Kinetics of temperature-dependent photoinduced redox reactions in a photoelectrochemical cell

The effect of temperature on the electrode kinetics of photovoltage generation in photoelectrochemical (PEC) cells consisting of a phenazine dye-EDTA system, separated from an aqueous solution of an electron acceptor like iodine by a salt bridge has been studied. The phenazine dyes used are phenosafranin, safranin-O, and safranin-T. The maximum photovoltages (V_oc) generated and the sunlight engineering efficiency (SEE) have been found to increase with increasing temperature, but there is a fixed critical temperature for each dye above which the V_oc decreases: 29°C for phenosafranin, 35°C for safranin-T, and 40°C for safranin-O. The photovoltage growth and decay follow the functional forms related to the relaxation times. The rate constants for the forward and backward reactions have been calculated from these relaxation times at different temperatures. The rate of the photoinduced chemical reaction increases with an increase in temperature from 20°C–50°C for all the dyes, with concomitant decrease for the backward reaction. The free energies of electron transfer across the electrode/electrolyte interface have been calculated. The activation energies calculated from the rate constants at different temperatures for phenosafranin-EDTA, safranin-T-EDTA, and safranin-O-EDTA reactions are 5.14, 5.60, and 5.63 kJ mol⁻¹ respectively.     

Comparison of dc electric field and tapered wiggler free electron laser efficiency enhancement schemes

A constant parameter wiggler free electron laser using a dc electric field for efficiency enhancement is compared to several tapered wiggler efficiency enhancement schemes. Analytical expressions for the efficiency in the plane wave, infinitesimally small radius electron beam limit are derived and compared. Numerical simulations for a Gaussian radiation field and finite radius electron beam with an output radiation wavelength of 2 μm are presented. For finite radius electron beams, the extraction efficiency using a dc electric field is somewhat greater than or equal to that using proposed tapering schemes. While the dc field offers flexibility in efficient, tunable laser design, the required field strengths for visible radiation are in the megavolt/meter range.     

Solar cells consisting of phenazine dyes in polymer matrix

We have constructed p−n heterojunction solar sandwich cells with phenazine dyes in a thin film of polyvinyl alcohol placed between a conducting glass coated with indium oxide and a platinum foil. The current-voltage relations of the cells have been measured in the dark and light under both forward and reverse biases.     

Neural perceptron & strict lossless secret sharing oriented cryptographic science: fostering patients’ security in the “new normal” COVID-19 E-Health

Multimedia Tools and Applications - Patients’ data security is an open challenge on any telemedicine system. The challenge has been extended enough in this unprecedented corona virus led...     

Physicochemical and Adhesion Characteristics of High-Density Polyethylene when Treated in a Low-Pressure Plasma under Different Electrodes

The present investigation studys the effects of different electrodes such as copper, nickel, and stainless steel under low-pressure plasma on physicochemical and adhesion characteristics of high-density polyethylene (HDPE). To estimate the extent of surface modification, the surface energies of the polymer surfaces exposed to low-pressure plasmas have been determined by measuring contact angles using two standard test liquids of known surface energies. It is observed that the surface energy and its polar component increase with increasing exposure time, attain a maximum, and then decrease. The increase in surface energy and its polar component is relatively more important when the polymer is exposed under a stainless-steel electrode followed by a nickel and then a copper electrode. The dispersion component of surface energy remains almost unaffected. The surfaces have also been studied by optical microscopy and electron spectroscopy for chemical analysis (ESCA). It is observed that when the HDPE is exposed under these electrodes, single crystals of shish kebab structure form, and the extent of formation of crystals is higher under a stainless-steel electrode followed by nickel and then copper electrodes. Exposure of the polymer under low-pressure plasma has essentially incorporated oxygen functionalities on the polymer surface as detected by ESCA. Furthermore the ESCA studies strongly emphasize that higher incorporation of oxygen functionalities are obtained when the polymer is exposed to low-pressure plasma under a stainless-steel electrode followed by nickel and then copper electrodes. These oxygen functionalities have been transformed into various polar functional groups, which have been attributed to increases in the polar component of surface energy as well as the total surface energy of the polymer. Therefore, the maximum increase in surface energy results in stronger adhesion of the polymer when the polymer is exposed under a stainless-steel electrode rather than nickel and copper electrodes.