Ratiometric Fluorescence Detection of Mg Based on Regulating Crown-Ether Modified Annihilators for Triplet-Triplet Annihilation Upconversion.

Detection of magnesium ion has been of great significance considering its critical physiological activities. Herein, we report ratiometric fluorescence detection of Mg with high sensitivity and selectivity based on triplet-triplet annihilation (TTA) upconversion for the first time. Crown-ether functionalized anthracene derivatives were synthesized, which bifunctionally acted as not only annihilators to construct TTA upconversion systems but also the recognition probes for Mg based on the photoinduced electron transfer (PET) mechanism. Their photophysical properties with the absence and presence of Mg were comprehensively studied. It was found that solvents strongly influenced the photophysical properties and Mg-responsiveness. TTA upconversion systems with PtOEP as the sensitizer were further established and investigated. It turned out PtOEP/9-AEC in DCM exhibited an excellent linear relationship ( = 0.9979) between the intensity ratio (the integrated upconverted luminescence intensity () over the integrated downshifted phosphorescence intensity (), /) and the concentration of Mg under the excitation of 532 nm with a limit of detection value of 2.52 μM and a high selectivity to Mg. This work opened a new perspective of designs and applications of TTA-upconversion-based ratiometric fluorescence for ion detection.