Highly synergistic antimicrobial activity of spherical and flower-like hierarchical titanium dioxide/silver composites

A spherical titanium dioxide/silver (TiO2/Ag) composite and a flower-like hierarchical TiO2/Ag composite were prepared via a template-induced method and a solvothermal method based on the Ag/Carbon spheres templates followed by calcination treatment, respectively. The morphologies of the composites were controlled by changing the concentration of reactants and calcination temperature. The antibacterial efficiency of the composites was evaluated with both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, respectively. The minimal inhibitory concentration, morphological evolution of bacteria and fluorescent-based cell wall/membrane integrity were assayed. The synergistic effects of reactive oxygen species (ROS) and silver ions were observed, which lead to superior antibacterial activities of these TiO2/Ag composites with a bacteriostatic rate as high as 99% even in the absence of light. The morphological effect of the composites on the antibacterial efficacy was also investigated. In addition, a durable antimicrobial coating was also fabricated by incorporating the hierarchical TiO2/Ag composite into a commercial emulsion solution of polyvinyl acetate, which exhibited a promising application in bacterial sensitive locations.