Oxygen Vacancy Defect Enhanced Nir-Ii Photothermal Performance of BiOxCl Nanosheets for Combined Phototherapy of Cancer Guided by Multimodal Imaging.

Narrow photo-absorption range and low carrier utilization are significant barriers that restrict the antitumor efficiency of two-dimensional (2D) bismuth oxyhalide (BiOX, X = Cl, Br, I) nanosheets (NSs). Introducing oxygen vacancy (OV) defects can expand the absorption range and improve carrier utilization, which is crucial but also challenging. In this study, a series of BiOxCl NSs with different OV defect concentrations (x = 1,0.7,0.5) was developed, which showed full spectrum absorption and strong absorption in the second near-infrared region (NIR-II). Density functional theory (DFT) calculations were utilized to calculate the crystal structure and density states of BiO x Cl, which confirmed that part of the carriers is separated by OV enhanced internal electric field (IEF) to improve carrier utilization. The carriers without redox reaction can be trapped in the OV, leading to great majority of photo-generated carriers promoting the photothermal performance. Triggered by single NIR-II (1064 nm), BiO x Cl NSs bidirectional efficient utilization of carriers achieved synchronously combined phototherapy, leading to enhanced tumor ablation and multimodal diagnostic in vitro and vivo. We thus believe that this work provides an innovative strategy to design and construct nanoplatforms of indirect band gap semiconductors for clinical phototheranostics. This article is protected by copyright. All rights reserved.