Chemie und Prozesstechnik
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Redox switches are applied in various fields of research, including molecular lifts, electronic devices and sensors. Switching the absorbance between UV and Vis/NIR by redox processes is of interest for applications in light harvesting or biomedicine.
Here, we present a series of push-pull benzothiadiazole derivatives with high fluorescence quantum yields in solution and in the crystalline solid state. Spectroelectrochemical analysis reveals the switching of UV-absorption in the neutral state to Vis/NIR absorption in the reduced state. We identify the partial irreversibility of the switching process, which appears to be reversible on the cyclic voltammetry timescale.
Removal of Etalon Features in the Far-Infrared–Terahertz Transmittance Spectra of Thin Polymer Films
(2020)
Etalon features in infrared spectra of stratified samples, their influence on the interpretation and methods to circumvent their presence in infrared spectra have been in discussion for decades. This paper focuses on the application of a method originally developed to remove interference fringes in the mid-infrared spectra for far-infrared Fourier transform spectroscopy on thin polymer films. We show that the total transmittance-reflectance technique, commonly used for mid-infrared, also works successfully in the far infrared spectral range where other approaches fail. Experimental spectra obtained by such technique are supported by model calculations and reveal the possibility and limits to obtain almost undisturbed far-infrared spectra which are suitable to determine low energy vibrations of ionomer salts under certain sample conditions.
We developed a setup for time- and lateral-resolved X-ray absorption fine structure (XAFS) spectroscopy. A dispersive element is placed behind the sample to investigate. The broadband incoming beam transmits the sample, is then dispersed and finally collected by a position sensitive detector. This allows the recording of a whole X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS) spectrum in a single shot. The dispersive element is a Si(111) crystal, bent by means of a so called wafer bender, developed in house. Our setup is very flexible, easy to adjust and allows a time resolution down to one second which can be used to follow chemical reactions with dynamics on this time scale.