Small-sized Au nanocage@Carbon quantum dots nanoprobe with high-efficiency imaging labeling and photothermal therapy

Nanoscale noble metals have attracted considerable research interest owing to their distinctive localized surface plasmon resonance (LSPR) properties, which enable diverse applications in photoelectric sensing, nanomedicine, and biological imaging. Among various hollow metallic nanostructures, gold nanocages (AuNCs) have emerged as particularly promising photothermal agents. However, conventional AuNCs face critical limitations: larger structures exhibit compromised biocompatibility, while smaller counterparts demonstrate restricted tunability of absorption wavelengths into the near-infrared (NIR) window-a crucial requirement for biomedical applications. To address these challenges, we developed a facile liquid-phase synthesis strategy employing a galvanic replacement reaction, utilizing Ag nanocube@CQDs-doped silica templates with HAuCl₄ as the oxidizing agent to fabricate small-sized AuNCs@CQDs nanostructures. The silica matrix serves dual functions: (1) enhancing structural integrity to prevent fragmentation, and (2) improving biocompatibility while maintaining NIR absorption capabilities essential for deep-tissue applications. Remarkably, the AuNCs@CQDs-doped silica nanoprobe demonstrates significantly enhanced fluorescence intensity through LSPR-mediated effects. Finite-difference time-domain (FDTD) simulations corroborate the experimental observations, revealing optimized electromagnetic field distributions that account for the observed photoelectric performance. The nanostructures achieve an exceptional photothermal conversion efficiency of 38.6%. In vitro evaluations confirm the dual functionality of these nanoprobes, demonstrating both targeted cellular labeling and efficient photothermal ablation. These findings establish AuNCs@CQDs-doped silica as a versatile platform for next-generation biosensing and theranostic applications.