A fluorescent chemosensor for Al3+ based on julolidine and tryptophan moieties

A new and simple fluorescent chemosensor 1, based on julolidine and tryptophan moieties, has been synthesized and characterized. The sensor 1 displayed a selective and sensitive detecting ability for aluminum (III) ion by 'OFF-ON' fluorescent response in aqueous solution. This sensing mechanism might be due to the inhibition of CN isomerization, and the activation of chelation enhanced fluorescence (CHEF). This sensing mechanism of 1 for Al3+ was supported by theoretical calculations. Moreover, sensor 1 had a low detection limit (6.4 μM), which is below than the WHO recommendation level (7.41 μM) for drinking water. Importantly, the chemosensor 1 could be applied to living cells to detect Al3+. Therefore, the sensor 1 can be employed as a practical fluorescent chemosensor for recognition of Al3+ in aqueous solution.