Simultaneous electrochemical and colorimetric detection of tri-heavy metal ions in environmental water samples employing 3D-MOF/nickel selenide as a synergistic catalyst

The detrimental growth of water pollutants such as heavy metal ions (HMI) has become a life-threatening problem in the modern era. Therefore, developing more efficient strategies to detect such compounds requires increased attention. In this study, we designed a dual-mode assay for electrochemical sensing and naked-eye (colorimetric) detection of HMI using the peroxidase mimic activity of the developed nanozyme. The nanozyme of choice, which possesses both the necessary electrochemical properties and the ability to be oxidized with 3,3′,5,5′-tetramethylbenzidine (TMB), was determined and studied. Flower-like nickel selenide (NiSe) was integrated with a zeolitic imidazole framework (ZIF-67) to enable its wider applicability. HMI detection with a wide linear range of about 0.029–764.8 µM (Cd2+), 0.299–355.5 µM (Pb2+), and 0.29–153.2 µM (Hg2+) with NiSe/ZIF showed excellent electrochemical performances, while the linear range in colorimetric detection was about 0.199–429.9 µM (Cd2+), 0.199–90.8 µM (Pb2+), and 0.149–276.8 µM (Hg2+). The limit of detection for the simultaneous detection was 5.2 nM (Cd2+), 4.7 nM (Pb2+), and 6.2 nM (Hg2+) for electrochemical sensing. The LOD obtained for the colorimetric analyses were 0.043 µM (Cd2+), 0.050 µM (Pb2+), and 0.091 µM (Hg2+). The real sample analysis of the environmental water samples showed good results for trace heavy metal ions. Thus, the developed NiSe/ZIF catalyst is more effective with dual detection and can be used for portable analysis of several targets with further modifications.