Cu(0) nanoparticle-decorated functionalized reduced graphene oxide sheets as artificial peroxidase enzymes: application for colorimetric detection of Cr(vi) ions

Abstract

Graphene oxide (GO) sheets were functionalized by a “click” chemistry approach using azide modified GO and alkynyl-terminated D(+)-glucose precursors to produce glucose terminated hydrophilic GO surfaces. This hydrophilic functionalized GO surface was utilized for the decoration of Cu(0) nanoparticles for sensitive colorimetric detection of Cr(VI) ions, which has not been explored to date. The nanocomposite exhibited excellent peroxidase mimic activity towards the colourless chromogenic substance, 3,3′,5,5′-tetramethylbenzidine (TMB), to yield a blue coloured substance 3,3′,5,5′-tetramethylbenzidinediimmine (TMBDI). In an acidic medium, Cr(VI) can decompose H₂O₂ to molecular O₂ and H₂O. Both O₂ and H₂O can form hydroxyl radicals (˙OH) by combining with the electron of the peroxidase substrate, resulting in enhanced TMB oxidation in the presence of Cr(VI). This colorimetric method was highly selective towards Cr(VI) ions with a limit of detection (LOD) of 67.13 nM.