Spark Ablation-Generated Nanoparticles on Filter Paper: A 3D SERS Platform for Cost-Effective and Rapid Thiram Sensing

Surface-enhanced Raman spectroscopy (SERS) is a highly specific technique for identifying the contents of an unknown sample. It is based on the plasmonic enhancement provided by a nanostructured surface called a SERS substrate. The enhancement is heavily influenced by the geometric features of the substrate, which can be manipulated through the fabrication of the nanostructure. Here, we propose a fabrication method that uses nanoparticles synthesized in the gas phase through spark ablation; the generated particles are deposited onto filter papers, forming 3D SERS active nanostructures along the depth of the filter. The SERS properties of the structure can be tuned through the configuration of the experimental properties: we present how the spark frequency and the compaction temperature can be used to affect the size and shape of the generated nanoparticles and how the choice of filter affects the overall SERS enhancement. The fabricated SERS substrates were then used to detect a widely used pesticide: thiram. Using our substrates, the direct detection of 1.2 ppm thiram was feasible. We also proposed a deep-learning-based scheme, with which even lower concentrationsin between 0.03 and 0.48 ppmcould be distinguished, with an accuracy of 94.44%.