An effective optical chemosensor film for selective detection of mercury ions

Abstract

we develop and design a novel chemosensor film for detecting Hg(II) ions. The determination process investigates within a concentration range between 0 and 0.10 µM. The optical chemosensor film is depending on 3,4-Dimethylthieno[2,3-b]thiophene-2,5-Dihydrazide (DTD). The fluorescent molecule emits a significant fluorescence emission at 430 nm under 310 nm. Moreover, the chelation process of the Hg(II) ions with DTD introduces a 2:1 (metal:ligand) complex which is escorted by the quenching of the maximum emission peak centered at 430 nm of DTD and the appearance of a second fluorescence peak at 475 nm. The ratiometric fluorescence influence is a characteristic proof for the complexation reaction between the DTD probe and Hg(II) and this could be easily noticed. The designed chemosensor was proposed depending on the significant fluorescence mechanism, (intramolecular charge transfer (ICT)). Density functional theory (DFT) and the time-dependent DFT (TDDFT) theoretical calculations were achieved to investigate Hg(II) complexation structures and their electronic characteristics in solution, the calculations support that the quenching of the fluorescence in this compound is the result of ICT. This chemosensor displays ultimate sensitivity and selectivity based on their significant fluorescence characteristics, distinctive Stocks shift ~120 nm, detection aptitudes within a substantial low detection limit for Hg(II) LOD 2.4 nM which is applied in a physiological pH medium (pH = 7.4); with a relative standard deviation RSDr (1%, n = 3). Furthermore, the DTD exhibits great binding attendance towards Hg(II) and the binding constant was calculated to be 1.02 × 106 M−1. Impressively, we introduce a significant optical sensor based on the DTD molecule.