Synchrotron Radiation Effects on Catalytic Systems As Probed with a Combined In-Situ UV−Vis/XAFS Spectroscopic Setup

Mesu, J. Gerbrand; Eerden, Ad M. J. van der; Groot, Frank M. F. de; Weckhuysen, Bert M.

doi:10.1021/jp045206r

Cited by 77 publications

(78 citation statements)

References 25 publications

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“…This is illustrated in Figure 9 by the spectra of sample a, obtained at three different stages in time. As reported recently, [22] the appearance of this pre-edge feature can be assigned to the reduction of Cu 2 + to Cu 1 + . Under influence of the X-ray beam, radiolysis of the water (present in the micropores of the zeolite material) occurs.…”

Section: Exafs Analysissupporting

confidence: 75%

Host–Guest Chemistry of Copper(II)–Histidine Complexes Encaged in Zeolite Y

Mesu¹,

Visser²,

Beale³

et al. 2006

Chemistry A European J

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Structural analysis has been carried out on copper(II)–histidine (Cu2+/His) complexes after immobilization in the pore system of the zeolites NaY and de‐aluminated NaY (DAY). The aim of this study was to determine the geometrical structure of Cu2+/His complexes after encaging, to obtain insight into both the effect of the zeolite matrix on the molecular structure and redox properties of the immobilized complexes. In addition to N2 physisorption and X‐ray fluorescence (XRF) analyses, a combination of UV/Vis/NIR, ESR, X‐ray absorption (EXAFS and XANES), IR, and Raman spectroscopy was used to obtain complementary information on both the first coordination shell of the copper ion and the orientation of the coordinating His ligands. It was demonstrated that two complexes (A and B) are formed, of which the absolute and relative abundance depends on the Cu2+/His concentration in the ion‐exchange solution and on the Si/Al ratio of the zeolite material. In complex A, one His ligand coordinates in a tridentate facial‐like manner through Nam, Nim, and Oc, a fourth position being occupied by an oxygen atom from a zeolite Brønsted site. In complex B, two His ligands coordinate as bidentate ligands; one histamine‐like (Nam, Nim) and the other one glycine‐like (Nam, Oc). In particular the geometrical structure of complex A differs from the preferred structure of Cu2+/His complexes in aqueous solutions; this fact implies that the zeolite host material actively participates in the coordination and orientation of the guest molecules. The tendency for complex A to undergo reduction in inert atmosphere to Cu1+ (as revealed by dynamic XANES studies) suggests activation of complex A by the interaction with the zeolite material. EXAFS analysis confirms the formation of a distorted four coordinate geometry of complex A, suggesting that the combination of zeolite and one His ligand force the Cu2+ complex into an activated, entactic state.

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Section: Exafs Analysissupporting

confidence: 75%

Host–Guest Chemistry of Copper(II)–Histidine Complexes Encaged in Zeolite Y

Mesu¹,

Visser²,

Beale³

et al. 2006

Chemistry A European J

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“…Reduction of Cu 2+ in the presence of chloride and bromide anions, but not in the case of nitrate and sulfate, can be explained by the ability of the nitrate and sulfate to scavenge the hydrated electron, whereas the chloride and bromide are known to be possible OH • radical scavengers. 13,25,35 Indeed with the exception of the imidazole ligand, in every case when the [SO 4 2-] is high (100 mM), copper reduction is suppressed. This leads us to conclude that the hydrated electron is most likely to be responsible for reduction of the copper in this solution, but it is not clear whether this occurs via direct interaction with the Cu 2+ or via the ligand.…”

Section: Resultsmentioning

confidence: 99%

“…It is most likely that this is caused by heating of the solution by the X-ray beam, which, over the period of time that these measurements were taken, can become significant. 4,13 However, the reduction process is much quicker than the rate of heat transfer, suggesting that physical heating is not a major contributor to the reduction process. From Figures 3b and 7b it can clearly be seen that the reduction process occurs rapidly on the right-hand site, where the X-ray beam enters the cuvette.…”

Section: Resultsmentioning

confidence: 99%

Probing the Influence of X-rays on Aqueous Copper Solutions Using Time-Resolved in Situ Combined Video/X-ray Absorption Near-Edge/Ultraviolet−Visible Spectroscopy

et al. 2006

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Time-resolved in situ video monitoring and ultraviolet-visible spectroscopy in combination with X-ray absorption near-edge spectroscopy (XANES) have been used for the first time in a combined manner to study the effect of synchrotron radiation on a series of homogeneous aqueous copper solutions in a microreactor. This series included both non biologically relevant (pyridine, bipyridine, neocuproine, terpyridine, dimethylpyridine, ammonia, ethylenediamine, and 1,10-phenanthroline) and biologically relevant (histidine, glycine, and imidazole) ligands. It was found that when water is present as solvent, gas bubbles are formed under the influence of the X-ray beam. At the liquid-gas interface of these bubbles, in particular cases colloidal copper nanoparticles are formed. This reduction process was found to be influenced by the type of copper precursor salt (SO 4 2-, NO 3 -, and Cl -), the ligands surrounding the copper cation, and the redox potential of the copper complexes (ranging between +594 and -360 mV). In other words, in some cases, no reduction was encountered (e.g., ammonia in the presence of SO 4 2-and NO 3 -), whereas in other cases reduction to either Cu + (neocuproine with SO 4 2-) or Cu 0 (e.g., histidine and imidazole both with SO 4 2-, NO 3 -, and Cl -) was observed. These results illustrate the added value of video spectroscopy for the interpretation of in situ XANES studies. Not only do the results give an illustration of the parameters that are important in the redox processes that occur in biological systems, they also show the potential problems associated with studying catalytic processes in aqueous solutions by XANES spectroscopy.

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“…Weckhuysen and coworkers [90,91] have designed a combined in-situ UVvis/XANES setup to probe the influence of X-rays on aqueous homogeneous copper solutions. They found that that X-rays had effect on the nucleation behavior of nanoparticles due to the radiolysis of water.…”

Section: Reviewsmentioning

confidence: 99%

X-ray absorption fine structure spectroscopy in nanomaterials

et al. 2015

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X-ray absorption fine structure (XAFS) spectroscopy has been widely used for decades in a wide range of scientific fields, including physics, chemistry, biology, materials sciences, environmental sciences, etc. This review article is devoted to the applications of XAFS in nanomaterials. The basic principles of XAFS are briefly described from the view point of practical application, including its theory, data analysis and experiments. Using selected examples from recent literatures, the power of XAFS in determination of local atomic/electronic structures is illustrated for various nanomaterials, covering metal and semiconductor nanoparticles, catalysts, core/shell structures, ultrathin nanosheets, and so on. The utilization of time-resolved XAFS technique is also briefly introduced, for in-situ probing the nucleation/growth processes of nanomaterials and identifying reaction intermediates of nanostructured catalysts under operando conditions.

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Synchrotron Radiation Effects on Catalytic Systems As Probed with a Combined In-Situ UV−Vis/XAFS Spectroscopic Setup

Cited by 77 publications

References 25 publications

Host–Guest Chemistry of Copper(II)–Histidine Complexes Encaged in Zeolite Y

Host–Guest Chemistry of Copper(II)–Histidine Complexes Encaged in Zeolite Y

Probing the Influence of X-rays on Aqueous Copper Solutions Using Time-Resolved in Situ Combined Video/X-ray Absorption Near-Edge/Ultraviolet−Visible Spectroscopy

X-ray absorption fine structure spectroscopy in nanomaterials

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