A novel Ni-MOF/rGO-TiO₂ sensor for detecting polystyrene microplastics: toward advanced environmental monitoring

Microplastics (MPs) have become a major environmental concern owing to their widespread occurrence in marine and aquatic environments and their potential to threaten human health. The development of rapid and precise methods for detecting MPs remains a major challenge despite increased research attention in the field. Herein, a nickel-based metal organic framework/ reduced graphene oxide-titanium dioxide modified glassy carbon electrode (Ni-MOF/rGO-TiO₂/GCE) was fabricated for the electrochemical detection of polystyrene microplastics (PS-MPs). The samples were characterized using XRD, UV-Vis, FTIR, Raman, and FESEM techniques. The sensor exhibited a linear response over the range from 0.001 to 0.01 mg/mL with a sensitivity of 231.15 mA·mg/mL·cm^-2, a limit of detection of 0.29 µg/mL, and a correlation coefficient of R² = 0.99. The calculated active surface area of the sensor was 0.62 cm², and the charge-transfer resistance (R_ct) was estimated to be 125.95 Ω. This demonstrates excellent conductivity. A fine reproducibility (1.78%) and repeatability (0.19%) were obtained for the sensor. Recovery studies conducted on real samples achieved up to 99% recovery within RSD below 0.6%, confirming its reliability for practical environmental water samples. Therefore, the proposed sensing mechanism of Ni-MOF/rGO-TiO₂/GCE acts as a promising, sensitive, and reusable platform for trace detection of PS-MPs in environmental monitoring applications, highlighting the role of conductive rGO, the catalytic activity of TiO₂ and the adsorption sites of Ni-MOF.