A facile preparation of CuS-BSA nanocomposite as enzyme mimics: Application for selective and sensitive sensing of Cr(VI) ions

Abstract

This work describes a selective and sensitive colorimetric approach for the detection of heavy metal Cr(VI) ions in water using the peroxidase-like property of CuS-BSA nanocomposite. CuS-BSA nanocomposite is synthesized via a simple chemical route and characterized by various sophisticated instrumental techniques like transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV/Vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis. The hydrodynamic size and surface charge of CuS-BSA nanocomposite were determined by using dynamic light-scattering (DLS) and zeta potential measurements. The peroxidase-like activity of CuS-BSA nanocomposite towards the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a blue colored charge transfer product (oxTMB), which is observable by the naked eye, is quantitatively assessed by UV/vis spectrophotometry at 654 nm. The CuS-BSA nanocomposite is subsequently applied for sensing of Cr(VI) metal ions. The sensor displays two linear ranges, 0–100 nM and 1–20 μM; the lower linear range was used to determine a detection limit of 50 nM towards Cr(VI), which is below the permissible limit determined by the United States Environmental Protection Agency (U.S. EPA). The practical performance of this sensor is successfully demonstrated using various environmental water samples spiked with different concentrations of Cr(VI). This method offers the advantages of being rapid, highly selective and sensitive platform, which holds great potential in environmental applications.