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Volume 181, 2015
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Kinetics of aggregation and growth processes of PEG-stabilised mono- and multivalent gold nanoparticles in highly concentrated halide solutions

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Abstract

5–6 nm gold nanoparticles were prepared by hydrolytic decomposition of [NMe4][Au(CF3)2] and functionalized in situ with mono- and multivalent thiolated PEG ligands. Time-dependent changes of the nanoparticles were monitored in aqueous NaCl, NaBr, and NaI solutions by UV-Vis spectroscopy, TEM, and HRTEM. The purely sterically protected particles are stable in ≤1 M NaCl and NaBr solutions, regardless of the valence of the ligands. At higher concentrations (≥2 M), the monovalent stabilized particles show minor reaction limited colloidal aggregation. In NaBr but not in NaCl solutions a minor Ostwald ripening also occurs. The divalent stabilized particles remain colloidally stable in both halide solutions, even if the temperature is raised or the concentration is increased above 2 M. In ≤1 M aqueous NaI solutions the particles remain stable. Above, the monovalent stabilized particles undergo an oxidative reaction, resulting in a time-dependent shift and broadening of the absorbance spectrum. Finally, this process slows down while the width of the spectra slightly narrows. The kinetics of this process can be described by a two-step sigmoidal process, comprising a slow induction period where active species are formed, followed by a fast growth and aggregation process. The increasing concentration of fused structures from the aggregates during this process results in a narrowing of the size distributions. The divalent stabilized particles show only some minor broadening and a slight shift of the absorbance spectra in ≤3 M NaI solutions. These observations confirm the excellent stability of the multivalent stabilized particles from this chloride-free particle synthesis.

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Submitted
16 Feb 2015
Accepted
19 Feb 2015
First published
19 Feb 2015

Faraday Discuss., 2015,181, 85-102
Article type
Paper
Author version available

Kinetics of aggregation and growth processes of PEG-stabilised mono- and multivalent gold nanoparticles in highly concentrated halide solutions

B. Stein, D. Zopes, M. Schmudde, R. Schneider, A. Mohsen, C. Goroncy, S. Mathur and C. Graf, Faraday Discuss., 2015, 181, 85
DOI: 10.1039/C5FD00024F

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