Thiol-Terminated Di-, Tri-, and Tetraethylene Oxide Functionalized Gold Nanoparticles:  A Water-Soluble, Charge-Neutral Cluster

Abstract

A series of gold nanoclusters stabilized by ligands containing short ethylene oxide oligomers of fixed length were prepared and characterized. The thiols CH3(OCH2CH2) n SH (where n = 2, 3, and 4) were substituted onto the surface of 1.8-nm hexanethiol-capped gold clusters by a thiol-exchange reaction, and the resulting nanoclusters were characterized by NMR, FTIR, and UV/vis spectroscopies; TGA; and TEM analysis. A degree of ligand exchange greater than 99% was achieved, and the gold core diameter remained unchanged in the final material. Of particular interest, the cluster with n = 2 was water-insoluble, whereas those with n = 3 or 4 were water-soluble. The thin-film electrical conductivities of these clusters were compared with those of alkanethiol-capped clusters of similar chain lengths and found to be roughly 1 order of magnitude greater. In a chemical vapor sensor configuration, this series of clusters displayed strong electrical responses that showed a correlation between the length of the ethylene oxide ligand and the polarity of the vapor.

Structure elucidation of nanoparticle-bound organic molecules by 1H NMR

“…One popular approach is to modify nanoparticles with hydrophilic polymers {e.g., cyclodextrin (CD) [48,49], carbohydrates [26,50], peptide [16,51] and polyethylene glycol (PEG) [52][53][54]}. The polymer-capped nanoparticles show enhanced solubility in aqueous solutions and reduced cytotoxicity.…”

Biomolecular Assembly of Gold Nanocrystals

“…To address this issue, researchers have coated the nanocrystals with a wide array of alternative passivation agents, including phosphines, polymers, and proteins [25][26][27][28][29][30]. Within these categories, a wide variety of sizes of molecules may be used to passivate the gold surfaces.…”

“…For example, Foos et al, reported a variety of ethylene oxide coated, charge-neutral gold nanocrystals that can be subsequently modified with thiols, including thiolated DNA [26]. Other work has shown neutral, polyethylene glycol (PEG) coated nanocrystals [36].…”

A tetraethylene glycol coat gives gold nanoparticles long in vivo half-lives with minimal increase in size

“…Among these, tetraethylene glycol (TEG) is particularly attractive because it has been found to confer properties comparable to those of PEG in vitro, but with less impact on overall particle size. [5][6][7][8][9] Currently, no articles document the effect of this coat on nanoparticles in vivo. We here describe the results of experiments aimed at rectifying this absence using particles synthesized with a gold core to facilitate observation with both light microscopy (LM) and transmission electron microscopy (TEM).…”