Li-intercalation into hexagonal boron nitride

A Li hexagonal boron nitride (hBN) intercalation compound (Li-hBNIC) was successfully synthesized by the annealing of powder or bulk hBN and Li at 1523 K. By an XRD analysis, a strong peak indicating the expansion of BN interlayer distance due to Li-intercalation was observed at an angle lower than that of hBN (0 0 2). In the sample, the interlayer distance and its expansion ratio were 3.76 Å and 12.6%, respectively, and these values were similar to those of a first stage Li-graphite intercalation compound (Li-GIC), LiC₆. The electrical conductivity of the sample was increased by several orders of magnitude, from 10⁻¹⁵ to 10⁻⁷ Ω⁻¹ cm⁻¹ at room temperature. Li de-intercalation was confirmed by the dispersion of the sample in purified water.     

Measurement of compound-nucleus lifetime by X-ray spectroscopy in the 106Cd(p,p')106Cd reaction

A new method for measuring compound-nucleus lifetimes in the range of 10^?18–10^?16 s is presented. The method is based on the comparison between the known lifetime of an atomic excited state used as a reference and the nuclear delay time to be measured. On-line coincidences performed between the nuclear reaction products and the emitted X-rays enable the selection of the atomic vacancies decaying during the compound stage of the nuclear interaction. The main characteristics of this technique are illustrated by measurements of lifetimes of the ¹⁰⁷In compound nucleus excited at 13.6 and 15.6 MeV in the ¹⁰⁶Cd(p, p')¹⁰⁶Cd reaction. They are found in agreement with statistical model calculations. The spurious effect associated with decay by internal conversion of final states populated by the competitive (p, n) reaction is emphasized.     

Tribological characterization of TiCN coatings deposited by two crossed laser ablation plasma beams

The simultaneous laser ablation of two targets (graphite and titanium) in an Ar-N₂ gas mixture was carried out to deposit thin films of the ternary compound TiCN at room temperature. The base conditions used to produce the TiN without carbon were taken from our previous studies. The experimental conditions for the ablation of the carbon target were varied so that the carbon content in the films could be changed depending on the carbon ion energy. The control of the experimental conditions was carried out using a Langmuir planar probe which permitted the determination of the mean kinetic ion energy. The maximum hardness value of 35 GPa, was obtained with a carbon ion energy of about 250 eV, which corresponds to a film with 5 at% carbon content. In order to perform tribological and scratch tests, two types of substrate were used: nitrided AISI 316 stainless steel and AISI 316 stainless steel previously coated with a thin titanium layer (～50 nm). Values of the wear rate in the range of 1.39×10^?6 to 7.45×10^?5 mm³?N^?1?m^?1, friction coefficient from 0.21 to 0.28 and adhesion from scratch test measurements up to 80 N for final critical load, were obtained.     

Synthesis of thiol-functionalized MCM-41 mesoporous silicas and its application in Cu(II), Pb(II), Ag(I), and Cr(III) removal

Thiol-functionalized MCM-41 mesoporous silicas were synthesized via evaporation-induced self-assembly. The mesoporous silicas obtained were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption analysis, Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The products were used as adsorbents to remove heavy metal ions from water. The mesoporous silicas (adsorbent A) with high pore diameter (centered at 5.27 nm) exhibited the largest adsorption capacity, with a BET surface area of 421.9 m² g^?1 and pore volume of 0.556 cm³ g^?1. Different anions influenced the adsorption of Cu(II) in the order NO₃ ^? < OAc^? < SO₄ ^2? < CO₃ ^2? < Cit^? < Cl^?. Analysis of adsorption isotherms showed that Cu²⁺, Pb²⁺, Ag⁺, and Cr³⁺ adsorption fit the Redlich–Peterson nonlinear model. The mesoporous silicas synthesized in the work can be used as adsorbents to remove heavy metal ions from water effectively. The removal rate was high, and the adsorbent could be regenerated by acid treatment without changing its properties.     

SPECTRAL STUDIES ON THE BINDING OF A BISACRIDINIUM DERIVATIVE LUCIGENIN WITH DOUBLE HELIX DNA

ABSTRACT

In this paper, the noncovalent binding of the cationic reagent lucigenin (LC) to DNA was investigated using spectroscopic methods. The results from absorption, circular dichroism and fluorescence studies demonstrated that LC could intercalate into the helix of DNA. Polarization and melting studies further supported the intercalation binding of LC with DNA. The binding constant was obtained by varying the DNA concentration, while keeping the concentration of LC constant. It was of the order of 10⁴ mol^?1 L in DNA base pairs. The experiment also showed that electrostatic interaction played a significant role in the intercalation of LC with DNA. It is supposed to be because of being attracted first by anionic DNA that LC can be intercalated into the interior of the DNA double helix. This research offers a new intercalation functional group to DNA-targeted drug design.     

Structure of the superdense LiC3 compound prepared by ball-milling

The intercalation of lithium into graphite by ball-milling leads to a powder whose X-ray pattern is close to that of LiC₆, but the density of the powder indicates the presence of an intercalation phase close to LiC₃. This compound is superdense since its volume concentration in lithium is twice that of LiC₆, the repeat distance along the c-axis being identical in both compounds. Moreover, contrarily to an other compound, LiC₂ synthesized under high pressure, which decomposes slightly (in several months) into LiC₆+Li, LiC₃ is stable.The ⁷Li NMR was very helpful to solve the different problems about this compound and the present work explains all the observations, how and why LiC₃ remains stable at ambient pressure.     

Validated HPLC-Fl Method for the Analysis of S-Adenosylmethionine and S-Adenosylhomocysteine Biomarkers in Human Blood

The natural methyl donor group, S-adenosylmethionine and its product, S-adenosylhomocysteine play an important role in many biochemical reactions involving transmethylation reactions. These compounds can be used as biomarkers in incipient diagnosis of various pathological disorders therefore the validation of a suitable method to routinely analysis of these compounds is very important. In this paper, a high performance liquid chromatrography method for S-adenosylmethionine and S-adenosylhomocysteine measurement as fluorescent 1,N ⁶-ethanoderivatives from biological samples was validated in terms of selectivity, linearity range of the response (R?>?0.9993), detection limit (9?×?10^?9 and 4.4?×?10^?9 molL^?1), the limit of quantitation (9.7?×?10^?9 and 5.7?×?10^?9?mol?L^?1), precision, trueness and robustness. The method for quantification simultaneous of these compounds is rapid, sensitive and precise and appropriate for clinical analysis.     

Characterization of crystallized LiMn2O4 thin films grown by pulsed laser deposition

LiMn₂O₄ thin films were grown on stainless steel substrates at 625°C and 100?mTorr of oxygen by pulsed laser deposition. The deposited film was highly crystallized with an average crystal size of about 260?nm. The initial discharge capacity of the film was about 53.8?µAh?cm^?2?µm^?1 and the capacity decayed at an average rate of about 0.29% per cycle when the film was cycled between 3.0 and 4.5?V vs. Li/Li⁺, with a current density of 20?µA?cm^?2. It was observed that the grains became smaller and the boundaries of grains became obscure after 100 cycles, indicating that manganese dissolution via loss of MnO may be the main factor leading to the capacity fade in pure thin film LiMn₂O₄ electrodes. The apparent diffusion coefficient of Li ions, obtained from cyclic voltammetry scans, was of the order of 10^?12?cm²?s^?1. High charge-transfer resistance was observed at high potentials. Ex-situ X-ray diffraction (XRD) and Raman spectroscopy were used to investigate the structure changes of LiMn₂O₄ thin film with intercalation/de-intercalation of lithium. XRD results revealed a relatively small lattice change with the removal of lithium in crystallized thin film, compared to that of powder LiMn₂O₄ cathode.     

Electrodeposition of Ag nanoparticles onto bamboo-type TiO2 nanotube arrays to improve their lithium-ion intercalation performance

Bamboo-type TiO₂ nanotube arrays prepared via anodic oxidation are modified with Ag nanoparticles by pulsed electrochemical deposition, for improved lithium-ion intercalation property as the anode material in lithium-ion batteries. Heat treatment converts as-formed nanotubes into anatase for Ag deposition. Bare and Ag-modified nanotubes are cycled at a current density of 800 μA?cm^?2 between 1.0 and 2.6 V (vs. Li/Li⁺). All Ag-modified nanotubes exhibit significantly improved or even doubled areal discharge capacities and better cycleability compared to bare nanotubes. Particularly, the nanotubes modified using 100 Ag deposition cycles deliver the highest initial discharge capacity of 199.6 μA?h cm^?2 and the largest final discharge capacity of 131.7 μA?h cm^?2 after 50 electrochemical cycles, while bare nanotubes exhibit an initial capacity of 93.5 μA?h cm^?2 and a final discharge capacity of 54.8 μA?h cm^?2. The former also exhibits 10 % higher capacity retention efficiency than the latter. In addition, an increase in the capacity of modified nanotubes is observed with more Ag deposition, but superfluous Ag content yields reduced capacities due to slower Li-ion transfer inside. Finally, kinetic characteristics of TiO₂ nanotubes are explored using cyclic voltammetry to understand the origin of improvements in electrochemical properties of Ag-modified nanotubes.     

Nano-scaled top-down of bismuth chalcogenides based on electrochemical lithium intercalation

A two-step method has been used to fabricate nano-particles of layer-structured bismuth chalcogenide compounds, including Bi₂Te₃, Bi₂Se₃, and Bi₂Se_0.3Te_2.7, through a nano-scaled top-down route. In the first step, lithium (Li) atoms are intercalated between the van der Waals bonded quintuple layers of bismuth chalcogenide compounds by controllable electrochemical process inside self-designed lithium ion batteries. And in the second step, the Li intercalated bismuth chalcogenides are subsequently exposed to ethanol, in which process the intercalated Li atoms would explode like atom-scaled bombs to exfoliate original microscaled powder into nano-scaled particles with size around 10 nm. The influence of lithium intercalation speed and amount to three types of bismuth chalcogenide compounds are compared and the optimized intercalation conditions are explored. As to maintain the phase purity of the final nano-particle product, the intercalation lithium amount should be well controlled in Se contained bismuth chalcogenide compounds. Besides, compared with binary bismuth chalcogenide compound, lower lithium intercalation speed should be applied in ternary bismuth chalcogenide compound.     

On the thermodynamic driving force for polymer intercalation in smectite clays

The view that the intercalation of a polymer in an unmodified smectite clay is driven by the entropic increase that results from displacement of adsorbed water is re-assessed in the light of experiments that show rapid melt intercalation into a clay that has been heat-treated to remove gallery water. Dehydrated smectite clays with collapsed layers take up poly(ethylene glycol) from the melt in only 1?ks or from aqueous solution in under 18?ks, re-establishing the basal plane spacing to that for intercalation in untreated clay, 1.8?nm. Differential scanning calorimetry showed that the intercalation of poly(ethylene glycol) into montmorillonite is exothermic with an enthalpy change of ?153?J?g^?1 based on the intercalated polymer and the heat of wetting for the internal surfaces of montmorillonite by poly(ethylene glycol) is ?0.08?J?m^?2. These results confirm the observation of re-expansion of heat-treated clays and imply that the reduction in free energy on intercalation results from a significant enthalpic change as well as an entropic change for clays with interlayer water, and primarily from an enthalpic change for clay in the absence of water.     

Characterization of organic–inorganic hybrid layered perovskite and intercalated compound (n-C12H25NH3)2ZnCl4

We report on some electrical properties and solid–solid phase transitions of organic–inorganic hybrid layered halide perovskite and intercalated compound (n-C₁₂H₂₅NH₃)₂ZnCl₄ which is one member of the long-chain compounds of the series (n-C_nH_2n+1NH₃)_2,(n = 8–18). The complex dielectric permittivity ?*(ω,T) and the ac conductivity σ (ω,T) were measured as functions of temperature 100 K < T < 390 K and frequency 5 kHz < f < 100 kHz. Moreover, the differential scanning calorimetery and the differential thermal analysis thermograms were performed. The analysis of our data confirms the existence of a structural phase transition at T ≈ (362?±?2) K, where the compound changes its state from intercalation to non-intercalation with a drastic increase in the c-axis by about 16.4%.

The behavior of the frequency-dependent conductivity follows the Jonscher universal power law: σ (ω, T) α?^s(?,T). The mechanism of electrical conduction in the low-temperature phase (phase II) can be described as quantum mechanical tunneling model.     

Ionic transport studies in hyperbranched polyurethane/clay nanocomposite gel polymer electrolytes

In the present work, we report a novel nanocomposite gel electrolytes based on intercalation of hyperbranched polyurethane (HBPU) into organically modified montmorillonite for application in Li-ion batteries. The nanocomposites have been prepared by solution intercalation technique with varying clay loading. The formation of partially exfoliated nanocomposites has been confirmed by X-ray diffraction. Nanocomposites were soaked with 1 M LiCO₄ in 1:1 (v/v) solution of propylene carbonate and diethyl carbonate to get the required gel electrolytes. AC impedance analysis shows that ionic conductivity increases with the increase of clay loading and attains the highest value of 8.3?×?10^?3 S/cm for 5 wt.% clay concentration. Surface morphology of the nanocomposite electrolytes has been examined by SEM analysis. Improvement of electrochemical properties, viz., electrochemical potential window and interfacial stability, is also observed in the clay-loaded HBPU samples.     

Synthesis,Spectral Characterization,DNA Binding Studies and Antimicrobial Activity of Co(II), Ni(II), Zn(II), Fe(III) and VO(IV) Complexes with 4-Aminoantipyrine Schiff Base of Ortho-Vanillin

A series of transition metal complexes of Co(II), Ni(II), Zn(II), Fe(III) and VO(IV) have been synthesized involving the Schiff base, 2,3-dimethyl-1-phenyl-4-(2-hydroxy-3-methoxy benzylideneamino)-pyrazol-5-one(L), obtained by condensation of 4-aminoantipyrine with 3-methoxy salicylaldehyde. Structural features were obtained from their FT-IR, UV–vis, NMR, ESI Mass, elemental analysis, magnetic moments, molar conductivity and thermal analysis studies. The Schiff base acts as a monovalent bidentate ligand, coordinating through the azomethine nitrogen and phenolic oxygen atom. Based on elemental and spectral studies six coordinated geometry is assigned to Co(II), Ni(II), Fe(III) and VO(IV) complexes and four coordinated geometry is assigned to Zn(II) complex. The interaction of metal complexes with Calf thymus DNA were carried out by UV–VIS titrations, fluorescence spectroscopy and viscosity measurements. The binding constants (K_b) of the complexes were determined as 5?×?10⁵ M^?1 for Co(II) complex, 1.33?×?10⁴ M^?1 for Ni(II) complex, 3.33?×?10⁵ M^?1 for Zn(II) complex, 1.25?×?10⁵ M^?1 for Fe(III) complex and 8?×?10⁵ M^?1 for VO(IV) complex. Quenching studies of the complexes indicate that these complexes strongly bind to DNA. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. The ligand and it’s metal complexes were screened for their antimicrobial activity against bacteria. The results showed the metal complexes to be biologically active, while the ligand to be inactive.     

插层化合物Li1+xV3O8的合成及其物理性能的初步研究

本文成功地合成了插层化合物Li_1+xV₃O₈,并用X射线粉末衍射和等离子体发射光谱元素定量分析进行了鉴定。同时进行了NMR研究。在298—400K之间观察到了锂离子的运动致窄效应,并以此求得它的离子运动激活能为0.18eV。还测得该材料的室温电导率为10^-3Ω^-1·cm^-1数量级。 关键词：     

Synthesis and characterisation of the Fe(II–III) hydroxy-formate green rust

A new methodology was envisioned in order to prepare green rust compounds build on organic anions that could intervene in microbiologically influenced corrosion processes of iron and steel. The formate ion was chosen as an example. The formation of rust was simulated by the oxidation of aqueous suspensions of Fe(OH)₂ precipitated from Fe(II) lactate and sodium hydroxide, in the presence of sodium formate to promote the formation of the corresponding green rust. The evolution of the precipitate with time was followed by transmission Mössbauer spectroscopy at 15 K. It was observed that the initial hydroxide was transformed into a new GR compound. Its spectrum is composed of three quadrupole doublets, D ₁ (δ?=?1.28 mm s^?1, Δ?=?2.75 mm s^?1) and D ₂ (δ?=?1.28 mm s^?1, Δ?=?2.48 mm s^?1) that correspond to Fe(II) and D ₃ (δ?=?0.49 mm s^?1, Δ?=?0.37 mm s^?1) that corresponds to Fe(III). The relative area of D ₃, close to the proportion of Fe(III) in the GR, was found at 28.5?±?1.5% (～2/7). Raman spectroscopy confirmed that the intermediate compound was a Fe(II–III) hydroxy-formate, GR(HCOO^?).     

Evaporation residue formation competing with the fission process in the197Au+16O,12C reactions and fission barriers at a specifiedJ window

Evaporation-residue excitation functions for¹⁶O and¹²C+¹⁹⁷Au reactions were measured by means of the activation technique. The competition between evaporation and fission of the compound nuclei was studied by comparing the observed evaporation-residue data with the published fission excitation functions. A newly devised analysis was applied in order to deduce a fission barrier height at a specified angular momentum and determine the relevant fissioning nucleus as well. We found the fission barriers to be 8.2 MeV for the²¹¹Fr nucleus at 16? and 8.2 MeV for the²⁰⁷At nucleus at 27?.     

Highly luminescent europium(III) complexes with naphtoiltrifluoroacetone and dimethyl sulphoxide

The synthesis, luminescence properties, experimental determination and theoretical calculation of the emission quantum yield of Eu(NTA)₃.2L complexes, where NTA is naphtoiltri-fluroacetone and L denotes H₂O or DMSO (dimethyl sulphoxide), were reported. The compounds were characterized by elemental analysis (carbon, hydrogen and europium), thermal analysis, UV-visible absorption and photoluminescence spectroscopies. The experimental quantum yields were determined based on a method previously proposed by Bril and collaborators. The Eu(NTA)₃.2DMSO compound shows a high value for the Ω₂ intensity parameter (35.8 × 10^?20 cm²), reflecting the hypersensitive nature of the ⁵D₀ → ⁷F₂ transition and indicating that the lanthanide ion is in a highly polarizable chemical environment. The experimental quantum yield measured for that compound, 0.75, is one of the highest so far reported for solid-state europium complexes. The theoretical calculations of the quantum yield were carried out by solving an appropriate set of rate equations and by using empirical spectroscopic parameters and energy transfer rates. The theoretical results agree well with the experimental data for both complexes. The photostability of Eu(NTA)₃.2DMSO at 358K was evaluated in order to verify whether this complex can be applied as a phosphor for blue light emitting devices.     

Lithium diffusion in Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-based electrodes: a joint analysis of electrochemical impedance,cyclic voltammetry,pulse chronoamperometry,and chronopotentiometry data

In order to establish the mechanism and to determine the parameters of lithium transport in electrodes based on lithium-vanadium phosphate (Li₃V₂(PO₄)₃), the kinetic model was designed and experimentally tested for joint analysis of electrochemical impedance (EIS), cyclic voltammetry (CV), pulse chronoamperometry (PITT), and chronopotentiometry (GITT) data. It comprises the stages of sequential lithium-ion transfer in the surface layer and the bulk of electrode material’s particles, including accumulation of lithium in the bulk. Transfer processes at both sites are of diffusion nature and differ significantly, both by temporal (characteristic time, τ) and kinetic (diffusion coefficient, D) constants. PITT data analysis provided the following D values for the predominantly lithiated and delithiated forms of the intercalation material: 10^?9 and 3 × 10^?10 cm² s^?1, respectively, for transfer in the bulk and 10^?12 cm² s^?1 for transfer in the thin surface layer of material’s particles. D values extracted from GITT data are in consistency with those obtained from PITT: 3.5–5.8 × 10^?10 and 0.9–5 × 10^?10 cm² s^?1 (for the current and currentless mode, respectively). The D values obtained from EIS data were 5.5 × 10^?10 cm² s^?1 for lithiated (at a potential of 3.5 V) and 2.3 × 10^?9 cm² s^?1 for delithiated (at a potential 4.1 V) forms. CV evaluation gave close results: 3 × 10^?11 cm² s^?1 for anodic and 3.4 × 10^?11 cm² s^?1 for cathodic processes, respectively. The use of complex experimental measurement procedure for combined application of the EIS, PITT, and GITT methods allowed to obtain thermodynamic E,c dependence of Li₃V₂(PO₄)₃ electrode, which is not affected by polarization and heterogeneity of lithium concentration in the intercalate.