Controllable preparation of mesoporous spike gold nanocrystals for surface-enhanced Raman spectroscopy detection of micro/nanoplastics in water

Microplastics and nanoplastics are emerging classes of environmental contaminants that pose significant threats to human health. In particular, small nanoplastics (<1 μm) have drawn considerable attention owing to their adverse effects on human health; for example, nanoplastics have been found in the placenta and blood. However, reliable detection techniques are lacking. In this study, we developed a fast detection method that combines membrane filtration technology and surface-enhanced Raman spectroscopy (SERS), which can simultaneously enrich and detect nanoplastics with sizes as small as 20 nm. First, we synthesized spiked gold nanocrystals (Au NCs), achieving a controlled preparation of thorns ranging from 25 nm to 200 nm and regulating the number of thorns. Subsequently, mesoporous spiked Au NCs were homogeneously deposited on a glass fiber filter membrane to form an Au film as a SERS sensor. The Au-film SERS sensor achieved in-situ enrichment and sensitive SERS detection of micro/nanoplastics in water. Additionally, it eliminated sample transfer and prevented the loss of small nanoplastics. Using the Au-film SERS sensor, we detected 20 nm to 10 μm standard polystyrene (PS) microspheres with a detection limit of 0.1 mg/L. We also realized the detection of 100 nm PS nanoplastics at the 0.1 mg/L level in tap water and rainwater. This sensor provides a potential tool for rapid and susceptible on-site detection of micro/nanoplastics, especially small-sized nanoplastics.