Coordination-driven room-temperature phosphorescent carbon dot nanozymes for dual-mode glutathione detection

Integrating long-lived room-temperature phosphorescence (RTP) into nanozymes to build multifunctional nanozymes can benefit biomedical analysis by expanding sensing modes and developing advanced sensing strategies but it is challenging. Herein, a general strategy for fabricating phosphorescent nanozymes by anchoring Co-N_x active centers on SiO₂ nanospheres with carbon dots (CDs) encapsulated inside (CDs@SiO₂@Co) is developed for dual-mode colorimetric-phosphorescent detection of glutathione (GSH). Specifically, surface Co-N_x active centers enhanced O₂ adsorption and activation (O₂ to ¹O₂), providing oxidase-like activity to induce the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), generating a distinct colorimetric signal. The SiO₂ layer inhibited non-radiative transitions of the CDs to promote RTP, and spatially separated Co ions from CDs to prevent RTP quenching caused by Co-CD interactions, resulting in CDs@SiO₂@Co with long-lived RTP (lifetime: 1.14 s), providing a phosphorescent channel free from autofluorescence interference. Upon introduction of GSH, the color product-oxidized TMB (oxTMB) was reduced, and the quenched RTP caused by the oxTMB internal filter effect was restored. Based on this principle, a sensitive and reliable dual-mode colorimetric-phosphorescent method was developed for detecting GSH in plasma and cells. Furthermore, owing to the tunable optical properties of CDs and the flexibility of substituting metal active centers, this strategy can be extended to construct various phosphorescent nanozymes with adjustable RTP emission wavelengths and diverse enzyme-like activities, advancing the development of nanozymes and bioanalytical platforms.