Hydrogenated Titanium Oxide Decorated Upconversion Nanoparticles: Facile Laser Modified Synthesis and 808 nm Near-Infrared Light Triggered Phototherapy

With multiphoton excited upconversion nanoparticles (UCNPs) as energy transducer, ultraviolet (UV) light responsive titanium dioxide (TiO2) can be triggered indirectly by near-infrared (NIR) light for deep-tissue photodynamic therapy (PDT) through the fluorescence resonance energy transfer (FRET) strategy. Compared to pristine TiO2, absorption of hydrogenated black TiO2 (H-TiO2) in visible (vis) and NIR regions presents a marked improvement in performance, which leads H-TiO2 to enhance its overall activity. Owing to the light absorption enhancement, the single component H-TiO2 can be served as vis-driven photosensitizers (PSs) for PDT as well as NIR-triggered photothermal agents (PTAs) for photothermal therapy (PTT) simultaneously. Herein, H-TiO2 decorated Nd3+-sensitized-UCNPs (Nd:UCNP5@H-TiO2) nanocomposites (NCs) were synthesized by Nd:Y3Al5O12 (Nd:YAG) pulsed-laser irradiation of Nd:UCNPs@TiO2 precursors in suspended aqueous solution. Pulsed-laser modified synthesis is the optimum selection for preparing H-TiO2 to meet the requirement for dispersion of biomaterials. Nd:UCNPs can convert 808 nm light energy to upconverting green emission for activating the attached H-TiO2 to produce reactive oxygen species (ROS). Meanwhile, H-TiO2 can directly convert 808 nm light energy to hyperthermia together with infrared photothermal and photoacoustic signals. The Nd:UCNP5@H-TiO2 NCs exhibit remarkable photoconversion effects as NIR-responsive theranostic agents for accurate diagnosis and efficient phototherapy of tumors.