Recent progress in excited-state intramolecular proton transfer-based ratiometry fluorescence probes for environmental detection and monitoring

Abstract

Over 150 years, fluorescence probes have remained a cornerstone for selective detection and imaging a wide range of analytes. Unlike classical monochromatic probes, ratiometric fluorescence probes (RFPs) can self-correct data distortion. In the 75^th year celebration of excited state intramolecular proton transfer (ESIPT) and its new role, ESIPT-RFPs and imaging agents provide dual confirmatory signals. RFPs are characterized by their major sensing mechanisms, including ICT, FRET, ESIPT, and monomer-excimer formation. In recent years, researchers have widely studied ESIPT-RFPs for various environmental and biological analytes, including anions, cations, and neutral analytes. As a result, several reports discuss the ESIPT-RFP for detecting and monitoring a numerous of environmental analytes. The 2-hydroxyphenyl benzothiazole and 3-hydroxy flavones ESIPT cores are most widely utilized for the design. This review examines the diverse mechanisms employed for sensing and signal changes of ESIPT-RFPs for environmental detection and monitoring, focusing on neutral molecules, anions, and cations. The ESIPT-RFP probes have two types of sensing signals: two reversible signals and fixed reference signals, which can be red-shifted or blue-shifted. The ESIPT-RFP sensing mechanisms are categorized into Types I, II, and III. This article reviews over 88 published articles on ESIPT-based RFPs for environmental detection and monitoring.