Understanding the fate of nanoplastics in the environment is essential for quantifying exposure, evaluating hazards, and ultimately assessing risk. As the extraction of real nanoplastic particles from the environment remains not feasible in the near future, achieving this requires high-quality, well-characterized test and reference particles. To synthesize such particles, several methods are commonly used, including reprecipitation, ball milling, and emulsion polymerization. Prior to analytical or toxicological studies, particles are typically characterized depending on polymer type, size, and surface charge. However, we found that test nanoplastic preparation methods critically affect other particle properties beyond the scope of conventional characterization. These method-dependent differences could affect spectroscopy-based detection and potentially toxicological studies.

Furthermore, comprehensively characterized test particles serve as tools to improve nanoplastics analysis and detection. Surface-enhanced Raman spectroscopy (SERS) has shown promising potential for achieving the necessary sensitivity to detect nanoplastics below the conventional Raman resolution limit (~500 nm), even at concentrations as low as ng/mL. However, many existing SERS approaches, which rely on aggregated plasmonic particles, suffer from weak reproducibility.

To address these limitations, we introduced a strategy that employs SERS tags to indirectly detect nanoplastics. By conjugating gold nanostars with a reporter molecule with an inherently strong Raman signal, we aim to measure signal changes of the reporter molecule in the presence of plastic particles. This signal change depends on the plastic concentration and thus allows us to semi-quantify nanoplastics in an artificial aqueous sample at low concentrations.