1′-hydroxy-2′-acetonaphthone: A simple fluorescence turn-on signaling probe with high selectivity and sensitivity for Al3+ in pure water

Abstract

Adverse effects of Aluminium ion (Al3+) on human health and the environment, when present above the acceptable concentration, have stimulated much attention to its detection. Many probes are being developed to detect Al3+, most of them suffer from protracted synthesis, less aqueous solubility, and limited selectivity and sensitivity. We report a highly selective and sensitive, fluorescence turn-on sensor for Al3+ detection in pure water by employing the simple, inexpensive commercial probe, 1′-hydroxy-2′-acetonaphthone (HAN). This probe displays remarkably high ~ 120 folds fluorescence enhancement upon complexing with Al3+, the highest reported so far in an aqueous solution for Al3+ sensing. The detection limit obtained was as low as 42 nM. The huge fluorescence enhancement towards Al3+ is attributed to the chelation enhanced fluorescence (CHEF) effect and consequent impediment on the excited-state tautomeric interconversion process between keto (K*) and twisted keto (KR*) tautomers of HAN associated to its ESIPT process. This Al3+ induced inhibition in the interconversion process between K* and KR* tautomers eventually lead to the complete tautomeric arrest of KR* form of the dye complexed with Al3+, a phenomenon not reported to date for the HAN dye in any system. Notably, the present system also illustrates an efficient response towards Al3+ in tap water, suggesting the practical applicability of the current sensor system in real biological and environmental samples.