Dielectric Spectroscopy Can Predict the Effect of External AC Fields on the Dynamic Adsorption of Lysozyme.

This report describes the application of dielectric spectroscopy as a simple and fast way to guide protein adsorption experiments. Specifically, the polarization behavior of a layer of adsorbed lysozyme was investigated using a triangular-wave signal with frequencies varying from 0.5 to 2 Hz. The basic experiment, which can be performed in less than 5 min and with a single sample, not only allowed confirming the susceptibility of the selected protein towards the electric signal but also identified that this protein would respond more efficiently to signals with lower frequencies. To verify the validity of these observations, the adsorption behavior of lysozyme onto optically transparent carbon electrodes was also investigated under the influence of an applied alternating potential. In these experiments, the applied signal was defined by a sinusoidal wave with an amplitude of 100 mV and superimposed to +800 mV (applied as a working potential) and varying the frequency in the 0.1-10000 Hz range. The experimental data showed that the greatest adsorbed amounts of lysozyme were obtained at the lowest tested frequencies (0.1-1.0 Hz), results that are in line with the corresponding dielectric features of the protein.

Innovative multifunctional hybrid photoelectrode design based on a ternary heterojunction with super-enhanced efficiency for artificial photosynthesis.

Electrochemical cells for direct conversion of solar energy to electricity (or hydrogen) are one of the most sustainable solutions to meet the increasing worldwide energy demands. In this report, a novel and highly-efficient ternary heterojunction-structured Bi4O7/Bi3.33(VO4)2O2/Bi46V8O89 photoelectrode is presented. It is demonstrated that the combination of an inversion layer, induced by holes (or electrons) at the interface of the semiconducting Bi3.33(VO4)2O2 and Bi46V8O89 components, and the rectifying contact between the Bi4O7 and Bi3.33(VO4)2O2 phases acting afterward as a conventional p-n junction, creates an adjustable virtual p-n-p or n-p-n junction due to self-polarization in the ion-conducting Bi46V8O89 constituent. This design approach led to anodic and cathodic photocurrent densities of + 38.41 mA cm-2 (+ 0.76 VRHE) and- 2.48 mA cm-2 (0 VRHE), respectively. Accordingly, first, this heterojunction can be used either as photoanode or as photocathode with great performance for artificial photosynthesis, noting, second, that the anodic response reveals exceptionally high: more than 300% superior to excellent values previously reported in the literature.