A visible light excitable (λex = 520 nm), rhodamine-based, perchlorate selective ‘turn on’ fluorescent probe, RHENTU, is prepared and characterized by spectroscopic techniques. The probe is suitable for use in the detection of ClO4− by the naked eye. It is also capable of detecting ClO4− in contaminated living cells under a fluorescence microscope. Common anions viz. F−, Cl−, Br−, I−, N3−, NCO−, NO2−, NO3−, SCN−, CN−, CH3COO−, SO42− and H2PO4− do not interfere with these processes. The binding constant of RHENTU for ClO4− has been determined to be 2.9 × 103 M−1/2 using the Benesi–Hildebrand equation. Addition of ClO4− to RHENTU afforded an intense red emission with a quantum yield (4.5 × 10−2) five times greater than that of free RHENTU. The lowest detection limit (LOD) of RHENTU for ClO4− is 1 × 10−7 M.
