Synthesis of flexible SERS sensing platform of graphene/Ag-popcorns/ PMMA for ultrasensitive detection

Surface-enhanced Raman scattering (SERS) with ultrahigh sensitivity has garnered significant attention for quantitative analysis and chemically specific detection. However, conventional SERS platforms, typically structured by depositing plasmonic micro/nanoparticles onto rigid substrates, face limitations in further advancement and applications. In this study, we present a novel method to prepare a flexible SERS film substrate composed of graphene overlayer (G) atop a self-assembled array of silver micropopcorns (Ag MPs) and a polymethyl methacrylate (PMMA) membrane. We show that adding an overlayer of graphene improves substantially overall SERS performance. This flexible G/Ag MPs/PMMA film substrate achieves a detection limit as low as 100 picomolar for rhodamine 6G (Rh6G) molecules and identifies mixtures containing Rh6G (10^-11 M) and crystal violet (CV, 10^-6 M) molecules. Furthermore, the flexible SERS structure enables quantitative detection of thiram, achieving a detection limit of 0.005 ppm, well below the allowable limit in food. This study provides a robust SERS platform that advances fundamental research and facilitates the development of practical applications in quantitative analysis, detection, and biological sensing. Combining graphene and Ag MPs on a flexible PMMA substrate offers a versatile and scalable approach to enhancing SERS performance, paving the way for future innovations.