Transient effects in the fluorescence quenching of a strong photoacid

Fluorescence quenching of 1-hydroxynaphthalene-4-sulfonate by water has been studied in methanol–water and ethanol–water mixtures. The fluorescence quenching has shown a significant deviation from the Stern–Volmer linearity at higher concentrations of water due to dynamic quenching along with transient effects and instantaneous quenching. Time-resolved fluorescence decay of the conjugate base of 1-hydroxynaphthalene-4-sulfonate in methanol–water mixture indicates the need of only one water molecule to hydrate the conjugate base aftermath of the dissociation of the photoacid.