NMR Characterization of Ligand Binding and Exchange Dynamics in Triphenylphosphine-Capped Gold Nanoparticles

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• 作者：Ramesh Sharma ; Gregory P. Holland ; Virgil C. Solomon ; Herbert Zimmermann ; Steven Schiffenhaus ; Samrat A. Amin ; Daniel A. Buttry ; Jeffery L. Yarger
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：September 17, 2009
• 年：2009
• 卷：113
• 期：37
• 页码：16387-16393
• 全文大小：183K
• 年卷期：v.113,no.37(September 17, 2009)
• ISSN：1932-7455

文摘

Triphenylphosphine (PPh₃)-capped 1.8 nm diameter gold nanoparticles (AuNPs) are characterized by a combination of ¹H, ²H, and ³¹P solution- and solid-state NMR. The ³¹P{¹H} NMR resonance associated with the surface-bound PPh₃ is clearly identified and is present as a broad peak centered at 56 ppm. ³¹P and ¹H hole burning NMR experiments show that the line broadening associated with the surface-bound PPh₃ is primarily due to a variety of different chemical shift environments at the surface of the nanoparticles. The surface bound PPh₃ can be displaced with either d₁₅-PPh₃ or Au(d₁₅-PPh₃)Cl in CD₂Cl₂ solution. In both cases, exchange results in loss of Au(PPh₃)Cl from the nanoparticle surface, with no evidence for loss of the PPh₃ ligand alone. Solution-state NMR was used to determine the room temperature rate constants for these exchange processes, with values of 0.17 and 0.20 min⁻¹, respectively. Thus, essentially the same rate is observed for displacement of Au(PPh₃)Cl from the surface with either d₁₅-PPh₃ or Au(d₁₅-PPh₃)Cl. The observed ³¹P chemical shift of surface-bound PPh₃ is consistent with mixed valence Au(0) and Au(I) at the nanoparticle surfaces, suggesting the presence of surface-bound Au complexes.