Confocal Raman imaging and atomic force microscopy of the surface reaction of NO2 and NaCl(100) under humidity

Polarized confocal Raman imaging combined with non‐contact atomic force microscopy (AFM) was used to study the three‐dimensional evolution of the NaCl(100) surface during its reaction with NO₂ at low pressure as a function of relative humidity (RH) from 0% to nearly 80%. Sea salt particles containing NaCl as the main constituent are believed to be the major source of reactive tropospheric chlorine and nitrate fallouts. At an RH of 0%, the reaction of dry NO₂ generates surface conversion to NaNO₃ monolayer capping the NaCl(100) surface and releases NOCl. The subsequent exposure of this NaNO₃ layer to RH below ∼45% induces the formation of rare NaNO₃ tetrahedral crystals less than 0.5 µm in size. The crystallization occurs through two‐dimensional NO₃⁻ migration under the H₂O monolayer regime. After another subsequent exposure to RH above 45% and below 75%, supermicrometric NaNO₃ rhombohedral plates were obtained under the H₂O multilayer regime. On the other hand, the simultaneous exposure of NaCl(100) to NO₂ and H₂O below ∼45% RH rapidly generates numerous submicrometric NaNO₃ tetrahedra on the NaCl(100) surface. The dramatic increase of NaNO₃ production in the presence of water vapour is explained by the formation of HNO₃ and its easy reaction with the NaCl(100) surface. For RH above 45% and below 75%, the tetrahedra evolve to rhombohedral plates of supermicrometric size. The exposure of NaCl(100) to NO₂/H₂O mixtures under RH above 75% induces the coexistence of both solid‐state NaNO₃ and dissolved NO₃⁻ in droplets. Copyright © 2008 John Wiley & Sons, Ltd.     

Solubility and acid-base properties and activity coefficients of chitosan in different ionic media and at different ionic strengths, at T = 25 °C

Studies on the acid-base properties and solubility of a polyammonium polyelectrolyte (chitosan) with different molecular weights (MW 310 and 50 kDa), were performed at T = 25 °C, in the pH range 2.5–7. The protonation of chitosan was investigated by potentiometry ([H⁺]-glass electrode) in NaCl, NaNO₃ and mixed NaNO₃ + Na₂SO₄ ionic media, at different ionic strengths. Protonation constants were calculated as a function of dissociation degree α by means of two different models, namely, a simple linear model and the modified Henderson–Hasselbalch equation. Experimental data were also fitted using a model independent of α (Diprotic-like model), according to which the acid-base properties can be simply described by two protonation constants in all the acidic pH range. The dependence on ionic strength of protonation constants in NaCl aqueous solution was modelled by Specific ion Interaction Theory (SIT). The ion pair formation between protonated chitosan and Cl⁻, NO₃⁻ and SO₄²⁻ was also considered, and the relative formation constants are reported.Solubility investigations were performed in NaCl aqueous solutions in a wide range of ionic strength (0.1 < I/mol L^− 1 < 3.0), with the aim to determine the activity coefficients of neutral species and the Setschenow coefficient of chitosan 310 kDa.     

The effect of NH<Subscript>4</Subscript>NO<Subscript>3</Subscript> towards the conductivity enhancement and electrical behavior in methyl cellulose-starch blend based ionic conductors

Solid polymer electrolytes based on methyl cellulose (MC)-potato starch (PS) blend doped with ammonium nitrate (NH₄NO₃) are prepared by solution cast technique. The interaction between the electrolyte’s materials is proven by Fourier transform infrared (FTIR) analysis. The thermal stability of the electrolytes is obtained from thermogravimetric analysis (TGA). The room temperature conductivity of undoped 60 wt.% MC-40 wt.% PS blend film is identified to be (1.04 ± 0.19) × 10^?11 S cm^?1. The addition of 30 wt.% NH₄NO₃ to the polymer blend has optimized the room temperature conductivity to (4.37 ± 0.16) × 10^?5 S cm^?1. Conductivity trend is verified by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and dielectric analysis. Temperature-dependence of conductivity obeys Arrhenius rule. Conductivity is found to be influenced by the number density (n) and mobility (μ) of ions. From transference number measurements (TNM), ions are found to be the dominant charge carriers.     

NH<Subscript>4</Subscript>NO<Subscript>3</Subscript> as charge carrier contributor in glycerolized potato starch-methyl cellulose blend-based polymer electrolyte and the application in electrochemical double-layer capacitor

Potato starch (PS)-methyl cellulose (MC) blend solid biopolymer electrolytes infused with ammonium nitrate (NH₄NO₃) and glycerol as plasticizer are made via the solution cast technique. Fourier transform infrared (FTIR) spectroscopy indicates that NH₄NO₃ has interacted with the polymer blend host. The addition of 40 wt% glycerol in the highest conducting plasticizer free electrolyte has improved the conductivity to the order of ～10^?3 S cm^?1. The thermal stability of the electrolytes is identified by thermogravimetric analysis (TGA). Result from X-ray diffraction (XRD) analysis shows that the electrolyte with maximum conductivity value has the lowest degree of crystallinity. Differential scanning calorimetry (DSC) analysis reveals that the highest conducting plasticized electrolyte possesses the lowest glass transition temperature (T _g) of ?27.5 °C. Conductivity trend is further verified by dielectric analysis. Transference numbers of ion (t _ion) and electron (t _e) for the highest conducting electrolyte are identified to be 0.98 and 0.02, respectively, confirming that ions are the dominant charge carriers. Linear sweep voltammetry (LSV) evaluates that the potential window for the electrolyte is 1.88 V. The internal resistance of the electrochemical double-layer capacitor (EDLC) is between 29 and 64 Ω. From the charged-discharged measurement, the value of C _s is 31 F g^?1. The EDLC is stable over 1000 cycles.     

Chondroitin sulfate template-mediated biomimetic synthesis of nano-flake hydroxyapatite

By Ca(NO₃)₂·4H₂O and (NH₄)₃PO₄·3H₂O as reagents and chondroitin sulfate (ChS) as a template, nano-flake hydroxyapatite (HA) is synthesized using a biomimetic method according to the biomineralization theory. HA crystals obtained are characterized in crystalline phase, microstructure, chemical composition and morphology by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), transmission electron microscopy (TEM) and elemental analysis respectively. UV-vis spectrum is adopted to investigate interactions between functional groups ChS and HA. The results show that HA crystal nucleation and growth take place in chemical interactions between HA crystals and ChS as a template. And elemental analysis indicates that obtained HA contains a small amount of ChS. Furthermore, ChS concentration significantly affects the morphology of HA crystals. Staple-fiber-like HA crystals can be obtained at a low concentration in ChS, and flake-like HA crystals synthesized at a high concentration (≥0.5 wt.%) of ChS as a template.     

Synthesis, characterization, DNA binding and cleavage studies of mixed-ligand Cu(II) complexes of 2,6-bis(benzimidazol-2-yl)pyridine

Four novel copper(II) complexes of the composition [CuLX] where L = 2,6-bis(benzimidazole-2yl)pyridine, X = dipyridophenazine (L₁), 1,10-phenanthroline (L₂), hydroxyproline (L₃) and 2,6-pyridine dicarboxylic acid (L₄) were synthesized and characterized by using elemental analysis, FT-IR, UV–vis, ESI-MS, molar conductance and magnetic susceptibility measurements. The complexes [CuLL₁](NO₃)₂ [1], [CuLL₂](NO₃)₂ [2], [CuLL₃](NO₃) [3] and [CuLL₄] (NO₃) [4] are stable at room temperature. In DMSO the complexes [1] and [2] are 1:2 electrolytes, [3] and [4] are 1:1 electrolytes. Based on elemental and spectral studies five coordinated geometry is assigned to all the four complexes. The interaction of four copper ion complexes with calf thymus DNA were carried out by UV–vis titrations, fluorescence spectroscopy, thermal melting and viscosity measurements .The binding constant (K_b) of the above four metal complexes were determined as 5.43 × 10⁴ M_,⁻¹ 2.56 × 10⁴ M⁻¹, 1.21 × 10⁴ M⁻¹ and 1.57 × 10⁴ M⁻¹ respectively. Quenching studies of the four complexes indicates that these complexes strongly bind to DNA, out of all complex 1 is binding more strongly. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. Thermal melting studies also support intercalative binding. The nuclease activity of the above metal complexes shows that 1, 2 and 3 complexes cleave DNA through redox chemistry.     

Mathematical model of ree separation using heat oscillating extraction

The influence of periodical oscillations of the temperature on extraction and stripping processes in the extraction systems is studied. Two extraction system were investigated, No.1: 6M NaNO₃ — Nd(NO₃)₃ — Pr(NO₃)₃ — TBP — kerosene and No. 2: [Nd(NO₃)₃·3TBP] — [Pr(NO₃)₃·3TBP] — kerosene — 0.1M HNO₃. Mathematical model of the non-stationary membrane extraction is presented including the dependence of extraction rate constants on temperature. The values of activation energy for direct and reverse reactions of extraction and stripping reactions of Pr and Nd were calculated from experimental time dependencies of metal concentrations and temperature by solving reverse kinetics problem using the proposed mathematical model. Series of experiments with the effect of periodical temperature oscillations on the extraction system for separation of rare earth elements using bulk liquid membrane between two extractors were made. The mathematical model describes experimental data adequately. On the basis of the extraction rate constants and activation energies the optimization of the extraction process of separation of rare earth elements by liquid membrane under the effect of periodical temperature oscillations has been carried out. The optimal conditions of separation by liquid membrane were found: frequency and amplitude of thermal oscillations, liquid membrane flow rate and optimal ratio between organic and aqueous phase in the extractors.     

Synthesis and Optical Properties of Eu3+ Ion Doped Nanocrystalline Hydroxyapatites

The Ca₁₀(PO₄)₆(OH)₂ hydroxyapatite (HA) nanopowders doped with Eu³⁺ ions were prepared using a wet synthesis method. Their structure and morphology were investigated. The XRD analysis has proven a single-phase of HA nanocrystallites. The average sizes of HA nanocrystallites calcinated at 400°C and 700°C were determined to be about 20 nm and 30 nm, respectively. The emission and excitation spectra as well as the fluorescence decay rates of Eu³⁺ ion doped HA nanocrystallites were measured. Particular attention was given to the spectroscopic properties of Eu³⁺ ions as a luminescent probe of nanocrystalline HA structure as a result of varying annealing temperature and dopant concentration. The Judd-Ofelt analysis of f-f transitions of Eu³⁺:HA nanocrystallites was performed. The effect of calcination temperatures on grain sizes and luminescence properties is noted and discussed.     

Conductivity, FTIR studies, and thermal behavior of PMMA-based proton conducting polymer gel electrolytes containing triflic acid

The addition of polymer to liquid electrolytes containing trifluoromethanesulfonic acid (HCF₃SO₃) in propylene carbonate (PC) has been found to result in an increase in conductivity of gel electrolytes. The increase in conductivity has been observed to be due to the dissociation of ion aggregates present in the electrolytes which has also been supported by Fourier transform infrared studies. The maximum ionic conductivity (at 25 °C) of 7.55?×?10^?3 S/cm has been observed for polymer gel electrolytes containing 1.5 wt% polymethylmethacrylate in 0.5 M solution of HCF₃SO₃ in PC. Polymer gel electrolytes have been found to be thermally stable up to a temperature of 125 °C by simultaneous differential scanning calorimetry/thermogravimetric analysis studies. The conductivity of polymer gel electrolytes does not show any appreciable change over a limited period of time.     

Novel Bioactive Co(II), Cu(II), Ni(II) and Zn(II) Complexes with Schiff Base Ligand Derived from Histidine and 1,3-Indandione: Synthesis,Structural Elucidation,Biological Investigation and Docking Analysis

Novel bioactive complexes of Co(II), Cu(II), Ni(II) and Zn(II) metal ions with Schiff base ligand derived from histidine and 1,3-indandione were synthesized and thoroughly characterized by various analytical and spectral techniques. The biological investigations were carried out to examine the efficiency of the binding interaction of all the complexes with calf thymus DNA (CT-DNA). The binding properties were studied and evaluated quantitatively by K_b and K_sq values using UV-visible, fluorescence spectroscopy and voltammetric techniques. The experimental results revealed that the mode of binding of all the complexes with CT-DNA is via intercalation. It is further verified by viscosity measurements and thermal denaturation experiments. From the results of the cleavage study with pUC19 DNA it is inferred that all the complexes possess excellent cleaving ability. The present investigation proved that the binding interaction of all the complexes are significantly strong and the order of binding strength of the complexes is [Ni(L)₂] (K_b = 3.11 × 10⁶ M^?1) > [Co(L)₂] (K_b = 2.89 × 10⁶ M^?1) > [Cu(L)₂] (K_b = 2.64 × 10⁶ M^?1) > [Zn(L)₂] (K_b = 2.41 × 10⁵ M^?1). The complexes were also screened for antibacterial and anticandidal activity. The in vitro cytotoxicity of the ligand and complexes on the NIH/3 T3 mouse fibroblast cell lines were examined using CellTiter-Blue® (CTB) Cell viability assay, which unveiled that all the complexes exhibit more potent activities against NIH/3 T3 cells. Among all the complexes [Zn(L)₂] complex showed the maximum efficiency.     

Effect of sodium citrate as complexing on electrochemical behavior and speciation diagrams of CoFeNiCu baths

In this study, the effects of addition of sodium citrate dosages and different pH levels on the electrochemical behavior of CoFeNiCu alloy baths (electrolytes containing metal ions) were investigated. Stability (Pourbiax) diagrams and also speciation diagrams of cobalt, iron, nickel and copper, in conventional and citrate-added CoFeNiCu bath, were calculated by ChemEQL V.3.0 software. Stability diagrams showed that addition of 20 g?L^?1 sodium citrate to the bath increased the pH of formed detrimental metal hydroxides (especially Fe(OH)₃ from pH 3.4 to pH?~?6.9) through forming stable complexed species that were more stable than metal hydroxides at low pH levels (< ~3). According to the speciation diagrams, both pH level and sodium citrate dosage had noticeable effect on the distribution of species in the baths. Generally, at low pH level and/or sodium citrate dosage, Co⁺⁺, Fe⁺⁺, Ni⁺⁺, and Cu⁺⁺ species were dominant. The concentration of complexed species of Co(C₆H₅O₇)^? ( at pH?>?~ 7.5 or sodium citrate dosage?>?~ 30 g?L^?1), Fe(C₆H₅O₇)^? (at pH?>?~ 5.5 or sodium citrate dosage?>?~ 25 g?L^?1), Ni(C₆H₅O₇)^? (at pH?>?~ 6 or sodium citrate dosage?>?~ 30 g?L^?1), and Cu(OHC₆H₅O₇)^2? ( at pH?>?~ 8 or sodium citrate dosage?>?~ 20 g?L^?1) became significant. The effects of sodium citrate and reverse potential (E _λ) on cyclic voltammetry curves were also studied. The addition of sodium citrate in the bath shifted the reduction potential of metals towards more negative potentials. Moreover, in order to deposit cobalt, iron, and nickel simultaneously with copper, it was necessary to increase E _λ value gradually with sodium citrate dosage; otherwise, only copper would have deposited from citrate-added CoFeNiCu bath. The study of speciation diagrams showed that reduction of metals from CoFeNiCu bath with natural pH (no acid or base is added to adjust pH and it was?~?5.2) and containing 20 g?L^?1 of sodium citrate mainly occurred directly from complexed species.     

Analysis of Cation-Dependent DNA (G<Subscript>3</Subscript>T<Subscript>1</Subscript>)<Subscript>4</Subscript> Shape Change Using Fluorescence Correlation Spectroscopy

In G-rich DNA, it is well known that the form changes from single-strand DNA to G-quadruplex due to cations. In this study, we analyze the diffusion coefficient and fluorescence intensity obtained by fluorescence correlation spectroscopy for short G-rich DNA of the (G₃T₁)₄ sequence labeled as 5-Carboxytetramethylrhodamine (TAMRA) with variation of the K⁺ ion concentration. At a K⁺ ion concentration of more than 200 mM, the single-strand DNA was changed to the G-quadruplex. The size of the G-quadruplex decreased to 86% than the size of the single strand DNA at K⁺ ion concentration of 0 M. The size of the G-quadruplex and the fluorescence intensity of TAMRA attached to the DNA were constant with an increase in the K⁺ ion concentration between 200 and 800 mM. This means that the size of the DNA and the fluorescence intensity of the TAMRA are not affected by the K⁺ ion concentration at the G-quadruplex structure because the binding structure of DNA and TAMRA dye leads to stability at a concentration of less than 100 mM K⁺. Based on our short G-rich DNA results, longer G-rich DNA is analyzed for the diffusion coefficient of the DNA and the fluorescence intensity variation of fluorescence dye attached to the DNA.     

Charge Transfer Photophysics of Tetra(α-amino) Zinc Phthalocyanine

The absorption, fluorescence, and transient absorption spectra of Tetra(α-amino) zinc phthalocyanine, ZnPc(α-NH₂)₄, have been measured in polar solvents and compared with that of ZnPc(α-R)₄ (R?=?H, NO₂, OCH(CH₃)₂). While the latter three showed the typical photophysics of phthalocyanines, ZnPc(α-NH₂)₄ exhibits distinct spectral properties, a very low fluorescence quantum yield and a relatively long fluorescence lifetime. These observations are explained by the substantial charge transfer characters in the absorption and fluorescence spectra of ZnPc(α-NH₂)₄. NMR indicates that intramolecular H-bonding makes atoms in NH₂ actually coplanar with other elements of ZnPc(α-NH₂)₄. The local excited state is non emissive and the weak emission is assigned to its charge transfer state. The transient absorption bands from laser flash photolysis located at 630 nm, 645 nm is assigned to the mono-charge transfer state, while that at 545 nm is assigned to the di-charge transfer state.     

Quantitative Analysis of Added Ammonium and Nitrate in Silica Sand and Soil Using Diffuse Reflectance Infrared Spectroscopy

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in both near infrared (NIR) and mid infrared (MIR) has been previously shown to be effective in quantifying soil nitrogen concentrations when calibrated using numerous field soil samples. However, such an approach incorporates samples that may contain substantial correlations between physical and chemical properties. To address these concerns, the performance of DRIFTS coupled with PLS regression in NIR regions, 5000–4000 cm^? 1 (2000–2500 nm) and 6500–5500 cm^? 1 (1540–1820 nm), and the MIR region, 3400–2400 cm^? 1 (2940–4170 nm), was assessed through analysis of the concentration of ammonium (NH₄ ⁺) (0–50 ppm) and nitrate (NO₃ ^?) (0–200 ppm) artificially incorporated into a series of silica sand samples with a consistent particle size. The influence of different particle sizes of sand was also analyzed quantitatively. The Pima clay loam soil was then evaluated with concentration ranges of 0–200 ppm NH₄ ⁺ and 180–1000 ppm NO₃ ^? added to the soil samples. With sand samples, accurate NH₄ ⁺ measurements could be performed using all three ranges. The MIR region was significantly more useful for NO₃ ^? measurement than those of NIR regions. The MIR region also performed reasonably well with soil samples but both NIR regions provided poor results. The detection limits for NH₄ ⁺ and NO₃ ^? measurements in sand were 9 ppm NH₄ ⁺ and 39 ppm NO₃ ^? with the correlation coefficients (R²) of roughly 97% and 96%, respectively, and in soil were 100 ppm NH₄ ⁺ and 330 ppm NO₃ ^? with the correlation coefficients (R²) of roughly 80% and 90%, respectively.     

Magneto-electrogyration in cubic Sr(NO3)2, Ba(NO3)2, and Pb(NO3)2

The simultaneous application of electric and magnetic fields on single crystals of Sr-, Ba-and Pb-dinitrate yields an additional term to the pure electrogyration and Faraday effect. The symmetric part of the fourth-rank tensor of this magneto-electrogyration has been completely determined with the aid of a high-resolution computer-aided polarimetric device. In Pb(NO₃)₂ a maximum magneto-electrogyration of about 10% of the magnitude of electrogyration is observed when a magnetic field of 1000 kA/m (1.2 Tesla) is applied along [111]. The effects in Sr(NO₃)₂ and Ba(NO₃)₂ are much smaller. Index of refraction, electrogyration, Faraday effect, and the new magneto-electrogyration obey the same sequence: Pb(NO₃)₂ > Ba(NO₃)₂ > Sr(NO₃)₂.     

Structural,thermal and electrical properties of polyvinyl alcohol/poly(vinyl pyrrolidone)–sodium nitrate solid polymer blend electrolyte

Sodium ion conducting solid polymer blend electrolyte thin films have been prepared by using polyvinyl alcohol (PVA)/poly(vinyl pyrrolidone) (PVP) with NaNO₃ by solution cast technique. The prepared films were characterized by various methods. The complexation of the salt with the polymer blend was identified by X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR), Differential scanning calorimetry was used to analyze the thermal behavior of the samples, and the glass transition temperature is low for the highest conducting polymer material. The scanning electron microscopy gives the surface morphology of the polymer electrolytes. The frequency and temperature dependent of electrical conductivities of the films were studied using impedance analyzer in the frequency range of 1 Hz to 1 MHz. The highest electrical conductivity of 50PVA/50PVP/2 wt% NaNO₃ concentration has been found to be 1.25 × 10^?5 S cm^?1 at room temperature. The electrical permittivity of the polymer films have been studied for various temperatures. The transference number measurements showed that the charge transport is mainly due to ions than electrons. Using this highest conducting polymer electrolyte, an electrochemical cell is fabricated and the parameters of the cells are tabulated.     

Static (hyper)polarizabilities and absorption spectra of single [2.2]<Emphasis Type="Italic">p</Emphasis>-cyclophane NO<Subscript>2</Subscript>/NH<Subscript>2</Subscript> substituted from DFT methods

We explore the behavior of the average of polarizability (< α >), total first hyperpolarizability (β_total) and average of second hyperpolarizability (< γ >) for single A/D (-NO₂/-NH₂) substituted [2.2]p-cyclophane. The geometric optimization was carried out at HF and DFT (SVWN, PBE, B3LYP, PBE0, BHHLYP and CAM-B3LYP) level, in gas phase, using the 6-31 + G(d,p) basis set. The static tensor components of < α > and β_total, in gas phase, were calculated using Field Finite (FF) methods with electric field intensities of E = ± 0.001 a.u. in each (x,y,z) axis direction. The substitution of A/D groups in positions 7–15 (structure 2 in Fig. 1) produced an increment in the < α > values. Regardless of the A/D positions, the < α > values showed not significant changes at all theory level. < α > DFT results are overestimated up to 20%, if HF values are taken into account, being SVWN and PBE functionals those that give the main deviation. There are monotonic and progressive behaviors of β_total for the 1–5 structure change as expected by orientation of the dipolar moment in both aromatic rings. With respect to the performance of DFT functionals, < γ > and β_total results are significantly overestimated if HF values are taken into account. In fact, the relative percentage error of β_total at DFT level with respect to HF ones is between 58 and 132%, being PBE functional those that give the main deviation. The close overlap of the orbitals between the rings facilitates chromophore delocalization to account for the observation of high β_total in these compounds. Therefore, we expected that the contribution by coupling of the transition moment between first and higher excited states should be lie much higher due to phane effect than that for ring units.

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Fig. 1 a Single [2.2]p-cyclophane core molecule. b Geometric parameters of interest c Highlights for the 4, 7, 12, and 15 positions, which are substituted by (-NO₂/-NH₂) acceptor/donor pair

     

Blends of hexanoyl chitosan/epoxidized natural rubber doped with EMImTFSI

Hexanoyl chitosan soluble in THF is prepared by acyl modification of chitosan. Epoxidation natural rubber (ENR25) (25 mol%) is chosen to blend with hexanoyl chitosan. Films of hexanoyl chitosan/ENR25 blends containing lithium bis(trifluoromethanesulfonyl)imide (LiN(CF₃SO₂)₂) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) are prepared by solution casting technique. FTIR results suggested that LiN(CF₃SO₂)₂ salt interacted with hexanoyl chitosan, ENR25, and EMImTFSI. EMImTFSI interacted with hexanoyl chitosan and ENR25 to form EMIm⁺-hexanoyl chitosan and EMIm⁺-ENR25 complexes, respectively. The effect of EMImTFSI on the morphology and thermal properties of the blends is investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC), respectively. The ionic conductivity of the electrolytes is measured by electrochemical impedance spectroscopy (EIS). Upon addition of 12 wt% EMImTFSI, a maximum conductivity of 1.3 × 10^?6 S cm^?1 is achieved. Methods based on impedance spectroscopy and FTIR are employed to study the transport properties of the prepared polymer electrolytes. The ac conductivity was found to obey universal law, σ(ω)?=?σ _dc ?+?Aω ^S . The temperature dependence of exponent s is interpreted by the small polaron hopping (SPH) model.     

Hybrid solid electrolytes with excellent electrochemical properties and their applications in all-solid-state cells

Three types of inorganic electrolytes [Li₁₀GeP₂S₁₂ (LGPS), 75Li₂S·24P₂S₅·1P₂O₅ (LPOS), Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP)] with different particle sizes and electrochemical properties are selected as active fillers incorporated into poly(ethylene oxide) (PEO) matrix to fabricate hybrid solid electrolytes. The optimum composition of each filler is found in consideration of ionic conductivity. Their electrochemical characteristics are investigated. The optimal conductivities are 1.60 × 10^?5, 1.18 × 10^?5, and 2.12 × 10^?5 S cm^?1 at room temperature for PEO-1%LGPS, PEO-1%LPOS, and PEO-20%LAGP, respectively. The electrochemical stability windows of these hybrid solid electrolytes are all above 5 V (vs. Li⁺/Li). The results show that these fillers have positive effects on the ionic conductivity, lithium ion transference number, and electrochemical stability. The relationship between the type of filler and electrochemical properties has been investigated. All-solid-state cells LiFePO₄/Li are fabricated and present fascinating electrochemical performance with high capacity retention and good cycling stability. This work provides promising electrolytes prepared by a simple method.     

Comparitive study of structure changes with temperature in univalent and divalent ionic nitrate crystals

The temperature dependence of the d.c. resistivity and dielectric constant of polycrystalline samples of Pb(NO₃)₂, Ba(NO₃)₂ and Sr(NO₃)₂ were found to show anomalies in the high temperature region. In addition, sharp peaks were obtained in both differential thermal analysis (DTA) and thermomechanical analysis (TMA) curves in the same temperature range. The observed anomalies were attributed to orientational disorder of the nitrate group leading to an order-disorder phase transition which is reported here for the first time. A comparison is made between the role of NO₃^?ions in both the divalent and univalent nitrates, taking NaNO₃ as representative. The TMA curve for Sr(NO₃)₂ showed a pronounced peak at 325°C. This peak was related to a sudden increase in the expansion coefficient associated with the rotation of the NO₃^? group leading to a solid state phase transformation. Energy diagrams describing the conduction mechanism and showing a fractionization of energy barriers in the case of divalent nitrates are introduced.