Fast and facile controlled synthesis of silver nanocubes using the solvothermal process to create SERS substrates for detecting polystyrene microplastics

Abstract

The approach for detecting trace amounts of microplastics using surface-enhanced Raman spectroscopy (SERS) faces a significant challenge because the size of individual nanoparticles is considerably smaller than that of microplastics. Therefore, it is imperative to develop a type of nanoparticle that can form a larger surface area while still preserving excellent surface plasmon properties to enhance SERS analysis. Silver nanocubes (AgNCs) are an ideal candidate for meeting these specific requirements. Although prior studies have successfully investigated the impact of chemical parameters, it remains a challenge to synthesize AgNCs homogeneously. The current research underscores other experimental refinements that have been minimally addressed in the existing literature. Choosing suitable conditions enabled the formation of AgNCs with distinctly defined corners and an average size centered around 75 $\pm$ 0.74 nm. The proposed SERS substrates have good sensitivity, with a detection limit (LOD) of 1.11 ppm and a quantitation limit (LOQ) of 3.66 ppm in detecting polystyrene (PS) microplastic. The method shows high stability and reproducibility, with an average relative standard deviation (RSD) of 4.86 %. Furthermore, with promising results in tap water tests and mixed microplastic evaluations, our nanosubstrate holds strong potential for real-world testing.