UV-Vis Spectroscopy with Optically Transparent Electrodes

These coated glasses can be used as working electrodes [optically transparent electrodes (OTE)] in standard three-electrode arrangements provided that both glass and coating are chemically and electrochemically stable and inert in the used electrolyte solution and the applied range of electrode potentials. The use of a modified infrared spectroscopy transmission cell equipped with quartz windows for UV-Vis spectroelectrochemistry has been described [18]. Platinum layers deposited onto the quartz served as an optically transparent working electrode and an additional platinum layer served as a pseudo-reference electrode. A counter electrode outside the thin layer zone (in one of the tubes used for solution supply) served as a counter 

Beyond numerous studies of soluble reaction intermediates and products (as an example see a study of electroreduction of nitrosobenzene [23] or investigations of chromium aryl complexes [24]) this design has also been employed successfully in studies of polymer films deposited onto these electrodes. Films showing redox activity and, in many cases, intrinsic electronic conductivity [intrinsically conducting polymers (ICPs)] have been studied for an overview see [25, 26]. In a typical set of spectra (Fig. 5.5) obtained with a film of poly aniline, optical absorptions corresponding to the 7T 7T transition (around 330 nm) and to further transitions involving species like radical cations (polarons) and dications (bipolarons) formed in the sequence of electrooxidation of the film are observed. 

Solid materials showing electrochemical activity can be studied by mechanically attaching them as small particles to an ITO-electrode [27]. The electroreduction of indigo has been studied using this approach. 

A considerably different approach employs a mini-grid electrode. This type of electrode can be made of a variety of metals (gold, platinum, etc.) and is basically a very fine mesh. Expanded metal-like structures, finely woven wires [28] or structures prepared via the LIGA-process [29, 30] are currently in use [31-33]. They are inserted into electrochemical cells of basically the same type as that used with OTE. The light beam passes the grid or the honeycomb structure of the LIGA element. Because the wires or the structural LIGA elements are extremely fine, only 

With only weakly absorbing solvents, low concentrations of the species to be detected or weak effects (i.e. small extinction coefficient), a long optical pathlength might be desirable. In a design described by Zak et al. [43], a cell body holding both the counter and the reference electrode is manufactured from PTFE. The working electrode is attached to the cell body with a spacer of about 0.1-mm thickness. The 

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