A computational characterization of CO@C60

The carbon monoxide encapsulation into C₆₀ is evaluated using the DFT and MP2 calculations. The CO encapsulation is attractive, yielding an energy gain of more than 12 kcal/mol. This substantial encapsulation energy should produce at the conditions used in the high-temperature and high-pressure synthesis (originally used for encapsulation of rare gases in fullerenes) an equilibrium CO@C₆₀ fraction of about 3.5% compared to the empty C₆₀. The computed IR and NMR spectra agree with the available observations for CO encapsulated into open-cage C₆₀ derivatives.     

Sc2O@C78: Calculations of the yield ratio for two observed isomers

The very recently observed production ratio 3:1 between Sc₂O@C₇₈(C_2v/3) and Sc₂O@C₇₈(D_3h/5) endohedrals can be reproduced in quantum-chemical calculations though only after a transition from the DFT to MP2 approach. It is concluded that the C_2v/3-cage-based species should be lower in the potential energy by about 1.5 kcal/mol.     

Fullerane,the Hydrogenated C60 Fullerene: Properties and Astrochemical Considerations

Abstract

Hydrogenated C₆₀ fullerene, C₆₀H₃₆ was prepared in different solvents using Zn/HCl as reducing agents. The structure of C₆₀H₃₆ was confirmed both by electronic and FT‐IR spectroscopy and the purity of the reaction product was checked by HPLC analysis. It has been confirmed that C₆₀H₃₆ is not stable in air, especially in presence of light which enhances the oxidation. The oxidation of C₆₀H₃₆ was studied by FT‐IR spectroscopy and by differential scanning calorimetry (DSC) in air; the formation of hydroxyl groups on the fullerene cage and ketonic groups (involving cage breakdown) have been detected. Furthermore, the action of O₃ on C₆₀H₃₆ was investigated and it has been found that O₃ exerts practically the same effect of air but causing an enhanced cage breakdown. The thermal stability of C₆₀H₃₆ was checked by a thermogravimetric analysis (TGA) coupled with a differential thermal analysis (DTA) under N₂ flow. The vaporization of C₆₀H₃₆ occurs at very high temperature: the DTA trace has shown an endothermic peak at 540°C (at a heating rate of 20°C/min). C₆₀H₃₆ shows an electronic absorption spectrum with a maximum at about 217 nm and it is able to match both in position and in half width the peak at 217.5 nm observed in the spectrum of the interstellar extinction of light which was attributed to hydrogenated, radiation processed and thermally annealed carbon dust. Similarly, the absorption spectrum of C₆₀H₃₆ is able to match several infrared emission bands (called UIBs) detected from certain astrophysical objects like the protoplanetary nebulae (PPNe). It is proposed that hydrogenated fullerenes can be used as model compounds in the laboratory simulation studies of interstellar carbon dust.     

Statistical Mechanical Study of Thermodynamic Properties of a Family of Fullerites from C36 to C96 in the Equilibrium with Their Vapors

Abstract

The temperature dependence of saturated vapor pressure of fullerites C₃₆–C₉₆ and their thermodynamic properties along with the sublimation curves up to the spinodal are calculated. The saturated vapor pressures along all the range of temperatures are approximated by logP _sat = A ? (B/T) ? CT. The coefficient A practically does not depend on the number of atoms in the molecule (varying only by 2.2%), B increases noticeably while C decreases from the C₃₆ to the C₉₆, both of them by approximately two. The isothermal bulk modulus B _T and the shear modulus C₄₄ vanish at the spinodal points.     

New Molecular Complex of Fullerene C60 with Porphyrin Dimer [FeTPP]2O: Synthesis and Crystal Structure

Abstract

New molecular complex of C₆₀ with covalently linked (Fe^IIITPP)₂O · C₆₀ dimer has been obtained. The complex has isolated packing of fullerenes in which fullerene molecule is embraced in a pocket built by porphyrins. (Fe^IIITPP)₂O preserves its initial geometry in the complex. The Fe···C(C₆₀) contacts are in the 3.239–3.513 Å range indicating the absence of Fe–C₆₀ coordination. This results in the similarity of the EPR spectra of the complex and parent (Fe^IIITPP)₂O.     

Mean polarizabilities and second and third virial coefficients of the gases C2H4, C2H6, and SF6

Mean polarizabilities ₀(₀, T) as well as second and third virial coefficients B(T) and C(T) of the equation of state of the gases C₂H₄, C₂H₆, and SF₆ have been determined from refractive index measurements with a Michelson interferometer for wavelength ₀=632.99 nm in the overall ranges 250 KT 340 K and 0p3 MPa of temperature T and pressure p. Some negative C(T) values at low temperatures have been obtained. The C(T) data could be fitted satisfactorily to the simple three-parameter function C(T)= a(T–T ₀) exp[ –b(T–T ₀)], with the maximum near the critical temperature T _c. A possible correlation between C(T) and the vapor pressure p _v(T) is discussed.     

Ab initio molecular dynamics simulation for the insertion process of Si and Ca atoms into C74

A large-scale ab initio molecular dynamics simulation for the insertion process of silicon and calcium atoms into C₇₄ is carried out for the first time by using the all-electron mixed-basis approach, where a one-electron wave function is expressed by superposing plane waves and numerical atomic orbitals. The present numerical results show that a silicon atom with more than a 40 eV kinetic energy can be inserted into C₇₄ through the center of a six-membered ring with a very short relaxation time of about 40 fs, and a calcium atom can be inserted with a 120 eV kinetic energy with a rather long relaxation time (>540 fs).     

Synthesis and characterization of novel nanostructured fishbone-like Cu(OH)2 and CuO from Cu4SO4(OH)6

The Cu₄SO₄(OH)₆ was synthesized by a simple hydrothermal reaction with a yield of ~ 90%. Using Cu₄SO₄(OH)₆ as the starting material, novel fishbone-like Cu(OH)₂ was produced by a direct reaction of Cu₄SO₄(OH)₆ with NaOH solution. The Cu(OH)₂ consists of many needle-like nanorods parallel to each other and perpendicular to the direction of backbone, forming fishbone-like structure. Using the fishbone-like Cu(OH)₂ as the sacrificial precursor, CuO with similar size and morphology was obtained through a simple heat treatment. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, X-ray photoelectron spectroscopy, BET nitrogen adsorption, and UV-Vis absorption spectroscopy were employed to characterize the as-prepared samples. The conversion of the Cu₄SO₄(OH)₆ to the fishbone-like Cu(OH)₂ was visualized by time-dependent SEM images. A mechanism was also proposed based on the observed results.     

The relative stability in and thermodynamic functions of the system of Si2H4(g) isomers: Comparison of results from two different evaluations of the system energetics

Thermodynamic consequences of the interplay of four recently found isomers of Si₂H₄(g) are studied. The partition functions and energetics of the isomers are constructed on the basis of available quantum-chemical data, and the results from two different approximations of potential energy are compared. Substantial values of isomerism contributions to the overall thermodynamics of the system are pointed out, as well as their sensitivity to interisomer energetics.     

The preparation of the anatase and rutile forms of Ag-TiO2 and hydrogen production from methanol/water decomposition

This study examined hydrogen production over Ag-TiO₂ photocatalysts containing Ag_xO, a conducting component. X-ray photon spectroscopy (XPS) confirmed that the Ag and Ag₂O components were dominant in the Ag-TiO₂ photocatalysts treated at 500 and 800 °C, respectively. The Ti2p bands in Ag-TiO₂ were shifted to lower binding energies, which were assigned to Ti³⁺, compared to pure TiO₂, and the shift was greater in the rutile structure than in the anatase. The measured full widths at half maximum (FWHM) of the Ag3d and Ti2p peaks were larger in the anatase structure than in the rutile structure in both TiO₂ and Ag-TiO₂. The H₂ production from methanol photodecomposition was greater over the rutile structure than over the anatase structure of TiO₂. Moreover, the amount of hydrogen was enhanced over Ag-TiO₂ compared to pure TiO₂; the production reached 17,124 μmol after 24 h over rutile Ag-TiO₂. After methanol photodecomposition, the amount of Ag component in the Ag-TiO₂ photocatalysts increased, while the Ag₂O component decreased.     

The mechanochemical reaction of C60 and Bi(NO3)3·5H2O

The mechanochemical reaction of C₆₀ and Bi(NO₃)₃·5H₂O was performed under ball-milling condition. The product was well characterized by spectroscopic methods such as IR, Raman, UV-vis, ¹³C NMR, as well as elemental analysis method. The spectroscopic investigation indicates that some hydroxyl and nitro groups are attached to the C₆₀ and no profound structural changes occur for the C₆₀ cage in the product. The elemental analysis gives an average composition of C₆₀(NO₂)₂(OH)₂₁ for the product. A possible mechanism is suggested for the reaction.     

Ab initio and TD-DFT study of the structural and spectroscopic properties of C30H10 as a new buckybowl

In this study, the structural and spectroscopic properties of the C₃₀H₁₀ as a sub-fullerene and a new buckybowl was carried out by quantum mechanical computations using B3LYP method and 6–311++G(d,p) basis set. All of the parameters were evaluated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were described which revealed different charge transfer possibilities for the molecule. The chemical shifts (δ, ppm) were predicted for ¹H and ¹³C atoms using GIAO method. Natural bond orbital (NBO) analysis was carried out to picture the charge transfer between the localized bonds and lone pairs. The Fukui function (FF) for local reactivity of C₃₀H₁₀ was calculated and related discussions were done.     

Influence of calcium hydroxide on the fate of perfluorooctanesulfonate under thermal conditions

To explore the potential fate and transport of perfluorochemicals in the thermal treatment of sludge, perfluorooctanesulfonate (PFOS), a perfluorochemical species commonly dominant in wastewater sludge, was mixed with hydrated lime (Ca(OH)₂) to quantitatively observe their interaction under different temperatures. The phase compositions of the mixtures after the reactions were qualitatively identified and quantitatively determined using X-ray diffraction technique. The results of the thermogravimetry and differential scanning calorimetry analyses indicate that PFOS gasified directly during the thermal treatment process when the temperature was increased to around 425 °C. However, the formation of CaF₂ at 350 °C suggests that the presence of Ca(OH)₂ in the mixture can lead to the decomposition of PFOS at 350 °C, which is lower than the decomposition temperature of PFOS alone (425 °C). The increase of temperature promoted a solid state reaction between PFOS and Ca(OH)₂, and also enhanced the interaction between the gaseous products of PFOS and CaO (or Ca(OH)₂). The preferred Ca/F molar ratio to achieve fluorine stabilization by Ca(OH)₂ was above 1:1 in the experiment involving 400 °C and 600 °C treatment. It also showed that equilibrium efficiency is achieved within 5 min at 400 °C and within 1 min above 600 °C.     

Synthesis and electrochemical properties of Ti doped Li3 − xFe2 − xTix(PO4)3/C cathode materials

Li_3 − xFe_2 − xTi_x(PO₄)₃/C (x = 0-0.4) cathodes designed with Fe doped by Ti was studied. Both Li₃Fe₂(PO₄)₃/C (x = 0) and Li_2.8Fe_1.8Ti_0.2(PO₄)₃/C (x = 0.2) possess two plateau potentials of Fe³⁺/Fe²⁺ couple (around 2.8 V and 2.7 V vs. Li⁺/Li) upon discharge observed from galvanostatic charge/discharge and cyclic voltammetry. Li_2.8Fe_1.8Ti_0.2(PO₄)₃/C has higher reversibility and better capacity retention than that of the undoped Li₃Fe₂(PO₄)₃/C. A much higher specific capacity of 122.3 mAh/g was obtained at C/20 in the first cycle, approaching the theoretical capacity of 128 mAh/g, and a capacity of 100.1 mAh/g was held at C/2 after the 20th cycle.     

Behavior of N atoms after thermal nitridation of Si1 − xGex surface

Behavior of N atoms after thermal nitridation of Si_1 − xGe_x (100) surface in NH₃ atmosphere at 400 °C was investigated. X-ray photoelectron spectroscopy (XPS) results show that N atomic amount after nitridation tends to increase with increasing Ge fraction, and amount of N atoms bonded with Ge atoms decreases by heat treatment in H₂ at 400 °C. For nitrided Si_0.3Ge_0.7(100), the bonding between N and Si atoms forms Si₃N₄ structure whose amount is larger than that for nitrided Si(100). Angle-resolved XPS measurements show that there are N atoms not only at the outermost surface but also beneath surface especially in a deeper region around a few atomic layers for the nitrided Si(100), Si_0.3Ge_0.7(100) and Ge(100). From these results, it is suggested that penetration of N atoms through around a few atomic layers for Si, Si_0.3Ge_0.7 and Ge occurs during nitridation, and the N atoms for the nitrided Si_0.3Ge_0.7(100) dominantly form a Si₃N₄ structure which stably remains even during heat treatment in H₂ at 400 °C.     

Conversion of V2O5·xH2O into orthorhombic V2O5 single-crystalline nanobelts

Orthorhombic V₂O₅ single-crystalline nanobelts have been synthesized by hydrothermal treating V₂O₅·xH₂O precipitate derived from aqueous solution of V₂O₅ and H₂O₂. The synthetic method is facile, fast, environmental friendly, and easy to scale up. The V₂O₅ single-crystalline nanobelts are 30-80 nm in width, 30-40 nm in thickness, and lengths up to several tens of micrometers. The V₂O₅·xH₂O precursor is crucial for the formation of orthorhombic V₂O₅ single-crystalline nanobelts. The influences of synthetic parameters, such as reaction time and reaction temperature, on the crystal structures and morphologies of the resulting products have been investigated. Time-dependent experiments show that V₂O₅·xH₂O are dehydrated gradually and converted into orthorhombic V₂O₅ single-crystalline nanobelts. High reaction temperature also favors the formation of orthorhombic V₂O₅ nanobelts.     

SERS property of Co complex on boron nitride nanosheets/silver nanoparticles aggregates and photophysical characterisation of interactions among Co complex ion-exchanged within zirconium phosphate

ABSTRACT

The Co(II) complex of [Co(bpy)₂(NO₃)]Cl·3H₂O, bpy = 2,2'-bipyridine, has been synthesised by the solution crystallisation method. The boron nitride nanosheets/silver nanoparticles/[Co(bpy)₂(NO₃)]Cl·3H₂O nanoaggregate was prepared in order to better analyse the adsorption orientation of the cobalt complex on the surface of silver nanoparticles. The result of the surface-enhanced Raman scattering measurement indicates that the molecular plane of the cobalt complex presents a tilted orientation with respect to the surface of silver nanoparticles. The luminescence property of [Co(bpy)₂(NO₃)]⁺ two-dimensional arrangements within the layers of zirconium phosphate (ZrP) was also investigated. Steady-state luminescence spectra of the [Co(bpy)₂(NO₃)]⁺-exchanged ZrP materials show an increase in the luminescence intensity.     

Synthesis and electrochemical properties of Nb-doped Li3V2(PO4)3/C cathode materials for lithium-ion batteries

Li₃V_2−xNb_x(PO₄)₃/C cathode materials were synthesized by a sol-gel method. X-ray diffraction patterns demonstrated that the appropriate addition of Nb did not destroy the lattice structure of Li₃V₂(PO₄)₃, and enlarged the unit cell volume, which could provide more space for lithium intercalation/de-intercalation. Transmission electron microscopy and energy dispersive X-ray spectroscopy analysis illustrated that Nb could not only be doped into the crystal lattice, but also form an amorphous (Nb, C, V, P and O) layer around the particles. As the cathode materials of Li-ion batteries, Li₃V_2−xNb_x(PO₄)₃/C (x ≤ 0.15) exhibited higher discharge capacity and better cycle stability than the pure one. At a discharge rate of 0.5C, the initial discharge capacity of Li₃V_1.85Nb_0.15(PO₄)₃/C was 162.4 mAh/g. The low charge-transfer resistances and large lithium ion diffusion coefficients confirmed that Li₃V_2−xNb_x(PO₄)₃/C samples possessed better electronic conductivity and lithium ion mobility. These improved electrochemical performances can be attributed to the appropriate amount of Nb doping in Li₃V₂(PO₄)₃ system by enhancing structural stability and electrical conductivity.     

Equation of State and Thermodynamic Properties of Pure D2O and D2O + H2O Mixtures in and Beyond the Critical Region

A parametric crossover model is adapted to represent the thermodynamic properties of pure D₂O in the extended critical region. The crossover equation of state for D₂O incorporates scaling laws asymptotically close to the critical point and is transformed into a regular classical expansion far from the critical point. An isomorphic generalization of the law of corresponding states is applied to the prediction of thermodynamic properties and the phase behavior of D₂O + H₂O mixtures over a wide region around the locus of vapor-liquid critical points. A comparison is made with experimental data for pure D₂O and for the D₂O + H₂O mixture. The equation of state yields a good representation of thermodynamic property data in the range of temperatures 0.8T _c(x)T1.5T _c(x) and densities 0.35_c(x)1.65_c(x).