A signal‐switchable fluorescent probe for detection of HPO42− based on 5,10,15,20‐(4‐sulphonatophenyl)porphyrin (TPPS4)

Abstract In this study, 5,10,15,20‐(4‐sulphonatophenyl)porphyrin (TPPS 4 ) was selected as a fluorescent probe due to its excellent characteristics including high quantum yield, good water solubility, and exceptional biocompatibility. With an excitation wavelength set at 515 nm, the optimal fluorescence emission wavelength for TPPS 4 was measured at 642 nm. At this moment, the fluorescence signal of TPPS 4 pink solution was in the ‘ON’ state. The fluorescence intensity of TPPS 4 was quenched when ascorbic acid (AA) was introduced, which was due to the electron transfer quenching effect between AA and TPPS 4 . The colour of the corresponding solution changed from pink to green, and the fluorescence signal was in the ‘OFF’ state. When HPO 4 2− was further introduced into the TPPS 4 –AA system, the quenched fluorescence intensity of TPPS 4 was recovered due to the unique interaction between HPO 4 2− and AA. At this time, the colour of the corresponding solution changed from green to red, and the fluorescence signal was in the ‘ON’ state. Therefore, an ‘ON–OFF–ON’ signal‐switchable fluorescent probe was constructed based on TPPS 4 to detect HPO 4 2− . The results showed that the linear range of HPO 4 2− was 4.0 × 10 −9 to 1.7 × 10 −6 M, and the detection limit was 1.3 × 10 −9 M (S/N = 3). The sensing system exhibited high accuracy and sensitivity, and it could be used successfully to detect HPO 4 2− in real samples.