Environmental-assisted shape-controlled synthesis and electrocatalytic performance of CuS nanostructures for vanillin detection in commercial food products

Vanillin is broadly used as a food additive in various foods and beverages. The rampant intake of vanillin has major side-effect on human health and hence the development of vanillin sensor is highly important in various fields. In this work, simple and eco-friendly approach for the fabrication of shape-controlled copper sulfide (CuS) nanostructures were studied by changing the type of alkaline sources in solvothermal method. Three specific nanostructures i.e. CuS hexagonal (without alkaline source), CuS intersect-hexagonal (sodium hydroxide) and CuS micro-flower (ammonia) shapes were formed and significantly depended on the choice of alkaline source. The XRD, FE-SEM and HR-TEM results revealed that as-formed CuS products had good crystallinity with high phase purity, and uniform surface morphologies. The shape-specific electrochemical detection of vanillin (VN) in neutral pH medium was performed over the prepared CuS nanostructures. It was observed that hexagonal shaped CuS nanostructure having thin and smooth surface showed the best performances with lower oxidation potential (610 mV), and higher oxidation peak current density (2.5 µA) when compared to other CuS nanostructures, suggesting that the CuS-hexagonal shape could be used as an effective sensing platform for the sensitive determination of VN. The fabricated CuS-hexagonal-based sensor showed a good linear detection range between 0.1 and 46.5 µM, low detection limit (53 nM), excellent sensitivity (0.85 µA/µM cm⁻²), selectivity, outstanding stability and repeatability. The optimized sensor was further applied into the determination of VN with acceptable recovery in real samples (biscuit, chocolate and milk powders).