Salt-induced Nano-trapping for sensitive SERS detection of Nanoplastics in drinking water.

Abstract

The widespread occurrence of micro- and nanoplastics in the environment and their associated health risks have created an urgent need for sensitive analytical methods, particularly for nanoplastics, whose detection remains challenging. Herein, a simple and efficient surface-enhanced Raman spectroscopy (SERS) methodology is reported based on filtration-assisted, salt-induced heteroaggregation of colloidal gold nanoparticles (AuNPs) and nanoplastics. The approach combines controlled NaCl-induced aggregation with subsequent filtration, concentrating nanoplastics within AuNP hotspot regions and increasing the number of heteroaggregated structures probed during SERS analysis. Optimal aggregation conditions were determined using a UV-vis absorbance-based strategy by maximizing absorbance at the SERS excitation wavelength, enabling enhanced and more reproducible signal generation compared with conventional approaches. Using this methodology, 50 nm and 100 nm polystyrene (PS) nanoplastics were detected with statistically determined limits of detection of 21.60 ng/mL and 19.90 ng/mL, respectively, representing a substantial improvement over previously reported salt-induced aggregation studies. Calibration curves exhibited good linearity (R2 = 0.946 and 0.944 for 50 nm and 100 nm PS, respectively). The low coefficients of variation indicate good SERS signal repeatability, while matrix-effect studies revealed generally modest variations in signal intensity, except for appreciable signal suppression in tap water at the lowest concentration investigated. These findings establish a simple, low-cost and sensitive SERS platform for nanoplastic detection in aqueous environments.

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