Water-soluble benzoselenadiazole-based conjugated polymer fluorescent sensor with high selectivity for ferric ions and mercury ions and possible applications as integrated molecular logic gates

Abstract

A conjugated polymer P-1 based on benzoselenadiazole was synthesized by the polymerization of 1,4-bis[3′-(N,N-diethylamino)-1′-oxapropyl]-2,5-diiodobenzene (M-1) and 4,7-diethynylbenzoselenadiazole (M-2) via Pd-catalyzed Sonogashira–Hagihara coupling reaction. The water-soluble conjugated polyelectrolyte P-2 was obtained by the reaction of P-1 with ethyl bromide. The responsive optical properties of P-1 and P-2 on various metal ions were investigated by fluorescence spectroscopy in real-time detection. P-1 showed highly sensitive and selective detection of Fe3+ by ‘turn-on’ fluorescence enhancement in DMSO/H2O. P-2 exhibited outstanding sense of Hg2+ using BSe as receptor by ‘turn-off’ fluorescence quench type and Fe3+ using unionized triethylamino group as receptor by ‘turn-on’ fluorescence enhancement type in MeOH/H2O, respectively. Additionally, the addition of EDTA to the P-2–metal complexes could result in the fluorescence recovery of the P-2 solution. Fluorescence spectral responses as output signals and two independent molecular input signals based on P-2 could be used to demonstrate important logic operation like INHIBIT and IMPLICATION gates.