Extended x-ray absorption fine structure thin-layer spectroelectrochemistry

Smith, D. A.; Elder, R. C.; Heineman, William R.

doi:10.1021/ac00289a044

Cited by 28 publications

(11 citation statements)

References 27 publications

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“…The electrolysis times obtained are a 10-fold improvement over previous results (28) and are reasonable on the time scale of EXAFS data collection times. This latter point is particularly significant considering limited X-ray beam availability.…”

Section: Resultssupporting

confidence: 73%

“…Recent reports have shown the diversity of interest in combining In situ electrochemical steps with X-ray absorption spectroscopy for the study of metal passivation (24,25) and inclusion of metallic clusters in organic conducting polymers (26). The first reports from this laboratory described an initial EXAFS thin-layer spectroelectrochemical cell design and the structure analysis of the iron(II/III) cyanide couple (27,28).…”

mentioning

confidence: 99%

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Development of extended x-ray absorption fine structure spectroelectrochemistry and its application to structural studies of transition-metal ions in aqueous solution

Dewald¹,

Watkins²,

Elder³

et al. 1986

Anal. Chem.

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Section: Resultssupporting

confidence: 73%

mentioning

confidence: 99%

Development of extended x-ray absorption fine structure spectroelectrochemistry and its application to structural studies of transition-metal ions in aqueous solution

Dewald¹,

Watkins²,

Elder³

et al. 1986

Anal. Chem.

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“…Thus, variants (Heineman, 1978) of this experiment could be of value in characterizing other compound I-like intermediates, produced from various heme enzymes (including cytochrome P-450), that have eluded structural study. One interesting option involves EXAFS spectroelectrochemistry (Smith et al, 1985;Igo et al, 1991) to study structures of enzyme intermediates.…”

Section: Resultsmentioning

confidence: 99%

Variable-Temperature Spectroelectrochemical Study of Horseradish Peroxidase

et al. 1995

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The reduction potentials of the compound II/ferric and compound I/compound II couples have been studied, using potassium hexachloroiridate as a mediator titrant, by thin-layer spectroelectrochemistry. Compound I, which is 2 equiv more oxidized than the ferric (i.e., resting) form of the enzyme, was reversibly formed via a compound II intermediate; no evidence for a ferric porphyrin pi-cation radical intermediate was obtained. At 25 degrees C, E degrees' (compound I/compound II) = 897.9 +/- 3 mV (NHE) and E degrees'-(compound II/ferric) = 869.1 +/- 2 mV. Redox thermodynamic parameters, obtained from the temperature dependences of the reduction potentials of both couples, are reported. The reaction entropies (delta S degrees rc) for the compound II/ferric and compound I/compound II couples are 19.8 +/- 3.9 and 12.1 +/- 3.7 eu, respectively. This result indicates that the reorganization energy for the macrocycle-centered couple is lower than that for the metal-centered one. Together with our observation that E degrees' for the former is ca. 30 mV greater than that for the latter, these results suggest that compound I is more reactive toward outer-sphere reductants than compound II. In particular, the electron self-exchange rates for the compound I/compound II and compound II/ferric couples are estimated to be 4.4 x 10(-1) and 4.9 x 10(-4) M-1 s-1, respectively. Surprisingly, the formation of compound I from ferric HRP is accompanied by an almost zero standard entropy (delta S degrees') change.

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“…(Ipi) gold minigrid as the working electrode to minimize diffusional distances (Figure 5). 8 The dimensions of the thin-layer cell were chosen so that all of the ca. 18 X 2 mm cross-sectional area of the available X-ray beam (at SSRL) passed through the working electrode.…”

Section: A Solution Cellsmentioning

confidence: 99%

“…Figure 2 shows the common experimental geometry used by Elder and Heineman in which both transmittance and fluorescence signals are measured simultaneously. 8 The X-rays are first diffracted by a double-crystal monochromator (Si(lll) or Si(220)) and simultaneously measuring X-ray fluorescence (If) and reflectance (Ir). Adapted from ref 11. then passed through a set of slits.…”

Section: Introductionmentioning

confidence: 99%