Study On Synthesis, Antibacterial Activity And Photocatalytic Properties Of Silver-doped TiO₂ Nanorod Arrays

Titanium dioxide（TiO₂）, as a multifunctional ceramic material, has been widely used in the fields of semiconductor, photocatalytic degradation and self-cleaning coating due to its excellent chemical stability, nontoxicity, lower cost as well as easier synthesis. However, as an antibacterial material, TiO₂ possesses antibacterial activity only under light irradiation; meanwhile, as a photocatalyst, TiO₂ has exhibited the following drawbacks: the wider bandgap, lower utilization of solar spectrum, easier recombining of photo-generated electron and hole pairs, and lower quantum efficiency. Metal surface modifications can improve the photocatalytic performance and antibacterial activity of TiO₂, which has expanded new application of TiO₂. Therefore, in this paper, silver was chosen for doping elements, to synthesize the nanorod arrays on titanium substrate. The microstructures, composition and chemical states of silver-doped TiO₂ nanorod arrays were analyzed by X-ray diffraction（XRD）, scanning electron microscope（SEM）, high resolution transmission electron microscope（HR-TEM） and X-ray photoelectron spectroscopy（XPS）, respectively. In addition, the antibacterial activity and photocatalytic properties were fully evaluated. The specific studies are as follows:（1） Firstly, silver-doped TiO₂ nanorod arrays were synthesized in silver nitrate and sodium hydroxide solution by one step hydrothermal treatment method. The results show that nanorod arrays are mainly composed of anatase phase. The addition of silver nitrate has an affect on morphology of nanorod arrays. The silver concentrations of silver-doped TiO₂ nanorod arrays are 1.5 at.% and 2.7 at.% respectively. The silver-doped TiO₂ nanorod arrays show excellent efficient antibacterial activity against Escherichia coli（E.coli） and Staphylococcus aureus（S.aureus）. The photocatalytic properties of the silver-doped TiO₂ nanorod arrays are even higher than TiO₂ nanorod arrays. Although hydrothermal preparation process of silver-doped TiO₂ nanorod arrays is uncomplicated. The addition of silver nitrate has a great impact on nanotopography and concentrations of silver. In addition, silver content cannot be easily controlled, and the results are often hard to replicate.（2） In order to improve the stability of the preparation process, the composite technology of magnetron sputtering and hydrothermal treatment method was adoped in the paper. Firstly, silver-titanium composite films were formed on pure titanium substrate by magnetron sputtering technology and then silver-doped TiO₂ nanorod arrays were synthesized in situ by hydrothermal treatment. The results reveal that the nanorods with the length of 10¹2 μm, diameter ranging from 80¹00 nm, are distributed homogeneously uniform, and mainly composed of anatase phase. By controlling the silver concentrations of the thin films, silver-doped TiO₂ nanorod arrays with silver concentrations of 0.5 at.% and 2.2 at.% were prepared. Silver is found to be evenly doped into TiO₂ nanorod and mainly exists in the zerovalent state. The s ilver-doped TiO₂ nanorod arrays show excellent efficient antibacterial activity against E.coli and S.aureus. Additionally, the silver-doped TiO₂ nanorod arrays can still kill most of the E.coli and S.aureus bacteria even after immers ion for 60 days, suggesting the long-term antibacterial activity. Compared with TiO₂ nanorod arrays, silver-doped TiO₂ nanorod arrays have a better photocatalytic performance. This process provides a new idea and experimental basis for doping with other ingredients nanorod arrays. The arrays prepared by this process can be extended to applications in the fields of sensors, self-cleaning coatings and biomedical materials, etc.