Simple excited state intramolecular proton transfer (ESIPT) based probe for pH and selective detection of copper(II) ion in aqueous alkaline environment: Sensitivity, selectivity and logic behavior

A low molecular weight ESIPT-based probe was synthesized and tested for detecting pH, cations, and anions in aqueous solutions. The probe exhibited a good emission in water due to aggregation induced by pi-pi* stacking. It gave an "off-on" fluorescent response to higher pHs because of blocking the non-radiative ESIPT after depro-tonating phenolic hydroxyl groups. Moreover, the fluorescence emission of the probe (water/ethanol = 3:1, pH 10) was quenched only by Cu2+ with limit of detection LOD = 3.2 mu M. The stoichiometric ratio of the probe/Cu2+ complex was found to be 1:1. Furthermore, changes of the probe's absorption and emission signals (as outputs) in response to the presence of H+ and HO- or Cu2+ and Br stimuli (as chemical inputs) mimics INHIBIT, IMPLI-CATION and NOT TRANSFER logic gates.