Fabrication of novel copper MOF nanoparticles for nanozymatic detection of mercury ions

Mercury (II) ions are considered the most harmful heavy metal ion and their accumulation in the human body causes several diseases so need to be detected at trace levels. The use of nanozyme-based colorimetric detection is an acknowledged and innovative method to detect heavy metal ions in water bodies. In this work, we report CuMOF nanoparticles (CuMOF NPs) synthesized using hand grinding technique. The MOF nanoparticles were characterized by FTIR, TGA, SCXRD, PXRD, FESEM and TEM. The SCXRD confirmed paddle wheel type structure and MOF exhibits interpenetrated pcu topology with point symbol {412.63}. BET analysis revealed a high surface area of 15.995 m2g-1 and pore diameter of 3.42 nm for CuMOF NPs. The MOF NPs were found to show peroxidase-like activity. The CuMOF NPs employed as the catalyst, where 3,3′,5,5′-tetramethylbenzidine (TMB) was oxidised by Hg2+ and a bluish solution of oxidised TMB was obtained and recorded by UV–vis spectroscopy. The activity was determined with a detection limit of 0.55 μM, Km of 0.0477 M, and Vmax of 0.3125 M s−1 for TMB, and Km of 2.646 M and Vmax of 0.126 M s−1 for H2O2. The selectivity of the method was excellent and the mechanism was supported by XPS analysis. So, we provide a low-cost, eco-friendly approach for the detection of Hg2+ using CuMOF NPs.