A portable highly uniform and reproducible microflower CuS/rGO hybrid sensor: An effective electrochemical and DFT evaluation method for nitrite in water

We report the facile and green approach for the preparation of hybrid nanostructures based on reduced graphene oxide (rGO)-copper sulfide microflowers (CuS) through a facile solvothermal process for nitrite detection. The FE-SEM, EDX-mapping, HR-TEM, and XRD investigations showed that the prepared hybrid nanostructure had high crystallinity and good phase clarity, and uniform flower-like morphologies by an effective interaction of rGO nanosheets over the CuS microflowers. As-obtained rGO-CuS hybrid nanostructure with different dosages of GO (15, 25, 35, 45, 55, and 65 mg) has been applied as an electrode surface for the electrochemical sensing of nitrite in a neutral medium. It was observed that rGO-CuS derived from 45 mg of GO modified glassy carbon electrode delivered good electrochemical analytical performance including less oxidation potential (750 mV), higher anodic nitrite oxidation peak current (5.7 mA cm ⁻²) when compared to alone CuS (920 mV/ 4.3 mA cm ⁻²), rGO (844 mV/ 4.24 mA cm ⁻²), and bare GCE (1001 mV/ 3.87 mA cm ⁻²) modified electrodes, implying that the rGO-CuS hybrid nanostructure could be served as an effective electrode material for the rapid detection of nitrite, which was further discussed and supported by density functional theory (DFT) studies. The rGO-CuS hybrid-based sensor delivered broad working range (5 µM – 8 mM), detection limit (2.2 µM), good sensitivity (2.002 mA/mM cm ⁻²), good anti-interference properties, excellent durability, and reproducibility. The evaluated sensor can be used for the accurate detection of nitrite in water samples with good recoveries.