Silver Nanoparticles @ Sulfur-Enriched Polymer for Quantitative SERS-Based Detection of Methyl Red, Methylene Blue, and Ciprofloxacin

Surface-enhanced Raman spectroscopy (SERS) is gaining attention, with ongoing efforts focused on refining substrate fabrication techniques to develop smart SERS substrates for real-world applications. This work presents a chemically and thermally stable polymer nanocomposite in which waste sulfur, functionalized with vinylic monomer (1,3-diisopropenylbenzene (1,3-DIB)) via inverse vulcanization, is integrated with silver nanoparticles (Ag NPs). The sulfur-enriched polymer (SEP) effectively stabilizes Ag NPs, providing a relatively uniform surface that enhances the efficiency of the SERS substrate (Ag@SEP). The fabricated Ag@SEP nanohybrid was analyzed using an array of spectroscopic methods such as scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy. The average particle size of distributed Ag NPs on the SEP surface was found to be 22.16 nm. The developed Ag@SEP SERS substrate achieved remarkable signal enhancement, detecting methyl red (0.06 μM), methylene blue (2.14 μM), and ciprofloxacin (0.79 μM) with ultralow detection limits, demonstrating high sensitivity. Experimental findings revealed that the relative standard deviation (RSD) of the Ag@SEP substrate was 4.55%, showing its excellent spot-to-spot uniformity. To understand the SERS mechanism, DFT calculations were also performed, which confirms that SERS detection is driven by a charge transfer mechanism. The proposed Ag@SEP SERS sensor featured an easy, low-cost fabrication process and demonstrated high stability, reproducibility, and detection efficiency, making it suitable for diverse analytical applications.