Electronic structure, magnetic properties, and microstructural analysis of thiol-functionalized Au nanoparticles: role of chemical and structural parameters in the ferromagnetic behaviour

Abstract

Gold nanoparticles (NPs) have been stabilized with a variety of thiol-containing molecules in order to change their chemical and physical properties; among the possible capping systems, alkane chains with different lengths, a carboxylic acid and a thiol-containing biomolecule (tiopronin) have been selected as protecting shells for the synthesized NPs; the NPs solubility in water or organic solvents is determined by the protecting molecule. A full microstructural characterization of these NPs is presented in the current research work. It has been shown that NPs capped with alkanethiol chains have a marked ferromagnetic behaviour which might be also dependent on the chain length. The simultaneous presence of Au-Au and Au-S bonds together with a reduced particle diameter, and the formation of an ordered monolayer protective shell, have been proved to be key parameters for the ferromagnetic-like behaviour exhibited by thiol-functionalized gold NPs.

Thiol-modified gold nanoparticles deposited on silica support using dip coating

“…The non-Landau diamagnetism contribution is due to the very strong polarization at the interface between the gold and the glass substrate. Also, strong diamagnetic contribution at 300 K was observed also by Guerrero et al [32] in thiol capped gold layer with COOH groups. The authors explained this diamagnetic observation by the formation of the polymeric behaviour of the sample.…”

“…The size of the gold particles (12 ± 3 nm), estimated from the HRTEM pictures, was almost the same for all studied samples, but the particles size distribution exhibit the narrower character in the thiol-capped gold samples in comparison to broader particle size distribution in pure Au NPs sample. This can be due to the ligand exchange reaction, which starts an etching process at around Au NPs [32]. In the TEM pictures of thiol-modified Au NPs, a diffuse contrast around the Au nanoparticles is clearly visible, which corresponds to glutathione (Fig.…”

Functionalization of magnetic nanowires for biomedical applications

“…When capping with organic molecules that form a self-assembled monolayer on Au, the ferromagnetic properties become more pronounced. In contrast, the polymeric-like phases having -Au-S-Au-S-bonds do not show any ferromagnetic response (Guerrero et al, 2008).…”

Synthesis and Characterization of Noble Metal Nanowires

“…Polymeric-like phases (-Au-S-Au-S-bonds) do not show magnetization properties. (Guerrero et al, 2008).…”