Highly selective colorimetric fluorescence sensor for Cu 2+: cation-induced ‘ switching on’ of fluorescence due to excited state internal charge transfer in the red/near-infrared region of emission spectra

Abstract

A 1,8-naphthalimide-based colorimetric fluorescence perinone dye, receptor 1 is reported herein for the selective detection of Cu 2+ over the other heavy and transition metal ions. Receptor 1 shows a strong colorimetric change from orange to purple and a dramatic enhancement of fluorescence intensity due to cation-induced excited state internal charge transfer during the sensing event, that is, a dual optical response that would facilitate naked-eye detection of Cu 2+.