Optical sensing of hydrogen sulphate using rhodamine 6G hydrazide from aqueous medium.

This communication reports the application of rhodamine 6G hydrazide (L) for the selective colorimetric and turn-on fluorescent sensing of hydrogen sulphate ions from aqueous medium. The ring opening of the colourless spirocyclic form of L was selectively triggered in the presence of HSO4 - among the other tested anions (F- , Cl- , Br- , I- , AcO- , H2 PO4 - , NO3 - , ClO4 - , CN- , HO- , AsO3 3- and SO4 2- ), which gives rise to a pink colour and strong fluorescence in the visible region. Sensor L showed a detection limit down to micromolar range without any interference from the other tested competitive anions. Sensor L was applied for the construction of two inputs (HO- and HSO4 - ) INHIBIT type molecular logic gate and naked-eye detection of HSO4 - using test paper strips.