Nanoporous Ag-Decorated Ag₇O₈NO₃ Micro-Pyramids for Sensitive Surface-Enhanced Raman Scattering Detection

Abstract

Porous noble metal nanomaterials can be employed to construct sensitive surface-enhanced Raman scattering (SERS) substrates, because the plasmonic nanopores and nanogaps of the porous materials can provide a larger number of hotspots, and can also serve as containers of analyte molecules. However, the fabrication processes of nanoporous noble metal are generally complicated. Here, a facile method is presented to prepare nanoporous Ag nanoparticles-decorated Ag7O8NO3 micro-pyramids, which are fabricated through the chemical reduction of the electrodeposited Ag7O8NO3 micro-pyramids using NaBH4. The Ag7O8NO3 micro-pyramids are fabricated by electrodeposition by using a simple aqueous solution of AgNO3 as electrolyte. Then, porous Ag-decorated Ag7O8NO3 micro-pyramids are achieved by the chemical reduction of the surface of the electrodeposited Ag7O8NO3 micro-pyramids with NaBH4. The high-density nanopores and nanogaps of the fabricated nanoporous Ag can provide plenty of hot spots for Raman enhancement. Additionally, the nanopores have an effective capacity to trap and enrich analytes. Using rhodamine 6G (R6G) as a probe molecule, the SERS performance of the fabricated SERS substrate has been investigated. It is found that a limit of detection (LOD) ~1.0 × 10−15 M can be achieved for R6G. Then, the SERS substrates are employed to detect dye molecule (crystal violet) and pesticide (thiram), and their LODs are calculated down to 9.6 × 10−13 M and 1.3 × 10−15 M, respectively. The enhancement factor of the fabricated SERS substrate is estimated to be as high as 5.6 × 108. Therefore, the nanoporous Ag-decorated Ag7O8NO3 micro-pyramids have shown promising application in the sensitive SERS detection of organic molecules.

Keywords

• surface-enhanced Raman scattering
• detection
• porous silver
• pesticide
• chemical reduction