Highly reusable nanoporous silver sheet for sensitive SERS detection of pesticides
Surface-enhanced Raman spectroscopy (SERS) enables pesticide detection at the point-of-need, but its practical application is limited by the expensive and disposable SERS substrates. Here, we report a reusable nanoporous silver (NPAg) sheet for the SERS detection of organochlorine pesticides, aiming to maximize the cost-efficiency in substrate regeneration. The NPAg sheet is prepared by a reduction-induced decomposition method without chemical induced random aggregations. This SERS substrate is sensitive to various analytes regardless of the affinity to metal surface such as rhodamine B, dichlorodiphenyl-trichloroethane (DDT), and lindane due to its large surface area and the coral rock-like morphology. The SERS signal of lindane, a typical organochlorine pesticide, is identified and quantified with a minimum detectable concentration of 3 x 10-7 M (87 ppb), which is below the maximum residue limits in various food set by the regulators across the world. More importantly, after a few minutes of ultrasonic cleaning in water, the NPAg sheet can be reused for at least 20 times with reproducible SERS activity. Furthermore, the NPAg sheet remains stable on their sensitivity and reusability after several months of bare strorage. Therefore, the NPAg sheet as SERS substrate holds great promise of mass productions and convenient applications for low-cost pesticide analysis.