Structure and antibacterial property of nano-SiO_2 supported oxide ceramic

摘要

SiO_2 doped samples with different cobalt loading and pure SiO_2 and Co_3O_4 nanopowders were synthesized by the solvothermal method and their antibacterial activities were studied. The morphology and crystallinity of the powders were analyzed by scanning electron microscopy and X-ray diffractometry patterns, respectively. The increase of particle size with doping concentration was obtained for cobalt-doped samples. The optical properties were studied using UV-vis spectroscopy. Optical studies showed a blue shift in the absorbance spectrum with increasing the doping concentration. The antibacterial activities of undoped SiO_2, Co-doped SiO_2 and pure Co_3O_4 nanoparticles against a Gram-negative bacterium Escherichia coli (E. coli, ATCC 25922) and a Gram-positive bacterium Staphylococcus aureus (S. aureus, ATCC 29213) were investigated under UV illumination and in the dark condition. Bactericidal effects were determined by the minimum inhibitory concentration (MIC) method. There was no activity for pure SiO_2 and Co_3O_4, however, cobalt doping significantly improved antibacterial activity against both bacteria. Bacterial growth inhibition was observed under dark condition with lower efficiency than under UV illumination. The antibacterial efficiencies were affected by the physiological status of the bacterial cells, different morphologies, particle sizes and optical properties of samples.