Machiko Takahashi

CO adsorption on Pt(111) and Pt(100) single crystal surfaces in aqueous solutions studied by infrared reflection-absorption spectroscopy

Abstract The adsorption of CO on Pt(111) and Pt(100) single crystal surfaces in an aqueous acid solution was studied by IRRAS and CV. On-top and bridge-bonded CO species adsorbed on Pt(111) and Pt(100) electrodes were detected.

Infrared reflection absorption spectra of carbon monoxide adsorbed on single crystal electrodes, Pd(111) and Pd(100)

Abstract Carbon monoxide (CO) adsorption on Pd(100) and Pd(111) single crystal electrode surfaces in an aqueous acid solution was studied by FT-IRAS. A surface preparation technique of well-ordered single crystal palladium electrodes was established by using iodine-coating and anneal-quenching of the electrodes. On Pd(111), bridge-bonded (1900–1960 cm −1 ) and three-fold (1840–1890 cm −1 ) CO was detected, while only the former species was observed on Pd(100). The structural changes in the CO overlayer were induced by the electrode potential and/or the coverage of CO on the electrode surfaces. The results were compared with those from previous UHV studies.

SERS application to some electroorganic reactions

Abstract SERS from four organic Sulfides adsorbed on Ag electrodes are studied. 2-Mercaptopyridine (MPy) adsorbed on the electrode surface takes the enol form. The SER spectrum from 2,2 - dipyridyl disulfide (DPyDS) is exactly the same as that of MPy, which indicates the cleavage of the S-S bond of DPyDS. DPhDS also cleaves on a Ag electrode, as DPhDS and PhSH give identical SER spectra. All of these organic sul fides thus chemisorb dissociatively on the electrode surface, taking sticking-up configurations through S atoms.

Surface-enhanced Raman scattering of phenazine. Large intensities of overtones and combination bands

Abstract SERS spectra of phenazine adsorbed on a silver electrode are observed. They are characterized by unusually large intensity and the clear appearance of overtones and combination bands exactly at the expected frequencies. These phenomena are explained by the CT mechanism.

Surface-enhanced raman spectra and molecular orientation of phthalazine adsorbed on a silver electrode

Abstract SERS from phthalazine adsorbed on an Ag electrode was investigated under several conditions of applied voltage and solution concentration. Spectral assignments of the Raman bands were successfully performed and two differently oriented adsorbates, i.e. flat and end-on species, were identified. The contribution of the image field to the SERS intensity was considerable.

Surface-enhanced Raman spectra of quinoxaline adsorbed at a silver electrode

Abstract Surface-enhanced Raman scattering from quinoxaline adsorbed at a Ag electrode was observed. The SER spectrum exhibited remarkable a concentration and potential dependence, and indicated of two types of adsorbed species. They were assigned as flat and end-on species on the electrode.

IR reflection-absorption spectroscopic study of benzotriazole on copper

Abstract Polarization-modulated infrared reflection absorption spectroscopy has been used to measure the infrared spectra of the surface films on copper grown in methanol or aqueous solutions containing benzotriazole. The spectra were compared with that of the copper-benzotriazole model complex. Surface protective films prepared in methanol containing benzotriazole are composed of infinite chains in which the Cu-benzotriazole complex is connected by strong charge-transfer interactions between benzotriazole molecules.

A surface-enhanced Raman study of the electrochemical reduction of 4-cyanopyridine

Abstract The adsorption and electroreduction of 4-cyanopyridine (4CP) on a silver electrode were studied by surface-enhanced Raman (SER) spectroscopy. The SER spectra indicate that the adsorbed 4CP takes end-on orientation on a silver electrode through the nitrogen atom in the pyridine ring. The softening and the cleavage of the C-C bond between the pyridine and the nitrile during the cathodic sweep were observed and discussed.

Oxidation of the cyanide ion at a platinum electrode studied by polarization modulation infrared reflection absorption spectroscopy

Abstract The anodic oxidation of the cyanide ion at a platinum electrode in aqueous solution was observed by polarization modulation infrared reflection absorption spectroscopy(PM IRRAS). The cyanide ion was adsorbed on the electrode surface in the potential region more negative than 0.4 V (versus Ag/AgCl). In the more positive region (> 0.4 V ), the adsorbed cyanide ion was oxidized to form the cyanate ion. Cyanogen was not detected during the oxidation reactions; this suggests direct electrochemical formation of the cyanate ion.

Vibrational frequency shift induced by protonation on pyridine studied by ab initio molecular orbital calculation

Abstract The vibrational frequency shift following protonation is studied by an ab initio molecular orbital method as the first step for elucidating the adsorption of pyridine at metal surfaces. Using a model such as pyridine hydrochloride and the appropriate scaling factors, we successfully predicted the small frequency shifts associated with the protonation.