Photoreduction Kinetics of Sodium Tetrachloroaurate under Synchrotron Soft X-ray Exposure

Fong, Yuen-Yan; Visser, Bradley; Gascooke, Jason R.; Cowie, Bruce C. C.; Thomsen, Lars; Metha, Gregory F.; Buntine, Mark A.; Harris, Hugh H.

doi:10.1021/la200463k

Cited by 65 publications

(70 citation statements)

References 45 publications

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“…4). As we as well as other researchers 20 have previously observed, Au + will also reduce to Au 0 ; which is not observed by prolonged X-ray analysis here. However, we consider the Au 0 -s species to be nothing more than a spectator species, since the reduced catalysts also contain these Au 0 -s nanoclusters and are inactive, although small gold clusters are active in a range of reactions such as CO oxidation.…”

Section: Correlation Between the Catalytic Activity And Gold Oxidatiosupporting

confidence: 87%

“…As it is well known that cationic Au species can be reduced to the zero-valent state by secondary electron emission during XPS analysis, the Au(4f) region was recorded at the beginning and end of the analysis. 20 The Au 3+ and Au 0 amounts are reported as the percentage of the total Au amount, and the absolute amount in mmol (see ESI †). 2.3.4 X-RAY POWDER DIFFRACTION.…”

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confidence: 99%

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Modifications of the metal and support during the deactivation and regeneration of Au/C catalysts for the hydrochlorination of acetylene

Conte

Davies

Morgan

et al. 2013

Catal. Sci. Technol.

102

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The effect of the gold oxidation state and carbon structure on the activity of Au/C catalysts for the hydrochlorination of acetylene was investigated by a combined approach using TPR, XPS and porosimetry determinations. The activity of the catalyst in the synthesis of vinyl chloride monomer was found to be dependent on the presence of Au 3+ species in the catalyst. However, by preparing catalysts with different Au 3+ content it was possible to determine the existence of a threshold Au 3+ amount, beyond which the excess of Au 3+ was not active for the reaction. This was explained by the existence of active sites at the Au/C interface, and not just by the presence of Au 3+ species on top of Au nanoparticles, as explained by current models for these catalysts. It was also possible to determine the existence of a subset of Au nanoclusters which do not take part in the reaction, as well as changes in the textural properties of the carbon that can affect its long term reusability.

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Section: Correlation Between the Catalytic Activity And Gold Oxidatiosupporting

confidence: 87%

mentioning

confidence: 99%

Modifications of the metal and support during the deactivation and regeneration of Au/C catalysts for the hydrochlorination of acetylene

Conte

Davies

Morgan

et al. 2013

Catal. Sci. Technol.

102

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show abstract

“…3B, Left). The Au 4f 7/2 peak for the salt precursor ink is at 84.9 eV, which is within the expected range for Au I ; this partial reduction could be attributed to either reduction by PEO or photoreduction during the measurement (26). After thermal annealing at T low , the Au 4f 7/2 peak shifts to 83.8 eV, indicating that the Au precursor has been reduced further by PEO (25).…”

Section: Resultssupporting

confidence: 63%

Delineating the pathways for the site-directed synthesis of individual nanoparticles on surfaces

Liu

Eichelsdoerfer²,

Rasin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

111

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Although nanoparticles with exquisite properties have been synthesized for a variety of applications, their incorporation into functional devices is challenging owing to the difficulty in positioning them at specified sites on surfaces. In contrast with the conventional synthesis-then-assembly paradigm, scanning probe block copolymer lithography can pattern precursor materials embedded in a polymer matrix and synthesize desired nanoparticles on site, offering great promise for incorporating nanoparticles into devices. This technique, however, is extremely limited from a materials standpoint. To develop a materials-general method for synthesizing nanoparticles on surfaces for broader applications, a mechanistic understanding of polymer-mediated nanoparticle formation is crucial. Here, we design a four-step synthetic process that enables independent study of the two most critical steps for synthesizing single nanoparticles on surfaces: phase separation of precursors and particle formation. Using this process, we elucidate the importance of the polymer matrix in the diffusion of metal precursors to form a single nanoparticle and the three pathways that the precursors undergo to form nanoparticles. Based on this mechanistic understanding, the synthetic process is generalized to create metal (Au, Ag, Pt, and Pd), metal oxide (Fe 2 O 3 , Co 2 O 3 , NiO, and CuO), and alloy (AuAg) nanoparticles. This mechanistic understanding and resulting process represent a major advance in scanning probe lithography as a tool to generate patterns of tailored nanoparticles for integration with solid-state devices.T he integration of nanoparticles into devices has enabled applications spanning sensing (1, 2), catalysis (3), electronics (2), photonics (4), and plasmonics (5, 6), but synthesizing individual nanoparticles with control over size, composition, and placement on substrates is challenging (1-3, 6, 7). With conventional approaches, nanoparticles are synthesized and subsequently positioned on a surface using techniques such as parallel printing (8), surface dewetting (9, 10), microdroplet molding (7), nanoparticle sliding (11), direct writing (4, 12, 13), and self-assembly (2, 14, 15). However, it is difficult and in most cases, impossible to use these methods to reliably make and position a single particle on a surface with nanometer-scale control.In contrast with the conventional synthesis-then-positioning paradigm, which is the basis for most single-particle device incorporation schemes, scanning probe block copolymer lithography (SPBCL) is an example of precursor positioning-then-synthesis. The technique uses concepts from the block copolymer community (16) and the positional control offered by dip-pen nanolithography (DPN) (17) to deliver attoliter volumes of a metalcoordinated block copolymer onto a surface, which then can be used to synthesize individual nanoparticles (18,19). Importantly, SPBCL allows one to directly synthesize arbitrary patterns of single nanoparticles over large areas on a surface, which has been usef...

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“…The spectra also show that the intensity of each Au oxidation state varies with evolution of sunlight irradiation, suggesting the sequential transformation of Au(III) to Au(I) and then to Au(0). 44 The C1s signals are given in Figure 5c …”

Section: +mentioning

confidence: 99%

Ecological Risk Assessment of Arsenic and Metals in Surface Sediments from Estuarine and Coastal Areas of the Southern Bohai Sea, China

Wang

et al. 2013

Human and Ecological Risk Assessment: An International Journal

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Naturally occurring Au nanoparticles (AuNPs) have been widely observed in ore deposits, coal, soil, and environmental water. Identifying the source of these naturally occurring AuNPs could be helpful for not only the discovery of Au deposits through advanced exploration methods, but also the elucidation of the biogeochemical cycle and environmental toxicity of ionic Au and engineered AuNPs. Here, we investigated the effect of natural/simulated sunlight and heating on the reduction of ionic Au by ubiquitous dissolved organic matter (DOM) in river water. The reductive process probed by X-ray photoelectron spectroscopy revealed that phenolic, alcoholic, and aldehyde groups in DOM act as reductive sites. Long-time exposure with thermal and photoirradiation induced the further fusion and growth of AuNPs to branched Au nanostructure as precipitation. The formation processes and kinetics of AuNPs were further investigated using humic acid (HA) as the DOM model, with comprehensive characterizing methods. We have observed that HA can reduce ionic Au(III) complex (as chloride or hydroxyl complex) to elemental Au nanoparticles under sunlight or heating. In this process, nearly all of the Au(III) could be reduced to AuNPs, in which HA serves as not only the reductive agent, but also the coating agent to stabilize and disperse AuNPs. The size and stability of AuNPs were highly dependent on the concentration ratio of Au(III) to HA. These results imply that, besides biological processes, this thermal or photochemical reduction process is another possible source of naturally occurring AuNPs in natural environments, which possibly has critical impacts on the transport and transformation of Au and engineered AuNPs.

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Photoreduction Kinetics of Sodium Tetrachloroaurate under Synchrotron Soft X-ray Exposure

Cited by 65 publications

References 45 publications

Modifications of the metal and support during the deactivation and regeneration of Au/C catalysts for the hydrochlorination of acetylene

Modifications of the metal and support during the deactivation and regeneration of Au/C catalysts for the hydrochlorination of acetylene

Delineating the pathways for the site-directed synthesis of individual nanoparticles on surfaces

Ecological Risk Assessment of Arsenic and Metals in Surface Sediments from Estuarine and Coastal Areas of the Southern Bohai Sea, China

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