gel method was used to synthesis TiO₂ nanoparticles and TiO₂:Ce nanoparticles. All the samples were characterized by XRD, UV–Vis, FTIR, PL, SEM, TEM and Raman analysis. The thermal properties were studied by TG/DTA analysis. XRD analysis confirms the formation of anatase TiO₂ phase with a preferred orientation along (101) direction and that the lattice constants increased with increasing the Ce doping level. The UV–Vis reflectance spectra showed that cerium doping shift in the reflectance spectra to the visible region and increase the bandgap. The TEM images indicate the particle sizes in the range between 10 and 15 nm for anatase phase TiO₂ at 400 °C. Raman spectroscopy was used to identify and quantity the amorphous and crystalline TiO₂ phases. All the Ce-doped TiO₂ samples showed higher PL intensity than undoped TiO₂. The visible emission peaks of pure and Ce-doped TiO₂ nanoparticles are mainly associated with oxygen vacancies. The impedance spectrum also exhibited a decreased semicircle radius with the exposure ammonia gas increase from 50 to 250 ppm thereafter slightly increased. Impedance spectroscopy analysis showed that the resistance variation due to grain boundaries significantly contributed to the gas sensor characteristics.