Synthesis of Uniformly Sized Mesoporous Silver Films and Their SERS Application
Hyunsoo Lim, Dabum Kim, Goomin Kwon, Hyun-Jong Kim, Jungmok You, Jeonghun Kim, Miharu Eguchi, Ashok Kumar Nanjundan, Jongbeom Na, Yusuke Yamauchi
Abstract
Nanostructured metal films and particles have been recently exploited as substrates for surface-enhanced Raman spectroscopy (SERS) studies because their intrinsic properties lead to substantial Raman scattering enhancement. Among metals, silver (Ag) is one of the efficient elements for SERS because of its potential for high Raman scattering enhancement and low molecular detection level. Substantial electric field enhancement takes place around the center of uniform mesopores as well as on the walls between the pores, leading to enhanced light scattering as well as SERS. However, aggregation and high surface energy, which are intrinsic to Ag structures, hamper the formation of mesoporous structures. In this study, we have successfully achieved the first synthesis of uniformly sized mesoporous silver films (MAgFs) using self-assembled polymeric micelles under controlled conditions. The synthetic conditions such as temperatures, applied potentials, and deposition times were fine-tuned to obtain the optimized mesoporous structure. The MAgF demonstrated a 10−9 M level of detection and 107 to 108 enhancement factor without any surface modification. The simple synthetic process, the potential of high performance, and a large detecting area of MAgFs enable us to realize the fabrication of a suitable SERS substrate.