Structural, morphological and optical properties of tin oxide nanoparticles synthesized by sol–gel method adding hydrochloric acid

Tin oxide (SnO2) nanoparticles were synthesized by sol–gel method from cost-effective tin chloride (SnCl2·2H2O) and ethanol by adding ammonia solution. In a separate experiment, 4 ml of concentrated hydrochloric acid was added to this solution and SnO2 nanoparticles were prepared. Further SnO2 nanoparticles prepared without and with adding the hydrochloric acid were annealed at 200 °C for 1 h. The structural, morphological and optical properties of the synthesized SnO2 nanoparticles were studied by X-ray diffraction, scanning electron microscope, UV–Vis spectroscopy, Fourier transform infrared spectroscopy and fluorescence spectroscopy techniques. As prepared SnO2 nanoparticles by adding hydrochloric acid in the synthesis process reduced the crystallite size to ~4 from ~10 nm size of the annealed SnO2 nanoparticles prepared without adding hydrochloric acid. Annealing the SnO2 nanoparticles prepared adding hydrochloric acid improved the crystallite size from ~4 to ~4.5 nm. Addition of hydrochloric acid effectively modified the morphology of the SnO2 nanoparticles from agglomerated spherical structure to cauliflower-like structure. The band gap is increased due to decrease in the crystallite size in the sample prepared adding hydrochloric acid. Fluorescence spectrum exhibits a strong emission peak at 350 nm. Addition of HCl plays a major role to suppress the hydrolysis rate and leads to the formation of SnO2 nanoparticles.