Adsorption of nonpolar benzene derivatives on single-walled carbon nanotubes

The adsorption of benzene, toluene, and chlorobenzene on single-walled carbon nanotubes (SWCNTs) with and without acid oxidation was conducted to investigate the influences of derivative groups on benzene rings and functional groups from SWCNTs on adsorption by SWCNTs. The SWCNTs of high purity were chosen and moderate acid oxidation was performed so that the surface physical properties remained unchanged after acid oxidation and the influences of acid oxidation on adsorption were only contributed from the modification of the surface chemistry of SWCNTs. The oxygen-containing surface groups introduced by acid oxidation obstructed the interactions between functional groups of nonpolar benzene derivatives and C-rings of SWCNTs significantly. The dispersive interaction between the partially positive H⁺ of the methyl group and the oxygen-containing surface groups slightly increased the adsorption of toluene on oxidized SWCNTs at high solution pH. The thermodynamic of adsorption was also studied at different temperatures.     

Mixtures of polar and nonpolar molecules

The site-site Ornstein-Zernike (SSOZ) equation with mean spherical approximation closure is solved analytically for a mixture of hard dumbbells and polar hard dumbbells. The solution reduces to that of the pure polar hard dumbbell fluid at the polar species density rather than the total density. The thermodynamic properties of the mixture are obtained using the zero-pole approximation (ZPA) to the free energy. The mixture is shown to separate into two mixed phases, one rich in the nonpolar species and the other rich in the polar species. This phase separation terminates in an upper critical solution temperature. The excess thermodynamic functions are presented and the mixture exhibits both positive and negative values of the excess volume. The negative values of the excess volume occur in mixtures rich in the polar component.     

Storage of hydrogen on single-walled carbon nanotubes and other carbon structures

The sorption of hydrogen on carbon structures and nanostructures offers a way to reduce the storage pressure of hydrogen with respect to compression storage while achieving interesting gravimetric storage densities. The most readily available carbon structures, activated carbons, can achieve reproducible, high gravimetric storage densities under cryogenic operating conditions: 5–6% at 35 bar and 77 K, in excess of the normal density that would be present in the pore volume under compression at the same temperature and pressure. We discuss and compare the adsorption of hydrogen on high specific surface activated carbons, nanofibres and nanotubes from experimental and theoretical considerations. In particular, we present gravimetric and volumetric hydrogen sorption measurements on single-walled carbon nanotubes (SWNTs) at (1 bar, 77 K) and (1 bar, 295 K) within the context of our ongoing work on the storage of hydrogen on activated carbon and carbon nanostructures. BET surface area and XRD characterization results on SWNTs are also presented. The experiments were performed on as received, chemically treated and metal-incorporated SWNT samples. Hydrogen sorption capacities measured on treated samples ranged from 0 to about 1 wt.% at 1 bar and 295 K and reached about 4 wt.% at 1 bar and 77 K. Our results show that under certain conditions, SWNTs have better hydrogen uptake performance than large surface area activated carbons. PACS 81.07.de; 81.05.Uw; 68.43.h     

Creation of polar and nonpolar ultra-long-range rydberg molecules

We predict the existence of a ubiquitous class of long-range molecular Rydberg states, whose Born-Oppenheimer potential curves are oscillatory in nature. These oscillations reflect the nodal structure of the atomic Rydberg state wave functions. The temperature and density of atoms in a Bose-Einstein condensate are particularly favorable for the laser excitation of ultra-long-range vibrational bound states localized at internuclear distances in the range 10(3)- 10(5) a.u. A surprising trilobitelike class of polar homonuclear diatomics should exhibit electric dipole moments in the kilodebye range.     

Electron spin resonance signal of Luttinger liquids and single-wall carbon nanotubes

A comprehensive theory of electron spin resonance (ESR) for a Luttinger liquid state of correlated metals is presented. The ESR measurables such as the signal intensity and the linewidth are calculated in the framework of Luttinger liquid theory with broken spin rotational symmetry as a function of magnetic field and temperature. We obtain a significant temperature dependent homogeneous line broadening which is related to the spin-symmetry breaking and the electron-electron interaction. The result crosses over smoothly to the ESR of itinerant electrons in the noninteracting limit. These findings explain the absence of the long-sought ESR signal of itinerant electrons in single-wall carbon nanotubes when considering realistic experimental conditions.     

Electronic structures and transport properties of sulfurized carbon nanotubes

The electronic and transport properties of side-walled sulfurized (8, 0) zigzag carbon nanotube were investigated by using density functional theory coupled with a non-equilibrium Green function approach. It is found that the adsorption of the sulfur chains largely reduces the bandgap of the semiconducting (8, 0) carbon nanotube, even changing it into a metallic one. More importantly, the transmission eigenstates around the Fermi level are contributed by not only the sulfur chains but also the complex system made of the sulfur chains and the single-walled carbon nanotube. Our results provide a method to improve the conductivity and utilization rate of the surface in the electrodes of supercapacitor which are made of the carbon nanotubes.     

Schottky contacts to polar and nonpolar n-type GaN

Journal of the Korean Physical Society - Using the current-voltage measurements, we observed the barrier heights of c-plane GaN in Pt and Au Schottky contacts to be higher than those of a-plane...     

Theory of polar liquids

Two recent contributions to the statistical theory of polar fluids, namely the perturbation theory of Stell, Rasaiah and Narang (SRN) and the meanspherical-approximation (MSA) results of Wertheim, and of Nienhuis and Deutch, are compared and contrasted for the conceptually simple model of hard spheres, diameter R, with central point dipoles, of strength μ (dipolar hard spheres). It is shown that the MSA approach replaces correlation functions which enter correctly into the SRN theory by their low-density limits : to this extent it is unsatisfactory. On the other hand the MSA work does suggest reasons why the naive Padé approximant featuring in SRN theory may be expected to do reasonable justice to the physics of the problem. Numerical comparisons of the excess free-energy (as compared with non-polar hard spheres) as a function of reduced density, ρ* = ρR ³, are given at two temperatures, T* = 2 and T* = 0·25, where T* = kTR ³/μ². Similar curves, for T* = 1 and T* = 0·5, are available from the authors. The gas-liquid (T*, ρ*)-phase boundary is located, near the critical point, on both theories, as are the vapour pressure curves. These are calculated using the Carnahan-Starling equation of state for hard spheres ; and critical comment is made in justification of employing this in the context of MSA results for the excess quantities. The two theories are found to have appreciably different numerical consequences.     

4A碳纳米管及相关结构的嵌锂特性(英文)

碳纳米管独特的一维结构和强烈的卷曲效应为外来原子提供了理想的嵌入通道。本文全面总结了近年来我们对直径仅为4A的三种单壁碳纳米管嵌锂特性的密度泛函研究工作。我们具体讨论了体系嵌锂后的结构、能量、电子、电化学等特性。由于这些超小直径的碳纳米管最初合成于沸石晶体的纳米管道,我们也讨论了碳纳米管?沸石晶体复合体系的嵌锂特性。另外,我们还研究了由(5,0)和(14,0)碳纳米管组成的双壁碳纳米管体系的嵌锂特性。我们的理论计算表明,超小直径碳纳米管及相关结构作为锂离子电池负极材料具有很好的应用前景。     

Equilibrium structures of carbon diamond-like clusters and their elastic properties

Physics of the Solid State - Three-dimensional carbon diamond-like phases consisting of sp 3-hybridized atoms, obtained by linking of carcasses of fullerene-like molecules, are studied by methods...     

Fluorescence of 3-monomethylamino-N-methylphthalamide in mixtures of polar and nonpolar solvents

Modifications occurring in the fluorescence and excitation spectra of 3-monoethylamino-N-methylphthalimide (3 MANP) dissolved in nonpolar solvents (-hexane and methylcyclohexane) as a function of added n-butanol and n-propanol between -90 and 90°C were measured. The modifications were due to the presence of two types of centres resulting from the interaction of the solvent molecules with the nonpolar solvent on the one hand, and with the polar solvent on the other. The mixed complex character of the fluorescence band was not affected by the concentration of the solution in the range 10^-7?5 x 10^-4 mol/l. An attempt was made to establish a relationship between the emission due to the centres resulting from the interaction with the alcohol molecules and the association degree of the respective molecules.     

Electromagnetodynamics of polar liquids and suspensions

We study electric and magnetic effects on the dynamics of polar liquids and of fluid suspensions of particles carrying electric and/or magnetic dipole moments. The hydrodynamic equations of motion are discussed in detail and compared with equations proposed in the literature. We derive simplified equations valid on a slow timescale.     

Photodynamics of intramolecular proton transfer in polar and nonpolar biflavonoid solutions

Using methods of steady state luminescence and femtosecond spectroscopy, we have studied the mechanism of intramolecular proton transfer in synthesized 3,7-dihydroxy-2,8-di(4-methoxyphenyl)-4H,6H-pyrano[3,2-g]chromen-4,6-dion in polar and nonpolar solutions, films, and polycrystals at 293 and 77 K. In an excited singlet state, intramolecular proton transfer occurs in two stages. At the first stage, a tautomer with one transferred proton (OTP tautomer) is formed from the Franck-Condon state within ??₁ = 0.6 ps. At the second stage, the second proton is transferred within ??₂ = 3.1 ps and a tautomer with two transferred protons (TTP tautomer) is formed, which fluoresces in toluene at 293 K with a high quantum yield, ?? _f = 0.66, and the fluorescence spectrum of which is characterized by a large Stokes shift, 9900 cm^?1. At 293 K, polar solvents (dimethylformamide, dimethyl sulfoxide, ethanol, etc.) solvate the BFV molecule in the ground state, while, in the excited state, an OTP tautomer is mainly formed. In polar ethanol at 77 K, a dual fluorescence spectrum is observed, which is caused by the fluorescence emission of polysolvates with ?? _max ^f = 460 nm and TTP phototautomers at ?? _max ^f = 610 nm.     

Quasi-one-dimensional structure of polar liquids

The model of hindered molecular rotation considers a dense polar liquid as an infinite statistical chain of particles bound by dipole forces. The applicability limits of this quasi-one-dimensional model and the nature of possible phase transitions in the system under consideration are discussed.     

Surface reconstructions on InN and GaN polar and nonpolar surfaces

We report a systematic and comprehensive computational study of surface reconstructions on GaN and InN surfaces in various orientations, including the polar c plane as well as the nonpolar a and m planes. For GaN we have identified several new metallic reconstructions under highly Ga-rich conditions on the nonpolar planes. For InN we find several distinct differences from the GaN case: the absence of a nitrogen-adatom reconstruction on the (0 0 0 1) plane; the presence of a single, metallic reconstruction over the entire stability range on the plane; and In-adlayer reconstructions on the (m) plane. An interesting “inverted polarity” defect structure on the (m) plane is also revealed.     

Difference of dispersion behavior between graphene oxide and oxidized carbon nanotubes in polar organic solvents

This study examined the dispersion behavior of graphene oxide (GO) and oxidized carbon nanotubes (o-CNT) in a polar solvent, as well as the differences in the behavior related to the Hansen solubility parameter windows. In polar aprotic solvents, GO and o-CNT showed similar dispersion behavior. On the other hand, in polar protic solvents, such as ethanol and isopropanol, GO did not show dispersion stability whereas the o-CNTs did. This difference in the dispersion behavior between GO and o-CNTs resulted from the stronger hydrogen bonding between the GO interlayer induced by a large amount of oxygen functional groups and flexible two-dimensional morphology with a large surface area.     

Investigation of polar and nonpolar ordering in a smectic liquid crystal layer

A molecular-statistical theory that describes a smectic layer where short molecular axes have both polar and nonpolar orders has been developed. Several types of dependences of each order parameter on temperature and external field were obtained, and all possible phase states of the layered structure were determined.     

Equilibrium theories of simple liquids

In this article, the theory of equilibrium properties of simple classical fluids is reviewed. The various relationships between the pair potential φ(r) and the pair correlation function g(r) are explored, from the usual integral equations and the perturbation theories to the generalized random phase approximation proposed recently. Particular attention is devoted to the extraction of the intermolecular forces from a given experimental data on the structure and thermodynamics of fluids. In particular, the propagation of errors in these calculations arising due to uncertainties in the input data is discussed. Finally, the recent use of BGY integral equation and the vacancy-cell model in the study of solid-liquid transition and melting is discussed.