Abstract
The ability to suspend plasmonic metal nanoparticles in apolar environments is an important feat towards harnessing their optical properties for use in amphiphilic biological environments. Pulsed laser Ablation in Liquids (PLAL) is a well-established method for the production of gold nanoparticles (AuNPs) in aqueous environments; however, ablation in organic liquids for the synthesis of hydrophobic AuNPs still has many unknowns, such as the relationship between colloidal stability and the ligand shell. In this study, hydrophobic AuNPs were produced by PLAL of gold in a 1-alkanethiol/n-decane solution and treated with laser fragmentation. Results demonstrate that longer chain length ATs produced particles with a smaller average size; however, there was no strong correlation between alkanethiol (AT) concentration and particle size. Stability was investigated by monitoring the temporal evolution of the extinction spectra which revealed that lower concentrations of AT stabilize the colloids while higher concentrations tend to result in quicker particle aggregation. Furthermore, longer chain length ATs demonstrated improved stability. Additionally, vibrational spectroscopy was employed to examine the AuNP surface chemistry, which pointed to the presence of oxidized carbon species and graphitic carbon.
Highlights
Published: 22 September 2021The application of organically functionalized gold nanoparticles (AuNPs) is quite prevalent in the literature, having been found to be advantageous in the areas of biochemical sensors [1,2,3], drug delivery systems [4,5], and cancer theranostics [6]
Of particular interest are AuNPs functionalized with alkanethiols (AT), where the thiol covalently bonds to the gold and tethers the alkane to the AuNPs, thereby imparting a hydrophobic ligand shell
We study the effect of alkanethiol concentration and chain length on particle size distribution, stability, and hydrophobicity
Summary
Published: 22 September 2021The application of organically functionalized gold nanoparticles (AuNPs) is quite prevalent in the literature, having been found to be advantageous in the areas of biochemical sensors [1,2,3], drug delivery systems [4,5], and cancer theranostics [6]. Of particular interest are AuNPs functionalized with alkanethiols (AT), where the thiol covalently bonds to the gold and tethers the alkane to the AuNPs, thereby imparting a hydrophobic ligand shell. This system of alkanethiol functionalized gold has garnered particular interest due to the formation of self-assembled monolayers (SAM), where the collective van der Waals interactions between alkane chains drives their assembly into a highly ordered phase with an upright orientation [7]. As shown by Dong et al, AT-capped AuNPs can result in unexpected effects such as enhanced magnetization, which scales with chain length [14].
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