pH-stimulus response dye-cucurbituril sensor for amino acids in aqueous solution

The host–guest inclusion complexes that comprise an inverted cucurbit[7]uril ( i Q[7]) and a quinoline derivative, 4-(4-dimethylaminostyryl) quinoline (DSQ) at different pHs were exploited as multiple supramolecular sensors to sense l -α-amino acids. DSQ complexation inside i Q[7] at different pHs leads to increased fluorescence and formation of different-colored i Q[7]-DSQ complexes. The enhanced fluorescence of DSQ after i Q[7] encapsulation may be attributed to limited dimethylamine rotation and the formation of a twisted internal charge transfer (TICT) state. The DSQ@ i Q[7] sensors have different affinities for l -α-amino acids at different pHs. Therefore, we propose a pH-stimulus response supramolecular sensor for the discrimination of structurally similar l -α-amino acids in aqueous solution.