Selective recognition of aluminum ions using an esculetin@Q[8] host-guest supramolecular fluorescence probe

In this paper, we prepared a new probe, a supramolecular compound composed of esculetin(ESC) and a cucurbit[8]uril(Q[8]). Ultraviolet, fluorescence and other methods have shown that ESC and Q[8] could formed a 2:1 (ESC2@Q[8]) inclusion compound with weak fluorescence, wihch could efficiently identify metal aluminum ions in a pH=5.0 water system, emit strong indigo blue fluorescence to achieve naked eye recognition. In the competition experiment, this probe showed the specific recognition of aluminum ions. Furthermore, its recognitionmechanism was explored through crystal diffraction and found that carbonyl oxygens on the port of Q[8] and the hydroxyl oxygen atoms of ESC together formed a ternary complex with Al3+ ((ESC2@Q[8])@Al3+), which made the host-guest fluorescent probe formed a hyper-conjugated system to achieve the effect of fluorescence enhancement. And the fluorescence intensity had a good linear correlation with the Al3+ concentration (R2 = 0.9838) in the range of 0.3–2.4 × 10–5 mol/L. The detection limit was 9.39 × 10–9 mol/L, which may have the potential and application prospects for detecting metal ions in water systems.