LAUSR

The low penetration depth of UV light in mammalian tissue is the critical limitation for the use of TiO2 based photocatalysis in biomedical applications. In this work, we develop an effective near infrared (NIR) active photocatalytic platform that consists of a shell structure of upconversion nanocrystals decorated on a core of Au/dark-TiO2. The heart of this system is the strong photocatalytic activity in the visible (vis) region enabled by the gold surface-plasmon resonance (Au-SPR) on dark TiO2 (D-TiO2). Simulation and experiment demonstrate for an optimized Au/D-TiO2 combination a highly enhanced light absorption in the vis range. Using ampicillin (AMP) as model drug, we exemplify the effective use of this principle by demonstrating a NIR light-triggered photocatalytic payload release. Importantly, the photocatalytically generated reactive oxygen species (ROSs) can effectively inactivate AMP-resistant bacteria strains, thus maintaining an antibacterial effect even after all drug is released. Overall, we anticipate that the here introduced NIR-light active photocatalytic cascade can considerably widen TiO2 based photocatalysis and its applications into the infrared range.