1-Hydroxy-2-naphthaldehyde: A prospective excited-state intramolecular proton transfer (ESIPT) probe with multi-faceted applications

► Excited-state intramolecular proton transfer probe 1-hydroxy-2-naphthaldehyde (HN12). ► ESIPT photophysics of HN12 in homogeneous solvents and computational support. ► Sensitive ESIPT spectral signatures to medium polarity/pH, temperature. ► Application of ESIPT emission as a probe for biological and biomimicking environments. ► Exploring protein denaturation, renaturation and phase-transition in lipid membranes.