Visible light photoinactivation of bacteria by tungsten oxide nanostructures formed on a tungsten foil

Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 degrees C and 400-800 degrees C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 degrees C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50-90 nm and crystalline phase of WO3) on surface of tungsten foils. By increasing the annealing temperature up to 800 degrees C, tungsten oxide microrods with K2W6O19 crystalline phase were formed on the foils. The WO3 nanorods showed a strong antibacterial property under visible light irradiation, corresponding to >92% bacterial inactivation within 24 h irradiation at room temperature, while the K2W6O19 microrods formed at 800 degrees C could inactivate only 45% of the bacteria at the same conditions. (C) 2015 Elsevier B.V. All rights reserved.