Near-Infrared Chiroptical Activity Titanium Dioxide Supraparticles with Circularly Polarized Light Induced Antibacterial Activity

Titanium dioxide (TiO₂) has attracted significant attention in the fields of antibacterial activity and pollutant degradation due to its well-known photocatalytic properties. However, the application of TiO₂ is significantly limited by its large band gap width, which only allows excitation by ultraviolet light below 400 nm. Here, we propose the use of surface chiral functionalization of TiO₂ to tune its band gap width, thus enabling it to be excited by near-infrared-region light (NIR), resulting in the effective separation of electron–hole pairs. By controlling the solvent polarity and forming numerous weak interactions (such as hydrogen bonding) between chiral ligands and TiO₂, we successfully prepared chiral TiO₂ superparticles (SPs) that exhibited a broad circular dichroism (CD) absorption at 792 nm. Under circularly polarized light (CPL) at 808 nm, the chiral SPs induced the separation of electron–hole pairs in TiO₂, thus generating hydroxyl and singlet oxygen radicals. Antibacterial tests under CPL in NIR showed that the chiral TiO₂ SPs exhibited excellent antibacterial performance, with inhibition rates of 99.4% and 100% against Gram-positive and Gram-negative bacteria, respectively. Recycling–reuse experiments and biocompatibility evaluation of the material demonstrated that the chiral TiO₂ SPs are stable and safe antibacterial materials, thus indicating the potential application of chiral TiO₂ SPs in antibacterial aspects of medical implants.