Insertable and reusable SERS sensors for rapid on-site quality control of fish and meat products

Surface-enhanced Raman spectrometry (SERS) is one of the most important on-site testing tools. However, it remains a great challenge for the SERS to achieve on-site safety evaluation for fish and meat products, due to their extremely complicated compositions of wide-ranging chemicals, the potential existence of unknown micro-organisms, and the difficulty to directly acquire spectra information from inside the product. Here, we report a convenient strategy for mass fabrication of a novel type of SERS sensors through electrochemical nanoetching of commercial Ag needles. The thus obtained SERS sensor features rich surface nanostructures of ultrahigh SERS sensitivity, making them highly compatible with low-cost portable Raman spectrometers to realize on-site detection. These sensors can be inserted into the products to read out the depth-profile information, e.g., from purine, proteins, and lipids. Unlike the conventional insertable SERS sensors that are coated with foreign plasmonic nanoparticles, the novel sensor possesses nano-carved plasmonic surface structures that are highly resistant to aggregation and materials loss, enabling much improved durability well suited for depth-profiling applications. Interestingly, these sensors can be repetitively regenerated by acid rinsing while maintain high enhancement effect. Instant detection of fish or meat spoilage at early stage is realized in a few minutes using the novel sensors reported here, demonstrating an attractive means for on-site food quality control in a rapid, low-cost, and convenient manner.