Nonmetallic Plasmon-Enhanced Hollow Upconversion Nanostructures for Fluorescent Thermometry and Photoactivated Drug Release

Hollow-structured upconversion nanoparticles (UCNPs) hold exceptional potential for biological sensing, nanothermometry, and targeted drug delivery due to their unique architecture and appealing optical properties. However, simultaneously achieving stable hollow architectures and intense fluorescence remains a significant challenge. Herein, we report stable hollow Bi2SiO5:Yb,Er@SiO2 NPs (BSO:Yb,Er HNPs) via interfacial diffusion-driven synthesis. By integrating low-cost nonmetallic plasmonic W18O49 nanowires (NWs) with BSO:Yb,Er HNPs, we engineered an optimized BSO:Yb,Er/W18O49 composite that delivers a significant 1970-fold enhancement at 520 nm UC emission. This remarkable amplification arises synergistically from the near-infrared (NIR)-activated localized surface plasmon resonance (LSPR) of W18O49 and the plasmonic photothermal effect, far surpassing conventional noble metals. The composites demonstrate superior performance as a fluorescent nanoprobe for thermometry, achieving a high absolute sensitivity of 3.7 × 10–3 K–1 over an exceptionally broad temperature range of 400–1529 K. Notably, exploiting the hollow cavity and plasmonic heating feature, BSO:Yb,Er/W18O49 composites enable high drug-loading capacity and NIR-triggered controlled release. This work pioneers a nonmetallic plasmon-enhanced hollow UC nanostructure, unlocking multifunctional platforms for advanced bioimaging, optical sensing, and drug therapy.