Ratiometric hypoxia detection by bright organic room temperature phosphorescence of uniformed silica nanoparticles in water

Abstract Organic room temperature phosphorescence (RTP) in water has attracted much attention recently for its potential biological applications. However, it remains a formidable challenge to achieve efficient RTP from pure organic compounds in aqueous phase due to the dramatic deactivation of triplet excited states in water and the poor water dispersibility of large organic particles/crystals. Represented herein is covalent incorporation of a pure organic monochromophore in silica nanoparticles (SiNPs) featuring fluorescence and bright phosphorescence in aqueous solution. The covalent bonding of organic phosphors in polysiloxane framework was found to show excellent water dispersibility, at the same time suppress the non‐radiative deactivation of triplet excited states especially from water, thus leading to high phosphorescence quantum yields (up to 22%) and long lifetimes (up to 3.5 ms) in aqueous phase. More strikingly, oxygen‐insensitive fluorescence as internal reference and oxygen‐dependent phosphorescence as oxygen indicator from the organic chromophore in the porous SiNPs realized ratiometric hypoxia detection with ultrasensitivity ( K SV = 449.3 bar −1 ).