CS2 Solution Research Articles

Neutron Diffraction with 34S/natS Isotopic Substitution Method on the Solvation Structure of S8 Molecule in Concentrated CS2 Solutions

Abstract Neutron diffraction measurements on 34S/natS isotopically substituted (natS: natural abundance) 6.9 mol% *S8 solutions in CS2 (natural abundance for both S and C atoms) have successfully been carried out in order to examine the possibility of the 34S/natS isotopic difference method neutron diffraction for liquid samples and to obtain novel structural insights into both intramolecular structure and the solvation structure of S8 molecule in concentrated CS2 solutions. Intramolecular structural parameters within the S8 molecule as well as the intermolecular parameters concerning the nearest neighbor *S⋯CS2 interaction have been determined through the least squares fitting analysis of the observed difference interference function, ΔS(Q), which has been derived from the numerical difference between scattering cross sections observed for *S8 with 34S-enriched and natural S solutions in natural CS2. MD simulations were performed with newly developed force field parameters for sulfur atoms in S8 molecule. The results derived by the simulations adequately agree with the neutron experiments.

The kinetics of dissolution and cluster formation of fullerene in polar and low polar solutions

Fullerene and fullerene like nanostructures play a main role in various research areas. Theamount of investigations of fullerene C60 and C70 has grown up considerably due to their several unique properties [1-2, 6]. In this report we present theoretical models for cluster growth, the modeling of small angle neutron scattering curves, and the results of structural analysis (SANS) for polar solutions of these macromolecules. Investigation of kinetics of dissolution and complex formation are studied for C60/Benzene, C60/Toluene and C60/Nmethyl-2-pyrrolidone (NMP) solutions of various concentrations by UV-Vis spectrometry. We model the kinetics of simultaneously occurring processes in the solution via a system of basic kinetic equations and obtain the corresponding parameters dependence on preparation conditions. The investigation of structural properties of fullerene solution in CS2 was performed at the YuMO instrument of the IBR-2 reactor. The results are compared tomolecular dynamics simulations, and other research works

Binding Sites, Vibrations and Spin-Lattice Relaxation Times in Europium(II)-Based Metallofullerene Spin Qubits.

To design molecular spin qubits with enhanced quantum coherence, a control of the coupling between the local vibrations and the spin states is crucial, which could be realized in principle by engineering molecular structures via coordination chemistry. To this end, understanding the underlying structural factors that govern the spin relaxation is a central topic. Here, we report the investigation of the spin dynamics in a series of chemically designed europium(II)‐based endohedral metallofullerenes (EMFs). By introducing a unique structural difference, i. e. metal‐cage binding site, while keeping other molecular parameters constant between different complexes, these manifest the key role of the three low‐energy metal‐displacing vibrations in mediating the spin‐lattice relaxation times (T 1). The temperature dependence of T 1 can thus be normalized by the frequencies of these low energy vibrations to show an unprecedentedly universal behavior for EMFs in frozen CS2 solution. Our theoretical analysis indicates that this structural difference determines not only the vibrational rigidity but also spin‐vibration coupling in these EMF‐based qubit candidates.

Facile preparation of super-hydrophobic fabrics composed of fibres with microporous or microspherical coatings using the static breath figure method

Fluorinated PTFOA-b-PS(2 h) and PTFOA-b-PS(4 h) block copolymers with controllable molecular weights were synthesised by atom transfer radical polymerisation (ATRP) and used to form microporous and microspherical coatings on fibres using the static breath figure (BF) method. The structures and properties of the coatings were examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and water contact angle (WCA) analysis. The fibre surface was complete coated with a microporous polymer in a water atmosphere using a 20 mg/mL PTFOA-b-PS(4 h) solution in CS2 as the finishing agent. The as-prepared fabric showed excellent hydrophobicity, with a WCA of 147.2 ± 1.6°. On the other hand, the fibre surfaces were coated with excellent polymer microspheres in a methanolic atmosphere using a 10 mg/mL PTFOA-b-PS(2 h) solution in THF; the WCA of the microsphere-coated fabric was 151.1 ± 0.1°. The WCA and EDS results reveal that synergism between the high roughness and low surface energy of the microspherical coating endows the fabric with super-hydrophobicity. At the same time, silanised block copolymers were synthesised by the silanisation of PTFOA-b-PS(2 h) and PTFOA-b-PS(4 h) and used to prepare microporous and microspherical coatings on fabrics. SEM showed that the silanised-PTFOA-b-PS(4 h)-coated fabric has a uniform and completely microporous morphology. A comparative study showed that both PTFOA-b-PS(2 h) and silanised-PTFOA-b-PS(2 h) form microspheres on fibre surfaces and that the latter exhibited hierarchical micro-nanostructures; the surface of fabric coated with this silanised polymer is super-hydrophobic, with a WCA of 152.2 ± 2.3°. Elemental distributions were determined by EDS, which revealed that the silanised-PTFOA-b-PS(2 h) microspheres contain more surface-migrating fluoropolymer segments, which produce hierarchical micro-nanostructures due to micro-phase separation. The air permeabilities and hardnesses of the silanised polymer-coated fabrics were also studied.

Comparison of three related imidazolium ionic liquids and their CS2 solutions

The aim of this paper is to give examples showing how computer simulation can be used to obtain insight into the behaviour of ionic liquids. Three related ionic liquids with cations containing imidazolium rings and alkyl groups were studied, namely the monocationic liquids 1-butyl 3-methyl imidazolium triflimide ([CHCHim][(CFSO)N]), 1-octyl 3-methyl imidazolium triflimide ([CHCHim][ (CFSO)N]) and the dicationic liquid ([CH(CHim)][(CFSO)N]). We find that the local structure of the liquids is similar in the dicationic and the C liquid but nanophase separation occurs in the C monocationic liquid, making the latter the odd one out for local structure. In contrast, for dynamical properties it is the liquid containing the dication which differs from the other two liquids showing that the dynamical properties are not necessarily correlated with equilibrium structure. The results of simulations of a probe molecule, CS, in the three liquids are compared.

Titanocene Selenide Sulfides Revisited: Formation, Stabilities, and NMR Spectroscopic Properties.

[TiCp2S5] (phase A), [TiCp2Se5] (phase F), and five solid solutions of mixed titanocene selenide sulfides [TiCp2SexS5−x] (Cp = C5H5−) with the initial Se:S ranging from 1:4 to 4:1 (phases B–E) were prepared by reduction of elemental sulfur or selenium or their mixtures by lithium triethylhydridoborate in thf followed by the treatment with titanocene dichloride [TiCp2Cl2]. Their 77Se and 13C NMR spectra were recorded from the CS2 solution. The definite assignment of the 77Se NMR spectra was based on the PBE0/def2-TZVPP calculations of the 77Se chemical shifts and is supported by 13C NMR spectra of the samples. The following complexes in varying ratios were identified in the CS2 solutions of the phases B–E: [TiCp2Se5] (51), [TiCp2Se4S] (41), [TiCp2Se3S2] (31), [TiCp2SSe3S] (36), [TiCp2SSe2S2] (25), [TiCp2SSeS3] (12), and [TiCp2S5] (01). The disorder scheme in the chalcogen atom positions of the phases B–E observed upon crystal structure determinations is consistent with the spectral assignment. The enthalpies of formation calculated for all twenty [TiCp2SexS5−x] (x = 0–5) at DLPNO-CCSD(T)/CBS level including corrections for core-valence correlation and scalar relativistic, as well as spin-orbit coupling contributions indicated that within a given chemical composition, the isomers of most favourable enthalpy of formation were those, which were observed by 77Se and 13C NMR spectroscopy.

Cathode Material Based on S/C Composite for Li-S Batteries

Sulfur-carbon composite (S/C) as cathode material for lithium-sulfur batteries (Li-S) was prepared by using carbon fibres prepared by electrospinning. Sulfur dissolved in CS2 solution was dropped to the carbon fibres. The sulfur-carbon based composite material is currently investigated due to the solution of scientific problems of Li-S batteries. The problems are nonconductivity of sulfur, the formation of intermediates during discharge processes, volume increase of sulfur and shuttle effect of polysulfides. Electrochemical testing was carried out by electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge-discharge. For the surface and structure analysis, the scanning electron microscopy was used.

A simulation study of CS2 solutions in two related ionic liquids with dications and monocations.

Atomistic simulations of solutions of CS2 in an ionic liquid, , with a divalent cation and in the corresponding ionic liquid with a monovalent cation, [C4C1im][NTf2], were carried out. The low-frequency librational density of states of the CS2 was of particular interest in view of recent optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). Compared to the monocation ionic liquid, the maximum shifts to higher frequencies in the dication ionic liquid under ambient conditions, but was found to be significantly pressure-dependent. CS2 molecules lie above and below the plane of the imidazolium rings and found to be close to the butyl tails of the monocation. The diffusion rates and embedding energies of solvent ions and CS2 in the two ionic liquids were measured.

Qubit crossover in the endohedral fullerene Sc3C2@C80.

The core-shell structure of endohedral fullerenes results in good protection of the encapsulated spin carriers from the environment. In this research, the quantum coherence behavior of the endohedral fullerene Sc3C2@C80 in CS2 solution is characterized from 5 K to room temperature. Below the critical temperature of around 140 K, the inner group is hindered, and the EPR spectrum consists of a single broad line. The spin carriers display a maximum phase memory time of 17.2(7) μs at 10 K. In the high temperature region, the inner group is mobile, and the EPR spectrum consists of 22 homogeneously broadened lines due to isotropic hyperfine coupling. The maximum phase memory time for each transition is around 139(1) ns at 200 K which allows arbitrary superposition state manipulations to be performed. This research demonstrates that Sc3C2@C80 displays temperature-crossover behaviour due to weak interaction between the Sc3C2 core and the C80 shell.

Photoluminescent Honeycomb Structures from Polyoxometalates and an Imidazolium-Based Ionic Liquid Bearing a π-Conjugated Moiety and a Branched Aliphatic Chain.

Honeycomb-structured films represent an intriguing class of two-dimensional porous materials. Specifically, polyoxometalate (POM) macroanions can be introduced into these films by complexing with oppositely charged, double-tailed surfactants. Here highly-ordered honeycomb structures are reported that can be constructed by the complexes between POMs and a room temperature ionic liquid (IL1) having an imidazolium moiety in the middle and a naphthyl unit and a branched aliphatic chain at the ends. The complexes can be produced through phase transfer between an aqueous solution of POMs (typically {Mo72 Fe30 }) and a CS2 (or chloroform) solution of IL1. Based on the intrinsic properties of {Mo72 Fe30 } and the functional groups of the IL1, the honeycomb structures show multiple functions with bright photoluminescence and rich electrochemical properties. This work shows that by simply engineering the organic ligands involved in the POM-based inorganic-organic complexes, supramolecular structures with improved properties and wide applications can be obtained.

Breath Figure in Reactive Vapor: A New Route to Nanopore Array.

A breath figure (BF)-inspired method for preparing ordered porous films has attracted more and more attention because of its simplicity, low cost, and easy implementation. However, it remains a challenge to use this method to fabricate nanoscale porous structures without designed polymer architecture and auxiliary. Herein, we first report a facile method to fabricate BF arrays with nanopores (nanoBFAs) in reactive vapor. Depending on the chemical reaction between the formic acid (FA) droplet template and the polyvinylpyridine (PVP) segments in copolymer, we successfully create nanoBFAs by casting a PVP-containing copolymer solution in CS2 in FA vapor. The condensed FA droplets can be instantly fixed by the PVP composition, and thus the growth and the aggregation of adjacent droplets are effectively restricted. Eventually, nanoBFAs are achieved in wide range solution concentration. In addition, binary porous structures with both nano- and microscale topology can be formed by using a FA/water mixed vapor with a one-step BF process. The produced nanoBFA films exhibit excellent antireflection performance with 0.5% reflectance, which is well-preserved even after hydrophobic treatment. This modified BF technique not only facilitates the elucidation of BFA formation mechanism but also opens a new way of fabricating nanoporous structures, which may have potential applications in electronic and optical devices.

XPS characterization of MWCNT and C60-based composites

ABSTRACTX-ray photoelectron spectroscopy was used for characterization of MWNT-C60 composites with assistance of scanning and transmission electron microscopy. The composites were received by immerison of nanotubes into fullerene solution in CS2 with consequent processing with green laser irradiation at aproximately 10 W/cm2. It was shown that C1s spectra of composites are different from simple addition of MWNT and C60 features. It found that preliminary nanotube purification by oxidative treatment influences strongly the nature of fullerene-nanotube bonding. Hydrophilic surface of oxidized nanotube material has lower affinity to C60 molecules and provides for concentration of C60 molecules into clusters, which show differential charging effect in XPS spectra. The differential charging effect disappears after laser processing, which induces photopolymerization of fullerene clusters. The as-synthesized nanotubes form composites with more evenly distributed fullerene.

(Invited) Near Infrared Photoluminescence of Endohedral Metallofullerenes

Physical properties of endohedral metallofullerenes can be tuned by changing the fullerene size as well as the metal atom(s) inside the fullerene cage. One of the most interesting characteristic properties of the metallofullerenes encapsulating lanthanide metal atoms is the near-infrared photoluminescence (NIR-PL) due to the f-f transition of M3+ (or M2+) in fullerene cages. Previously, we reported that (Er2C2)@C82 (III) has exhibited the strongest PL in isomer-separated Er2@C82 (I, II, III) and (Er2C2)@C82 (I, II, III) in CS2 solution [1]. The encapsulated C2 molecule enhances the PL intensity by increasing the efficiency of the energy transfer from the C82 cage to the encapsulated Er3+. In this talk, we will report the NIR-PL from Tm atom(s) in Tm metallofullerenes for the first time. The PL spectra and their intensities strongly depend on the electronic states of Tm ions and the fullerene cages. The detailed mechanisms will be discussed. [1] Y. Ito, T. Okazaki, S. Okubo, M. Akachi, Y. Ohno, T. Mizutani, T. Nakamura, R. Kitaura, T. Sugai and H. Shinohara, ACS Nano, 1, 456-462 (2007).

Characterisation of dihydroazulene and vinylheptafulvene derivatives using Raman spectroscopy: The CN-stretching region

The effect of adding electron donating and withdrawing groups on the dihydroazulene (DHA)/vinylheptafulvene (VHF) photochromic system has been investigated using Raman spectroscopy in CS2 solutions. The photoswitching between DHA and VHF is often characterised with UV–Vis spectroscopy. However, Raman spectroscopy can also be used for this purpose and give structural insight, as the light induced ring-opening from DHA to VHF causes changes in the CN-stretching frequencies. The CN-stretching frequencies in DHA and VHF are isolated and optimal for the identification of DHA and VHF. The DHA system is also investigated in the solid state.

Populations of Ethanol Conformers in Liquid CCl4 and CS2 by Raman Spectra in OH Stretching Region

Combining Raman spectroscopy with density functional theory, the populations of the trans- and gauche- ethanol conformers are investigated in carbon tetrachloride (CCl4) and carbon disulfide (CS2). The spectral contributions of two ethanol conformers are identified in OH stretching region. The energy difference between both conformers is estimated with the aid of the calculated Raman cross sections. It can be seen that the trans- ethanol is more stable in CCl4 and CS2 solutions. The spectra are also obtained at different temperatures, and it is found the van't Hoff analysis is invalid in these solutions. By taking accounts of the Boltzmann distribution and theoretical Raman cross section, the energy difference is found to be increased with temperature, which shows the weak intermolecular interactions can enhance the population of trans- ethanol.

Well-defined monocarboxyl-terminated polystyrene with low molecular weight: A candidate for the fabrication of highly ordered microporous films and microspheres via a static breath-figure process

Aiming at the fabrication of highly ordered microporous films, a series of well-defined monocarboxyl-terminated polystyrenes (PSCOOH) with low molecular weight (PS13KCOOH: Mn=13kgmol−1, Mw/Mn=1.04; PS10KCOOH: Mn=10kgmol−1, Mw/Mn=1.05; PS4.4KCOOH: Mn=4.4kgmol−1, Mw/Mn=1.05 and PS2.1KCOOH: Mn=2.1kgmol−1, Mw/Mn=1.08) were synthesized firstly via reversible addition-fragmentation chain transfer (RAFT) polymerization using S-1-dodecyl-S’-(α, α’-dimethyl-α’’-acetic acid) trithiocarbonate as chain transfer agent. Then, a facile static breath-figure (BF) process was employed to fabricate microporous films of PSCOOHs. The influencing factors on the morphology of such microporous films, such as relative humidity, temperature, solvent, polymer concentration and molecular weight of polymer were investigated. Highly ordered microporous film with average pore size of 1.33μm and better regularity was fabricated through a static BF process using PS10KCOOH solution in CS2 (40mgmL−1) at 22°C in relative humidity of 95%. It was noteworthy that highly ordered microporous film (the average pore sizes from 0.77μm to 0.83μm) can be successfully fabricated using PSCOOH with very low Mn of 2.1kgmol−1 for the first time. Moreover, microsphere pattern of PSCOOH with the average diameters from 0.85μm to 5.40μm was formed when replacing water with methanol as environmental vapor in the chamber for the static BF process.

Solvent atmosphere controlled self-assembly of unmodified C60: A facile approach for constructing various architectures

Abstract A facile approach for constructing diverse architectures of unmodified C60 was developed via simple evaporation of pure C60 solution in CS2 under various poor solvent atmospheres. Diverse architectures such as belts, sheets, and starfishes were successfully constructed under different experimental conditions. C60 belts obtained under EtOH atmosphere were confirmed to be a face-centered cubic (fcc) structure. The solvent atmospheres not only slowed down the evaporation speed, but also could reorganize the self-assembly of C60 by partially re-dissolving the initially formed architectures. This concept represents a novel method for preparation of nanostructures of C60 and could also be applied for controlling of the self-assembly of other functional organic molecules.

Fabrication of morphology-controlled nano/microstructural polyfluorene in mixed nonsolvent vapor atmospheres

Under mixed water and methanol vapor atmospheres, a poly(9,9-dihexylfluorene)/CH2Cl2 solution self-assembles to form various nano/microstructures, such as porous films, spherical segments and microspheres. The water droplet template and the polymer precipitation by methanol were the driving forces that fabricated the patterns. Porous films with different pore sizes were obtained in CS2 solution by altering the mixed vapor atmosphere. Changes in the spreading coefficient and solvent polarity led to the formation of different morphologies. The introduction of miscible solvent vapors in aqueous atmospheres is a facile way to design and fabricate polymeric nano/microstructures.

Electric conductivity of solid solutions in Cs2 − 2x Fe2 − x A x O4 systems (A = P, V)

Solid solutions based on CsFeO2 in Cs2 − 2x Fe2 − x A x O4 systems (A = P, V) were synthesized. Their crystal structure and the temperature and concentration dependences of the total conductivity and its electronic component were studied. The ranges of temperature and composition in which cesium-cation conductivity was dominant were determined. The obtained data were compared with the results of studies of other cesium-conducting solid electrolytes.

Formation of well-defined Cu2S dendrites on TEM grids from sulfur/CS2 under ambient conditions

The Cu2S dendrites were formed on TEM grids from elemental sulfur (S) in CS2 solution by one day's ageing under ambient conditions and became denser with ageing. The shape and structures were stable in air for at least a month. If S/ethanol solution was dropped on Cu grid, uniform Cu2S nanowires were produced one day later, which could only be obtained by one week's ageing when using S/ethanol suspension as source in our previous work. The influence of the sulfur dispersion and concentration in several kinds of solvent on the growth and structures of Cu2S was discussed based on electron microscopic observation. This simple synthesis method from elemental reactants without any additives was useful for studying formation mechanism of hierarchical nanostructures, and more importantly, it was environmentally friendly.