Universal Platform for Ratiometric Sensing Based on Catalytically Induced Inner-Filter Effect by Cu2+

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-NH2) and 2,3-diaminophenazine (DAP), a new sensitive ratiometric fluorescent sensor has been developed for Cu2+ on the basis of in situ converting o-phenylenediamine (OPD) into DAP through the catalysis of Cu2+. Here, the presence of Cu2+ induced the emission of DAP, which acted as an energy acceptor to inhibit the emission of PTA-NH2. This dual-emission reverse change ratiometric profile based on the inner-filter effect improved sensitivity and accuracy, and the highly sensitive determination of Cu2+ with a detection limit of 1.7 nmol.L-1 was obtained. The proposed sensing platform displayed the wide range of detection of Cu2+ from 5 to 200 nmol.L-1 by modulating the reaction time between Cu2+ and OPD. Moreover, based on the specific interaction between glutathione (GSH) and Cu2+, this fluorescent sensor showed high response toward GSH in a range of 0.5-80 mu mol.L-1 with a detection limit of 0.16 mu mol.L-1. 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.