A Novel Near-Infrared Antibacterial Material Depending on the Upconverting Property of Er3+-Yb3+-Fe3+ Tridoped TiO2 Nanopowder

A novel near-infrared antibacterial material, Er3+-Yb3+-Fe3+ tridoped TiO2 nanopowder, was synthesized and applied to kill Aeromonas hydrophia with a maximal bactericidal rate of 65% in 90 min under 980 nm laser irradiation. However, Fe3+-TiO2 or Er3+-Yb3+-TiO2 nanopowders obtained under the same conditions barely could kill Aeromonas hydrophia. The initial energy applied in the photocatalysis antibacterial process is supplied by the upconversion emission of Er3+ and Yb3+ and the codoping of Fe3+, which has intensified the light absorption intensity and enlarged the absorption range. The analyses of phase structure and the optical properties including XRD, UV−vis diffuse reflectance spectra, and upconversion photoluminescence spectra of Er3+-Yb3+-Fe3+ tridoped TiO2 nanopowder have been performed in detail to reveal the complex energy transfer and change mechanism. According to our experimental results, the mechanism has been demonstrated involving the upconversion emission, multistep excitation by means of intermediate energy level, capture and transfer electrons of Fe3+, and so on. The photocatalystic antibacterial function of Er3+-Yb3+-Fe3+-TiO2 under near-infrared instead of ultraviolet light is also reported. Because of the strong penetrability of near-infrared, this kind of material may be used in photodynamic therapy (PDT) to kill bacteria or tumors directly.