AVS 60th International Symposium and Exhibition
    Applied Surface Science Thursday Sessions
       Session AS+BI+EM+NL+NS+SS-ThM

Paper AS+BI+EM+NL+NS+SS-ThM11
Comparison of the Structure and Solution Behaviors of 20nm Silver and 20nm Silver-Shell-Gold-Core Nanocomposites in Aqueous Biological Media

Thursday, October 31, 2013, 11:20 am, Room 204

Session: Nanoparticle Surface Chemistry
Presenter: D.R. Donald, Pacific Northwest National Laboratory
Authors: P. Munusamy, Pacific Northwest National Laboratory
S. Chen, Imperial College London, UK
L.B. Yen, Imperial College London, UK
C.W. Wang, Pacific Northwest National Laboratory
M. Engelhard, Pacific Northwest National Laboratory
A. Porter, Imperial College London, UK
D.R. Donald, Pacific Northwest National Laboratory
Correspondent: Click to Email
Different synthesis routes have made it possible to produce silver nanoparticles with variety of structure properties such as size, shape, and surface functionality. Synthesizing or processing silver nanoparticles under different conditions can impart variations in properties and reactivity which can influence the biological end points. In this study we have examined how silver nanoparticles of nearly identical size, as measured by dynamic light scattering, but produced with and without gold core behave in the biological media RPMI 1640 with FBS, the cell culture media used in our laboratory for in vitro nanotoxicity studies. The initial physico-chemical characterization of citrate capped nanoparticles using DLS size and surface charge measurement showed particles of average size 27nm with negative surface charge. Structure and compositional analysis using STEM and XPS confirmed the presence of gold core of size ~7nm in one set of particles. The detailed structure of the pure silver and the core-shell particles differ significantly. Based on TEM images and XRD measurements, the pure silver particles are highly crystalline, made up of ~ 15-20 nm crystallites with well-defined grain boundary or slip plane defect structures. The silver surrounding the gold core is made up of smaller highly disordered crystallites. After 24h incubation in culture media, STEM images showed that the particles with Au core dissolved significantly and non-uniformly indicating solution attack down to the gold core. In contrast, pure silver particles underwent more uniform dissolution with some indication of varying rates for different crystal faces. In addition to the dissolution of the primary particles of both types, new smaller “daughter” silver particles were observed both nearby or some distance away from the initial nanoparticles. Centrifugation followed by ICP-MS analysis of the supernatant was used to quantify the amount of dissolved silver. The dissolution extent for core-shell particles in 24h was 3 times higher than that for pure Ag. These results highlight the significance of synthesis route and sample structure on the solution behavior of similar nanoparticles in biologically relevant environmental conditions.