Conductivity Plots Research Articles

Characterization of Novel Castor Oil-Based Polyurethane Polymer Electrolytes

Castor oil-based polyurethane as a renewable resource polymer has been synthesized for application as a host in polymer electrolyte for electrochemical devices. The polyurethane was added with LiI and NaI in different wt% to form a film of polymer electrolytes. The films were characterized by using attenuated total reflectance-Fourier transform infrared spectroscopy, dynamic mechanical analysis, electrochemical impedance spectroscopy, linear sweep voltammetry and transference number measurement. The highest conductivity of 1.42 × 10−6 S cm−1 was achieved with the addition of 30 wt% LiI and 4.28 × 10−7 S·cm−1 upon addition of 30 wt% NaI at room temperature. The temperature dependence conductivity plot indicated that both systems obeyed Arrhenius law. The activation energy for the PU-LiI and PU-NaI systems were 0.13 and 0.22 eV. Glass transition temperature of the synthesized polyurethane decreased from −15.8 °C to ~ −26 to −28 °C upon salts addition. These characterizations exhibited the castor oil-based polyurethane polymer electrolytes have potential to be used as alternative membrane for electrochemical devices.

Variable range hopping (VRH) conductivity, ac conductivity and dielectric studies on Sm3+ doped Cd0.8Zn0.2S semiconductor compounds

Polycrystalline semiconductor compounds of Cd0.8Zn0.2S and Sm3+ (0.01, 0.02, 0.03, 0.04 and 0.05mol%) doped Cd0.8Zn0.2S samples have been synthesized by a controlled co-precipitation technique. The samples are characterized by X-ray diffraction (XRD). DC conductivity studies were performed in the temperature region 77–300K by using a two probe method. The dc conductivity plots show the Arrhenius behavior with three different activation energies (Ea) in three different temperature regions (I (300–220K), II (220–160K), III (160–105K), and they exhibited the variable range hopping conduction (VRH) mechanism at low temperature region (105–77K). From the impedance, and dielectric measurements bulk resistance (Rg), capacitance (Cg), relaxation time (τ) and dielectric constant (ε̕) parameter values were calculated. And explained their variations with temperature and dopant (Sm3+) concentration changes.

Tight Junction Elaboration Aids Hypersaline Secretion in Euryhaline Teleost Fish

We examined how the Na+ conductive paracellular pathway between ionocytes and accessory cells is modified in hypersaline conditions to allow Na+ secretion in extreme environments. Mummichogs (Fundulus heteroclitus) were acclimated to seawater (SW) or hypersaline conditions (2SW, 64 ‰) for 30 days. In 2SW fish, invasive cellular projections of accessory cells with increased area of simple tight junctions were detected by the punctate distribution of CFTR immunofluorescence and by TEM ultrastructure of the opercular epithelium (OE), a gill‐like tissue rich in mitochondrion‐rich ionocytes. Punctate CFTR distribution was not explained by membrane raft organization, as chlorpromazine (50 μM) and filipin (1.5 μM) were ineffective in changing electrophysiology of OE. Isolated OE from SW fish with SW on the mucosal side had a transepithelial potential (Vt) of +40.1 + 0.9 mV (n = 24), sufficient to allow passive Na+ secretion (Nernst equilibrium potential ≡ ENa = +24.11 mV). OE from fish acclimated to 2SW and bathed in 2SW (mucosal side) had significantly higher Vt of +45.1 + 1.2 mV (n = 24; P < 0.001) and plasma Na+ was slightly elevated, sufficient for passive Na+ secretion (ENa = +40.74 mV), but with a severely diminished net driving force. Paradoxically, estimates of shunt conductance from epithelial conductance (Gt ) vs. short‐circuit current (Isc) plots (extrapolation to zero Isc) revealed significant reduction in total epithelial shunt conductance in 2SW acclimated fish. We conclude that whereas most epithelial tight junctions become less conductive in hypersaline conditions, those localized to the paracellular Na+ exit pathway become more conductive, compensating for lower driving force. Funded by NSERC and CFI.

Enhanced ionic conductivity in La3+ and Sr2+ co-doped ceria: carbonate nanocomposite

A series of ceria-based nanocomposites consisting of Ce0.85La0.125Sr0.025O1.9125 (LSCO) and binary carbonate mixture Li2CO3–Na2CO3 (LNCO) have been prepared as functional electrolytes for low-temperature solid oxide fuel cells (LT-SOFCs). These have been characterized using powder X-ray diffraction, scanning electron microscope, differential thermal analysis, and measurement of conductivity as a function of temperature using complex plane impedance analysis. Crystalline ceria-based single phase formation has been found in all the composites. Carbonates are present as an amorphous phase in the composites. Impedance analysis has been used to study the electrical behavior of the composites. A jump in the conductivity vs temperature plots has been observed in all the composites containing different carbonate contents. This is related to superionic transition at the interfaces. Conductivity of the composites increases with increasing amount of carbonate. This is due to the increase in the interfacial area between the two phases, which promotes interfacial interaction between them. Composition, LSCO/35LNCO, shows conductivity of 0.203 S cm−1 at 500 °C with an activation energy of conduction of 0.19 eV.

Alternating-current conductivity and dielectric relaxation of bulk iodoargentate

An inorganic-organic hybrid compound Cu(en)2Ag2I4 (en=ethylenediamine) (1) was synthesized and single crystal structurally characterized. Along the [001] direction, the inorganic parts form an infinite 1-D chain and [Cu(en)2]2+ cations are separated by inorganic chain. The electrical conductivity and dielectric properties of 1 have been investigated over wide ranges of frequency. The alternating-current conductivities have been fitted to the Almond–West type power law expression with use of a single value of S. It is found that S values for 1 are nearly temperature-independent, which indicates that the conduction mechanism could be quantum mechanical tunneling (QMT) model. The dielectric loss and electric modulus show single dielectric relaxation process. The activation energy obtained from temperature-dependent electric modulus compare with the calculated from the dc conductivity plots.

Modeling contact formation between atomic-sized gold tips via molecular dynamics

The formation and rupture of atomic-sized contacts is modelled by means of molecular dynamics simulations. Such nano-contacts are realized in scanning tunnelling microscope and mechanically controlled break junction experiments. These instruments routinely measure the conductance across the nano-sized electrodes as they are brought into contact and separated, permitting conductance traces to be recorded that are plots of conductance versus the distance between the electrodes. One interesting feature of the conductance traces is that for some metals and geometric configurations a jump in the value of the conductance is observed right before contact between the electrodes, a phenomenon known as jump-to-contact. This paper considers, from a computational point of view, the dynamics of contact between two gold nano-electrodes. Repeated indentation of the two surfaces on each other is performed in two crystallographic orientations of face-centred cubic gold, namely (001) and (111). Ultimately, the intention is to identify the structures at the atomic level at the moment of first contact between the surfaces, since the value of the conductance is related to the minimum cross-section in the contact region. Conductance values obtained in this way are determined using first principles electronic transport calculations, with atomic configurations taken from the molecular dynamics simulations serving as input structures.

Diffuse phase ferroelectric vs. Polomska transition in (1-x) BiFeO3-(x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) solid solutions

Investigations on the solid solutions (1-x) BiFeO3 - (x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) in the temperature range 300–750 K show colossal permittivity behavior and the occurrence of diffuse phase ferroelectric transition along with frequency dependent anomaly which disappears at temperature ∼450 K. For x = 0.3, these anomalies have been verified through differential scanning calorimetry and dielectric/impedance/conductivity measurements. The occurrence of peak in pyrocurrent (dPs/dT) vs. T plots also supports phase transition. With the increasing x, transition temperature decreases and diffusivity increases. This anomaly is absent at high frequencies (>100 kHz) in conductivity plots, indicating Polomska like surface phase transition, which is supported by modulus study.

Voltage Gating in Nanopores Containing Anthraquinone Mimics Biological Membrane Proteins

Ion channels formed by membrane bound proteins play a key role in the proper functioning of the human body. These membrane proteins are able to regulate the transport of water, ions, and larger molecules through small openings in the protein under a transmembrane potential. Much study has gone into illuminating how these membrane proteins sense voltage. Some mechanisms include charged residues in proteins that can reorient in an electric field or side chains that have an intrinsic dipole moment. Here we report the first synthetic nanopore to mimic and explore these possible mechanisms.We chemically attached a 9, 10 Anthraquinone (AQ) to the interior of an Alumina nanopore. In the presence of an applied voltage we found the AQ responds in a manner similar to biological pores exhibiting voltage gating. The conductivity verse voltage of the AQ modified nanopore followed a classic sigmoidal gating curve, identical to biological membrane proteins. Through this plot, it is possible determine the exact mechanism of the gating effect. In our system, we determined that the AQ was gaining one electron when the applied voltage reached a certain level. At this voltage level the AQ was reduced to form a radical semiquinone. The potential required to form the semiquinone state can be determined from the conductivity plot. This technique can also be applied to other molecules where the chemical reaction changes it response to an electric field, such as deprotonation, cation incorporation and radical formation.

Thermodynamic Parameters of Complexation Calixpyrrole Derivative with Lanthanides Cations (Lu3, Ho3, Eu3+ and Pr3+) in Nonaquoeus Media

Calix [4] pyrrole derivative was used to target lanthanide cations. Meso tetramethyl-tetrakis-[(4-N, N-diethylacetamide) phenoxymethyl] calix [4] pyrrole, L2 was synthesised. This receptor constituted of hard donor atoms at the lower rim which interact with lanthanide cations being hard cations. 1H NMR investigations showed that both, the pyrrolic N and the acetamide arm group provide sites for interaction with lanthanide metal cations. These findings are verified by conductance measurements in acetonitrile, plots of molar conductance against the ligand/metal cation ratio reveal the formation of 1:2 complexes between this ligand with lanthanide metal cations. Standard thermodynamics parameters of complexation (log Ks, ΔHᵒc, ΔSᵒc, ΔGᵒc) of L2 with lanthanide cations in acetonitrile were determined using the Nano ITC (isothermal titration calorimetry). The complexation process between these metal cations and the receptor L2 was enthalpically controlled.

Photovoltaic and Impedance Properties of Hierarchical TiO2 Nanowire Based Quantum Dot Sensitized Solar Cell

Growth and characterization of TiO2 nanowire (NW) assemblies on FTO glass using a typical hydrothermal synthesis have been reported. CdS quantum dots (QDs) have been deposited on TiO2 nanowires by successive ion layer adsorption and reaction (SILAR) method. FESEM image exhibits the flower‐like hierarchical TiO2 bunch of nanowires. HRTEM image confirms the size of CdS QDs between 5 and 6 nm. XRD and absorption studies revealed proper growth of CdS quantum dots on TiO2 nanowires. At AM 1.5 illumination intensity, the solar cell, with the configuration FTO/TiO2‐NW/CdS‐QDs/Pt‐FTO, displays a short circuit current (Jsc) of 1.295 mA and an open circuit voltage (Voc) of 0.38 V. The Voc and Jsc showed linear behavior at higher illumination intensities. The peak in power‐voltage characteristics at various illuminations showed a shift towards higher Voc values. Capacitance‐voltage (C-V), conductance‐voltage (G-V), and series resistance‐voltage (Rs‐V) measurements of the cell in the frequency ranging from 5 kHz to 5 MHz showed decreasing trend of capacitance with increase of frequency whereas increase in conductance and decrease in resistance have been noticed with increase of frequency. All the results including the individual behavior of the plots of capacitance, conductance, and series resistance as a function of bias voltage have been discussed.

Fundamental Studies of Synthesizing Novel Calix[4]arene Derivative as Host for Treatment of Toxic Metal Cations (Hg2+, Cd2+, Pb2+ and Ag+)

Novel calix[4]arene derivative containing mixed pendant arms in its lower rim, 25, 27- bis (diethylamino) ethoxy- 26, 28- (bis-methoxyethoxy) calix[4]arene, L3, has been synthesized to target the heavy metal cations. 1H NMR investigations seems to indicate that the receptor L3 interacts preferentially with Hg2+, Cd2+, Pb2+ and Ag+ in acetonitrile. Complexation studies in acetonitrile show that the lower rim groups of the receptor L3 are the active sites of its interaction with metal ions. These findings are corroborated by conductance measurements in acetonitrile, plots of molar conductance against the ligand/metal cation ratio reveal the formation of 1:1 complexes between this ligand with these cations. Standard thermodynamics parameters of complexation (log Ks, ΔHAiµ’ c, ΔSAiµ’ c, ΔGAiµ’ c) of L3 with Hg2+, Cd2+, Pb2+ and Ag+ in acetonitrile were determined using the Nano ITC (isothermal titration calorimetry). For all the systems investigated, the complexation process between these metal cations and the receptor L3 was enthalpically controlled. The enthalpic and entropic contributions to the Gibbs energy associated with these processes are analysed.

Paracellular pathway remodeling enhances sodium secretion by teleost fish in hypersaline environments.

In vertebrate salt-secreting epithelia, Na(+) moves passively down an electrochemical gradient via a paracellular pathway. We assessed how this pathway is modified to allow Na(+) secretion in hypersaline environments. Mummichogs (Fundulus heteroclitus) acclimated to hypersaline [2× seawater (2SW), 64‰] for 30 days developed invasive projections of accessory cells with an increased area of tight junctions, detected by punctate distribution of CFTR (cystic fibrosis transmembrane conductance regulator) immunofluorescence and transmission electron miscroscopy of the opercular epithelia, which form a gill-like tissue rich in ionocytes. Distribution of CFTR was not explained by membrane raft organization, because chlorpromazine (50 μmol l(-1)) and filipin (1.5 μmol l(-1)) did not affect opercular epithelia electrophysiology. Isolated opercular epithelia bathed in SW on the mucosal side had a transepithelial potential (Vt) of +40.1±0.9 mV (N=24), sufficient for passive Na(+) secretion (Nernst equilibrium voltage≡ENa=+24.11 mV). Opercular epithelia from fish acclimated to 2SW and bathed in 2SW had higher Vt of +45.1±1.2 mV (N=24), sufficient for passive Na(+) secretion (ENa=+40.74 mV), but with diminished net driving force. Bumetanide block of Cl(-) secretion reduced Vt by 45% and 29% in SW and 2SW, respectively, a decrease in the driving force for Na(+) extrusion. Estimates of shunt conductance from epithelial conductance (Gt) versus short-circuit current (Isc) plots (extrapolation to zero Isc) suggested a reduction in total epithelial shunt conductance in 2SW-acclimated fish. In contrast, the morphological elaboration of tight junctions, leading to an increase in accessory-cell-ionocyte contact points, suggests an increase in local paracellular conductance, compensating for the diminished net driving force for Na(+) and allowing salt secretion, even in extreme salinities.

Ionic Conductance, Thermal and Morphological Behavior of PEO-Graphene Oxide-Salts Composites

Thin films composites of poly(ethylene oxide)-graphene oxide were fabricated with and without lithium salts by solvent cast method. The ionic conductivity of these composites was studied at various concentrations of salt polymer-GO complexes and at different temperatures. The effects of temperature and graphene oxide concentration were measured from Arrhenius conductance plots. It is shown that the addition of salts in pure PEO increases conductance many times. The graphene oxide addition has enhanced the conductance approximately 1000 times as compared to that of pure PEO. The activation energies were determined for all the systems which gave higher values for pure PEO and the value decreased with the addition of LiClO4and LiCl salts and further decreases with the addition of graphene oxide. The composite has also lowered the activation energy values which mean that incorporation of GO in PEO has decreased crystallinity and the amorphous region has increased the local mobility of polymer chains resulting in lower activation energies. SEM analysis shows uniform distribution of GO in polymer matrix. The thermal stability studies reveal that incorporation of GO has somewhat enhanced the thermal stability of the films.

Optical And Electrical Properties Of Conducting Polyaniline Nanofibers Synthesized By Interfacial And Rapid Mixing Polymerization

One dimensional conducting polymer nanostructures have been the focus of quite extensive studies worldwide due to their high aspect ratio, high porosity apart from high surface area to volume ratio. Conducting polyaniline nanofibers can be synthesized by various methods. In this paper, we report the preparation of polyaniline nanofibers with an average diameter of 40–70 nm by two different simple approach rapid mixing and interfacial polymerization. The key to producing polyaniline nanofibers is to suppress secondary growth. Based on this, interfacial polymerization and rapidly mixed reactions have been developed that can readily produce nanofibers by slightly modifying the conventional chemical synthesis of polyaniline without the need for any template or structural directing agent. Synthesized polyaniline (PANI) nanofibers were characterized by FTIR spectroscopy, Xray diffraction, transmission electron microscopy for their structural and UV-Vis absorption spectroscopy for optical properties. Direct and indirect transition energy gaps were determined from their Tauc plots. The absorption spectra show a linear fit for the transition. Electrical properties of the synthesized polyaniline nanofibers have been studied and the Arrhenius plots of electrical conductivity for the samples synthesized by rapid mixing and interfacial polymerization method show an approximate equal in their activation energy. The results obtained from optical and electrical properties are well compared, correlated and explained with respect to interfacial and rapid mixing polymerization techniques. Copyright © 2014 VBRI press.

Microstructural and ionic transport studies of hydrothermally synthesized lanthanum fluoride nanoparticles

This article presents the structural and transport characteristics of hydrothermally synthesized LaF3 nanoparticles with an average crystallite size of 35nm. The phase formation of the material is confirmed by both X-ray diffraction and transmission electron microscopy techniques. In addition, phase purity of the LaF3 nanoparticles is corroborated by micro-Raman spectroscopy studies. The complex impedance plots at different temperatures reveal that the conductivity is predominantly due to the intrinsic bulk grains and the conductivity relaxation is non-Debye in nature. The frequency variation of conductivity exhibits dispersion at higher frequencies that can be explained with the frame work of Almond-West formalism. The conduction process is controlled by the mobility of the charge carriers and the charge of transport of mobile fluoride ions occur through hopping mechanism. The scaling behavior of both frequency dependence of conductivity and complex impedance plots at different temperatures confirm that the relaxation mechanism of the mobile fluoride ions is independent of temperature.

Effect of N-Decyl-N-N-Dimethyl-3-Ammonio-1-Propanesulfonate on the Solution Properties of Sodium Dodecyl Sulfate

Conductivity measurements have been used to study the solution properties of mixtures of sodium dodecyl sulphate (SDS) and n-decyl-n,n-dimethyl-3-ammonio1-propanesulfonate (DPS) at 35 and 40 oC and various concentrations of DPS. The critical micelle concentrations (CMCs) of the solution of SDS and its mixtures with DPS were extrapolated from the inflection points on conductivity versus concentration curves. The CMCs increased as the temperature of the solution increased but decreased with increasing concentration of DPS. The degree of ionization of the mixed micelles calculated from the slope before and after the inflection point on concentration versus conductivity plots increased with increasing concentration of DPS but decreased with temperature. These results have been fully discussed based on the effect of non-charged DPS headgroup on the charged SDS headgroup. © JASEM

A New Approach in Determining Limiting Molar Conductivity value for Liquid Electrolyte

Abstracts Accurate determination of limiting molar conductivity ( Λ 0 ) value for an electrolyte at infinite dilution is an important physical quantity that reviews the strength of an electrolyte. Therefore, in this study, a power law comprised of a double-logarithmic plot of electrolytic conductivity ( κ ) and salt concentration ( C salt ) has been introduced to determine Λ 0 accurately at a corresponding reference salt concentration ( C ref ). Furthermore, the reliability of the experimental data is verified after Kohlrausch's law for LiClO 4 (aq.) at 25.0 °C which is perfectly identical with the reference data. The workability of the power law is tested for LiClO 4 (aq.) and LiClO 4 in acetonitrile (ACN) at a range of C salt at 25.0 °C. Thus, the Λ 0 for both systems correspond at 106 and 177.4 S cm 2 mol −1 respectively, after the power law deviated only 2% of the reported value. From the study, it is noted that the corresponding C ref is approximately half of the lowest C salt concentration that obeys the power law at infinite dilution which responds to Λ 0 for an electrolyte system. This alternative method shows a nice linearity for C salt (10 −5 - 10 −9 mol cm −3 ) between the experimental and reference data before it deviates from the linearity above C salt > 10 −5 mol cm −3 .

Excess conductivity analysis of heavy ions irradiated TlBa2(Ca2−yMgy)Cu3O10−δ superconductor

The excess conductivity analysis of resistivity versus temperature data of TlBa2(Ca2−yMgy)Cu3O10−δ (y=0.5, 1.0, 1.5) superconductor samples have been performed in the light of Aslamasov-Larkin and Lawrence-Doniach theories before and after irradiation with a beam of gold (Au4+) ions of energy 20MeV having a fluence of 1×1015 ions/cm2. The microscopic parameters such as zero temperature coherence length {ξc(0)}, inter-plane coupling constant (α), and Fermi velocity (VF) have been calculated from the ln-ln plot of excess conductivity (Δσ) versus reduced temperature (ε) using the Lawrence and Doniach model. The cross-over temperatures separating different fluctuation regions in the ln-ln plot are also determined. It is observed from the excess conductivity analysis that all the microscopic parameters have been decreased after the irradiations. Whereas, calculations have shown that critical magnetic fields (Bc) and critical current density (Jc) are increased after the ion irradiation, which, confirms the validity of the results because Bc and Jc are increased by the formation of artificial pinning centers after bombardment of energetic heavy ion beam.

Investigation into the optoelectrical properties of tungsten oxide thin films annealed in an oxygen air

Tungsten oxide (WOx) thin film have been deposited onto glass substrates using the thermal vacuum evaporation technique, monitored by an annealing process in a variable oxygen atmosphere. Analysis by X-ray diffraction and Raman spectroscopy showed the structural changes from orthorhombic to monoclinic which depend on the annealing temperature and the oxygen content. AFM study shows that the increase of oxygen content leads to a decrease of the root-mean-square from 94.64nm to 2nm. Ellipsometric measurements have been used to evaluate the optical constants. Further, it is found that when the oxygen content increases, the band gap of the annealed layer varies from 3.01eV to 3.52eV by against, the Urbach energy decreases. The AC conductivity plot showed a universal power law according to the Jonscher model. Moreover, at high frequency semiconductor-to-metallic behavior has been observed. Finally, the effect of annealing in oxygen atmosphere on their structural modifications, morphological, optical properties and electrical conductivity are reported.

Physical and CO2-Absorption Properties of Imidazolium Ionic Liquids with Tetracyanoborate and Bis(trifluoromethanesulfonyl)amide Anions

Ionic liquids with tetracyanoborate ([TCB]−) and bis(trifluoromethanesulfonyl)amide ([Tf2N]−) anions generally have low viscosities and high CO2 capacities, and thus they are attractive solvents for CO2-related applications. Herein, we have investigated physical and CO2-absorption properties of 1-ethyl-3-methylimidazolium tetracyanoborate ionic liquid ([emim][TCB]) to discuss the anion effects of [TCB]− in comparison with the previous results of [emim][Tf2N]. The density, viscosity, electrical conductivity, and isobaric molar heat capacity were measured as a function of temperature at atmospheric pressure. [emim][TCB] has both lower density and isobaric molar heat capacity than [emim][Tf2N]. [emim][TCB] shows superior transport properties (lower viscosity and higher electrical conductivity) compared to [emim][Tf2N], whereas the Walden plots of molar conductivity against fluidity (reciprocal of viscosity) have smaller values in [emim][TCB] than in [emim][Tf2N] at certain fluidities. The high-pressure CO2 solubilities were also determined in [emim][TCB]. The mole fraction scaled solubility of CO2 in [emim][TCB] is slightly larger than that in [emim][Tf2N] at certain pressures and temperatures. The former ionic liquid shows much higher molarity scaled solubility of CO2 than the latter because of the smaller molar volume. It is suggested that both anions have similar strength of intermolecular interaction with CO2 and comparable changes in the solvent structure between neat and CO2 solution, in view of the thermodynamic parameters of dissolution.