Self-Assembly of Alkylthiosulfates on Gold: Role of Electrolyte and Trace Water in the Solvent

Abstract

Spontaneous self-assembly of alkylthiosulfates on gold produce monolayers similar to the corresponding alkanethiols. Alkylthiosulfate self-assembly from THF solutions is inhibited in the presence of tetrabutylammonium tetrafluoroborate electrolyte. The mechanism of alkylthiosulfate self-assembly and the role of electrolyte and trace water in the solvent are investigated using open-circuit potential measurements, contact angle goniometry and redox electron transfer blocking experiments to explore the hypothesis that trace water present in the solvent facilitates monolayer formation on gold. Furthermore, the unique behavior of tetrabutylammonium tetrafluoroborate, compared to other tetrabutylammonium electrolytes, on the inhibition of alkylthiosulfate self-assembly has been explained.

Use of 3,3-Thiobis(1-propanesulfonate) to Accelerate Microvia Filling by Copper Electroplating

“…[58][59][60][61][62] Thus, the surface coverage of thiol molecules on these substrates is higher when the pH is lower. The TBPS molecule has no thiol group; however, it contains two sulfonic acid groups.…”

Water-soluble gold nanoparticles stabilized with cationic phosphonium thiolate ligands

“…The differences in size between the AuNPs derived from the PPTS zwitterion and PPTA salt can be explained on the basis of the differing passivation kinetics of the two types of ligand. [22][23][24][25][26] The first stage of the synthesis should be adsorption of the ligand on the surface of the growing particles and the thioacetate might be expected to be a more weakly binding ligand than the thiosulfate. Secondly, transformation of the thiosulfate or thioacetate to the thiolate occurs.…”

“…Recent studies into the formation of monolayers on gold surfaces from alkylthiosulfates show hydrolysis by trace amounts of water present in the solvent to be crucial. 23,24 The phosphonium-AuNPs reported here were prepared in a two-phase water/dichloromethane mixture. 20,21 However we cannot exclude the possibility that the growing gold nanoparticles and/or the reducing agent are involved in the cleavage of the thiosulfate S-S or thioacetate S-C bonds.…”

“…Cleavage of the sulfur-sulfur or sulfur-carbon bonds in the thiosulfate and thioacetate species generates thiolate anions in situ leading to water-soluble, cationic, phosphonium-functionalised AuNPs. The mechanisms of the formation of self-assembled monolayers on gold using alkyl thiosulfates (Bunte Salts) [22][23][24] as the precursor ligands has been the subject of recent studies which show that hydrolysis by trace amounts of water facilitates monolayer formation. Similarly, a number of studies have focused on the use of alkyl thioacetates as precursors for the formation of monolayers on gold.…”

Highly stable noble metal nanoparticles dispersible in biocompatible solvents: synthesis of cationic phosphonium gold nanoparticles in water and DMSO

“…However, the presence of water traces in the solvent used for the synthesis of colloidal gold nanoparticles, has shown to be crucial for the hydrolysis of the thiosulfate and thioacetate ligands and formation of alkylthiolates. 46,47 These thiolate anions will lead to the formation of phosphonium-functionalised gold nanoparticles. The presence of reducing agent in the solution also influences the cleavage of sulfur-sulfur and sulfur-carbon bonds.…”