Microstructure-Modulated Antibacterial Performance of Chemically Precipitated SnO2 Nanoparticles

Tin oxide (SnO 2 ) nanoparticles were synthesized via a facile chemical precipitation route using tin chloride (SnCl 2 •2H 2 O) as precursor and ammonia as precipitant. The as-synthesized nanoparticles were subjected to post-calcination at 300°C, 400°C and 500°C and thoroughly characterized by advanced techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy. XRD patterns revealed the formation of tetragonal SnO 2 crystalline phase with average crystallite sizes of 11.9 nm, 13.9 nm and 17.2 nm for the samples calcined at 300°C, 400°C and 500°C respectively. SEM micrographs demonstrated agglomerated and irregular morphology of the calcined SnO 2 nanoparticles. FTIR spectra confirmed the presence of characteristic Sn-O and O-Sn-O vibrational modes in the calcined SnO 2 samples. The antibacterial activity of the synthesized nanoparticles was evaluated against model Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial strains by standard zone of inhibition assays. Remarkably, the SnO 2 nanoparticles exhibited excellent antibacterial activity due to their high specific surface area. A systematic increase in the inhibition zone diameter was observed with decrease in crystallite size of SnO 2 for both bacterial strains, suggesting an inverse relationship between crystallite size and antibacterial behavior. The present work demonstrates a simple, eco-friendly synthesis of antibacterial SnO 2 nanoparticles with controlled crystallite size by tuning the calcination temperature.