Facile fabrication of a large-area and cost-effective PDMS-SERS substrate by sandpaper template-assisted lithography

In this study, a highly reproducible Ag NP loaded polydimethylsiloxane (PDMS) SERS substrate was fabricated by a simple template lithography method. Sandpaper, a widely available material with various roughnesses, was used as the template, which allowed convenient large-area preparation (similar to 154 cm(2)) of the flexible SERS substrate with extremely low costs. In order to obtain the highest SERS sensitivity, the roughness of sandpaper and the loading amount of Ag NPs were optimized. With Rhodamine 6G (R6G) as the probe, the limit of detection (LOD) reached 4 femto moles. It is also worth mentioning that, even in the case of large-area production, the substrate has high signal stability (relative standard deviation (RSD) approximate to 11.9%) and sensitivity. Furthermore, different from previous reports in the literature, this substrate can not only be used for Raman enhancement but also provide the direct surface sampling capability. In addition, the SERS properties of the substrate before and after stretching were also investigated, and the results showed that the stretching had minimum impact on the SERS performance, which ensured the practical applications of the substrate. Cherry tomatoes spiked with pesticides (triazophos and methyl parathion) were successfully analyzed with virtually no sample pretreatment. The LOD of the substrate was found to be 7.9 ng for both pesticides.