Intercalant Concentration Research Articles

In Ukrainian

Unique physical properties of multi-walled nanosystems have been the subject of keen interest lately. Their specific energy-band structures with a zero band gap and linear dependence of electron and hole energy spectrum on the wave-vector cause the electric charges to behave like relativist particles with zero effective mass. Anomalous transportation and field effects open a wide prospect of their applying in nanoelectronics. Such nanostructures are assumed to be promising spintronics materials due to the long electron free path, weak spin-orbital interaction and the long spin scattering. What is more, the chemical or physical modification of multi-walled nanosystems enables to reveal their new extraordinary features. Thus, intercalation with molecules allows to change the Fermi level position, relative electron and hole concentration without considerable changes in energy-band structure of source nanomaterials. On the other hand, unique optical, electrical and magnetic, and also biological behaviour of cyclopentadienyl complexes stimulates creation on their base of intercalates with multi-walled CNT, since the capability of these complexes to coordinate with MWCNT allows to obtain new materials as effective elements for photo- and magnetosensitive devices, drug delivery, imaging and therapy, as well to use these materials as an antidetonant in motor and aviation fuels. By employing the methods of MM+, РМ3 and Monte-Carlo, there has been studied the positioning of molecules of bis(cyclopentadienyl)nickel in a double-walled (5,5)@(10,10) carbon nanotube depending on intercalate concentration and intercalation temperature. The temperature increase (over ~455 K) causes gradual bond ruining followed by extrusion of interwall intercalate. Further temperature increase up to 620 K is characterised with intercalate external surface desorption, stabilising the whole system and keeping the interwall intercalate only. There have been calculated the UV-spectra for (5,5)@(10,10) DWCNT depending on the intercalate concentration as well as an association constant of the system which makes 36,2 l·mol -1 .

Thermodynamic Complexing of Monocyclopentadienylferrum (II) Intercalates with Double-Walled Carbon Nanotubes.

By employing the methods of molecular mechanics, semi-empirical quantum-chemical РМ3 and Monte-Carlo, the positioning of monocyclopentadienylferrum (II) molecules in double-walled (5,5)@(10,10) carbon nanotubes (CNT) depending on their concentration and temperature has been studied. The molecules have been found out to form stable bonds with CNT walls, with a tendency between intercalate stability and the CNT structure. The temperature growth (over ~500 K) causes gradual bond ruining followed by extrusion of interwall intercalate. Further temperature increase up to 600–700 K is characterised with intercalate external surface desorption, stabilising the whole system and keeping the interwall intercalate only. The CNT’s UV-spectrum (5,5)@(10,10) depending on the intercalate concentration and association constant of the “double-walled CNT–intercalate” system have been calculated. A combination of unique optical, electrical and magnetic behaviour of cyclopentadienyl complexes with their ability to form high-stable intercalate with CNT opens a prospect of their applying in nanotechnology.

“Guest‐host” intercalate of double‐walled carbon nanotube with tricarbonyl (cyclopentadienyl)manganese

The positioning of tricarbonyl(cyclopentadienyl)manganese molecules in double‐walled (5.5)@(10.10) carbon nanotubes depending on their concentration and temperature was studied using the methods of molecular dynamics, semi‐empirical quantum‐chemical parameterized model number 3 and Monte‐Carlo. The molecules were found to form stable bonds with the carbon nanotubes walls, with a tendency between intercalate stability and the carbon nanotubes structure. A temperature increase (above ˜460 K) causes gradual bond ruining followed by extrusion of interwall intercalate. Further temperature increase up to 600–750 K is characterised with intercalate external surface desorption, stabilising the whole system and keeping the interwall intercalate only. Double‐walled carbon nanotubes UV‐spectra depending on the intercalate concentration and association constant of the “double‐walled carbon nanotubes‐intercalate” system were calculated. A combination of unique optical, electrical and magnetic behaviour of cyclopentadienyl complexes with their ability to form high‐stable intercalate with carbon nanotubes opens a prospect of their application in nanotechnology.

Exfoliated graphite with relative dielectric constant reaching 360, obtained by exfoliation of acid-intercalated graphite flakes without subsequent removal of the residual acidity

Exfoliated graphite (obtained by rapid heating of sulfuric-acid intercalated and subsequently deacidified graphite flakes) is optionally subjected to residual acidity removal, which involves repeated washing with water, such that the pH of the wash water increases from 2 to 7. Compared to washed exfoliated graphite, the unwashed material exhibits lower specific surface area (24 vs. 45m2/g), a higher value (360 vs. 38 at 50Hz) of the relative dielectric constant (real part), a similar value of the conductivity (50S/m), a higher value of the specific carbon–contact interfacial capacitance (1.17 vs. 0.04μF/m2), and a lower value of the carbon–contact interfacial resistivity (0.08 vs. 0.27Ωcm2). The greater concentration of residual intercalate (containing sulfur and oxygen) present without washing contributes to the polarizability without interfering the conduction. The carbon–contact interface is superior when the exfoliated graphite has not been washed. At 2.0MHz, the relative dielectric constant (real part) remains high (280) and the carbon–contact interfacial specific capacitance remains high (1.13μF/m2). The imaginary part of the relative dielectric constant and the dielectric loss angle are not affected by the washing. The relative dielectric constant of 360 is even higher than the value of 121 for potassium-hydroxide-activated graphite nanoplatelet.

Simple, Fast and Cost-Effective Electrochemical Synthesis of Few Layer Graphene Nanosheets

We report an efficient and green approach for mass production of few layered graphene nanosheets (FLGNSs) by intercalation and exfoliation of pyrolytic graphite sheet in a simple protic, H2SO4electrolyte. The as-prepared FLGNSs at the optimum intercalate concentration of 0.5 M H2SO4is able to produce large domain of lateral dimension of 11–26 μm consisting of 4–6 stacked graphene layers, as confirmed by field emission scanning electron microscopy and atomic force microscopy, respectively. Surface oxygenation and a characteristic absorbance peak at 228 nm are well observed for electrochemical exfoliated FLGNSs from Fourier transform infrared spectroscopy and UV–Vis spectra respectively. (002) planes of the obtained graphene sheets have been confirmed from X-ray diffraction pattern. The characteristic Raman bands have been observed at 1354 cm-1and 1590 cm-1in the exfoliated FLGNSs.

Electrical and optical properties of Al3+-intercalated InSe and GaSe

We have studied the electrochemical, electrical, and optical properties of aluminum-intercalated indium and gallium monoselenides. Electron probe X-ray microanalysis data demonstrate that aluminum ions are incorporated into the host together with their solvation shell. Such Al3+ incorporation leads to changes in the electrical properties of InSe layered crystals when the intercalate concentration reaches the level NAl ∼ 1020 to 1021 cm−3, which corresponds to the formation of the final reaction product [Alx+ (R-PC)y]InSe− (where PC stands for propylene carbonate). At 77 K, the energy position of the exciton peak in the AlxInSe and AlxGaSe intercalation compounds is a nonmonotonic function of aluminum concentration.

The effect of intercalants on the host liposome

When phospholipids are vigorously dispersed in water, liposomes are formed. In the present study, we have explored the effect of intercalant concentration on various properties of unilamellar liposomes. Liposomes were sonically intercalated with vitamin E acetate (VitEAc) and hypericin (Hy) until no difference in light transmission was observed, which reflects the formation of liposomes of minimal diameter. Our studies indicate that the intercalant structure and concentration have an influence on the liposome diameter, which could be directly measured by cryogenic transmittance electronic microscopy. Thus, intercalated VitEAc substantially decreased the diameter of unilamellar dimyristoylphosphatidylcholine liposomes, whereas Hy did not. In addition, we followed peak intensities in the absorbance and fluorescence spectra of Hy as a function of intercalant concentration in the liposomal solution. Initially, the fluorescence intensity increased linearly with concentration; however, the curve then arched asymptotically, followed by a decrease in fluorescence at yet higher concentrations. Because the Hy monomer is the only species that emits fluorescence, we believe that the decrease of fluorescence intensity is the result of Hy aggregation.

High-Density Chemical Intercalation of Zero-Valent Copper into Bi2Se3 Nanoribbons

A major goal of intercalation chemistry is to intercalate high densities of guest species without disrupting the host lattice. Many intercalant concentrations, however, are limited by the charge of the guest species. Here we have developed a general solution-based chemical method for intercalating extraordinarily high densities of zero-valent copper metal into layered Bi(2)Se(3) nanoribbons. Up to 60 atom % copper (Cu(7.5)Bi(2)Se(3)) can be intercalated with no disruption to the host lattice using a solution disproportionation redox reaction.

Fire protection performance of oxidized graphite modified with boric acid

We have studied intercalation in the graphite-H2SO4-H3BO3-K2Cr2O7 system with the acids in the weight ratio 1: 0, 12: 1, 6: 1, or 3: 1. The results demonstrate that, with decreasing sulfuric acid (active intercalant) concentration in solution, the stage number of the resultant graphite intercalation compounds increases. Boric acid modification raises the oxidation onset temperature of oxidized graphite by 200–300°C and improves its fire protection performance, with little or no effect on the bulk density of exfoliated graphite.

Torsional Mechanics of DNA Are Regulated by Small-Molecule Intercalation

Whether the bend and twist mechanics of DNA molecules are coupled is unclear. Here, we report the direct measurement of the resistive torque of single DNA molecules to study the effect of ethidium bromide (EtBr) intercalation and pulling force on DNA twist mechanics. DNA molecules were overwound and unwound using recently developed magnetic tweezers where the molecular resistive torque was obtained from Brownian angular fluctuations. The effect of EtBr intercalation on the twist stiffness was found to be significantly different from the effect on the bend persistence length. The twist stiffness of DNA was dramatically reduced at low intercalator concentration (<10 nM); however, it did not decrease further when the intercalator concentration was increased by 3 orders of magnitude. We also determined the dependence of EtBr intercalation on the torque applied to DNA. We propose a model for the elasticity of DNA base pairs with intercalated EtBr molecules to explain the abrupt decrease of twist stiffness at low EtBr concentration. These results indicate that the bend and twist stiffnesses of DNA are independent and can be differently affected by small-molecule binding.

Copper-Intercalated TiS2: Electrode Materials for Rechargeable Batteries as Future Power Resources

We report results of first-principles total-energy calculations of structural and optical properties of the TiS(2) single crystals intercalated with copper. Calculations have been performed using an all-electron, full potential, linearized, augmented, plane-wave method based on density functional theory using generalized gradient approximation for the exchange correlation energy functional. To complete the fundamental characteristics of these compounds, we have calculated and analyzed their linear optical susceptibilities. We demonstrate the efficiency of using a full potential on the band structure, density of states, and the optical properties. We compare our results of the intercalated Cu in different sites and concentrations with the host TiS(2) compound to ascertain the effect of Cu intercalation on the electronic and optical properties. Our calculations have shown that the electronic and optical properties are influenced significantly by the location and concentration of the Cu intercalate in the host compound. The Cu-s and Cu-p bands are very broad and do not contribute much to the density of states. The density of states and the electron charge density show that all Ti-Ti and S-S bonds are basically of ionic character and that Ti-S bonds are of covalent character. No covalent electrons are found between Cu and S atoms; that is, no covalent bond exists between the Cu and S atoms. The Cu atoms are ionic in the intercalated compounds.

Thermoelectric Properties and Electrical Transport of Graphite Intercalation Compounds

Graphite intercalation compounds (GICs) have high electrical conductivities, large Seebeck coefficients, and low thermal conductivities as compared with their host graphite materials. Due to these properties, GICs are expected to act as effective thermoelectric materials. The thermoelectric figure of merit of the GICs is not as high as that of other thermoelectric materials; this is because of the small Seebeck coefficient and high thermal conductivity of GICs. However, the thermoelectric power factor of GICs is sufficiently high at present. In previous works, it was suggested that an increase in concentration of the intercalated species improves the thermoelectric performance of GICs. To better understand the thermoelectric properties of GICs, the dependence of thermoelectric properties with the electrical carrier density and mobility were investigated through the measurements of galvanomagnetic properties. As a result, the electrical conductivity of GICs slightly increases with the carrier density and the thermal conductivity increases with the carrier mobility. Furthermore, the carrier mobility decreases with an increase in the carrier density. In conclusion, the thermoelectric performance of GICs is suggested to be improved by an increase in the carrier density, that is, by an increase in the intercalate concentration.

Phosphonium salt intercalated montmorillonites

Tri-phenyl vinylbenzyl phosphonium chloride and tetraoctyl phosphonium bromide salts have been used as intercalant agents for Na-montmorillonite. Fourier Transform Infrared spectroscopy (FTIR) and Thermogravimetric Analysis coupled with Mass-spectrometry (TG/DTG-MS) were used to characterize the modified montmorillonites and the thermal decomposition products. X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) techniques were used to evaluate the increase of the basal spacing. An easier and more effective intercalation takes place with the tetraoctyl phosphonium salt giving rise to a higher concentration of intercalant with a sensible increase in the interlayer spacing. This phosphonium salt modified montmorillonite is thermally more stable and easier to exfoliate during the compounding process.

고등학교 화학 교과서의 ‘용액’ 단원에 대한 입자 수준의 컴퓨터 보조 수업자료 개발 및 적용 효과 분석

Alpha Nickel hydroxide samples have been synthesized by electrodeposition on platinum and nickel substrates at current densities of 1, 5, 6, 7 and 10 mAcm？2 at a controlled temperature of 30.00 oC from Ni(NO3)2 bath. Platinum substrate shows a tendency to incorporate less nitrate ions with increase in current density thus producing less hydroxy-deficient nickel hydroxide layers. On the whole the interlayer distance (d003) is found to be inversely proportional to the amount of nitrate ions incorporated in-between the lattice. For the first time we have observed a decrease in lattice spacing with increase in concentration of intercalant (anions) and the reason for lattice contraction is attributed to the columbic attractive forces exerted by the oppositely charged nitrate ion and positively charged slabs. The Infrared spectra of the samples with expanded interlayers show two types of OH vibrations corresponding to hydrogen bonded and non-hydrogen bonded OH groups whereas the contracted interlayers show only hydrogen-boded OH groups. Although the faradaic efficiency is found to increase with increase in applied current there is a local minimum at 6.0 mAcm？2 current density on both platinum and nickel substrates. In this manuscript, GC-MS data is provided which clearly demonstrates the electrodeposited nickel hydroxide sample to consist of huge amount of carbonate ions although the electrolyte solution in nickel nitrate.

Superconducting phase sequence inRxC60fullerides (R=Smand Yb)

The true superconducting phase in rare-earth ${\mathrm{C}}_{60}$ fullerides ${R}_{x}{\mathrm{C}}_{60}$ ($R=\mathrm{Yb}$ and Sm) is not ${R}_{2.75}{\mathrm{C}}_{60}$ previously reported. Moreover, no superconductivity is observed in $\mathrm{Sm}\text{\ensuremath{-}}{\mathrm{C}}_{60}$ fullerides. The phase sequence between $\mathrm{Yb}\text{\ensuremath{-}}{\mathrm{C}}_{60}$ fullerides and $\mathrm{Sm}\text{\ensuremath{-}}{\mathrm{C}}_{60}$ ones as a function of the intercalant concentration of $x$ is shown to be greatly different, although Yb and Sm are the same family of rare-earth elements with the divalent valence state. This can explain the loss of superconductivity in ${\mathrm{Sm}}_{x}{\mathrm{C}}_{60}$ and suggests the true superconducting phase. The whole picture of rare-earth ${\mathrm{C}}_{60}$ fullerides is described.

Superconductivity appearing from C60 doped with rare-earth metals

The superconductivity observed in rare-earth C60 fullerides RExC60 (RE ¼ Yb and Sm) and La–C60 compounds are described. It is shown that RE2.75C60’s do not superconduct and the true superconducting phase in Y–bC60 fulleride resides in the t1g band. No superconductivity is observed in Sm–C60 fullerides. The phase sequence between Yb–C60 fullerides and Sm–C60 ones as a function of the intercalant concentration is shown to be greatly different, although Yb and Sm are the same family of divalent rare-earth elements. This seems to explain theloss of superconductivity in SmxC60, and suggests that the true superconducting phase is most likely YbxC60 ðx43Þ with the primitive cubic lattice. In addition, the superconductivity observed in C60 with La is shown to result from La2C3 carbides with two transition temperatures.

Electrochemical Synthesis of Co-intercalation Compounds in the Graphite-H2SO4-H3PO4System

Anodic oxidation of highly oriented pyrolytic graphite in an electrolyte containing concentrated sulfuric and anhydrous phosphoric acids is studied for the first time. The synthesis was carried out under galvanostatic conditions at a current I = 0.5 mA and an elevated temperature (t = 80°C). Intercalation compounds of graphite (ICG) are shown to form at all concentration ratios of H2SO4 and H3PO4 acids. The intercalation compound of step I forms in solutions containing more than 80 wt % H2SO4, a mixture of compounds of intercalation steps I and II forms in 60% H2SO4, intercalation step II is realized in the sulfuric acid concentration range from 10 to 40%, and a mixture of compounds of intercalation steps III and II is formed in 5% H2SO4 solutions. The threshold concentration of H2SO4 intercalation is ∼2%. With the decrease in active intercalate (H2SO4) concentration, the charging curves are gradually smoothed, the intercalation step number increases, and the potentials of ICG formation also increase. As the sulfuric acid concentration in the electrolyte changes from 96 to 40 wt %, the filled-layer thickness d i in ICG monotonously increases from 0.803 to 0.820 nm, which apparently is associated with the greater size of phosphoric acid molecules. With further increase in H3PO4 concentration in solution, d i remains unchanged. According to the results of chemical analysis, both acids are simultaneously incorporated into the graphite interplanar spacing and their ratio in ICG is determined by the electrolyte composition.

Numerical simulation of polymer nanocomposites using self-consistent mean-field model

Clay-containing polymeric nanocomposites (PNC) are mixtures of dispersed clay platelets in a polymeric matrix. These materials show enhancement of physical properties, such as modulus, strength, and dimensional stability, as well as a reduction of gas permeability and flammability. The performance is related to the degree of clay dispersion (i.e., intercalation or exfoliation) and the bonding between the clay and the matrix. The main goal of this work has been to map the degree of dispersion as a function of independent variables (viz., magnitude of the interaction parameters, molecular weights, composition, etc.). In this paper, we present the results of the numerical analysis of the equilibrium thermodynamic miscibility using one- and two-dimensional (1D and 2D) models based on the self-consistent mean-field theory. In the limit, the 2D model reproduced the 1D model published results. The adopted 2D model considers the presence of four PNC components: solid clay platelets, low molecular weight intercalant, polymeric matrix, and end-functionalized compatibilizer. The simulations, with realistic values of the binary interaction parameters, were analyzed for potential exfoliation of PNC with a polyolefin as the matrix. The simulation results show that intercalation and exfoliation is expected within limited ranges of the independent variables. The presence of a bare clay surface (e.g., generated by thermal decomposition of intercalant or extraction by molten polymer) has a strong negative effect on the dispersion process. The simulation successfully identified the most influential factors, e.g., optimum ranges of the compatibilizer and the intercalant concentration.

Influence of the Mn intercalation on magnetic properties of TiSe2

Using the measurements of the magnetic susceptibility and magnetization we have investigated the magnetic properties of Mn-intercalated MnxTiSe2 compounds having a hexagonal crystal structure of a quasi-two-dimensional type. Unlike other 3d-transition metals, intercalation of Mn ions between Se–Ti–Se tri-layers increases the c-parameter of the lattice. All compounds of MnxTiSe2 exhibit a paramagnetic behavior above ∼15K. The effective magnetic moment μeff of Mn in MnxTiSe2 is found to be less than μeff for the free Mn2+ ion. In a low-temperature region a spin-glass or cluster-glass behavior depending on the intercalant concentration is observed. The paramagnetic Curie temperature θp takes negative values and decreases monotonically with increasing x, while the freezing temperature shows non-monotonous change at the intercalation. The obtained results are discussed taking into account Mn 3d–Ti 3d hybridization effects and variations of intralayer and interlayer exchange interactions with intercalation.

Enhanced CDW Transitions in Nb3X4 (X = S, Se, Te): Intercalation and Surface Effects

A x Nb 3 X 4 (A = In, Tl, ZnHg; X = S, Se, Te) compounds show CDW instabilities dependent on the type and concentration of intercalate. Tl or In intercalation flattens the Fermi surfaces and supports CDW formation. In the corresponding DOS spectrum the Fermi level is shifted towards coincidence with a small peak, derived mainly from the Nb dz 2 orbital. Localized modulated regions observed in STM images of Nb 3 X 4 at room temperature represent precursor effects to full CDW formation.