Highly regenerative, fast colorimetric response for organo-toxin and oxo-anions in an aqueous medium using a discrete luminescent Cd(ii) complex in a heterogeneous manner with theoretical revelation

Abstract

The highly luminescent complex [CdQ₂(H₂O)₂] (1) shows ultra-selectivity and high sensitivity to the explosive organo-toxin trinitrophenol (TNP). This detection is extremely fast with a high quenching constant (5.3 × 10⁴ M⁻¹) and a very low limit of detection (LOD) of 137 nM/59 ppb. This motivated us to detect the lethal carcinogenic arsenical drug roxarsone (ROX), which is reported here for the first time. The quenching constant and LOD for ROX using 1 were found to be 4.9 × 10⁴ M⁻¹ and 86 nM (or 37 ppb), respectively. Moreover, the probe also recognizes three lethal toxic oxo-anions (MnO₄⁻, Cr₂O₇²⁻ and CrO₄²⁻) with outstanding quenching constant (2.2 × 10⁴ M⁻¹, 1.4 × 10⁴ M⁻¹ and 1.1 × 10⁴ M⁻¹) and very low LODs (141 nM/61 ppb, 178 nM/78 ppb and 219 nM/95 ppb). Compared to the previously reported homogeneous sensing nature of the discrete complexes, our complex showed the detection of toxic pollutants in a heterogeneous manner, which results in high recyclability and hence multi-cycle sensing capability. Interestingly, 1 shows the possibility for real-time monitoring through naked eye detection by visible colorimetric changes in solid, solution and strip paper methods, i.e., triphasic detection ability. In addition, the sensor also exhibited the cross-sensing ability for these pollutants. The experimental sensing mechanism is strongly supported by the exhaustive theoretical investigation. Based on the fluorescence signal shown by each analyte, an integrated AND-OR logic gate is constructed. Furthermore, the sensing ability of 1 remains intact towards the detection of versatile real field samples including lethal carcinogenic arsenical drug roxarsone in the real food sample.