Ionic Behavior Research Articles

Relationship between Ionic Interation and NMR Relaxation Behavior in LiClO4-PC Solution Coexisting with Fumed Metal Oxide

Lithium ion battery (LIBs) is indispensable to various electrochemical devices in practical use such as a cell phone, electric vehicle due to its high energy density, high voltage. Although the extended use of LIBs technology, batteries which have higher capacity and can stand up to high speed charge/discharge than those of LIBs are demanded. Various studies have reported that the liquid phase occurring adjacent to solid particles has an anomalous behavior when compared to bulk solution[1]. Solid-liquid interface is performed as a base in charge-discharge of LIBs, so an elucidation of liquid phase properties of solid-liquid interface in the non-aqueous electrolyte solution system is important for improving the performance of energy storage devices such as LIBs. In addition, properties of the highly-concentrated electrolytes for performance improvement of LIBs are attracted. In this study, NMR spectroscopic behavior of non-aqueous LiClO4 solution mixed with fumed oxide nanoparticles as model system of gel electrolyte for LIBs, and their dynamic properties and influences to solvent molecules from solid phase or Li+ ion by measurement of the spin-spin (T 2) relaxation time and electrochemical measurement. Samples were prepared in Ar glovebox by mixing propylene carbonate(PC) or LiClO4/PC of predetermined concentration (1-3 mol L-1) and fumed silica(FS) (200 ± 20 m2 g-1), amorphous silica nanoparticles with self-cohesive properties, fumed alumina(FA) (130 ± 20 m2 g-1) and fumed titania(FT) (90 ± 20 m2 g-1) in NMR tube. A content of liquid phase were ranged from 90-100 vol% by gravimetry. We measured 1H and 7Li NMR spectroscopy (Varian INOVA 400; 9.39 T) and 1H spin–spin relaxation time; T 2measurements (XiGo Nanotools Acorn area ; 0.3 T). In 1H NMR spectra, a broad signal was confirmed under the existence solid-phase. It was shown that the dynamic property of PC molecules largely decreased in comparison with the case only for liquid phases. In PC/FS and PC/FA system, 1H NMR spectra shifted to higher magnetic field with the decrease of liquid content. For the shielding effect to the 1H nucleus of the PC molecules by the surface charge of fumed silica, a signal continues to shift to highly-magnetic field as a content of solid-phase increases. This result suggested that the apparent charge densities around the proton of PC molecules increased by fumed silica because fumed silica has a negative charge. In alumina dispersion, NMR signal shifted to higher magnetic field than that of fumed silica. From this result, alumina gives more influence on dynamics properties of liquid phase. A similar result was observed in 1-3 mol L-1 LiClO4/PC and solid coexisting system. From the liquid content dependences of the 1H NMR detection ratios of propylene carbonate, almost same amount of PC molecules were detected in PC/FS coexisting system. This result indicated that fumed silica formed network structure but H of PC molecules remained its dynamics. On the other hand, in fumed alumina or fumed titania dispersion, values of PC molecules detected by NMR decreased compared to the theoretical value of detected amount of PC by 1H NMR. It suggests that the mobility of PC molecules in fumed alumina and titania system were restricted than that in silica system. T2 in solid-liquid coexisting system is also shown in Fig. 1. From Fig.1, in all systems, the T2 value decreases because the dynamics of water molecules of the liquid phase decrease. The T2 value decreased in order of PC/FA, PC/FT, PC/FS system. The influence of the solid surface to solvent mobility in fumed alumina dispersion is the least of the three. This result supports a signal of the NMR and the result of 1H qNMR measurement. We will also discuss the NMR relaxation behavior for LiClO4-PC solution coexisting with te same fumed metal oxides. This study was supported by the JST Core Research for Evolutional Science and Technology (CREST). 【Reference】 [1] M. Mizuhata et al., J. Mol. Liq., 83, 179, (1999). Figure 1

Electricity modulation of a water motion active transducer via surface functionality control

Recently, the water motion active transducer, an electricity generator which uses water contact variations, has attracted much attention as an eco-friendly energy harvesting device. In order to understand the electricity generation induced by ionic behavior in water at the solid-liquid interface of a water motion active transducer accurately and apply it to a wide range of applications, fundamental study of the surface functionalities at the solid-liquid interface of the water motion active transducer is essential. However, most studies in the field of water motion active transducer still remain them for a high power performance. Herein, through an investigation of surface functionality control at a solid-liquid interface, we modulate the generating electricity of a water motion active transducer and successfully demonstrate its potential toward the realization of a novel self-powered pH sensor. For both hydrophobicity and surface functionality control at the solid-liquid interface, we used a self-assembled monolayer technique with APTES ((3-aminopropyl) triethoxysilane) and POTS (1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane). Through control of the surface functionalities at the interface, we show substantial potential for the modulation of the generating electricity. In addition, the unique electric characteristics of this device offer a fundamental understanding of the origin of electricity generation at solid-liquid interfaces induced by water motion and provide a more accurate understanding of the ionic behaviors occurring at solid-liquid interfaces toward the novel ion-functional devices.

Ionic release behavior of polymer-coated and uncoated metal nanoparticles (MNPs) in various conditions: effects of particle shape, size, and natural media reactivity

Metal nanoparticles (MNPs), due to its increasingly wide applications in consumer products, raises its concern towards ecotoxicology. Once released into the environment, the zero-valent metal (M°) readily oxidized to ionic metal (M+) which is reported as the main source of toxicity related to MNPs. The current study investigated the oxidative dissolution and M+ release profiles, from polymer-coated and uncoated MNPs. The polyethylene imine coated silver nanoparticles (PEI@AgNPs), polyethylene glycol coated zinc oxide micro-rods (PEG@ZnOMRs), and uncoated titanium dioxide nanoparticles (TiO2NPs) were synthesized with different size, shape, and surface functionalities, and M+ flow behavior was investigated through column transport experiment. The results obtained revealed that the ionic dissolution and M+ loss was 1.6–3.3% for PEI@AgNPs, 8.3–12.6% for TiO2NPs, and 13.6–19.0% for PEG@ZnOMRs. These results suggested that PEI surface coating greatly inhibit the M+ release and maximum column retention occurs in order of PEI@AgNPs ˃ TiO2NPs ˃ PEG@ZnOMRs.

Nano grained Sr and Zr co-doped BaCeO3 electrolytes for intermediate temperature solid oxide fuel cells

Abstract Electrolyte materials in solid oxide fuel cells play a vital role in the performance of the cell. In the present work we are going to report a nano grained perovskite materials used for intermediate temperature (450–650 °C) solid oxide fuel cell. Here electrolytes having composition Ba1−xSrxCe1−yZryO3-δ where x = 0.2, 0.3 and y = 0.2, 0.3 were synthesized by sol-gel method. Two prepared samples were named as BSCZ1 and BSCZ2 for x = y = 0.2&0.3, respectively. Structural analysis and surface morphology were performed using XRD and SEM, respectively. The particle size of BSCZ1 and BSCZ2 electrolyte materials calculated by Scherer's formula were found to be 25 nm and 28 nm, respectively. The protonic conductivities were determined by four probe method and maximum results of measurements were found to be 0.007 and 0.008 S/cm for BSCZ1 and BSCZ2, respectively at temperature of 650 °C. Electrical impedance spectroscopy results show ionic behavior which is suited for good electrolytes. It has been noted that the BSCZ2 electrolyte material executes maximum power density of 250 mW/cm2 at 650 °C.

Protein adsorption onto diethylaminoethyl dextran modified anion exchanger: Effect of ionic strength and column behavior

Abstract Our previous studies on bovine serum albumin (BSA) adsorption to diethylaminoethyl dextran (DEAE dextran, DexD, grafting-ligand) and DEAE (D, surface-ligand) modified Sepharose FF resins found that all the grafted resins (FF-DexD and FF-D-DexD) exhibited extremely fast uptake rate (effective diffusivity, De, De/D0 > 1.4), which was six times greater than the ungrafted resins (De/D0 1.1) at the their working/binding IS range. Moreover, the DEAE dextran-FF resin displayed much higher adsorption capacities and De values than commercial ungrafted resin in their working condition. Furthermore, the column results of DEAE dextran-FF resins presented higher dynamic binding capacities than and similar elution ISs with DEAE Sepharose FF to achieve similar (or even higher) recoveries suggest the excellent chromatographic column performance of the DEAE dextran-FF resins. Finally, both high recovery and purity of BSA and γ-globulin could be easily achieved using the typical DEAE dextran-FF column, FF-D60-DexD160, to separate their binary mixtures, by step gradient elution. The research has provided new insights into the practical application of the series of DEAE-dextran grafted resins in protein chromatography and proved their superiority.

Engineering Single Nanopores on Gold Nanoplates by Tuning Crystal Screw Dislocation.

Compared with the large variety of solid gold nanostructures, synthetic approaches for their hollow counterparts are limited, largely confined to chemical and irradiation-based etching of preformed nanostructures. In particular, the preparation of through nanopore structures is extremely challenging. Here, a unique strategy for direct synthesis of gold nanopores in solution without the need for sacrificial templates or postsynthesis processing is reported. By controlling the degree of crystal screw dislocation, a single through pore with diameter ranging from sub-nanometer to tens of nanometers, in the center of large gold nanoplates, can be engineered with precision. Ionic current rectification behaviors are observed using the gold nanopore, potentially enabling new capabilities in biosensing, sequencing, and imaging.

Redox switch of ionic transport in conductive polypyrrole-engineered unipolar nanofluidic diodes

Controlling ion transport in nanoconfined spaces is a key task for the creation of smart nanofluidic devices. In this work, redox-active polypyrrole (PPy) polymers are introduced into anodic aluminum oxide (AAO) nanochannels to form smart unipolar nanofluidic diodes (UNDs) for the first time. The ionic transport behavior of the present polypyrrole-engineered UNDs can be controlled through the redox reactions of PPy. Under an applied oxidation potential, conductive PPy exhibits several redox states carrying different charges, following the formation of polarons and bipolarons with different oxidation states. Combined with the asymmetric distribution of PPy in the AAO nanochannels, the UNDs investigated here exhibit redox-switchable ion rectification and ion-gating properties. The influence of the charge asymmetry of the UNDs on their ionic transport behavior is assessed by precisely controlling the length of oxidized PPy segments in the AAO nanochannels and by carrying out theoretical simulations based on the Poisson and Nernst–Planck (PNP) equations.

Ionic transport properties in AgCl under high pressures

Ionic transport behaviors of silver chloride (AgCl) have been revealed with impedance spectra measurement under high pressures up to 20.4 GPa. AgCl always presented ionic conducting under experimental pressures, but electronic conduction can coexist with ionic conduction within the pressure range from 6.7 to 9.3 GPa. The ionic conductivity of AgCl decreases by three orders of magnitude under compression, indicating that Ag+ ion migrations are suppressed by high pressure. A parameter, fW, was defined as the starting frequency at which Ag+ ions begin to show obvious long-distance diffusion in AgCl. fW showed a similar trend with the ionic conductivity under high pressures, indicating that the speed of Ag+ ion diffusion slows down as the pressure increases. Unlike AgI, Ag+ ion diffusion in AgCl is controlled by the indirect-interstitial mechanism. Due to stronger ionic bonds and larger lattice deformation, Ag+ ion diffusion in the rigid Cl− lattice is more difficult than in the I− lattice under high pressures.

Performance enhancement of poly (vinylidene fluoride-co-hexafluoro propylene)/polyethylene oxide based nanocomposite polymer electrolyte with ZnO nanofiller for dye-sensitized solar cell

Nanocomposite polymer electrolytes (NCPEs) were prepared by blending poly (vinylidene fluoride-co-hexafluoro propylene) copolymer (PVdF-HFP) and polyethylene oxide (PEO) polymers and incorporation of ZnO inorganic nanofiller (PVdF-HFP:PEO:EC:PC:NaI:I2:ZnO). The highest ionic conductivity value of 8.36 mS cm−1 was recorded when 3 wt.% of ZnO inorganic nanofiller was incorporated into the NCPE system. Temperature-dependant ionic conductivity behaviour of NCPEs was analysed and proven to follow the Arrhenius thermal activated model. Structural studies of NCPEs were carried out using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analysis. NCPEs were used to fabricate Dye-sensitized solar cells (DSSCs). Enhancements in the solar light to electricity conversion efficiency (η) of DSSCs were observed in the presence of ZnO inorganic nanofiller in the NCPE system and NCPE with 3 wt.% ZnO represented the highest η of 7.33% under full sun irradiation.

Adapting the ionic transfer behavior of cation exchange membrane incorporated with SiO2/PAA composite nanoparticles

In this study, silicon dioxide nanoparticles (SiO2 NPs) were functionalized by polyacrylic acid (PAA) then used as the modifier agent in polyvinyl chloride (PVC)-based heterogeneous cation exchange membranes (CEMs). FTIR technique and SEM images were employed to characterize the synthesized SiO2/PAA. All the experiments were carried out at ambient condition. According to the experiments, CEMs modified by SiO2/PAA have more hydrophilic and smoother surface. Membrane water content reduced from 32.2% for the base membrane to 20.1% for modified membrane containing 4.0%wt SiO2/PAA. Modified CEMs showed an improved potential, transport number, selectivity, and electrical conductivity. The selectivity of modified membrane (containing 0.5%wt SiO2/PAA) is 87.3%, and its electrical conductivity is about 37% less than the base membrane. The mechanical stability of prepared membranes was also improved about 25.4%. Moreover, sodium flux increased sharply (21%) loading 0.5%wt NPs in the structure and then reduced by more SiO2/PAA concentration. In addition, membrane ionic flux decreased obviously for bivalent ions by using SiO2/PAA nanoparticles. The prepared membranes showed higher permeability/flux for monovalent ions compared to bivalent type.

Tailoring the electrochemical properties of ED ion exchange membranes based on the synergism of TiO2 nanoparticles-co-GO nanoplates

In this paper, the synergetic influence of various weight ratios of TiO2 nanoparticles (NPs)/graphene oxide nanoplates (GONs) in the matrix of ion exchange membranes was examined in order to adapt their electrokinetic properties based on the combination of the high specific surface area of GONs and the antifouling ability of TiO2 nanoparticles. The morphology, physico-chemical features and ionic transport behavior of prepared membranes was studied. Scanning optical microscopy (SOM) and scanning electron microscopy (SEM) images showed a uniform surface for the lab-made membranes relatively. It was found that surface hydrophilicity of the membrane was increased in the presence of GONs and TiO2 NPs. All modified membranes showed a higher water uptake than unmodified membranes. Furthermore, a higher ion exchange capacity, fixed ionic concentration, ionic permeability and flux were observed for all modified membranes in comparison with unmodified membranes. The membrane potential, transport number and selectivity improved in NaCl solutions by using GONs and TiO2 nanoparticles. Furthermore, the membrane ionic conductivity showed an increasing trend by utilizing TiO2-co-GONs NPs. As an overall conclusion, the modified membrane containing 3wt% GONs and 1wt% TiO2 NPs with superior transport number and permselectivity (∼99%), highest current density and cation flux and the lowest areal electrical resistance (∼4–5Ωcm2) showed the best performance.

MarkoLAB: A simulator to study ionic channel's stochastic behavior

SummaryMathematical models of the cardiac cell have started to include markovian representations of the ionic channels instead of the traditional Hodgkin & Huxley formulations. There are many reasons for this: Markov models are not restricted to the idea of independent gates defining the channel, they allow more complex description with specific transitions between open, closed or inactivated states, and more importantly those states can be closely related to the underlying channel structure and conformational changes. MethodsWe used the LabVIEW® and MATLAB® programs to implement the simulator MarkoLAB that allow a dynamical 3D representation of the markovian model of the channel. The Monte Carlo simulation was used to implement the stochastic transitions among states. The user can specify the voltage protocol by setting the holding potential, the step-to voltage and the duration of the stimuli. ResultsThe most studied feature of a channel is the current flowing through it. This happens when the channel stays in the open state, but most of the time, as revealed by the low open probability values, the channel remains on the inactive or closed states. By focusing only when the channel enters or leaves the open state we are missing most of its activity. MarkoLAB proved to be quite useful to visualize the whole behavior of the channel and not only when the channel produces a current. Such dynamic representation provides more complete information about channel kinetics and will be a powerful tool to demonstrate the effect of gene mutations or drugs on the channel function. ConclusionsMarkoLAB provides an original way of visualizing the stochastic behavior of a channel. It clarifies concepts, such as recovery from inactivation, calcium- versus voltage-dependent inactivation, and tail currents. It is not restricted to ionic channels only but it can be extended to other transporters, such as exchangers and pumps. This program is intended as a didactical tool to illustrate the dynamical behavior of a channel. It has been implemented in two platforms MATLAB® and LabVIEW® to enhance the target users of this new didactical tool. The computational cost of implementing a stochastic simulation is within the range of a personal computer performance; making MarkoLAB suitable to be run during a lecture or presentation.

Plasmonic effects of quantum size metal nanoparticles on dye-sensitized solar cell

Gel polymer electrolytes (GPEs) based on poly(ethylene oxide) (PEO) and phthaloyl chitosan (PhCh) for dye-sensitized solar cells (DSSCs) have been synthesized and characterized. The GPEs have been prepared using different weight fractions of PEO and PhCh that have been added to a fixed composition solution of tetrapropylammonium iodide (TPAI), dimethylformamide (DMF) and iodine (I-2) crystals. The ionic conductivity behavior of prepared GPEs was studied using impedance spectroscopy. The sample having 70 wt.% PEO and 30 wt.% PhCh showed the highest ionic conductivity of 7.36 mS cm(-1) at room temperature. The photoanode of the DSSC consists of two TiO2 layers. The first or compact layer has a thickness of similar to 5 mu m and the TiO2 nanoparticles have an average size of 14 nm. The second layer of TiO2 nanoparticles has an average size of 21 nm. In order to adsorb dye molecules, the TiO2 photoanodes were soaked in anthocyanin and ruthenium 535 (N3) dye solutions. The GPE has been deposited between the dye/ TiO2 photoanode and platinum (Pt) counter electrode in a sandwich-like structure. Results showed that the fabricated DSSC with an electrolyte containing 70 wt.% PEO: 30 wt.% PhCh exhibited the highest efficiency for both anthocyanin and N3 dyes and the efficiency and ionic conductivity trend versus PEO content are similar. On addition of different amounts of Ag nanoparticles (0, 10, 20, 30, 40 mu L), with average size of 10 nm to the second TiO2 layer, the performance of DSSCs with anthocyanin sensitizer and N3 dye improved. The cell with anthocyanin/(TiO2 + 10 mu L Ag nanoparticles) showed a 21%, 17.2% and 39.6% increase in short circuit current density (J(sc)), fill factor (FF), and light to electricity conversion efficiency (.) respectively compared to the cell without Ag nanoparticle. The DSSC fabricated with TiO2 photoanode containing 20 mu L Ag nanoparticles soaked in N3 dye exhibits Jsc, FF, and. of 15.24 mA cm(-2), 57% and 5.21% respectively. The incorporation of Ag nanoparticles has resulted in a 17% and 13% increase in Jsc, and., respectively, for N3 based cells. This performance enhancement with the addition of Ag nanoparticles can be attributed to improvement of light scattering and charge transport as a result of plasmonic resonance.

Analysis of different current density conditions in the electrodialysis of zinc electroplating process solution

ABSTRACTThe use of currents below and above the limiting one for the treatment by electrodialysis of a solution prepared as a surrogate of a rinse water of the acid zinc electroplating processes was studied. The ionic transport behavior was evaluated by chronopotentiometry. The limiting current values were obtained through current–voltage curves. The trials performed with different current densities showed that the electrodialysis removed at least 98% of the contaminants without insoluble species precipitation on membrane surfaces. The water reuse is possible after electrodialysis treatment with current densities above the limiting one and considering a demineralization rate of 60%.

Polymer electrolytes for electrochromic devices through solvent casting and sol-gel routes

Ionically conductive membranes of gelatin and d-PCL(530)/siloxane doped with cyano-based ionic liquids (ILs) were prepared through solvent casting and sol-gel methods, respectively. The membranes were characterized in terms of ionic conductivity, thermal behavior, morphology, and structure. All samples, except the d-PCL(530)/siloxane matrix, exhibited a predominantly amorphous morphology. The samples prepared through solvent casting and sol-gel displayed a minimum thermal stability of 170 and 230°C, respectively. The ionic conductivity varied according with the type, quantity, and length of the alkyl chain of the cation of the ILs. The sample with the highest ionic conductivity was gelatin0.5[C2mim][N(CN)2] with 2.40×10−3Scm−1 at 25°C and 1.68×10−2Scm−1 at 95°C. The good results of ionic conductivity encouraged the assembly and characterization of prototypes of electrochromic devices (ECDs). The best results were obtained with glass/ITO/WO3/gelatin1[C2mim][SCN]/CeO2-TiO2/ITO/glass configuration that showed a fast color switching time (~15s) and a good open circuit memory (~4h). The ECD changed its color from pale blue to transparent, and its charge density decreased from −17.53 to −2.71mCcm−2 during 640 color/bleaching cycles.

Spectra and magneto optical behavior of CeO2 doped heavy metal diamagnetic glass

CeO2 shows interesting redox atmosphere dependent properties and ionic polarizing behavior in glass. In this paper, we report the fabrication and characterization of diamagnetic glass with composition of xCeO240PbO50Bi2O3(10−x) B2O3 (x=0, 0.1, 0.2, 0.4, 0.6 and 1mol%). The Ce3+ and Ce4+ co-existence influences the glass forming ability, glass structure and properties through characterization such as X-ray diffraction, XPS, Raman, UV/ Fourier transforms infrared spectra and Faraday rotation measurement.Due to the high optical basicity and high polarization of host glass, Ce4+ formed in 0.1% CeO2 doped glass and improved the glass thermal stability, optical cutoff and Verdet constant (0.1304min/g·cm).

(Invited) Semiconductor-Based Biosensing Technology for Clinical Diagnosis

In this study, we report a biosensing method to analyze and monitor simply and easily biological phenomena such as DNA recognition events, antigen-antibody reaction and cell functions in vitro by use of a semiconductor device. As the most important point, we focus on a direct detection of ions or ionized molecules with charges, because most biological phenomena are related to ionic behaviors such as sodium or potassium ions through ion channel at cell membrane resulted from cell-cell communications, and biomolecules such as DNA molecules have intrinsic molecular charges. That is, the principle of semiconductor-based biosensing device contributes to directly detect biomolecular charges. Thus, the platform based on a semiconductor-based biosensor is suitable for a label-free and noninvasive biosensing detection device in the field of in vitro diagnosis (IVD).

A Mobility Evaluation Method of Strong Electrolytes with an Accurate Low-Frequency Measurement

INTRODUCTION A mobility evaluation method through an accurate measurement, combining simulation of Least-Square Error Method (LSEM), is reported. The results reveal better accuracy of strong electrolytes with a higher concentration of 10-3 M. The evaluated mobility (μ) decreases with increase in concentration and strongly correlated the results of the conventional calculation from the interpolation method (Table)[1]. The calculated parameter of effective restoring force (k) increases with increase both in the frequency and concentration. Results are verified from Newton Equation, which can be widely developed on the ionic movement analysis. EXPERIMENT Fig ure 1( a) shows the device and system including a function generator (AFG-3252) and a lock-in amplifier (SR-830). F ig . 1 (b) shows the standard deviation (SD) versus frequency of NaCl solutions from 10-4 to 10-3 M. With a higher concentration, the SD of NaCl solutions becomes smaller[2]. Fig. 1(c) is our device photo. The device contains a precision cut square reservoir on the resin surface. Au/Ge/Ni alloy and Auelectrodes were evaporated on both sidewalls. The system was finally enclosed in a shielding box to ensure the system grounded properly. For clearer understanding the fundamental electrolytic properties, eight reagent grade electrolytes were prepared because of their univalent, simple, and spherical structures (NaCl, KCl, NaBr, KBr, HCl, HBr, NaOH, and KOH). MODEL DERIVATION In our mathematical model, the mass of cation and anion are m1 and m2 respectively. E=V/d is electric field. Ionic behavior can be described as Newton's differential equation (Eq. (1)(2)), where S is relative displacement, k is effective restoring force parameter. The corresponding footnotes of each parameter is 1 and 2, respectively. The AC conductivity (σ(ω)), dielectric constant (ε') and dielectric loss (ε") can be derived as Eq.(3) and (4). The optimal μ and kcan be solved numerically from LSEM of six unknown parameters and eight equations. RESULTS AND DISCUSSION F ig ure 2(a) shows the the frequency dispersion of σ(ω) of NaCl solutions from 10-4 to 10-3 M, computed from ten measurements. All experiments in this paper are under 100 mVp-p bias and room temperature (298 K). Results reveal better accuracy of the proposed experiments. Fig. 2(b) shows the stable conductivity (σ) and bulk resistance (Rb) versus NaCl concentration at f=1 kHz, where Rb is calculated through the Nyquist plots[3]. In concentrated electrolytes, the charge increases and Rb decreases. The σ(ω) of NaCl increases with increase in frequency[4] with fixed concentration because ions cannot pass through the electrodes region, hence face highest resistivity. At higher frequencies, rapid periodic reversal of electric field makes ions difficult to diffuse, leading to mobility improvement. With a given frequency, all σ(ω) are also increased with increase in concentrations, which results in more effective charges and σ(ω) increases. In concentrated cases, the frequency- independent region in σ(ω) clearly occurs at higher frequencies. Fig.3 (a) shows the frequency dispersion of σ(ω) for different electrolytes of 10-3 M. All σ(ω) also increases with increase in frequency. In addition, σ(ω) of acids is much higher than neutral and basic electrolytes which can be ascribed to proton transfer[ 5 ]. Fig. 3(b) shows the frequency-independent region of σ and Rb. Fig. 4(a) shows frequency dispersion of dielectric constant (ε’) for different electrolytes under 10-3 M. Strong dispersion relation of ε’ at low frequencies, and saturates at higher frequencies. It can be explained as ions not only accumulating at the interface but also aligning themselves along the electric field. As frequency is increased, ions cannot follow rapid inversion in electric field and hence diminish their contribution to the polarization. Due to extra assistance of proton transfer, larger ε’ exists in acids compared to other electrolytes. Fig. 4(b) shows the frequency dispersion of dielectric loss (ε’’). As shown in figure, ε’’ increases up to a specific frequency after which it decreases. All electrolytes appear relaxation frequency at each peak value, which presents the relaxation of total polarization. The relaxation frequency of acids occurs at a higher frequency which is also attributed to the proton transfer, which enhances the conduction as well as the lower resistance. Figure 5(a) shows the frequency dispersion of μ from eight electrolytes under 10-3 M. The initial μ value is small, then increases with increase in frequency, finally saturates at higher frequencies. Fig. 5(b) shows the frequency dispersion of k under 10-3 M. The initial k is also small, then increases with increase in frequency, and finally saturates at higher frequencies. Fig. 6(a) and Fig. 6(b) shows the stable value (at f=1kHz) calculated from LSEM of μ and k. With the concentration increases, the mobility decreases but k increases, which is reasonable in physical explanation. Figure 1

Discrimination of Polynucleotide Transport through a Highly Hydrophobic Uncharged Nanopore

The importance of DNA structures in medicine has motivated researchers to develop sequencing methods with low costs and high speeds. The potential use of nanofluidics for the analysis of the translocation of polynucleotides through a nanopore is a very interesting solution. Herein, we demonstrate both by experiments and by explicit solvent molecular dynamics simulations that the translocation of polyadenylic acid and polycytidylic acid can significantly affect the ionic flux behavior. In particular, the nanochannel enhances the velocity difference between polynucleotides during the translocation process. Our results revealed the important role of the strand structures during their translocation, as already observed in biochannels. The folding/unfolding process leads to stronger interactions with the nanopore wall that decrease the velocity of the strands. This behavior could lead to the detection of different polynucleotides in a mixture.

Physical properties of fluorine based perovskites for vacuum-ultraviolet-transparent lens materials

Density functional theory (DFT) is used to study the bonding nature as well as the structural, electronic, and optical properties of the SrLiF3, SrNaF3, SrKF3 and SrRbF3 fluoroperovskite compounds. The findings are based on the total energy calculations where the Khon Sham (KS) equation is solved by means of an ab-initio full-potential linearized augmented plane wave (FP-LAPW) method. The structural properties including the lattice constant (ao), ground state energy (E), bulk modulus (B), and their pressure derivative (B′) are evaluated using the Local Density Approximation (LDA) and the Generalized Gradient Approximation (GGA) exchange correlation potential. Furthermore, to avoid the underestimation of the band profile by other DFT schemes we highlight the GGA plus Trans-Blaha modified Becke–Johnson (TB-mBJ) potential in lieu of attaining opto-electronic trends close to the expected experimental findings. Detailed analysis of the band dispersion curves is done with five different exchange and correlation schemes at the (Γ-Γ), (R-R), (M-M) and (X-X) symmetry points. A predominant characteristic associated with cation replacement shows that Li by Na, Na by K, and K by Rb significantly reduce the direct bandgap in these compounds. This crucial variation is responsible for working in different UV regions of the spectrum. The calculations of the band structure show that these compounds have a wide and direct energy bandgap at (Γ-Γ). The total and partial density of state curves are used to define the contributions of the different bands. In addition to this, contour plots of the electron density verify that the ionic behavior increases as we go from SrLiF3 to SrRbF3 while the brittleness, which dominates in them, decreases from SrLiF3 to SrRbF3. To verify the opto-electronic behavior bandgap dependent optical parameters, such as the complex dielectric function Ԑ(ω), optical conductivity σ(ω), energy loss function L(ω), and effective number of electrons neff, the sum rules are analyzed. All the calculated results are in favorable agreement with the previous theoretical and existing experimental data. Furthermore, the opto-electronic properties from the (TB-mBJ) potential are reported, which reveals that the fluorine based strontium series of perovskites are wide and direct band gap ionic insulators. The comprehensive present methodology represents an effective and influential tool for calculating the whole set of opto-electronic parameters, which can provide support for the understanding of various physical phenomena and empower device engineers for implementing these materials in UV based devices.