ESIPT-based AIE luminogens: Design strategies, applications, and mechanisms

In this review, we present a systematic and comprehensive summary of the recent development and applications of excited-state intramolecular proton transfer-based (ESIPT-based) aggregation-induced emission luminogens (AIEgens), a type of promising materials that inherit the advantages of ESIPT and AIE, such as large Stokes shift, excellent photostability, and low self-quenching. We first summarize the backbones that have been used to construct the ESIPT-based AIEgens and classify the constructed ones based on the relation between ESIPT and AIE unit. According to the sensing mechanisms and design strategies, we have reviewed the applications of ESIPT-based AIEgens in bioimaging, drug delivery systems, organic light-emitting diodes, photo-patterning, liquid crystal, and the detection of metal cations, anions, small molecules, biothiols, biological enzymes, latent fingerprinting, and so on. We have also reviewed the recent advances in the development of new theoretical methods for investigating molecular photochemistry in crystals and their applications in ESIPT-based AIEgens. We discussed the remaining challenges in this field and the issues that need to be addressed. We anticipate that this review can provide a comprehensive picture of the current condition of research in this field, and promote researchers to make more efforts to develop novel ESIPT-based AIEgens with new applications.