Electrolysis-Induced Shrinking Surface Microbubbles for Localized Nanoplastic Deposition and Raman Identification: A Preliminary Proof-of-Concept Study

Nanoplastic detection sensitivity employing Raman Spectroscopy is often restricted by their low abundance, weak scattering response, and spatially dispersed distribution. This study presents a proof-of-concept electrolysis-induced shrinking surface microbubble platform for the localized accumulation and Raman spectroscopic identification of polystyrene nanoplastics (PS-NPs). The gas bubble generated electrochemically contacted a fused-silica surface and subsequently shrank after the removal of the applied voltage, resulting in a spatially confined deposit of particles. Characteristic Raman bands of polystyrene at approximately 1000 cm−1 were subsequently identified from the deposited region. This investigation involved a qualitative assessment of enrichment of plastics via the formation of localized deposits. A femtosecond laser-induced plasmonic microbubble platform operating at 920 nm was included as an operational reference. The lowest empirically identifiable PS-NPs concentrations among those tested were 31 µg/mL for electrolysis and 0.24 µg/mL for femtosecond excitation under their respective experimental conditions. Since the protocols lack synchronization for a controlled analytical comparison, these values do not offer a basis for relative sensitivity. The electrolysis platform enabled bubble generation without an ultrafast laser source, supporting further investigation of this approach. Future studies should quantify recovery and enrichment, establish statistically supported detection thresholds and reproducibility, evaluate matrix effects, and examine applicability to additional polymer types.