Direct detection of polystyrene microspheres by using easily fabricated Ag core embedded Au film SERS substrates with high sensitivity

Plastics as very important materials have been extensively utilized, and they make people’s lives comparative and economic. However, recent studies find that the micro/nano-plastic particles degenerating from plastic materials especially for food containers may lead to some unknown diseases when they enter into the human lung or stomach. The methods of detecting micro/nano-plastic particles are urgently required, and conventional methods necessitate intricate pre-processing steps and specialized equipment. Hence, this paper introduces a highly sensitive and direct detection method based on Surface-Enhanced Raman Spectroscopy (SERS) in quantitatively and qualitatively analyzing polystyrene (PS) nanoplastics that are drop cast on substrate. The mechanism of SERS performance of the proposed Ag core embedded Au film (Ag@AuFilm) SERS substrate is studied by using the finite-different time-domain (FDTD) method. By optimizing the gap distance between the Ag core and the Au film, PS nanoplastics with three diameters were used to validate the effectiveness of the SERS substrate. The limits of detection (LOD) for PS nanoparticles with diameters of 50 nm, 70 nm, and 310 nm in DI water and real-river water were the same and the corresponding LODs were 50, 50, and 25 μg/mL, respectively. Thus, this study proposes an easily fabricated SERS substrate and provides a rapid, quantitative, and qualitative method for detecting PS nanoplastics. This new way of addressing the pervasive issue of nanoplastics pollution provided an accurate, efficient, and rapid detection of the nanoplastics.