Portable and Reliable Metallic-Nanoparticle-Based Surface-Enhanced Raman Scattering (SERS) Substrate for Sensing Applications

The rapid detection and identification of harmful bacteria for food quality control, environmental pollution, medical diagnostics, and chemical and biological crises constitutes a crucial issue. Here, we demonstrate a strategy for sensing bacteria based on the surface-enhanced Raman scattering method. The procedure involves the synthesis of gold nanoparticles (AuNPs) via a simple chemical reduction method and subsequent studies on bacteria. The concentrated AuNPs, coupled with aluminum foil, form a SERS-active substrate and then the bacterial sample is placed on this substrate to identify the strain of bacteria present. After an interaction time of approx. 5 min, the substrate is put on the sample stage of a Raman spectroscope and a laser source of 785 nm is incident on it. The cell walls and intracellular components of the bacteria have consistent and distinctive characteristic bands which aid in the identification of the bacterial strains present in the sample. This substrate offers advantages such as a rapid acquisition time at an extremely low power, great sensitivity, and a simple operating technique that does not require any complex procedures or protocols to collect bacteria. The substrate shows an enhancement factor tothe order of 10⁷ and a limit of detection of 10^-7 M for Rhodamine 6G. The developed SERS-active substrate, with its low cost, reproducibility, and outstanding detection capability, has a wide range of applications, including food safety and tracking the environment.