Surface-enhanced Raman scattering of silver-gold bimetallic nanostructures with hollow interiors

Abstract

Surface-enhanced Raman scattering (SERS) activity of silver-gold bimetallic nanostructures (a mean diameter of ∼100nm) with hollow interiors was checked using p-aminothiophenol (p-ATP) as a probe molecule at both visible light (514.5nm) and near-infrared (1064nm) excitation. Evident Raman peaks of p-ATP were clearly observed, indicating the enhancement Raman scattering activity of the hollow nanostructure to p-ATP. The enhancement factors (EF) at the hollow nanostructures were obtained to be as large as (0.8±0.3)×106 and (2.7±0.5)×108 for 7a and 19b (b2) vibration mode, respectively, which was 30–40 times larger than that at silver nanoparticles with solid interiors at 514.5nm excitation. EF values were also obtained at 1064nm excitation for 7a and b2-type vibration mode, which were estimated to be as large as (1.0±0.3)×106 and (0.9±0.2)×107, respectively. The additional EF values by a factor of ∼10 for b2-type band were assumed to be due to the chemical effect. Large electromagnetic EF values were presumed to derive from a strong localized plasmas electromagnetic field existed at the hollow nanostructures. SERS activity of hollow nanostructures with another size (a mean diameter of ∼80nm) was also investigated and large EF for 7a and b2-type band are obtained to be (0.6±0.3)×106 and (1.7±0.7)×108, respectively, at 514.5nm excitation and (0.2±0.1)×106 and (0.6±0.2)×107, respectively, at 1064nm excitation. Although the optical properties of the hollow nanostructures have not yet been well studied, high SERS activities of the nanostructures with hollow interiors have been exhibited in our report.

Recent Advances in the Synthesis of Plasmonic Bimetallic Nanoparticles

“…Au/Ag plasmon shifts have also been studied in a variety of other morphologies and applications. Studies of the surface-enhanced Raman scattering of Au/Ag hollow nanostructures [31], hyper-Raleigh scattering of Au core, Ag shell particles [32], and other spectroscopic techniques have been examined, as well as direct imaging of the nanoparticles [33].…”

Recent advances in surface‐enhanced Raman scattering detection technology for microfluidic chips

“…On the other hand, Tian et al [57] have carried out excellent work to generate SERS directly on transition metals (e.g., Pt, Ru, Rh, Pd, Fe, Co, Ni, and their alloys) by developing various roughening procedures and optimizing the performance of the confocal Raman microscope. More recently, functional nanocolloids, such as mixed silver/gold colloids [58] and hollow gold nanospheres (HGNS) [59][60][61], have been introduced. Silver-coated gold colloids can be prepared by growing the seeds of silver nanoparticles on gold surfaces by chemical reduction methods.…”

Nanoparticle SERS Substrates

“…Similar research was done by Rivas et al, who prepared Ag-coated Au and Au-coated Ag colloidal particles through chemical reaction and found that the composition of Ag/Au colloidal particles depends on the relative amount of the depositing metal; the SERS activity of the bimetallic nanoparticles was found to be placed between that of Ag and Au particles [103]. Silver/gold bimetallic nanoparticles with hollow interiors were made by our group and these showed great enhancement for the probe molecules [106]. Composite Au/Ag or Ag/Au core-shell nanoparticles were also fabricated for SERS substrate [107,108] and used for single-molecule detection [100].…”