Direct Evidence of Oxidized Gold on Supported Gold Catalysts

Fu, Lei; Wu, Nianqiang; Yang, Jing; Qu, Fengyu; Johnson, D. Lynn; Kung, Mayfair C.; Kung, Harold H.; Dravid, Vinayak P.

doi:10.1021/jp045117e

Cited by 110 publications

(72 citation statements)

References 33 publications

(52 reference statements)

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“…The difference spectrum between the as-deposited (0.0 min) and the 10 min-sputtered samples could be fitted with two 4f7/2 XPS peaks at 85.0 and 86.5 eV. The peaks at 85.0 and 86.5 eV are plausibly assign- 33 consistent with our XPS result showing the same oxidation states. However, they observed only metallic Au by XPS without any indication of ionic Au species.…”

Section: Resultssupporting

confidence: 87%

The Interfacial Nature of TiO₂and ZnO Nanoparticles Modified by Gold Nanoparticles

Do¹,

Choi²,

Kim³

et al. 2010

Bulletin of the Korean Chemical Society

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The surfaces of TiO2 and ZnO nanoparticles have been modified by gold (Au) nanoparticles by a reduction method in solution. Their interfacial electronic structures and optical absorptions have been studied by depth-profiling X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectroscopy, respectively. Upon Au-modification, UVvis absorption spectra reveal a broad surface plasmon peak at around 500 nm. For the as-prepared Au-modified TiO2 and ZnO, the Au 4f7/2 XPS peaks exhibit at 83.7 and 83.9 eV, respectively. These are due to a charge transfer effect from the metal oxide support to the Au. For TiO2, the larger binding energy shift from that (84.0 eV) of bulk Au could indicate that Au-modification site of TiO2 is different from that of ZnO. On the basis of the XPS data with sputtering depth, we conclude that cationic (1+ and 3+) Au species, plausibly Au(OH)x (x = 1-3), commonly form mainly at the AuTiO2 and Au-ZnO interfaces. With Ar + ion sputtering, the oxidation state of Ti dramatically changes from 4+ to 3+ and 2+ while that (2+) of Zn shows no discernible change based on the binding energy position and the full-width at half maximum (FWHM).

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Section: Resultssupporting

confidence: 87%

The Interfacial Nature of TiO₂and ZnO Nanoparticles Modified by Gold Nanoparticles

Do¹,

Choi²,

Kim³

et al. 2010

Bulletin of the Korean Chemical Society

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“…Surface charge for the systems studied ranged only within -2, -1, 0, or +1 (i.e., cationic +1 for a PbSe/RCO 2 H system), and was altered by the surfactants/ligands selected and amounts used. [32] Hence, relatively small net charges seemingly impart considerable DLVO-type stability, but perhaps not adequate for reliable stabilization in physiological milieu (i.e., 0.14 M salt and >50 mg mL -1 soluble proteins). Alternatively, NPs well-stabilized "as prepared" may become very unstable (or more stable) as a function of their changing surface ligation in biological milieu.…”

Section: All Of These Surface Modifications Intentional or Not Can mentioning

confidence: 99%

Nanobiomaterials and Nanoanalysis: Opportunities for Improving the Science to Benefit Biomedical Technologies

2008

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Nanomaterials advocated for biomedical applications must exhibit well‐controlled surface properties to achieve optimum performance in complex biological or physiological fluids. Dispersed materials with extremely high specific surface areas require as extensive characterization as their macroscale biomaterials analogues. However, current literature is replete with many examples of nanophase materials, most notably nanoparticles, with little emphasis placed on reporting rigorous surface analysis or characterization, or in formal implementation of surface property standards needed to validate structure‐property relationships for biomedical applications. Correlations of nanophase surface properties with their stability, toxicity and biodistributions are essential for in vivo applications. Surface contamination is likely, given their processing conditions and interfacial energies. Leaching adventitious adsorbates from high surface area nanomaterials is a possible toxicity mechanism. Polydimethylsiloxane (PDMS), long known as a ubiquitous contaminant in clean room conditions, chemical synthesis and microfabrication, remains a likely culprit in nanosystems fabrication, especially in synthesis, soft lithography and contact molding methods. New standards and expectations for analyzing the interfacial properties of nanoparticles and nano‐fabricated technologies are required. Surface science analytical rigor similar to that applied to biomedical devices, nanophases in microelectronics and heterogeneous catalysts should serve as a model for nanomaterials characterization in biomedical technologies.

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“…This includes transfer of activated oxygen from the support (i.e., reducible or irreducible support), or special active sites at the metal/oxide boundary [8,[54][55][56][57][58][59][60][61][62][63][64]. Finally, there are a number of reports of catalysts consisting of single or a few Au + ions in the support [27,[65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81]. We note that combinations of the above effects can come into play; the gold-support interaction may for instance determine the morphology of the gold particles and thus influence the number of low-coordinated atoms or the strain.…”

Section: Introductionmentioning

confidence: 99%

Insights into the reactivity of supported Au nanoparticles: combining theory and experiments

et al. 2007

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The origin of the extraordinary catalytic activity of gold nanoparticles is discussed on the basis of density-functional calculations, adsorption studies on single crystal surfaces, and activity measurements on well characterized supported gold particles. A number of factors are identified contributing to the activity, and it is suggested that it is useful to consider lowcoordinated Au atoms as the active sites, for example, CO oxidation and that the effect of the support can be viewed as structural and electronic promotion. We identify the adsorption energy of oxygen and the Au-support interface energy as important parameters determining the catalytic activity.

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Direct Evidence of Oxidized Gold on Supported Gold Catalysts

Cited by 110 publications

References 33 publications

The Interfacial Nature of TiO₂and ZnO Nanoparticles Modified by Gold Nanoparticles

The Interfacial Nature of TiO₂and ZnO Nanoparticles Modified by Gold Nanoparticles

Nanobiomaterials and Nanoanalysis: Opportunities for Improving the Science to Benefit Biomedical Technologies

Insights into the reactivity of supported Au nanoparticles: combining theory and experiments

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Direct Evidence of Oxidized Gold on Supported Gold Catalysts

Cited by 110 publications

References 33 publications

The Interfacial Nature of TiO2and ZnO Nanoparticles Modified by Gold Nanoparticles

The Interfacial Nature of TiO2and ZnO Nanoparticles Modified by Gold Nanoparticles

Nanobiomaterials and Nanoanalysis: Opportunities for Improving the Science to Benefit Biomedical Technologies

Insights into the reactivity of supported Au nanoparticles: combining theory and experiments

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The Interfacial Nature of TiO₂and ZnO Nanoparticles Modified by Gold Nanoparticles

The Interfacial Nature of TiO₂and ZnO Nanoparticles Modified by Gold Nanoparticles