Universal Platform for Ratiometric Sensing Based on Catalytically Induced Inner-Filter Effect by Cu.

Integrating two kinds of fluorescent probes in one system to develop a ratiometric sensing platform is of prime importance for achieving an accurate assay. Inspired by the efficient overlapped spectrum of 2-aminoterephthalic acid (PTA-NH) and 2,3-diaminophenazine (DAP), a new sensitive ratiometric fluorescent sensor has been developed for Cu on the basis of in situ converting -phenylenediamine (OPD) into DAP through the catalysis of Cu. Here, the presence of Cu induced the emission of DAP, which acted as an energy acceptor to inhibit the emission of PTA-NH. This dual-emission reverse change ratiometric profile based on the inner-filter effect improved sensitivity and accuracy, and the highly sensitive determination of Cu with a detection limit of 1.7 nmol·L was obtained. The proposed sensing platform displayed the wide range of detection of Cu from 5 to 200 nmol·L by modulating the reaction time between Cu and OPD. Moreover, based on the specific interaction between glutathione (GSH) and Cu, this fluorescent sensor showed high response toward GSH in a range of 0.5-80 μmol·L with a detection limit of 0.16 μmol·L. The successful construction of this simple ratiometric sensing platform without the participation of enzymes provides a new route for the detection of small biological molecules that are closely related to human health.