Optical properties, spectroscopy solution spectra

A very simple spectroelectrochemical experiment based on a conventional cuvette for UVA is spectroscopy with electrodes immersed in the solution phase is shown in Fig. II.6.4. The optically transparent working electrode is located directly in the beam path and additionally a large surface area counter electrode (Pt wire) and a reference electrode (e.g. a coated silver wire) are located in the solution phase above the beam path. After filling the cuvette with electrolyte solution, the reference spectrum can be recorded taking into account the transparency of the OTE and optical properties of the solution. This reference spectrum is later used to subtract the absorption of the cuvette, the electrolyte, and the OTE from experimental data obtained after applying a potential. Next, the redox reagent is added and the first spectrum of the starting material is recorded. The potential is applied... 

The optical properties of D-A copolymers are usually assessed by UV-vis absorption spectroscopy. The extinction coefficient of a polymer film is typically of the order of 10 cm The optical bandgap can be estimated from the onset of the absorption band of polymer thin films. Additionally, the shift between the absorption maximum of polymer solution spectrum and that of the polymer thin-film spectrum is used to estimate the degree of interchain interaction. Stronger stacking and aggregation of polymers in film is usually accompanied by a larger red shift of the absorption maximum from the solution to the film. 

Another consequence of the strong absorption properties of water is the spectral impact of the displacement of water by dissolved solutes. Generally, in absorption spectroscopy, the solvent is selected not to absorb over the wavelength range of interest. When the absorption properties of the solvent are negligible, any displacement of solvent molecules from the optical path by the dissolution of solute molecules has a negligible effect on the measured spectrum. For near-infrared spectra of aqueous solutions, however, the absorption spectrum depends heavily on the degree of water displacement by solutes in the sample. 

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