%0 Journal Article
%T Nonuniform Distribution of Capping Ligands Promoting Aggregation of Silver Nanoparticles for Use as a Substrate for SERS
%A Yanwei Zhang
%A Fangli Wang
%A Handong Yin
%A Min Hong
%J Advances in Nanoparticles
%P 104-111
%@ 2169-0529
%D 2013
%I Scientific Research Publishing
%R 10.4236/anp.2013.22018
%X <span>Citrate-reduced silver nanoparticles (Ag-NPs) are used extensively for surface-enhanced Raman scattering (SERS) studies</span><span>,</span><span> but are typically found to aggregate using an aggregation agent. This study is aimed at developing a simple, stable, and reproducible aggregated method for Ag-NPs without any aggregation agents in aqueous solutions. The aggregation is induced by the process of centrifugation, water washing and ultrasonication. A mechanism based on the nonuniform distribution of capping ligands is proposed to account for the aggregated structure formation. UV-Vis-NIR extinction spectra and TEM allowed us to identify the existence of Ag-NPs aggregation. Further, due to the polydisperse mixture of Ag-NPs (20~65 nm) used in the present work, Ag-NPs are aggregated closely, which contribute to the observation of low-concentration SERS from the residual citrate layer or even the single-molecule SERS of R6Gon aggregation. After the evaporation of droplet of Ag-NPs aggregation on the Si substrate, citrate or R6Gcould also be detected but with marked redor blue-shifts.</span> 
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%K Silver Nanoparticle
%K Aggregation
%K SERS Analysis
%K Citrate
%K R6G
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=31476