Highly sensitive and fast responsive “turn-on” fluorescent sensor for selectively sensing Fe3+ and Hg2+ in aqueous media based on an oligothiophene derivative and its application in real water samples

Abstract

A novel fluorescent “turn-on” sensor 3TB for simultaneous sensing of Fe3+ and Hg2+ in aqueous media based on an oligothiophene Schiff base has been successfully synthesized and its fluorescent sensing properties were investigated in details. 3TB can selectively detect Fe3+ and Hg2+ by fluorescent spectroscopy among a series of various metal ions. Upon addition of Fe3+ or Hg2+ leads to a 44-fold or 19-fold fluorescence enhancement with a strong green fluorescence color. The binding stoichiometry ratio of 3TB–Fe3+ is recognized as 2:1 and 3TB–Hg2+ as 1:1 proved by the method of fluorescence measurements, FT-IR and 1H NMR, and the possible binding mode of the sensing system is also proposed. The sensor 3TB toward Fe3+ and Hg2+ was found to possess the excellent advantages of high association constants (1.34×106 and 8.99×104M−1), low detection limits (13.6 and 61.7nM), high selectivity and sensitivity, good anti-interference performance, instataneous response, wide pH response range (5.0–10.0), and outstanding fluorescence capacity to detect Fe3+ from water. These investigated results indicate that 3TB is an ideal sensor for Fe3+ and Hg2+ recognition. Moreover, the proposed sensor was successfully applied to effectively detect Fe3+ in real water samples.