Au-NP-Decorated Cotton Swabs as a Facile SERS Substrate for Food-Safety-Related Molecule Detection

Recently, food safety has received considerable attention, and various analytical techniques have been employed to monitor food quality. One of the promising techniques in this domain is the surface-enhanced Raman scattering (SERS) technique. This study developed a facile, cost-effective SERS method by supporting a wipe-type substrate with a small-head cotton swab. We fabricated Au-nanoparticle (NP)-decorated cotton swabs (CS-Au NP) via the dropwise addition of gold colloid on the cotton fibers. These swabs exhibit reduced gold colloid consumption and a compact fiber structure, allowing for the uniform distribution of Au NPs and easy capture of molecular signals. Experiments were conducted to obtain a CS-Au NP wiper performance optimized for cotton swab selection, NaCl concentration, and Au NP layers. The Raman reporter molecule 4-mercaptopyridine was detected at a concentration of 1 × 10^-8 M and a relative standard deviation of ≤10%. The proposed SERS platform enables the facile and reliable detection of food-safety-related molecules such as malachite green on the surface of fruits and vegetables. This paper describes the development of an easy, cost-effective, and environment-friendly method of detecting food-safety-related molecules on various food surfaces through SERS.