Aggregation and Precipitation of Gold Nanoparticle Clusters in Carbon Dioxide-Gas-Expanded Liquid Dimethyl Sulfoxide

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• 作者：Jennifer N. Duggan ; Christopher B. Roberts
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：July 3, 2014
• 年：2014
• 卷：118
• 期：26
• 页码：14595-14605
• 全文大小：623K
• ISSN：1932-7455

文摘

Previous post-synthesis nanoparticle processing techniques have demonstrated that carbon dioxide (CO₂)-gas-expanded liquids can be used as a tool to controllably induce nanoparticle precipitation and size-selective fractionation. Until now, these previous studies have been limited to using nonpolar solvents (e.g., hexane) in CO₂-gas-expanded liquids as a method to control nanoparticle precipitation by exploiting subtle changes in dispersive forces. We demonstrate a facile, post-synthesis nanoparticle processing technique to controllably aggregate gold (Au) nanoparticles into supraparticle clusters using CO₂-gas-expanded dimethyl sulfoxide (DMSO), a polar, aprotic solvent, as well as the subsequent ability to precipitate these Au nanoparticle clusters from the DMSO solvent media at moderate applied CO₂ pressures. Dispersions of Au nanoparticles have been prepared in three different DMSO solutions (where DMSO can serve as both the solvent and a stabilizing ligand): (i) neat DMSO, (ii) DMSO + oleic acid, and (iii) DMSO + stearic acid. UV鈥搗is spectroscopy was used to monitor the surface plasmon resonance band of the Au nanoparticle dispersions where it was determined that the post-synthesis aggregation of the Au nanoparticles in DMSO is a direct function of the applied CO₂ pressure. Furthermore, it was observed that the subsequent precipitation of the Au nanoparticle clusters in DMSO was induced by the applied CO₂ pressure whereby the Au nanoparticle clusters would precipitate as a function of time (at a specified pressure). These findings illustrate the markedly different dispersibility of nanoparticles in CO₂-gas-expanded nonpolar and polar solvent systems.