In situ polymerization and covalent functionalisation of trithiocyanuric acid by MoS2 nanosheets resulting in a novel nanozyme with enhanced peroxidase activity

Abstract

A hydrothermal method was used to synthesise 2D MoS₂. The resulting nanosheets had a 1T stacking sequence (tetragonal symmetry) as the dominant form, and some 2H stacking (hexagonal symmetry), with an interlayer basal spacing of 6.81 Å. The material was used as a catalyst in the one step polymerisation of trithiocyanuric acid (TTCA) to polythiocyanuric acid (PTCA), resulting in PTCA-functionalisation of the edge sites of the MoS₂ to form a continuous, porous, polymeric network. This novel material showed enhanced peroxidase activity relative to native MoS₂. Using TMB as a colorimetrically monitored co-substrate, kinetic analysis of the PTCA–MoS₂ peroxidase action revealed that the catalyst functioned by a ping-pong mechanism, unlike MoS₂ itself where the mechanism was sequential. The PTCA–MoS₂ composite exhibited a higher value of V_max than native MoS₂ for an equal quantity of catalyst and could be used for the colorimetric measurement of H₂O₂ in the range 5 μM to 1000 μM (LOD = 3.8 μM, r² = 0.992) and the indirect measurement of glucose, using glucose oxidase, in the range 20 μM to 800 μM (LOD = 18.34 μM, r² = 0.981). The PTCA–MoS₂ catalyst was stable for two months when stored at 4 °C.