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Tin dioxide-modified Pt electrodes with different coverages ( θ SnO 2 ) were prepared by potentiostatically depositing tin on a Pt electrode in 0.1 M H2SO4 solutions containing various concentrations of SnCl2, followed by oxidizing in air. The θ SnO 2 was controlled by the SnCl2 concentration. The CO-stripping voltammogram of the Pt/SnO2 electrode with θ SnO 2 = 0.61 (Pt/SnO2(0.61)) exhibited two peaks, a prepeak due to the oxidation of adsorbed CO at Pt sites adjacent to SnO2 and a main peak due to that at Pt sites far from SnO2. In the kinetic analysis of both peaks using CO-stripping voltammograms at various sweep rates, the rate-determining steps for the prepeak and main peak were the coupling of adsorbed CO on Pt with OH on SnO2 surface by bifunctional effect and the dissociatively adsorption reaction of water to adsorbed OH on Pt, similar to the Pt electrode, respectively. In the linear sweep voltammograms of Pt/SnO2 electrodes in a (0.1 M HClO4 + 1 M ethanol) solution, the current for ethanol oxidation reaction (EOR) was the highest for θ SnO 2 = 0.61. The analysis of EOR products at different potentials for the Pt/SnO2(0.61) electrode by in situ infrared reflectance-absorption spectroscopy exhibited the Pt/SnO2(0.61) electrode facilitated acetic acid production. Moreover, rhodium was electrochemically deposited on the Pt sites adjacent to SnO2 using the limited CO-stripping technique. The area-controlled Rh deposition did not change the rate-determining steps of both peaks, but it not only enhanced EOR activity, but also decreased acetic acid selectivity and increased CO2 selectivity. [ABSTRACT FROM AUTHOR]

PtxRh1−x (x = 0.76, 0.54, and 0.27) solid solutions were prepared by arc-melting. For these solid solutions, the lattice constant was linearly related to the Pt content. The surface compositions of the solid solutions determined by X-ray photoelectron spectroscopy were quite similar to their bulk compositions estimated by energy dispersive X-ray spectroscopy. The CO-stripping voltammograms demonstrated that the onset potential of CO oxidation current density (Eonset) shifted negatively as the surface Pt content decreased, suggesting an increased CO-poisoning resistance. Linear sweep voltammograms of the solid solution electrodes in an Ar-saturated (1 M ethanol + 0.1 M HClO4) solution exhibited that the onset potentials of ethanol oxidation reaction (EOR) current for all solid solution electrodes were lower than of a Pt electrode, and Pt0.54Rh0.46 gave the highest specific activity (SA) of 312 μA·cm−2, which was about 1.8 and 2.5 times higher than the SAs of Pt and Rh, respectively. In situ infrared reflection-absorption spectra exhibited that the Pt0.54Rh0.46 electrode had the bands due to the linear-bonded CO on Pt and bridge-bonded CO on Rh as EOR intermediates around 0.2 V vs. the reversible hydrogen electrode, but the band due to the linear-bonded CO on Rh was not observed even at 0.6 V, suggesting that the existence of the adjacent Pt-Rh sites and the preferential formation of bridge-bonded CO on Rh accelerated the C-C bond cleavage and improved the EOR activity. [ABSTRACT FROM AUTHOR]

In this report, we established a new electrochemical method for the detection of conformational changes in large, non-metalloproteins such as bovine serum albumin, using flow injection analysis coupled with hydrogenterminated, boron-doped diamond electrodes. The oxidation current was used as a signal reporter in the monitoring of urea-induced BSA denaturation. In the denatured state at high urea concentrations, the electrochemical signal increased, and the amperometric responses for the oxidation potential at 1300 mV were consistent with the results of conventional methods of denaturation monitoring using fluorescence spectroscopy. The oxidation involved at least five redox-active species (cysteine, tryptophan, tyrosine, methionine, and disulfide bonds). Furthermore, the method also showed high sensitivity for quantitative analysis of protein. A linear dynamic in the concentration range 50-400 [micro]g/mL ([r.sup.2] = 0.977) with a lower detection limit of 190 ng/mL was achieved for BSA. Direct electrochemical detection of conformation changes of proteins using BDD electrodes can be performed with advantages in terms of simplicity and sensitivity.