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Fabrication and surface enhanced Raman spectroscopy of single Au@SiO 2 dimers linked by benzenedithiol
Author(s) -
Guo Qinghua,
Xu Minmin,
Yuan Yaxian,
Gu Renao,
Yao Jianlin
Publication year - 2016
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.4845
Subject(s) - linker , dimer , raman spectroscopy , raman scattering , yield (engineering) , dithiol , plasmon , materials science , molecule , surface plasmon resonance , nanoparticle , steric effects , cluster (spacecraft) , crystallography , nanotechnology , chemical physics , chemistry , optoelectronics , stereochemistry , optics , physics , organic chemistry , computer science , metallurgy , programming language , operating system , biochemistry
Metal nanoparticle dimers with controllable gap distance have attracted considerable attention because of their promising application in plasmonics. Generally, gaps with nanometer or subnanometer dimensions generate localized surface plasmon resonance (LSPR) coupling effect, thus contributing to a strong electromagnetic field for improving surface enhanced Raman scattering (SERS) effect. Here, we developed a facile approach to fabricate Au@SiO 2 dimers through the steric hindrance effect, in which the SiO 2 shell functioned as a block and a rigid dithiol molecule was employed as linker. The thickness of the SiO 2 shell played a critical role in improving the yield of dimers. The dimerization efficiency increased significantly as the shell thickness decreased to ~1 nm. When 1,4‐benzenedithiol was used as linker molecule, the yield of dimers was ~30%. Few dimers were obtained when mecaptobenzonic acid was used as linker. A thicker shell is associated with a low yield of dimer, whereas a thinner shell resulted in the formation of multimers and linear structures. The low number of linker molecules on the exposed area of monodisperse single nanoparticles and the lack of LSPR coupling effect (‘hot spots’) resulted in the disappearance of SERS signals of the linkers. The estimated SERS enhancement factor was about eight fold because of the strong coupling effect in the gap of the dimer with the distance of the dithiol molecular length. From the above results, SERS combined with SEM could be developed into powerful tools for monitoring the formation of dimers and positioning of single dimers. It may aid the control of assembly of Au nanoparticles and in probing key issues about SERS enhancements. Copyright © 2015 John Wiley & Sons, Ltd.