Stability and Electrostatics of Mercaptoundecanoic Acid‐Capped Gold Nanoparticles with Varying Counterion Size

Abstract

The solubility of charged nanoparticles is critically dependent on pH. However, the concentration range available with bases such as NaOH is quite narrow, since the particles precipitate due to compression of the electric double layer when the ionic strength is increased. The stability of mercaptoundecanoic acid-capped Au nanoparticles is studied at a set pH using the hydroxide as base and different cations of various sizes. The counterions used are sodium (Na(+)), tetramethylammonium (TMA(+)), tetraethylammonium (TEA(+)), and tetrabutylammonium (TBA(+)). The particles precipitate in the 70-90 mM range with Na(+) as the counterion, but with quaternary ammonium hydroxides the particles are stable even in concentrations exceeding 1 M. The change in solubility is linked to a strongly adsorbed layer on the surface of the ligand shell of the nanoparticles. The increased concentration range obtained with TEAOH is further used to facilitate thiol exchange which occurs at a greater extent than would be achieved in NaOH solution.

Bioaccumulation and in-vivo dissolution of CdSe/ZnS with three different surface coatings by Daphnia magna

“…In addition, hardness is reported to play a significant role in the aggregation and sedimentation by compressing the diffuse double layer of NPs (Lee and Ranville, 2012). Here, the sedimentation of QSA was independent of the hardness of the three synthetic water types, indicating that the soft water already exceeded the critical coagulation concentration level (Kim and Berg, 1999;Laaksonen et al, 2006). Also it appears that QSA was also not sterically stabilized by the polymer coating.…”

Effect of surface coating on the biodistribution profile of gold nanoparticles in the rat

“…The administrated doses are in the range of those used in previous studies (summarized in Table 1 of [10]). The selection of the capping agents was based on previous reports on their stability and solubility in aqueous dispersions, as well as their ability to prevent nanoparticle aggregation [24,37]. Functionalization of the reference AuNPs (Cit-AuNPs) by 11-MUA and the pentapeptides CALNN, CAL-NS and CALND did not induce a significant change in size and surface charge ( Table 1), indicating that any change in the distribution pattern of the tested AuNPs would most likely be due to surface-ligand interactions with cells and biomolecules.…”

Tailoring the surface potential of gold nanoparticles with self-assembled monolayers with mixed functional groups

“…The cleaning procedure was repeated three times to remove impurities and byproducts as well as excess layers of surfactant formed on SAMs through acid-base reaction. A drop of 1 M HCl was sometimes added to ensure that Na + ions were displaced from the 16-mercaptohexadecanoic acid groups [22].…”