Mechanism of Spontaneous Formation of Monolayers on Gold from Alkyl Thiosulfates

Fealy, Ryan J.; Ackerman, Steven R.; Ferguson, Gregory S.

doi:10.1021/la200143b

Cited by 13 publications

(29 citation statements)

References 20 publications

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“…45 Based on the 1 H NMR spectra, which did not show the presence of α H from free dialkyldisulfide or alkylthiolate in the organic phase (Figure 1b), the possibility of alkanethiolate formation before the adsorption of alkylthiosulfates on PdNP surfaces can be eliminated. In addition, another possibility of S -dodecylthiosulfate being reduced to dodecylthiolate was also examined by reacting S -dodecylthiosulfate with NaBH 4 in the absence of Pd 2+ complex.…”

Section: Resultsmentioning

confidence: 99%

Controlling Surface Ligand Density and Core Size of Alkanethiolate-Capped Pd Nanoparticles and Their Effects on Catalysis

2012

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This article presents systematic investigations on the relationship between the catalytic property and the surface ligand density/core size of thiolate ligand-capped Pd nanoparticles (PdNPs). The systematic variations in the two-phase synthesis of PdNPs generated from sodium S-dodecylthiosulfate were performed. The resulting PdNPs were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and 1H NMR and UV–vis spectroscopy. The decrease in the molar equivalent of sodium S-dodecylthiosulfate (Bunte salts) resulted in the formation of nanoparticles with lower surface ligand density and larger particle core size. A decrease in the molar equivalent of tetra-n-octylammonium bromide or an increase in reaction temperature generated nanoparticles with higher surface ligand density and smaller particle core size. As the molar equivalent of NaBH4 decreased, the particle core size increased. The catalysis studies on various PdNPs with different surface ligand density and average core size showed a strong correlation between the PdNP composition and the turnover frequency (TOF) of the isomerization of allyl alcohol. Optimized “good” PdNPs with lower surface ligand coverage and larger core size catalyzed the isomerization of various allyl alcohols to carbonyl analogues with high activity and selectivity.

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Section: Resultsmentioning

confidence: 99%

Controlling Surface Ligand Density and Core Size of Alkanethiolate-Capped Pd Nanoparticles and Their Effects on Catalysis

2012

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“…The ws-MUA-PdNP was generated after the assembly of thiosulfate ligands on the nanoparticle surface and the ensuing cleavage of sulfite moiety. 40,45-50 …”

Section: Resultsmentioning

confidence: 99%

Water-Soluble Pd Nanoparticles Synthesized from ω-Carboxyl-S-Alkanethiosulfate Ligand Precursors as Unimolecular Micelle Catalysts

Gavia

Maung

Shon

2013

ACS Appl. Mater. Interfaces

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This report describes a two-phase synthesis of water-soluble carboxylate-functionalized alkanethiolate-capped Pd nanoparticles from ω-carboxyl-S-alkanethiosulfate sodium salts. The two-phase methodology using the thiosulfate ligand passivation protocol allowed a highly specific control over the surface ligand coverage of these nanoparticles, which are lost in a one-phase aqueous system because of the base-catalyzed hydrolysis of thiosulfate to thiolate. Systematic synthetic variations investigated in this study included the concentration of ω-carboxyl-S-alkanethiosulfate ligand precursors and reducing agent, NaBH4, and the overall ligand chain length. The resulting water-soluble Pd nanoparticles were isolated and characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), 1H NMR, UV–vis, and FT-IR spectroscopy. Among different variations, a decrease in the molar equivalent of NaBH4 resulted in a reduction in the surface ligand density while maintaining a similar particle core size. Additionally, reducing the chain length of the thiosulfate ligand precursor also led to the formation of stable nanoparticles with a lower surface coverage. Since the metal core size of these Pd nanoparticle variations remained quite consistent, direct correlation studies between ligand properties and catalytic activities against hydrogenation/isomerization of allyl alcohol could be performed. Briefly, Pd nanoparticles dissolved in water favored the hydrogenation of allyl alcohol to 1-propanol whereas Pd nanoparticles heterogeneously dispersed in chloroform exhibited a rather high selectivity towards the isomerization product (propanal). The results suggested that the surrounding ligand environments, such as the ligand structure, conformation, and surface coverage, were crucial in determining the overall activity and selectivity of the Pd nanoparticle catalysts.

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“…16−21 For Ir nanoparticles, however, such stable alkanethiolate-capped nanoparticles were unattainable by employing alkanethiols directly as a ligand and NaBH 4 as a reducing agent thus far. 22 In this article, we relate a facile synthesis of ∼1.2 ± 0.3 nm Ir nanoparticles by employing the modified Brust–Schiffrin system along with the aforementioned thiosulfate ligand precursor strategy.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insights into the Formation of Dodecanethiolate-Stabilized Magnetic Iridium Nanoparticles: Thiosulfate vs Thiol Ligands

Gavia

et al. 2014

J. Phys. Chem. C

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The synthesis of stable and isolable iridium nanoparticles with an average core size of ∼1.2 ± 0.3 nm was achieved by employing sodium S-dodecylthiosulfate as a ligand precursor during the modified Brust–Schiffrin reaction. Transmission electron microscopy (TEM) of the isolated Ir nanoparticles revealed a high degree of monodispersity. Further characterizations with 1H NMR, FT-IR, UV–vis spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) confirmed that the synthesized Ir nanoparticles are stabilized by dodecanethiolate ligands produced upon the adsorption/cleavage of S-dodecylthiosulfate on the growing Ir nanoparticle surface. By comparison, synthetic attempts employing dodecanethiol as a stabilizing ligand led to the formation of Ir-thiolate species (Ir(SR)3) as an intermediate and Ir-hydroxide species at the completion of reaction. Mechanistic investigations of these two reactions using S-dodecylthiosulfate and dodecanethiol provided deeper understandings on the novelty of thiosulfate ligands, which allow the successful formation of stable thiolate-capped Ir nanoparticles. Moreover, these Ir nanoparticles were shown to have strong magnetic properties.

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Mechanism of Spontaneous Formation of Monolayers on Gold from Alkyl Thiosulfates

Cited by 13 publications

References 20 publications

Controlling Surface Ligand Density and Core Size of Alkanethiolate-Capped Pd Nanoparticles and Their Effects on Catalysis

Controlling Surface Ligand Density and Core Size of Alkanethiolate-Capped Pd Nanoparticles and Their Effects on Catalysis

Water-Soluble Pd Nanoparticles Synthesized from ω-Carboxyl-S-Alkanethiosulfate Ligand Precursors as Unimolecular Micelle Catalysts

Mechanistic Insights into the Formation of Dodecanethiolate-Stabilized Magnetic Iridium Nanoparticles: Thiosulfate vs Thiol Ligands

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