Abstract
We use the aurophilic interactions shown by lanthanides to overcome the sulfur-gold interaction. UV-vis and X-ray photoelectron spectroscopy confirm that yttrium or lanthanide chlorides easily displace sulfur ligands from the surface of thiol-stabilized gold nanoparticles.
Highlights
The modification of gold surfaces with thiol derivatives has been extensively explored[1, 2, 3, 4] in the past two decades since the first report in 1993 by Mulvaney and Giersig[5] and the very wellknown Brust-Schiffrin bi-phasic method developed in 1994.6 The thiolate bond resulting from sulfur-gold interaction has proven even stronger than the gold-gold metallic bond[7] and the modification of gold surfaces, gold nanoparticles (AuNPs), with thiolate ligands is considered the most stable passivation method for AuNPs.[8, 9, 10]
As is well known, thiol compounds have strong affinity for Au surfaces due to the formation of a strong Au−S bond; 7, 21 we show here that the Au surface thiol passivation can be defeated in the presence of rare earth (RE) ions
AuNPs were subjected to ligand displacement in the presence of RE salts Yttrium (YCl3), Ytterbium (YbCl3) and Thulium (TmCl3) and studied by UV-vis and XPS spectroscopy
Summary
The modification of gold surfaces with thiol derivatives has been extensively explored[1, 2, 3, 4] in the past two decades since the first report in 1993 by Mulvaney and Giersig[5] and the very wellknown Brust-Schiffrin bi-phasic method developed in 1994.6 The thiolate bond resulting from sulfur-gold interaction has proven even stronger than the gold-gold metallic bond[7] and the modification of gold surfaces, gold nanoparticles (AuNPs), with thiolate ligands is considered the most stable passivation method for AuNPs.[8, 9, 10] The exchange of ligands at the. AuNPs surface has been studied as many applications need to recover either the ligand,[11] the AuNP or both.[12, 13] Aurophilic interactions between the surface of gold nanoclusters (AuNCs) and lanthanides, namely Ln3+-Au+, have recently been reported.[14] the relative strength of the Ln3+-Au+ interaction is still unknown, especially compared to the well-known stability of the sulfur-gold bond. We use lanthanides as a new chemical strategy for sulfur ligand displacement from thiol-stabilized AuNPs. Nowadays, the use of lanthanides is mainly related to the formation of up-conversion nanoparticles for bioanalytical applications.[15, 16] The inner electronic configuration of these elements is suitable for electronic excitation that gives rise to the photon-upconversion process. UV-vis and XPS analysis prove that the sulfur material is released from the surface of the Au nanostructure upon addition of RE salts, possibly through the mechanism proposed in Scheme 1
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