Sensitive and rapid detection of trace microplastics concentrated through Au-nanoparticle-decorated sponge on the basis of surface-enhanced Raman spectroscopy

•Gold-modified sponge substrates were successfully synthesized.•The SA substrate can be used to detect the particle size of 39 ∼ 155 μM.•It can be used in different testing environments without sample pretreatment. Microplastics is a type of widespread contaminant found in numerous aquatic ecosystems. Conventional methods of microplastic identification and quantitation require tedious sample pretreatment procedures and complex instrument, therefore, it is highly in demand to develop portable sensitive methods for rapid field application of detection. Herein, a sensitive detection method based on surface enhanced Raman spectroscopy (SERS) for trace microplastics in non-pretreated water samples was reported, which used a sponge supported Au nanoparticle (NPs) layer as the SERS substrate and locally concentrating microplastics. The sponge pores decorated with Au nanoparticles could effectively capture and concentrate microplastics in the pores from aquaes sample. Interestingly, the adjustable size of the sponge could allow the distance between the “hot spots” on the substrate surface to be controlled, hence controlling the SERS signal intensity. The Raman signal for microplastics in water was greatly enhanced on the proposed substrate, whereas no Raman signal enhancement was observed on the un-supported Au NPs. It has been demonstrated that trace microplastics could be readily detected when higher sample volume was used. Furthermore, the practical applicability of the developed method has been demonstrated by the successful detection of microplastics in snow water, seawater, river water, and rainwater. This sensitive platform provided a possible opportunity for in-field microplastic detection without pretreatment coupled with a portable Raman instrument. [Display omitted]