Ternary Bi₂WO₆/TiO₂–Pt Heterojunction Sonosensitizers for Boosting Sonodynamic Therapy

Abstract

Engineering Z-scheme heterojunctions represents a promising strategy for optimizing the separation and migration of charge carriers in semiconductor sonosensitizers for enhanced reactive oxygen species (ROS) generation. Nevertheless, establishing a continuous and directional pathway for ultrasonic-induced charge flow in Z-scheme heterojunctions remains a significant challenge. In this study, we present a ternary Bi 2 WO 6 /TiO 2 –Pt heterojunction sonosensitizer achieved through the precise growth of Pt nanocrystals on a directionally assembled Bi 2 WO 6 /TiO 2 Z-scheme structure. The construction of the Bi 2 WO 6 /TiO 2 –Pt heterojunction involves directional growth of Bi 2 WO 6 in situ on the highly exposed (001) crystal facet of TiO 2 nanosheets, followed by the precise deposition of nano Pt on the edge (101) crystal facet. The Z-scheme Bi 2 WO 6 /TiO 2 in the ternary heterojunction ensures effective electron separation, while the Schottky TiO 2 –Pt interface establishes a well-defined charge flow path and robust redox capabilities. Moreover, nano Pt confers the Bi 2 WO 6 /TiO 2 –Pt heterojunction with excellent peroxidase-mimic and catalase-mimic activities, facilitating interactions with endogenous H 2 O 2 to produce the hydroxyl radicals and O 2 . It effectively alleviates tumor hypoxia and enhances ROS production. This results in significantly higher efficiency in sonodynamically induced ROS generation compared to pure TiO 2 or binary Bi 2 WO 6 /TiO 2 heterojunctions, as confirmed by DFT theoretical calculation and experiments with both in vitro and in vivo anticancer performance. This study offers valuable insights for designing high-performance Z-scheme sonosensitizer systems.