Surface-Enhanced Raman Scattering-Active Gold Substrates with Silver Nanoparticle Overlayers

T.-C. Hsu, K.-H. Yang, Y.-C. Liu
Taipei Medical University, TW

Keywords: surface-enhanced Raman scattering, underpotential deposition, coverage, stability

Summary:

Because Ag and Au nanoparticles (NPs) possess well-defined localized surface plasmon resonance (LSPR) they are generally employed in the studies of surface-enhanced Raman scattering (SERS). The advantage of SERS-active Ag NPs is their higher SERS enhancement than Au NPs. On the other hand, the disadvantage of SERS-active Ag NPs compared to Au NPs is their serious decay of SERS enhancement in ambient laboratory air. In this work, we modify the idea of underpotential deposition (UPD) to develop a new electrochemical strategy to prepare highly SERS-active Ag NPs deposited on a roughened Au substrate with high coverage of 0.95. Experimental results indicate that the SERS of Rhodamine 6G (R6G) observed on this developed substrate with Ag/Au NPs exhibits a higher intensity by ca. 50-fold of magnitude, as compared with that of R6G observed on the blank substrate with Au NPs. The limit of detection (LOD) for R6G measured on this substrate is markedly reduced to 2 × 10-15 M. Moreover, aging of SERS effect observed on this developed substrate is significantly depressed, as compared with that observed on a generally prepared SERS-active Ag substrate, in an atmosphere of 50% RH and 20% (v/v) O2 at 30 oC for 60 day.