Nanoporous silver nanorods as surface-enhanced Raman scattering substrates

Structures with dense nanopores are desirable as surface-enhanced Raman scattering (SERS) sensing substrates because the nanopores can behave as both analyte containers and SERS-active sites (known as hot spots). Inspired by the dealloying process to prepare nanoporous structures through selectively removing active metals from their alloy, we developed a method to prepare nanoporous Ag nanorods through chemical reduction of the electrodeposited Ag7O8NO3 nanorods using a strong reducing agent (e.g., NaBH4). The length and the thickness of the Ag7O8NO3 nanorods could be controlled by the electrodeposition voltage and time. Nitrogen and oxygen elements were immediately removed from Ag7O8NO3 nanorods by the reducing agent, leaving behind a tremendous number of nanopores with a mean size of 20 nm, which can efficiently trap and enrich analytes. Meanwhile, the densely packed nanopores can behave as SERS hot spots to provide strong SERS enhancement. The nanoporous Ag nanorods as SERS substrates were used to sensitively detect adenine, spike glycoprotein, and polychlorinated biphenyls pollutants, as well as identify different types of bacteria. The simple fabrication process and the outstanding SERS performance of the nanoporous Ag nanorods make them promising candidates for SERS applications towards trace detection of pollutants, narcotics, food additives, and biomolecules.