Energy Migration-Directed Orthogonal Emissive Nanocrystals for NIR-IIb Imaging Navigation toward Precise UV Photoactivation.

Upconversion-based photoactivation offers a transformative approach to precision medicine by leveraging near-infrared light to trigger specific chemical and biological activities. However, the lack of favorable photoswitchable agents combining deep-tissue high-resolution imaging with orthogonal photoactivation hinders precise and site-specific interventions. This work reports the precise modulation of energy transfer within Yb/Tm/Er codoped nanocrystals via an energy migration strategy, achieving orthogonal emissions from Er3+ (NIR-IIb) and Tm3+ (UV) by adjusting the excitation between 808 and 980 nm. These rationally designed core-shell-shell optical conversion-switching nanocrystals (OCSNs) do not require a complicated multilayer doping design, as both activators reside within the same luminescent core. Furthermore, Ce3+ is incorporated to enhance Er3+-mediated 1550 nm emission. As proof of concept, the OCSNs are functionalized with mesoporous silica and UV-responsive azobenzene, enabling real-time navigation and controlled release of drug guests under orthogonal optical control. This OCSN offers immense potential for spatiotemporally precise photoactivation in various biomedical applications.