A naked eye colorimetric sensor for alcohol vapor discrimination and amplified spontaneous emission (ASE) from a highly fluorescent excited-state intramolecular proton transfer (ESIPT) molecule

A highly fluorescent HPI-based excited-state intramolecular proton transfer (ESIPT) molecule is designed and adopted as a naked-eye colorimetric sensor to distinguish methanol, ethanol and isopropanol vapors. Amplified spontaneous emission was also observed for the C1-form single crystal of the molecule attributed to its intrinsic four-level energy states.