Mechanically\nFlexible, Large-Area Fabrication of Three-Dimensional\nDendritic Au Films for Reproducible Surface-Enhanced Raman Scattering\nDetection of Nanoplastics

The escalating crisis\nof nanoplastic pollution in water and food\nproducts demands the development of novel methodologies for detection\nand recycling. Despite various techniques available, surface-enhanced\nRaman scattering (SERS) is emerging as a highly efficient technique\nfor the trace detection of micro/nanoplastics. However, the development\nof highly reproducible and stable, flexible SERS substrates that can\nbe used for sensitive detection in environmental medium remains a\nchallenge. Here, we report a fabrication of large-area, three-dimensional\n(3D), and highly flexible SERS substrate based on porous dendritic\nAu films onto a flexible indium tin oxide (ITO) substrate via facile,\nthermal evaporation of Au over the vacuum-compatible deep eutectic\nsolvent (DES)-coated glass substrate and subsequent direct transfer\nprocess. The as-fabricated 3D dendritic Au/ITO flexible substrates\ncan be used for ultrasensitive SERS detection of crystal violet (CV)\nas probe analyte molecules with the limit of detection (LOD) as low\nas 6.4 × 10<sup>–15</sup> M, with good signal reproducibility\n(RSD of 11.3%). In addition, the substrate showed excellent sensitivity\nin detecting nanoplastics such as poly(ethylene terephthalate) (200\nnm) and polystyrene (100 nm) with LODs reaching up to 0.051 and 8.2\nμg/mL, respectively. This work provides a facile approach for\nthe preparation of highly flexible plasmonic substrates, showing great\npotential for the SERS detection of a variety of environmental pollutants.