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We describe a method for addressing redox enzymes adsorbed on a carbon electrode using synchrotron infrared microspectroscopy combined with protein film electrochemistry. Redox enzymes have high turnover frequencies, typically 10-1000 s(-1), and therefore, fast experimental triggers are needed in order to study subturnover kinetics and identify the involvement of transient species important to their catalytic mechanism. In an electrochemical experiment, this equates to the use of microelectrodes to lower the electrochemical cell constant and enable changes in potential to be applied very rapidly. We use a biological cofactor, flavin mononucleotide, to demonstrate the power of synchrotron infrared microspectroscopy relative to conventional infrared methods and show that vibrational spectra with good signal-to-noise ratios can be collected for adsorbed species with low surface coverages on microelectrodes with a geometric area of 25 × 25 μm(2). We then demonstrate the applicability of synchrotron infrared microspectroscopy to adsorbed proteins by reporting potential-induced changes in the flavin mononucleotide active site of a flavoenzyme. The method we describe will allow time-resolved spectroscopic studies of chemical and structural changes at redox sites within a variety of proteins under precise electrochemical control.

In dieser Arbeit wurde im Wesentlichen die elektrochemische Sauerstoffreduktion auf Germanium durch eine Kombination aus elektrochemischen Experimenten und in situ Infrarotspektroskopie in abgeschwächter Totalreflexion (ATR-IR) untersucht. Dabei konnten Superoxid und Peroxid, beide aufrecht auf der Oberfläche stehend, auf der Ge-Elektrode als Intermediate nachgewiesen werden. Die Zuordnung der Banden im IR-Spektrum war durch Experimente mit isotopenmarkiertem Sauerstoff sowie mit DFT-Rechnungen möglich. In saurer Lösung konnte gezeigt werden, dass der Beginn der Sauerstoffreduktion mit einer elektrodenpotenzialabhängigen Oberflächenumwandlung zwischen OH-terminierter und H-terminierter Oberfläche zusammenhängt. Weiterhin wurde damit begonnen, den experimentellen Ansatz auf für in Anwendungen hochgradig relevantes Zinkoxid (ZnO) zu übertragen. Dazu wurden dünne Filme von ZnO auf Ge präpariert. Auch auf diesen konnte Superoxid als Intermediat nachgewiesen werden.

Optoelectronic devices based on hybrid halide perovskites have shown remarkable progress to high performance. However, despite their apparent success, there remain many open questions about their intrinsic properties. Single crystals are often seen as the ideal platform for understanding the limits of crystalline materials, and recent reports of rapid, high-temperature crystallization of single crystals should enable a variety of studies. Here we explore the mechanism of this crystallization and find that it is due to reversible changes in the solution where breaking up of colloids, and a change in the solvent strength, leads to supersaturation and subsequent crystallization. We use this knowledge to demonstrate a broader range of processing parameters and show that these can lead to improved crystal quality. Our findings are therefore of central importance to enable the continued advancement of perovskite optoelectronics and to the improved reproducibility through a better understanding of factors influencing and controlling crystallization., Single crystals of lead halide perovskites exhibit good optoelectronic properties. Here, the authors study and deduce the mechanism for crystallisation and show how controlling dissolution of colloids through varying the acidity and temperature can improve the quality of the single crystals.