Electrochemical capture and size-dependent sensing of polystyrene nanoplastics

Nanoplastics (NPs), defined as plastic particles smaller than 1 μm, pose emerging environmental and health concern due to their ability to penetrate biological membranes and accumulate in living organisms. Conventional analytical methods for NPs sampling and detection, generally restricted to NPs >100 nm, are often limited by complexity, high cost, and lack of suitability for rapid or on-field monitoring. In this study, we developed a novel electrochemical strategy for the in-situ capture and detection of polystyrene nanoplastics (PSNPs) using a gold screen-printed electrode, modified by mesoporous silica thin film, followed by proline functionalization via epoxy-silane. The adsorption of negatively charged PSNPs is electrochemically controlled and enhanced by selective accumulation potentials, resulting in a decreased ferricyanide anodic current. The sensor exhibits good sensitivity and reproducibility, as well as size-dependent detection of PSNPs as small as 34 kDa. Calibration curves, obtained by differential pulse voltammetry, demonstrate linear response across environmentally relevant concentration levels for all investigated PSNPs sizes (34, 564, and 2530 kDa), with increasing sensitivity for decreasing particle diameter - a trend consistent with surface coverage and mass transport considerations. Finally, the sensor's real-world applicability was evaluated by the determination of PSNPs in a spiked commercial brand of drinking water, with resulting recoveries between 86.7% and 102.1%. This straightforward, reagent-free electrochemical platform offers rapid response times, simple operational methodology, and suitability for on-site monitoring of NPs contamination in aquatic environments.