Introduction

Disinfectants and antibiotics are antimicrobial agents extensively used in various in vitro and in vivo settings. They are essential for infection control and aid in the prevention of nosocomial infections. Compared to antibiotics, which provide comparatively selective activity against microorganisms, disinfectants typically have a broader biocidic spectrum and are usually used with inanimate objects [1,2]. Traditional chemical-based disinfectants, such as alcohols, aldehydes, iodine, phenols, and chlorine, have been used for centuries in environmental cleaning. Although these disinfectants are highly efficient against pathogenic microbes, they also have problems. These disinfectants are usually volatile, and their byproducts can be toxic and carcinogenic to humans. As the widespread use of antibiotics and the emergence of more-resistant and -virulent strains of microorganisms became great clinical challenges [3–۸], the establishment and development of novel antibacterial strategies is, therefore, significant in the control of human pathogens and prevention of infectious diseases. From this point of view, photocatalyst-based antibacterial agents are conceptually feasible alternative approaches.

Classical photocatalyst generates pairs of electrons and holes (electron vacancy in valence band) upon ultraviolet light (UV) illumination. The electrons and holes induced by the reactions have strong reducing and oxidizing activities, and subsequently react with atmospheric water and oxygen (H2O and O2) to yield reactive oxygen species (ROS), such as hydroxyl radicals (•OH), superoxide anions (O2 −), and hydrogen peroxide (H2O2) [9]. These ROS can oxidize organic substances and exert the antibacterial function [10]. Titanium dioxide (TiO2) is the most widely used UV-responsive photocatalyst [11], which has been demonstrated to exert antibacterial effect in various forms that includes nanoparticles, thin films and polymer-composites [12–۲۳]. The UV-light, however, can damage eyes and skin [24]. These side effects limit the use of UVresponsive photocatalysts in our living environments.