A highly sensitive and selective turn-on fluorescent sensor for dihydrogen phosphate in living cells

•A sensitive and specific sensor is designed for H2PO4− detection.•The probe provided remarkable fluorescence intensity change and clear color change.•The background anions showed small or no interference.•The confocal fluorescent images demonstrated that the probe was cell-permeable. A novel visible light excitable chemosensor based on a rhodamine 6G naphthylurea conjugate was successfully synthesized, which shows highly selective and sensitive recognition ability toward H2PO4− in H2O-CH3CN (1/1, v/v). In response to H2PO4−, the probe provided remarkable fluorescence intensity change and clear color change from colorless to pink and the background anions showed small or no interference. The confocal fluorescent images demonstrated that the probe was cell-permeable and could effectively detect intracellular dihydrophosphate in living cells.