Inversion of the Photogalvanic Effect of Conductive Polymers by Porphyrin Dopants

Conductive polymers are widely used as active and auxiliary materials for organic photovoltaic cells due to their easily tunable properties, high electronic conductivity, and light absorption. Several conductive polymers show the cathodic photogalvanic effect in pristine state. Recently, photoelectrochemical oxygen reduction has been demonstrated for nickel complexes of Salen-type ligands. Herein, we report an unexpected inversion of the photogalvanic effect caused by doping of the NiSalen polymers with anionic porphyrins. The observed effect was studied by means of UV-Vis spectroscopy, cyclic voltammetry and chopped light chronoamperometry. While pristine NiSalens exhibit cathodic photopolarization, doping with porphyrins inverts the polarization. As a result, photoelectrochemical oxidation of the ascorbate proceeds smoothly on the NiSalen electrode doped with zinc porphyrins. The highest photocurrents were observed on NiSalen polymer with o-phenylene imine bridge, doped with anionic zinc porphyrin. Assuming this, porphyrin serves both as a catalytic center for the oxidation of ascorbate and an internal electron donor, facilitating the photoinduced charge transport and anodic depolarization.

A Multiple-Technique Approach to Inferring Bio-electrochemical Reaction Parameters

Uncovering the secrets of the biological Faradaic reactions, essential to the understanding of complex metalloenzymes, requires an information recovery process that is robust, rapid and replicable. This paper is a description of the workflow we have developed over the course of inferring chemical reaction parameters for a simple protein system, a bacterial cytochrome domain from \textit{Cellvibrio japonicus}. This was a challenging task, as the signal-to-noise ratio in such protein-film voltammetry experiments is significantly lowered relative to the voltammetric data generated by simple chemicals. We have overcome these challenges by using a multiple-technique approach, which compensates for the difficulties inherent to analysis of the individual voltammetry experiments. We have shown that the parameters inferred are robust across multiple experiments performed for different preperations of the protein. This is an important proof-of-concept result for analysis of more complex metalloenzymes, which incorporate catalytic processes and multiple internal electron-transfer sites. <br>

A Multiple-Technique Approach to Inferring Bio-electrochemical Reaction Parameters

Uncovering the secrets of the biological Faradaic reactions, essential to the understanding of complex metalloenzymes, requires an information recovery process that is robust, rapid and replicable. This paper is a description of the workflow we have developed over the course of inferring chemical reaction parameters for a simple protein system, a bacterial cytochrome domain from \textit{Cellvibrio japonicus}. This was a challenging task, as the signal-to-noise ratio in such protein-film voltammetry experiments is significantly lowered relative to the voltammetric data generated by simple chemicals. We have overcome these challenges by using a multiple-technique approach, which compensates for the difficulties inherent to analysis of the individual voltammetry experiments. We have shown that the parameters inferred are robust across multiple experiments performed for different preperations of the protein. This is an important proof-of-concept result for analysis of more complex metalloenzymes, which incorporate catalytic processes and multiple internal electron-transfer sites. <br>

Lifetime measurements of yrast states in $$^{\mathbf {178}}$$Pt using the charge plunger method with a recoil separator

Lifetime measurements in $$^{178}$$ 178 Pt with excited states de-exciting through $$\gamma $$ γ -ray transitions and internal electron conversions have been performed. Ionic charges were selected by the in-flight mass separator MARA and measured at the focal plane in coincidence with the $$4_1^+\rightarrow 2_1^+$$ 4 1 + → 2 1 + $$257\,$$ 257 keV $$\gamma $$ γ -ray transition detected using the JUROGAM 3 spectrometer. The resulting charge-state distributions were analysed using the differential decay curve method (DDCM) framework to obtain a lifetime value of 430(20) ps for the $$2_1^+$$ 2 1 + state. This work builds on a method that combines the charge plunger technique with the DDCM analysis. As an alternative analysis, ions were selected in coincidence with the $$^{178}$$ 178 Pt alpha decay ($$E_{\mathrm {alpha}} = 5.458(5)$$ E alpha = 5.458 ( 5 ) MeV) at the focal plane. Lifetime information was obtained by fitting a two-state Bateman equation to the decay curve with the lifetime of individual states defined by a single quadrupole moment. This yielded a lifetime value of 430(50) ps for the $$2_1^+$$ 2 1 + state, and 54(6) ps for the $$4_1^+$$ 4 1 + state. An analysis method based around the Bateman equation will become especially important when using the charge plunger method for the cases where utilising coincidences between prompt $$\gamma $$ γ rays and recoils is not feasible.