Daniel Blackwood

PHOTOCORROSION OF N-SI IN AMMONIUM FLUORIDE SOLUTIONS : AN INVESTIGATION BY IN-SITU FOURIER TRANSFORM INFRARED SPECTROSCOPY

Abstract The illuminated n-Si/aqueous NH 4 F (pH 4.5) interface has been studied by attenuated reflectance Fourier transform infrared spectroscopy under conditions where photocorrosion of the silicon surface takes place. The progressive evolution of an anomalously strong Si-H stretch band in the 2100 cm −1 region was observed when the silicon was illuminated with visible light. The intensity of this band was found to increase linearly with the charge passed during illumination, rapidly exceeding values consistent with monolayer hydrogen coverage. The absorbance decayed slowly in the dark. The results were interpreted as evidence for the formation of a porous silicon layer during illumination, which then dissolved slowly in the dark.

Electrochemistry of Ferrocene in Acetonitrile. Evidence for Irreversible Kinetic Behavior Due to Passive Film Formation

Abstract : Montenegro and Pletcher have recently pointed out that measurement of the heterogeneous electron transfer rate constant of the ferrocene/ferrocenium couple at ultramicroelectrodes in acetonitrile solutions gives values that are several orders of magnitude larger than those measured at conventional electrodes. In addition, Bond et al. have pointed out that there is ambiguity in the interpretation of the electrochemical behavior of this couple in organic solvents. There are large discrepancies between the results from different workers on similar electrolyte/solvent systems which serves to show the difficulty in marking reliable measurements on this supposedly ideal electrochemical system. The situation is further confused since it has been proposed as a potential standard couple for non-aqueous electromechanical calibration. In his work on similar measurements on ferrocene/ferrocenium in acetonitrile at an ultramicroelectrode, Bond has discussed in detail several possible reasons for these discrepancies. Keywords: Reprints.

The Behavior of the Infrared Spectrum of Carbon Monoxide Adsorbed at Platinum Electrodes from Non-Aqueous Solvents

Abstract : Electrochemical oxidation of vanadium hexacarbonyl anion, V(CO)6 in aprotic solvents results in formation of the V(0) complex which decomposes to form Carbon Monoxide in high concentrations next to the electrode surface. As a result, CO is more rapidly adsorbed on the surface than by conventional methods. Surface reflection infrared spectroscopy shows that the potential dependent frequency shift for the infrared active bands due to CI adsorbed on platinum is 19/cm/V in 1,2-dichloroethane and 22/cm/V in acetonitrile, which are considerably less than the 30/cm/V observed in aqueous systems.

The effect of solvent type on the infrared spectrum of carbon monoxide adsorbed at platinum electrodes

Abstract The infrared spectrum of CO adsorbed on a platinum electrode from several solvents was investigated. In N-methylformamide, acetonitrile, and 1,2-dichloroethane, the infrared band attributed to linearly bonded CO had experimental Stark tuning rates of 20 cm−1/V, 22 cm−1/V, and 19 cm−1/V, respectively. For each of these solvents, the potential dependence of the band position was found to be linear for the entire potential range investigated. When methanol was the solvent, the plot of the band position versus potential had three distinctly linear portions, each with a different value for the slope. The behavior is explained in terms of the ability of the solvent molecules to approach the electrode surface closely, the polarity of the solvent, and the orientation of solvent molecules with respect to the polarization of the electrode.

An in-situ surface fourier transform infrared study of the adsorption of isoquinoline at a stationary mercury electrode

Abstract Subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS) was used to follow the potential dependent reorientations undergone by isoquinoline molecules that are adsorbed at a mercury electrode surface. The differences in the relative intensity changes on reorientation between the in-plane and out-of-plane vibrational modes have been explained in terms of field-induced infrared absorption.

An infrared study of thiocyanate at the mercury electrode interface

Abstract FTIR surface infrared spectroscopy of the mercury solution interface shows the adsorption of complex ions of mercury thiocyanate at potentials more positive than −200mV vs SCE, and indicates that thiocyanate ion is adsorbed by electrostatic physiadsorption at more negative potentials.

SNIFTIRS study of the behavior of the spectrum of carbon monoxide adsorbed on a platinum electrode in alcoholic solvents

Abstract The vibrational spectrum of carbon monoxide as a function of coverage in various alcoholic solvents was investigated using the SNIFTIRS technique. At low coverage the potential dependence of the band position was found to be linearly dependent on the inverse of the bulk dielectric constant of the solvent. An electrostatic model was developed to represent the interaction between adjacent adsorbate molecules. This model provides evidence in support of an island formation mechanism.