Experimental and theoretical studies on naphthalene based fluorophores: Applications in detection of Al3+ ions in water, soil, food and live cells

Abstract

Simple naphthalene based fluorescent chemosensors OHN &OHHN were prepared by single step procedures and utilized to detect Al3+ ion by absorption and emission spectroscopy. These studies confirmed that receptor OHHN showed significant selectivity and sensitivity towards Al3+ ion compared to other metal ions whereas there was no notable selectivity in the case of the receptor OHN. A significant enhancement in the fluorescence intensity was observed during the addition of Al3+ ions to the chemosensor OHHN. According to the emission studies, a plausible mechanism was proposed based on three reasons, i.e i) arrest of the Photoinduced Electron Transfer (PET), ii) CN isomerization and iii) Chelation Enhanced Fluorescence Effect (CHEF). The1H NMR and IR studies further confirmed the binding mechanism of the chemosensor OHHN with Al3+ ions. The fluorescence intensity changes in the Job’s plot predicts that the Al3+ ions bind with the receptor OHHN leading to the formation of a 1:2 stoichiometric ratio binding mode. The association constant and the limit of detection of the receptor OHHN with Al3+ ions were found to be 6.6×10−2M−1 and 0.176×10−5 M respectively. To test its real level effectiveness, the receptor OHHN has been tested with water, soil, food samples and live bacterial cell imaging.