A Nile Red-assisted colorimetric and SERS dual-mode strategy for the rapid and highly sensitive detection of nanoplastics

Background Nanoplastics are progressively recognized as a significant global pollutant and a severe threat to human health. Owing to their tiny particle size and low environmental concentrations, nanoplastics detection currently relies on sophisticated laboratory instrumentation. Colorimetric assays represent a rapid, user-friendly strategy, as the testing results can be readily identified by the naked eye. However, this technique is generally limited by unsatisfactory detection sensitivity. Surface-enhanced Raman scattering (SERS) technique allows for the highly sensitive analysis of samples in aqueous solutions without direct contact. Nevertheless, the complicated preparation of high-performance SERS substrates greatly hinders their practical application in nanoplastics detection. Results Herein, a novel colorimetric/SERS dual-mode sensing strategy was developed via Nile Red labeling for rapid and sensitive detection of nanoplastics (≥100 nm). Nanoplastics labeled with Nile Red (referred to as NPs@NR) demonstrated a visually discernible coloration to the naked eye, as well as an obvious SERS signal under a portable Raman spectrometer. Moreover, the SERS signal of NPs@NR was collected from a straightforward SERS substrate with an RSD of 9.93% that fabricated by transferring Ag nanoparticles film (ANF) onto the end of a hydrophilic polyvinylidene fluoride (PVDF) strip in one step. Colorimetric assays were capable of qualitative identification and quantitative detection of NPs@NR at a concentration of 10 μg/mL and higher. Furthermore, the ANF-based SERS substrate achieved a low limit of detection (LOD) of 0.01 μg/mL toward NPs@NR. More importantly, the proposed colorimetric/SERS dual-mode strategy presented excellent feasibility for the detection of nanoplastics spiked in real environmental samples. Significance Given integrating the advantages of facile detection through colorimetric analysis and highly sensitive trace assays using SERS, the proposed dual-mode method demonstrates potential for on-site monitoring of nanoplastics in aquatic environments.