Structural, morphological and electrochemical impedance study of CS: LiTf based solid polymer electrolyte: Reformulated arrhenius equation for ion transport study

This paper discusses ion conduction mechanism in terms of reformulated Arrhenius equation. Understanding the fundamental concepts of Li ion transport is crucial for Li battery technology. Structural and morphological investigations are significant to understand the structure-properties relationships. The broadening of X-ray peaks of chitosan upon the addition of LiTf salt reveals that the crystalline domains are reduced. The SEM micrographs reveal that the samples have a smooth surface. Electrochemical impedance spectroscopy (EIS) was used to obtain the electrical and dielectric parameters. The dielectric constant and DC ionic conductivity follows the same trend with salt concentration. The behavior of Arrhenius and modified Arrhenius equations versus temperature are clarified. The influence of dielectric constant on DC conductivity experimentally achieved. The reformulated Arrhenius equation exhibited more linearity between the DC conductivity and 1000/(ε'×T). The shortcoming of Arrhenius equation can be understood from the less linear behavior of DC conductivity versus 1000/T. The pre-exponential factor is almost constant at different temperature and independent on dielectric constant. The calculated activation energy from the reformulated Arrhenius equation is greater than that obtained from Arrhenius equation

Effect of silver nanoparticles on the DC conductivity in chitosan-silver triflate polymer electrolyte

A solid polymer electrolyte composed of chitosan and silver triflate (AgCF(3)SO(3)) has been prepared by the solution cast technique. The formation of polymer-salt complex has been confirmed by X-ray diffraction. The DC electrical conductivity of chitosan-silver triflate electrolyte has been investigated between 303 and 423 K, using electrochemical impedance spectroscopy over the frequency range from 50 Hz to 1000 kHz. The conductivity was found to increase with increase in AgCF(3)SO(3) concentration at room temperature. The DC conductivity obeys Arrhenius relationship up to a particular temperature and decreases at higher temperatures due to decrease in silver ions as a result of the formation of silver nanoparticles. The presence of an additional semicircular arc in the Cole-Cole plot obtained above 328 K indicates the existence of grain boundaries, which can be attributed to the silver particles. The presence of silver particles also have been proven by XRD after heating at 333, 363, and 393 K where the (1 1 1) peak of Ag is observed to increase with temperature. The silver particles were shown to be of nanosize using transmission electron microscopy (TEM). (C) 2010 Elsevier B.V. All rights reserved

Effect of the reduction of silver ions to silver nanoparticles on the dielectric properties of chitosan-silver triflate electrolyte

Films of solid polymer electrolyte based on chitosan and silver triflate (AgCF3SO3) have been prepared by casting technique. As a confirmation, the UV-vis results show the temperature dependence of silver nanoparticles. The dielectric constant increases with increasing salt concentration. The dielectric constant and dielectric loss curves show the higher values in the low frequency region and they are almost constant at higher frequencies. The dielectric constant and dielectric loss values are decreased above 358 K, as a result of transformation from silver ion to silver nanoparticles. The loss tangent peaks are broad and their heights decrease above 358 K. The broadness of loss tangent peaks indicates the distribution of relaxation time

Spectroscopic studies of chlorophyll a from Opuntia ficus-indica

Green pigment obtained from Opuntia ficus-indica intact plant was solvent extracted with absolute ethanol. The pigment solution was subjected to various photoexcitations at wavelengths of 222, 308, 337 and 448 nm. Fluorescence from the excited state exhibit peaked in the regions 450-485 nm and 650-680 nm. Upon comparison with the literature, the green solution is chlorophyll a. Fluorescence intensity ratio ( blue to red) differs with excitation wavelengths. It is known that chlorophyll a fluoresces at 673 nm. From the absorption spectrum, the peaks at similar to 404, similar to 501, similar to 605 and similar to 663 nm correspond to the singlet 4 (S4), singlet 3 (S3), singlet 2 (S2), and singlet 1 (S1) peaks, respectively

A High Efficiency Chlorophyll Sensitized Solar Cell with Quasi Solid PVA Based Electrolyte

The objective of this work is to investigate the performance of chlorophyll sensitized solar cells (CSSCs) with gel electrolyte based on polyvinyl alcohol (PVA) with single iodide salt (potassium iodide (KI)) and double salt (KI and tetrapropylammonium iodide (TPAI)). Chlorophyll was extracted from the bryophyte Hyophila involuta. The CSSC with electrolyte containing only KI salt produced a short circuit current density () of 4.59 mA cm−2, open circuit voltage () of 0.61 V, fill factor (FF) of 0.64, and efficiency () of 1.77%. However, the CSSC with double salt electrolyte exhibited of 5.96 mA cm−2, of 0.58 V, fill factor FF of 0.58, and of 2.00%. Since CSSC with double salt electrolyte showed better efficiency, other cells fabricated will use the double salt electrolyte. On addition of 0.7 M tetrabutyl pyridine (TBP) to the double salt electrolyte, the cell’s efficiency increased to 2.17%,  mA cm−2,  V, and FF = 0.73. With 5 mM chenodeoxycholic acid (CDCA) added to the chlorophyll, the light to electricity efficiency increased to 2.62% with of 8.44 mA cm−2, of 0.54 V, and FF of 0.58