Electrochemical performance of Zn2SnO4@graphene oxide nanocomposites towards waterborne microplastic detection: Experimental and DFT study

Microplastics (MPs) are emerging contaminants of growing concern in seawater desalination and water treatment systems due to their persistence and potential risks to human health. Traditional detection methods are often limited due to their complexity, high costs, and inability to provide real-time monitoring. This work demonstrates the hydrothermal synthesis of zinc stannate (Zn 2 SnO 4 , ZnTO) and graphene oxide (GO) nanocomposite (NCs), ZnTO@GO NCs, comprised of varied weight percentage (wt%) of GO (1 mg/ml - 10 mg/ml) with ZnTO and employed as an electrode material in electrochemical sensor towards the detection of polystyrene (PS, 100 nm). The cubic-spinel crystal structure of ZnTO@GO NCs was confirmed by analyzing the crystal phases, structure, and element compositions. ZnTO@GO NCs (5 mg/ml) based fabricated sensor demonstrated a promising sensitivity of ~278.7 μA.μM −1 .cm −2 , low LOD of ~7.8 μM with full LDR of 10 μM – 60 μM and regression coefficient (R 2 ) = ~0.98222. Moreover, the MP's sensing mechanism over ZnTO@GO NCs was further studied by DFT calculations, showing the surface interaction of MPs at the molecular level of ZnTO@GO NCs. The developed sensor exhibits improved sensitivity, faster electron transfer kinetics, and a lower detection limit due to the heterostructure formation and efficient charge transport pathways, which distinguishes it from previously reported MPs sensing approaches.