UV-visible Reflectance Spectroscopy of Thin Organic Films at Electrode Surfaces

UV-visible Reflectance Spectroscopy of Thin Organic Films at Electrode Surfaces 

In this chapter, we are concerned with UV-visible reflectance spectroscopy for an electrode covered with a thin organic film. The UV-visible reflectance spectroscopy is a simple optical measurement What one needs is a sensitive UV- 

This chapter is devoted to describing the basic aspects of the measurement, instmmentation, measurement techniques, and practical applications of potential-modulated UV-visible spectroscopy as a representative spectroelectrochemi-cal tool to characterize thin organic films on electrode surfaces and to track the kinetics of the electrode surface processes. At the same time, miscellaneous features of the measurement, which may be important for those who intend to apply for the first time the potential-modulated UV-visible spectroscopic method in their experiments, will also be included. However, because of the Hmit to the chapter length as well as the existence of superior review articles on UV-visible reflectance spectroscopy at electrode/solution interfaces [2,6-9], detailed comprehensive description is minimized. With the intention of overviewing the UV-visible spectroscopic method for the benefit of experimental electrochemists, optical issues, especially optical reflection theory, are not detailed. 

The Basis of UV-visible Reflection Measurement at an Electrode Surface 

The basic optical theory of reflection for a soHd surface covered with a thin film has already been well established. We do not intend to review it here in full detail. Instead, readers can refer to the textbook of optics [12] or review articles on UV-visible reflection spectroscopy at electrode surfaces [2, 6-8]. It must be noted that for some electrode/solution interfaces it is stiU an extremely difficult task to establish the modeling of the interface through the use of classical light reflection theory, as described in the later sections. 

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I 2 UV-visible Reflectance Spectroscopy of Thin Organic Films at Electrode Surfaces 2.11.3... 

Recent decades have witnessed spectacular developments in in-situ diffraction and spectroscopic methods in electrochemistry. The synchrotron-based X-ray diffraction technique unraveled the structure of the electrode surface and the structure of adsorbed layers with unprecedented precision. In-situ IR spectroscopy became a powerfiil tool to study the orientation and conformation of adsorbed ions and molecules, to identify products and intermediates of electrode processes, and to investigate the kinetics of fast electrode reactions. UV-visible reflectance spectroscopy and epifluorescence measurements have provided a mass of new molecular-level information about thin organic films at electrode surfaces. Finally, new non-hnear spectroscopies such as second harmonics generation, sum frequency generation, and surface-enhanced Raman spectroscopy introduced unique surface specificity to electrochemical studies. 

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