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.