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

• Surfactant-assisted solvothermally synthesis of SnO2 powders.
• As-synthesized SnO2 samples with different morphologies displayed different optical properties.
• Band gap modification induced visible light bacterial photoinactivation against E. coli.
• All catalysts showed sufficient antibacterial efficiency under dark condition.

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 70–92 nm 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.