Enhanced bactericidal action of SnO2 nanostructures having different morphologies under visible light: influence of surfactant.

The practical use of visible-light for bactericide treatment has been established by tin oxide nanostructures synthesized using a surfactant-assisted solvothermal method. Anionic (sodium n-dodecyl sulfate, SDS), cationic (cetyltrimethyl ammonium bromide, CTAB) and non-ionic (Tritron X-100) surfactants were used as morphology controlling agents. The as-synthesized nanoparticles are characterized by X-ray powder diffraction (XRD), UV-vis spectroscopy and scanning electron microscopy (SEM). The XRD patterns of the as-synthesized tin oxide nanoparticles were well indexed to the tetragonal rutile structure. Nanostructure tin oxide powders of about 70-92nm in size have been obtained with different morphologies. The spherical, cauliflower, flower petals morphologies of surfactant-mediated SnO2 were obtained using X-100, CTAB, and SDS, respectively and the spherical-like for surfactant-free SnO2 was observed in the SEM micrographs. The surfactant-mediated SnO2 samples showed absorption edges red shift to longer wavelength and increased absorption intensities compared to surfactant-free SnO2. Antibacterial effectiveness of SnO2 samples was tested against general Escherichia coli (E. coli ATCC 25922) under UV-, visible-light and dark conditions. The surfactant promoted antimicrobial effect under visible light by SnO2 band gap modification. In contrast, the surfactant-free SnO2 possessed higher photokilling activity under UV-light. The antibacterial performance of SnO2 samples as a function of their structural and morphological features such as particle size, surface area and visible/UV light absorbing capacity was discussed.