A ratiometric Al3+ ion probe based on the coumarin-quinoline FRET system

• A coumarin-quinoline probe based on Al3+ induced fluorescence resonance energy transfer (FRET) response has been studied.
• The probe exhibited ratiometric fluorescence recognition for Al3+ ions.
• The probe is suitable for fluorescent imaging of Al3+ in living cells.
• The probe detects Al3+ with a very low detection limit in neutral aqueous medium.
• Test paper studies provided an easy way to detect Al3+, which suggests this system is a good candidate for Al3+-sensing.

A coumarin-quinoline based fluorescence resonance energy transfer (FRET) system (TCQ) has been synthesized and employed as a ratiometric fluorescence probe. The selective fluorescent response of the probe TCQ toward Al3+ was devised by employing a quinoline moiety as a FRET energy donor with a coumarin moiety as an energy acceptor. The quinoline emission at 390 nm decreased and the coumarin emission at 480 nm increased concurrently on addition of Al3+ under excitation wavelength at 253 nm. The TCQ probe exhibited high selectivity for Al3+ as compared to other tested metal ions and the ratiometric sensing of Al3+ was determined by plotting the fluorescence intensity ratio at 480 nm and 390 nm versus Al3+ ion concentration. Moreover, test strips based on TCQ were fabricated, which were found to act as a convenient and efficient Al3+ ion detection kit. Furthermore, this system has been used for imaging of Al3+ in living cells.