Unprecedented 2D GNR-CoB nanocomposite for detection and degradation of malachite green - A computational prediction of degradation pathway and toxicity

Abstract

In the present work, we have synthesized a novel 2D GNR-CoB composite and was applied it for electrochemical sensing and photocatalytic degradation of the malachite green (MG). The physicochemical properties of the 2D GNR-CoB were analyzed using X-ray diffraction, Transmission electron microscopy, Energy dispersive X-ray diffraction which depicts the morphological and crystalline nature of the prepared composite. The pencil graphite electrode modified with 2D GNR-CoB composite showed excellent electrochemical response for MG detection with a LOD of 1.92 nM, linear range of 25-350 nM with a high sensitivity of 1.714 μA μM^-1 cm^-2. Besides, the 2D GNR-CoB modified PGE exhibited good recovery for the detection of MG in real samples such as green peas and lady's fingers. Furthermore, the 2D GNR-CoB modified electrode showed excellent photocatalytic activity for the degradation of MG. It suggests that under visible light, GNR-CoB material generates superoxide (·O₂^-) and hydroxyl (·OH) radicals for MG degradation. The prepared composite showed an efficiency of 91.28% towards the degradation of MG. Based on the experimental analysis and density functional theory calculations, a photocatalytic degradation mechanism pathway for MG is proposed. A quantitative structure-activity relationship study was used to examine the toxicity of the degradation intermediates.

Keywords: Density functional theory; Electrochemical sensor; GNR-CoB; Malachite green; Photocatalytic degradation; Toxicity.