Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5C9 Canada.
Anal Chem. 2011 May 15;83(10):3632-9. doi: 10.1021/ac200250s. Epub 2011 Apr 18.
Synchrotron infrared radiation has been successfully coupled through an infrared (IR) microscope to a thin-cavity external reflectance cell to study the diffusion controlled redox of a ferrocyanide solution. Excellent signal-to-noise ratios were achieved even at aperture settings close to the diffraction limit. Comparisons of noise levels as a function of aperture size demonstrate that this can be attributed to the high brilliance of synchrotron radiation relative to a conventional thermal source. Time resolved spectroscopic studies of diffusion controlled redox behavior have been measured and compared to purely electrochemical responses of the thin-cavity cell. Marked differences between the two measurements have been explained by analyzing diffusion in both the axial (linear) and radial dimensions. Whereas both terms contribute to the measured current and charge, only species that originate in the volume element above the electrode and diffuse in the direction perpendicular to the electrode surface are interrogated by IR radiation. Implications for the use of ultramicroelectrodes and synchrotron IR (SIR) to study electrochemical processes in the submillisecond time domain are discussed.
同步辐射红外辐射已成功通过红外（IR）显微镜耦合到一个薄腔外反射池，以研究亚铁氰化物溶液的扩散控制氧化还原。即使在接近衍射极限的孔径设置下，也能获得优异的信噪比。孔径大小与噪声水平的比较表明，这归因于相对于传统热光源，同步辐射的高亮度。已测量了扩散控制氧化还原行为的时间分辨光谱研究，并与薄腔池的纯电化学响应进行了比较。通过分析轴向（线性）和径向两个维度的扩散，对两种测量结果之间的明显差异进行了解释。虽然这两个术语都对测量电流和电荷有贡献，但只有起源于电极上方体积元并沿垂直于电极表面的方向扩散的物质才会被红外辐射探测到。讨论了使用超微电极和同步辐射红外（SIR）在亚毫秒时间域研究电化学过程的意义。
