Ultrasonically anchored core–shell Au–Pt nanoparticles on g-C3N4-modified screen-printed carbon electrode for efficient electrochemical detection of diclofenac in aquatic environments

The widespread occurrence of pharmaceutical residues, particularly diclofenac (DCF), in aquatic environments poses serious ecological and health risks due to their persistence and inefficient removal by conventional treatment systems. This study reports a highly sensitive electrochemical sensor based on a core–shell AuPt nanoparticles (Au⁰-Pt⁰NPs) decorated graphitic carbon nitride (g-C3N4) heterostructure modified screen-printed carbon electrode (SPCE) for DCF monitoring. The Au⁰-Pt⁰NPs/g-C3N4 nanocomposite was prepared using the ultrasonication method, in which ultrasonic energy facilitated hydrogen bonding between the Au⁰-Pt⁰NPs and g-C3N4 support. The incorporation of Au⁰-Pt⁰NPs onto the g-C3N4 surface provides strong interfacial adhesion, which effectively enhances charge carrier separation and promotes rapid electron transfer across the interface on the SPCE surface during DCF analysis. Optimization of experimental parameter showed that the electrode fabricated at 1.5 mg mL⁻¹nanocomposite concentration, 15 s interval time analysis, a scan rate of 100 mV s⁻¹and PBS buffer at pH 7.0 exhibited the highest peak current. The Au⁰-Pt⁰NPs/g-C3N4/SPCE sensor displayed a wide linear range of 0.25–1000 μmol L⁻¹, which LOD of 0.25 μmol L⁻¹, along with excellent reproducibility (%RSD = 1.12%) and stability (%RSD = 0.24%, after storage for 30 day). The electrode demonstrated strong selectivity against interfering species. Validation with aquatic environments samples achieved recoveries of 98.88–103.49%, and ANOVA analysis confirmed no significant difference (p = 0.527 > 0.05) compared with HPLC results (R² > 0.99). The synergistic effect of Au⁰-Pt⁰NPs/g-C3N4 enhanced catalytic performance, making the developed SPCE platform a reliable, and cost-effective sensor for detecting of DCF pollutants.