A theoretical and experimental examination of systematic ligand-induced disorder in Au dendrimer-encapsulated nanoparticles

Yancey, David F.; Chill, Samuel T.; Zhang, Liang; Frenkel, Anatoly I.; Henkelman, Graeme; Crooks, Richard M.

doi:10.1039/c3sc50614b

Cited by 67 publications

(89 citation statements)

References 50 publications

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“…The pH was lowered to 3.2 and galvanic exchange of Cu for Pt was carried out by adding 147 equiv. of Pt 2+ (from a freshly prepared 0.10 M stock solution of PtCl 4 2− ) to the Cu DENs solution so that the Pt 2+ :Cu ratio was 1.0. After reacting for several minutes the N 2 purge was stopped and the pH of the resulting Pt DENs solution was raised to ∼8.5.…”

Section: Synthesis and Characterization Of Pt Dens-the Synthesis Ofmentioning

confidence: 99%

A Theoretical and Experimental In-Situ Electrochemical Infrared Spectroscopy Study of Adsorbed CO on Pt Dendrimer-Encapsulated Nanoparticles

Anderson

Zhang

et al. 2015

J. Electrochem. Soc.

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We present a combined experimental and theoretical study of CO ads on Pt 147 dendrimer-encapsulated nanoparticles (DENs). In-situ electrochemical IR spectroscopy reveals an 8 cm −1 redshift of the CO ads stretching frequency on Pt 147 DENs relative to a Pt (111) crystal. This value is in good agreement with the shift calculated by density functional theory. Importantly, the wavenumber shift observed in this study is significantly smaller than has been found previously. We attribute this primarily to the absence of support effects and the narrow size distribution of DENs. The agreement between experiment and theory validates the model nanoparticle system used for the calculations, and this will make it possible to use the CO ads frequency as a probe to study more complex DEN structures and as a descriptor of the catalytic activity of DENs toward reactions such as formic acid oxidation and methanol oxidation.We are interested in developing a better understanding of how small changes in the structure of nanoparticles in the 1-2 nm size range impact important electrocatalytic reactions like oxygen reduction and CO oxidation. We approach this problem by directly comparing theory and experiments. 1 This is important, because previous results from our groups and others have shown that nanoparticle structures in this size range are dynamic. For example, core@shell nanoparticles are able to invert, 2,3 ligands can drive shape changes, 4 and interactions with a substrate can result in major electronic and shape changes. [5][6][7] One effective method for gaining insight into nanoparticle surface structure is to measure changes in the vibrational frequency of adsorbed CO (CO ads ) using infrared (IR) spectroscopy. 8,9 Spectroscopic results from single-crystal surface models are relevant for understanding the structure of Pt nanoparticles (PtNPs) having size >4 nm, but for smaller nanoparticles the connection to bulk surfaces is more tenuous. 8 This is because the dominance of discrete facets is reduced, while the contribution of edge and corner sites increases. These latter sites can be identified because they bind CO more strongly, thereby decreasing its stretching frequencies. 8,10 It has previously been shown that the CO ads frequency decreases as the size of PtNPs supported on carbon (C/PtNP) decreases. 8,11,12 For example, frequency shifts on the order of 20 cm −1 have been reported as nanoparticle size decreases from ∼4 nm to ∼2 nm. 8 However, these studies have been carried out on commercial C/PtNP catalysts, which exhibit wide variations in the size and shape of the PtNPs and also effects exerted by the support. 12,13 This in turn makes it difficult to precisely correlate IR spectra to particular nanoparticle structures.We sought to better understand the interaction between CO and PtNPs by developing a more refined model system that could be directly compared to first principles theory. The model we chose are dendrimer-encapsulated nanoparticles (DENs), which are welldefined materials in the size range of 1-2 nm. 1,...

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Section: Synthesis and Characterization Of Pt Dens-the Synthesis Ofmentioning

confidence: 99%

A Theoretical and Experimental In-Situ Electrochemical Infrared Spectroscopy Study of Adsorbed CO on Pt Dendrimer-Encapsulated Nanoparticles

Anderson

Zhang

et al. 2015

J. Electrochem. Soc.

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“…In fact, theoretical modeling approaches are now used to fill the gaps in experimental data (6,17). For example, the use of ab initio simulations within the density functional theory (DFT) formalism allows one to model relaxation processes in metallic NPs, and it has been used to predict the properties and structure of nanosized catalysts (18)(19)(20). Molecular dynamics (MD) and Monte Carlo (MC) simulations using interatomic forces that are derived either from ab initio calculations (15,18) or from empirical force fields (17,(21)(22)(23) can be employed, in turn, to model thermal disorder and anharmonic effects.…”

Section: Introductionmentioning

confidence: 99%

Solving the Structure and Dynamics of Metal Nanoparticles by Combining X-Ray Absorption Fine Structure Spectroscopy and Atomistic Structure Simulations

Timoshenko

Duan

Henkelman

et al. 2019

Annual Rev. Anal. Chem.

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Extended X-ray absorption fine structure (EXAFS) spectroscopy is a premiere method for analysis of the structure and structural transformation of nanoparticles. Extraction of analytical information about the three-dimensional structure and dynamics of metal–metal bonds from EXAFS spectra requires special care due to their markedly non-bulk-like character. In recent decades, significant progress has been made in the first-principles modeling of structure and properties of nanoparticles. In this review, we summarize new approaches for EXAFS data analysis that incorporate particle structure modeling into the process of structural refinement.

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“…Another step forward in EXAFS characterization of Au NC surface structure or the thiolate-Au interface is possible by combining DFT-molecular dynamics simulations and ab initio calculation of EXAFS spectra. Yancey et al took this experimentaltheoretical approach to study the surface structural disorder of Au ∼147 clusters protected by dendrimer molecules with increasing amounts of terminal thiols (12,24,50, and 72 thiols per Au ∼147 cluster) [75]. Remarkable similarities were reported for each Au ∼147 cluster with varied thiolate-Au interactions.…”

Section: Outlook and Summarymentioning

confidence: 99%

Bonding properties of thiolate-protected gold nanoclusters and structural analogs from X-ray absorption spectroscopy

Chevrier

Yang

Chatt

et al. 2015

Nanotechnology Reviews

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Abstract:Subnanometer, atomically precise thiolateprotected gold nanoclusters represent an important advancement in our understanding of thiolate-protected gold nanoparticles and thiolate-gold chemistry. Aside from being a link between larger gold nanoparticles and small gold complexes, gold nanoclusters exhibit extraordinary molecule-like optical, electronic, and physicochemical properties that are promising for next-generation imaging agents, sensing devices, or catalysts. The success in elucidating a number of unique thiolate-gold surface and gold core structures has greatly improved our understanding of thiolate-gold nanoclusters. Nevertheless, monitoring the structural and electronic behavior of thiolate-protected gold nanoclusters in a variety of media or environments is crucial for the next step in advancing this class of nanomaterials. Not to mention, there are a number of thiolateprotected gold nanoclusters with unknown structures or compositions that could reveal important insights on application-based properties such as luminescence or catalytic activity. This review summarizes some of the recent contributions from X-ray absorption spectroscopy (XAS) studies on the intriguing bonding properties of thiolate-protected gold nanoclusters and some structural analogs. Advantages from XAS include a local structural, site-and elementspecific analysis, suitable for ultra-small particle sizes (1-2 nm), along with versatile experimental conditions.

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A theoretical and experimental examination of systematic ligand-induced disorder in Au dendrimer-encapsulated nanoparticles

Cited by 67 publications

References 50 publications

A Theoretical and Experimental In-Situ Electrochemical Infrared Spectroscopy Study of Adsorbed CO on Pt Dendrimer-Encapsulated Nanoparticles

A Theoretical and Experimental In-Situ Electrochemical Infrared Spectroscopy Study of Adsorbed CO on Pt Dendrimer-Encapsulated Nanoparticles

Solving the Structure and Dynamics of Metal Nanoparticles by Combining X-Ray Absorption Fine Structure Spectroscopy and Atomistic Structure Simulations

Bonding properties of thiolate-protected gold nanoclusters and structural analogs from X-ray absorption spectroscopy

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