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 H2O, achieving the transformation of ACQ molecule to AIE. Experimental analysis and theoretical calculations show that H2O is inserted into DDL molecules through hydrogen bonds, and its spatial configuration makes an angle between the H2O 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-H2O, 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.