H2O brace molecules to slip stack: Transform ACQ to AIE for latent fingerprints recognition

Aggregation-induced emission (AIE) materials have received a lot of attention in recent years, however, it remains a great challenge to develop a facile method for the conversion of aggregation-caused quenching (ACQ) molecules to AIE. In this paper, the ACQ molecule, 3,5-diacetyl-1,4-dihydro-2,6-lutidine (DDL), is successfully transformed from face-to-face stacking to slip stacking under the induction of H 2 O, achieving the transformation of ACQ molecule to AIE. Experimental analysis and theoretical calculations show that H 2 O is inserted into DDL molecules through hydrogen bonds, and its spatial configuration makes an angle between the H 2 O and DDL planes, thus increasing the horizontal and vertical distances between adjacent DDL molecules, so that DDL is arranged in a slip stacking pattern. Meanwhile, hydrogen bonds fix the DDL molecules in a relatively rigid structure, leading to the generation of other weak interactions, which further restrict the molecular motion and reduce the non-radiative transitions, so that the DDL possesses the AIE property, and the quantum yield increases from 0.95 % to 25.60 %. Based on the high fluorescence intensity of DDL-H 2 O, it has been successfully applied to the first-, second- and tertiary-level structures of latent fingerprints (LFPs) identification, which provides more possibilities for the practical application of ACQ molecules.