Regulation of Hierarchical Structure on Surface-enhanced Raman Scattering Characteristics of Nanoporous Metals

Hierarchical nanoporous materials with high-density "hot spots" were obtained by constructing secondary mesopores on the single-stage nanoporous metal ligaments. The finite difference time domain method was used to simulate the local electromagnetic field intensity and distribution of hierarchical nanoporous structures, and the SERS characteristics of dealloyed hierarchical nanoporous metals were detected with the help of Raman spectroscopy. Combined experimental results with theoretical analysis, it can be seen that the local electromagnetic field intensity and hot spots density of the hierarchical nanoporous metals are higher than that of the single-stage nanoporous metals, resulting in better SERS activity. The detection limit of hierarchical nanoporous gold and hierarchical nanoporous copper for crystal violet molecules can reach 10(-11) mol.L-1, and the SERS enhancement factor is about two orders of magnitude higher than that of single-stage nanoporous metals. The study indicates that the introduction of secondary structure can greatly improve the local electromagnetic field intensity of single-stage nanoporous metals, which provides a new method for preparing of high-performance SERS substrate.