Multichromatic Anti-Stokes Photon Upconversion through BNOSe Sensitization

Triplet-triplet annihilation upconversion (TTA-UC) has become an important sensing technique due to its ability to eliminate tissue autofluorescence interference. However, its quantitative application in oxygen sensing within complex systems remains fundamentally constrained. To overcome this limitation and explore synergistic anti-Stokes mechanisms, we developed a heavy-metal-free photosensitizer (BNOSe) via multiresonance architecture engineering. This innovation enables the creation of the first integrated platform capable of simultaneous TTA-UC and oxygen-resistant single-photon absorption upconversion (SPA-UC). The optimized system exhibits remarkable performance: it converts deep-red light (640 nm) into dual emissions at 617 nm (orange) and 412 nm (blue), achieving a record TTA-UC quantum yield of 19.3% with a 1.07 eV anti-Stokes shift, the largest value reported for visible-to-blue TTA-UC using metal-free sensitizers. Importantly, the oxygen-dependent TTA-UC and oxygen-resistant SPA-UC channels establish a self-calibrating sensing paradigm, showcasing multimodal capabilities in oxygen-probing bioimaging and multicolor analyte detection.