Chemical Physics Letters (v.677, #C)
Editorial Board (IFC).
Velocity map ion imaging and velocity-resolved action spectroscopy of H atom photofragments via Doppler-free multiphoton ionization by Michael Epshtein; Yaakov Monsa; Alexander Portnov; Ilana Bar (1-6).
Display OmittedHydrogen atom photofragments with high velocities in the laboratory frame lead to strong Doppler broadening of the (2 + 1) resonance-enhanced multiphoton ionization transition. Here, an alternative setup for Doppler-free ion imaging is demonstrated and explored for predissociation of methylamine and probing of H photofragments, at close wavelengths. This approach enables measurement of the entire velocity distributions in each laser pulse, enhances sensitivity and consequently provides acquisition of high quality H images and action spectra. These results shed light on dissociation dynamics and can be foreseen to be useful in revealing the dynamics in other molecular systems.
Facile syntheses of 3-dimension graphene aerogel and nanowalls with high specific surface areas by Lina Zhou; Zhongbo Yang; Jun Yang; Yonggang Wu; Dongshan Wei (7-12).
Display OmittedWe propose facile synthesis methods to prepare two three-dimension (3D) multi-porous graphene structures including graphene aerogel and graphene nanowalls. The graphene aerogel was prepared via the hydrothermal reduction and tert-butanol freeze-drying. The graphene nanowalls were prepared by growing the obtained graphene aerogel via a plasma enhanced chemical vapor deposition (PECVD). High specific surface areas of these two structures up to 795 m2/g were obtained by BET analyses. The crystallized, multi-porous, and thermal stable features of these two 3D graphene structures were verified via the X-ray diffraction, SEM, Raman spectroscopy and thermal gravity analysis characterizations.
Keywords: Graphene oxide; Graphene aerogel; Graphene nanowall; Specific surface area; Freeze-drying;
Theoretical study on the formation process of Cross-Linked β-Cyclodextrin molecular tubes by Vitória S. Reis; Eliziane S. Santos; Daniela N.F. Bonsolhos; Luciana Guimarães; Wagner B. De Almeida; Clebio S. Nascimento (13-18).
Display OmittedThis paper reports a theoretical investigation using semiempirical and DFT calculations in order to evaluate structural and energetic properties related to the formation process of Cross-Linked β-Cyclodextrin molecular tubes. As result, TT spatial orientation was found to be the most favorable among the dimeric tubes. The overall stability order, TT > HH > HT, does not change with the number of cross-linking groups. Besides, we have shown that tubes with 3 cross-linking in their structures are the most stable ones due to steric and repulsion factors which is in perfect agreement with experimental data.
Keywords: β-Cyclodextrin; Molecular tubes; Cross-linking; Theoretical calculations; DFT; PM3;
Preparation, characterization, kinetic and thermodynamic studies of MgO-La2O3 nanocatalysts for biodiesel production from sunflower oil by Mostafa Feyzi; Nahid Hosseini; Nakisa Yaghobi; Rohollah Ezzati (19-29).
MgO-La2O3 nanocatalysts were prepared. The activity of optimal catalyst was studied at different operational conditions. Ea = 77.6 kJ·mol−1, A = 3.5 × 107 l·mol−1 s−1,Δ rHθ = 162 kJ·mol−1 K−1, Δ rSθ = 0.54 kJ·mol−1 K−1 were obtained.Display OmittedA series of MgO-La2O3 nanocatalysts were prepared via a co-precipitation method and used for biodiesel production from sunflower oil. The results showed that with increasing Mg/La weight percent the catalytic activity increases obviously. Also the results showed that the catalyst with Mg/La = 60 wt.% (based on weight of La) is an optimal nanocatalyst. The best operational conditions were the CH3OH/oil = 18/1 at 338 K with mechanical stirring 700 rpm for 5 h. Furthermore, the optimal nanocatalyst showed high catalytic activity for biodiesel production and the biodiesel yield reached 97.7% under the optimal conditions. Furthermore, this nanocatalyst was used for 4 runs in biodiesel production without significant decrease of catalytic performance. Also kinetic and thermodynamic of reaction has been studied in the presence of optimal nanocatalyst. From the kinetic and thermodynamic studies, Ea = 77.6 kJ·mol−1, A = 3.5 × 107 l·mol−1 s−1, Δ r H θ = 162 kJ·mol−1 K−1, Δ r S θ = 0.54 kJ·mol−1 K−1 were obtained. Characterization of catalysts was carried out by using scanning electron microscopy (SEM), X-ray diffraction (XRD), temperature programmed desorption (TPD), Fourier transform-infrared spectroscopy (FT-IR) and N2 adsorption–desorption measurement methods.
Keywords: Biodiesel; Kinetic; Thermodynamic; Operational conditions; Nanocatalyst;
A DFT study on the chiral synthesis of R-phenylacetyl carbinol within the quantum chemical cluster approach by Omar Alvarado; Ignacio Lizana; Gonzalo Jaña; Iñaki Tuñon; Eduardo Delgado (30-34).
Display OmittedThe reaction pathway leading to R-phenylacetyl carbinol within the quantum chemical cluster approach is addressed by means of density functional theory (DFT) calculations. The study includes calculation of Fukui functions, activation free energies, and potential energy surface scans, both in gas and solution phase. The protonation states of the nitrogen atoms of the pyrimidine moiety are determined. The reaction appears to be slightly exergonic (ΔG0 = −5.6 and −4.0 kcal/mol for gas and solution phase, respectively) following a concerted synchronous mechanism having activation free energy barriers of 16.2 and 13.3 kcal/mol, in gas phase and solution phase, respectively.
Electrochemical and theoretical characterization of the electro-oxidation of dimethoxycurcumin by Lily Arrue; Tomas Barra; María Belén Camarada; Ximena Zarate; Eduardo Schott (35-40).
Display OmittedDimethoxycurcumin (DMC) ((1E,6E)-1-(3,4-dimethoxycyclohexyl)-7-(3,4-dimethoxyphenyl) hepta-1,6- diene-3,5-dione) is a natural polyphenolic compound that appears together with curcumin in turmeric. Both molecules have wide range biological activities as antioxidant, anti-inflammatory and anti-carcinogenic agent. To evaluate the oxidation process and kinetics for DMC, the rate constant, electron transfer and diffusion coefficients for the electrochemical oxidation were determined. Therefore, its electrochemical behavior over a platinum electrode in anhydrous media was investigated. Furthermore, DFT calculations were performed to give a rational explanation to the obtained results. All the results support the fact that the central ―CH2 ― group is the most reactive against an oxidation process.
Keywords: Electrochemical oxidation; Dimethoxycurcumin; DFT; Voltammetry;
Non-opioid analgesic drug flupirtine: Spectral analysis, DFT computations, in vitro bioactivity and molecular docking study by D.R. Leenaraj; I. Hubert Joe (41-49).
Display OmittedSpectral features of non-opioid analgesic drug flupirtine have been explored by the Fourier transform infrared, Raman and Nuclear magnetic resonance spectroscopic techniques combined with density functional theory computations. The bioactive conformer of flupirtine is stabilized by an intramolecular C―H⋯N hydrogen bonding resulting by the steric strain of hydrogen atoms. Natural bond orbital and natural population analysis support this result. The charge redistribution also has been analyzed. Antimicrobial activities of flupirtine have been screened by agar well disc diffusion and molecular docking methods, which exposes the importance of triaminopyridine in flupirtine.
Keywords: DFT; NBO; NPA; Molecular docking; Bioactivity;
Study of carrier-mobility of organic thin film by dark-injection time-of-flight and electric-field-induced optical second-harmonic generation measurements by Xin Li; Masashi Sunaga; Dai Taguchi; Takaaki Manaka; Hong Lin; Mitsumasa Iwamoto (50-54).
Display OmittedBy using dark-injection time-of-flight (ToF) and time-resolved electric-field-induced optical second-harmonic generation (EFISHG) measurements, we studied carrier mobility μ of pentacene (Pen) thin film of ITO/Pen/Al and Au/Pen/polyimide/ITO diodes where pentacene film is ∼100 nm in thickness. ToF showed that determination of transit time t r from trace of transient currents is difficult owing to large capacitive charging current. On the other hand, optical EFISHG is free from this charging current, and allows us to calculate hole and electron mobility as μ h = 1.8 × 10 - 4 cm2/Vs and μ e = 7.6 × 10 - 7 cm2/Vs, respectively, by using the relation t r = d / μ ∫ t c t r E ( 0 ) dt ( d : Pen thickness, E ( 0 ) : electric field across Pen), instead of the conventional relationship t r = d 2 / μ V ( V : voltage across Pen). Time-resolved EFISHG measurement is useful for the determination of carrier mobility of organic thin film in organic devices.
Keywords: Electric-field-induced optical second-harmonic generation; Carrier transport; Carrier mobility; Thin film; Time-of-flight;
K–Al-based mixed oxides as high-capacity carbon dioxide adsorbents by Keita Ikeue; Masashige Suzuki; Munetoshi Sakai; Tarun Chand Vagvala; Vit Kalousek (55-59).
Display OmittedK–Al-based mixed oxides (KAl6O9.5) with mullite structures were synthesized as CO2 adsorption materials using a polymerized complex method. Al3+ sites in the octahedral AlO6 units of K–Al-based mixed oxides were substituted with various metal ions with +2 or +3 valence states to enhance basicity. Among these samples, the Fe-introduced sample (KAl5.5Fe0.5O9.5) showed 130 times higher CO2 adsorption capacity than that of Li4SiO4. Raman spectra of these samples indicated that large distortions of the AlO6 unit were observed only for the Fe-introduced sample. Local polarization caused by such distortions could induce increased basicity of this sample.
Keywords: Carbon dioxide; Solid adsorbent; Mullite; CO2 adsorption;
Probing the impact of the cation acidity on the cation-anion interaction in ionic liquids by X-ray photoelectron spectroscopy by Shuang Men; Jing Jiang (60-64).
Display OmittedThe impact of the cation acidity on the cation-anion interaction in ionic liquids is revealed by X-ray photoelectron spectroscopy, employing four cations with different acidity. A two-component fitting model for carbon regions of trioctylmethylammonium ionic liquids is developed. It is found that for more basic anions, the less acidic the cation, the less charge is transferred from the anion to the cation; for anions with lower basicity, such effect concentrates more on the component bearing more point charges.
The synergy effect and reaction pathway in the oxygen reduction reaction on the sulfur and nitrogen dual doped graphene catalyst by Jian Song; TianFu Liu; Sajjad Ali; Bo Li; DangSheng Su (65-69).
Display OmittedThe first-principle calculations are performed to explore the synergy effects between two dopants (N, S) and the detailed reaction pathway of oxygen reduction reaction (ORR) on the graphene catalysts. The co-doping N and S induces the significant spin density and has a strong chemical bonding with oxygen molecule which is not observed on the mono-doped cases. Three different reaction pathways are revealed from the calculations. Due to the large barrier of the O―O breaking, the hydrogenation of the adsorbed oxygen molecule is kinetically more favorable. The free energy change of reaction under different electrode potential is also evaluated.
Keywords: ORR; Doping; Spin density;
Synthesis of flower-like copper sulfides microspheres as electrode materials for sodium secondary batteries by Bin Shi; Wen Liu; Kai Zhu; Jingying Xie (70-74).
Display OmittedFlower-like copper sulfides (CuS) microspheres, with a diameter of about 10 μm, are synthesized via a facile hydrothermal method and employed to sodium secondary batteries for the first time. The complex structure of CuS is composed by nanosheets with thickness around 50 nm. Na/CuS cell delivers an initial discharge capacity of 348.6 mAh/g. However, half of initial specific capacity maintains after 4 cycles, accompany with the structure degradation. Despite all that, CuS is a promising cathode material due to its high specific capacity for sodium batteries, which needs much more efforts to improve the cycle stability.
Keywords: Copper sulfides; Flower-like structure; Sodium secondary batteries; Structure degradation;
Cabbage-like α-Ni(OH)2 with a good long-term cycling stability and high electrochemical performances for supercapacitor applications by L. Aguilera; Y. Leyet; R. Peña-Garcia; E. Padrón-Hernández; R.R. Passos; L.A. Pocrifka (75-79).
Display OmittedNanostructured Ni(OH)2 is a promising candidate to be used as an extrinsic pseudocapacitors material. Here, nickel hydroxide (Ni(OH)2) was grown on the surface of a Ti plate, galvanostatically via electrodeposition method. In the electrodeposited films a stable α-Ni(OH)2 phase with particles in cabbage form and average crystallite size of 20 nm is obtained. The α-Ni(OH)2 sample exhibits excellent electrochemical performance at different current densities and good cycling stability. A maximum specific capacitance of 1903 F g−1 is achieved at a current density of 1 mA cm−2. The energy and power density values found are 42.31 W h kg−1 and 430 W kg−1.
Keywords: α-Nickel hydroxide; Electrodeposition; Supercapacitor; Electrochemical performance; Cycling stability; Electrochemical impedance spectroscopy;
Role of oxygen functionality on the band structure evolution and conductance of reduced graphene oxide by Rajarshi Roy; Ranjit Thapa; Soubhik Chakrabarty; Arunava Jha; Priyanka R. Midya; E. Mathan Kumar; Kalyan K. Chattopadhyay (80-86).
Display OmittedHere we report, structural and electrical transport properties of reduced graphene oxide as a function of oxygen bonding configuration. We find that mainly epoxy (C ― O ― C) and carbonyl (C ＝ O) functional groups remain as major residual components after reduction using three different reducing agents. We calculate the band structure in the presence of epoxy and carbonyl groups and defects. Finally, we calculate the theoretical band mobility and find that it is less for the carbonyl with epoxy system. We correlate the distortion of linear dispersion and opening of bandgap at K-point with conductance for different graphene system in presence of oxygen moieties.
Keywords: Graphene oxide; Band structure; DFT; Transport;
Dynamics of photogenerated polarons and polaron pairs in P3HT thin films by M. Menšík; J. Pfleger; P. Toman (87-91).
Display OmittedOn the basis of the analysis of the experimental data of the transient absorption spectroscopy of thin films of regioregular poly(3-hexyl thiophene) we suggest a mechanism of the polaron pairs decay based on the coherent up and down conversion cycling between hot polaron pairs and free polarons. Compared to previously adopted models, based on single molecular processes or bimolecular collisions, the suggested model reproduced well both the polaron pairs and polaron population kinetics at short time after photoexcitation. For longer times, when the polaron pairs are already thermalized, they decay via 1-D diffusion limited bi-molecular collision processes.
Configuration interaction study of electronic structures of CdCl including spin-orbit coupling by Shutao Zhao; Jicheng Cui; Rui Li; Bing Yan (92-98).
Display OmittedAdiabatic potential energy curves (PECs) and the dipole moments (DMs) for the 14 low-lying Λ-S states of CdCl were computed at configuration interaction method including Davidson correction (+Q). To quantitatively evaluate the spin-orbit coupling (SOC) effect, the SOC integrals involving the X2Σ+ and 22Σ+ were investigated. The spectroscopic constants of 9 bound Λ-S states and 4 lowest bound Ω states were derived. Moreover, the radiative lifetimes of the vibrational levels of bound states were predicted for the first time. Finally, the feasibility and challenges of laser cooling of CdCl were discussed based on a three-laser cooling scheme.
An extrapolation scheme for solid-state NMR chemical shift calculations by Takahito Nakajima (99-106).
Display OmittedConventional quantum chemical and solid-state physical approaches include several problems to accurately calculate solid-state nuclear magnetic resonance (NMR) properties. We propose a reliable computational scheme for solid-state NMR chemical shifts using an extrapolation scheme that retains the advantages of these approaches but reduces their disadvantages. Our scheme can satisfactorily yield solid-state NMR magnetic shielding constants. The estimated values have only a small dependence on the low-level density functional theory calculation with the extrapolation scheme. Thus, our approach is efficient because the rough calculation can be performed in the extrapolation scheme.
Keywords: Solid-state NMR; Chemical shifts; Extrapolation scheme;
Spectroscopic and theoretical studies of anionic corroles derived from phosphoryl and carbomethoxyphenyl substituted corroles by Pinky Yadav; Muniappan Sankar (107-113).
Anionic corroles of 1–3 were generated by adding aliquots of basic anions such as CN−, F−, OAc− and H2PO4 − in aprotic solvents and studied their spectral properties and structural aspects by DFT calculations. The anion-induced deprotonation constants (Kd) of corroles 1–3 depend on the basicity of the anion employed and acidity of free base corrole core.Display OmittedAnionic corroles were obtained by the addition of aliquots of basic anions such as CN−, F−, OAc− and H2PO4 − to free base corroles 5,10,15-triphenylcorrole (1), 5,10,15-tris(4′-diethoxyphosphorylphenyl)corrole (2) and 5,10,15-tris(4′-carbomethoxyphenyl) corrole (3) in aprotic solvents at 298 K. The 1:2 (corrole-to-anion) stoichiometry was confirmed by Hill plot and DFT studies. The dianionic corroles derived from 2 and 3 exhibited a dramatic red-shift (Δλmax = 14–24 nm) in B band as compared to that of free base corroles (2–3) while the opposite trend was observed in fluorescence spectral features with the enhanced fluorescence intensity. The anion-induced deprotonation constants (Kd) of corroles (1–3) depend on the basicity of the anion used and the acidic nature of free base corrole core. The presence of excess protic solvent disfavors the formation of dianionic corroles.
Keywords: Dianionic corroles; Anion-induced deprotonation; Spectral properties; DFT studies;
The first-principles study for the novel optical properties of LiTi2O4, Li4Ti5O12, Li2Ti2O4 and Li7Ti5O12 by Yuxiang Liu; Jie Lian; Zhaozong Sun; Minglin Zhao; Yujun Shi; Haonan Song (114-119).
The electron density contour plots of (1 1 0) plane for LiTi2O4, Li4Ti5O12, Li2Ti2O4 and Li7Ti5O12.Display OmittedWith the first-principles method based on the density functional theory (DFT), we studied novel optical properties of LiTi2O4, Li4Ti5O12, Li2Ti2O4 and Li7Ti5O12, respectively. According to the calculated electronic structures, the electron redistribution upon Li-ion intercalation has an obvious influence on the electronic transitions between O 2p and Ti 3d states, resulting in distinctions of optical properties between LiTi2O4, Li4Ti5O12, Li2Ti2O4 and Li7Ti5O12. These results not only reveal the fundamental origin of optical properties but also provide practical guidance on optical applications for these materials.
Keywords: LTO compounds; The DFT method; Optical properties;
Fine-tuning of atomic point charges: Classical simulations of pyridine in different environments by Marina Macchiagodena; Giordano Mancini; Marco Pagliai; Gianluca Del Frate; Vincenzo Barone (120-126).
Display OmittedA correct description of electrostatic contributions in force fields for classical simulations is mandatory for an accurate modeling of molecular interactions in pure liquids or solutions. Here, we propose a new protocol for point charge fitting, aimed to take into the proper account different polarization effects due to the environment employing virtual sites and tuning the point charge within the polarizable continuum model framework. The protocol has been validated by means of molecular dynamics simulations on pure pyridine liquid and on pyridine aqueous solution, reproducing a series of experimental observables and providing the information for their correct interpretation at atomic level.
Keywords: Molecular dynamics; Static dielectric constant; Force fields; Virtual sites; Pyridine; Aqueous solution; Organic liquids; Charge fitting;
Infrared observation of a new mixed trimer, CO – (CO2)2 by A.J. Barclay; A.R.W. McKellar; N. Moazzen-Ahmadi (127-130).
Display OmittedThe infrared spectrum of the weakly-bound trimer CO – (CO2)2 is observed in the carbon monoxide CO stretch region. Both 12C16O – (12C16O2)2 and 12C16O – (12C18O2)2 isotopologues are studied. The trimer band which is composed uniquely of b-type transitions and with missing levels establishes the trimer structure as that of a CO2 dimer plus a CO monomer aligned along the dimer C 2 symmetry axis. The dimer to monomer center of mass separation is 3.55 Å, and the structural parameters within the CO2 dimer subunit are about 3.45 Å and 58°. It is not certain if the (CO2)2 remains planar within the trimer.
Highly-polarized spin currents through protein-like single-helical molecules by Hai-Na Wu; Xiao Wang; Wei-Jiang Gong (131-136).
Electronic transport through a protein-like single-helical molecule is theoretically studied. By introducing an additional terminal to couple to the molecule, we construct a two-channel mesoscopic circuit, and then calculate the charge and spin currents in the two drain terminals. It is found that in one drain terminal, a pure spin current has an opportunity to appear without an accompanying charge current. Besides, the polarization direction of the spin current can be inverted by altering the system chemical potential. With respect to the current in the other drain, it is also found to be highly-polarized, with its polarization direction different from that in the other terminal. These results suggest that the protein-like single-helical molecule is a promising candidate for building the two-channel setup in spintronics.Display OmittedElectronic transport through a protein-like single-helical molecule is theoretically studied. By introducing an additional terminal to couple to the molecule, we construct a two-channel mesoscopic circuit, and then calculate the charge and spin currents in the two drain terminals. It is found that in one drain terminal, one pure spin current has an opportunity to appear without any accompanying charge current. Besides, the polarization direction of the spin current can be inverted. With respect to the current in the other drain, it is also found to be highly polarized, with its polarization direction different from that in the other terminal. These results suggest that the protein-like single-helical molecule is a promising candidate for building the two-channel setup in spintronics.
Keywords: Single-helical molecule; Electron transport; Spin polarization;
Understanding the graphene-based electric double layer from dielectric perspective: A density functional study by Ke Ma; Xuewei Wang; Yuefei Cui; Fenghuang Lin; Chun Deng; Haosen Shi (137-142).
Display OmittedWe apply density functional calculations to electrical double layer system of ionic liquids near graphene-based electrode of various layers. Dielectric screening extends deep into the inside of the electrode. Across graphene sheets, non-uniform charge distribution indicates a highly polarizable electrode. The quantum capacitance obtained from density of states functional is validated by calculating quantum capacitance from definition, i.e. dividing excess charges by corresponding potential shift. In systems of charged interface, Fermi level experiences a shift relative to Dirac point. The shift region is dominated by projected density of states on graphene with a rather invariant shape compared to pristine graphene.
Microbial reduction of graphene oxide by Azotobacter chroococcum by Youhu Chen; Yufang Niu; Tian Tian; Juan Zhang; Yuanfei Wang; Yunpeng Li; Lu-Chang Qin (143-147).
Display OmittedWe report an eco-friendly route for the reduction of graphene oxide (GO) by Azotobacter chroococcum at room temperature. Examinations using X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy indicate the formation of reduced graphene oxide (rGO) with a low degree of agglomeration. Quantitative analyses of electron diffraction data show that the produced rGO consists of single-layer sheets with a random stacking. It is suggested that the GO was reduced directly by the nitrogenase via sequential additions of electrons and protons followed by dehydration. This approach avoids the use of toxic chemical agents and also reduces the agglomeration of rGO.
Effects of Ho3+ concentration on the photoluminescence of the ZnO Up-conversion films by Danping Wang; Xiaoqi Meng; Boxu Xu; Kaishun Zou; Changjiang Zhao; Juncheng Liu (148-151).
Display OmittedThe ZnO up-conversion films were prepared by sol-gel and spin-coating methods. The results showed that ZnO remained the hexagonal wurtzite structure after rare earth ions were doped. The light transmittance of the films at near-infrared (800–1250 nm) wavelengths decreased at first and then increased, and the lowest value appeared when the concentration of Ho3+ was 7 mol%. There were two intense emission bands in the up-conversion emission spectrum, namely the 545 nm green light and the 660 nm red light. The up-conversion luminescence intensity of the films increased at first and then declined, and the maximum was at 7 mol%.
Keywords: Photoluminescence; Sol-gel; ZnO film; Ho3+ ions; Up-conversion;
Temperature induced transition from acceleration to deceleration of the diffusion of polymers by soft nanoparticles in their composite by Gui-Sheng Jiao; Hu-Jun Qian; Zhong-Yuan Lu (152-155).
Display OmittedIt is well known that the presence of nanoparticles in polymer melt can dramatically influence the dynamics of the polymers. Here from a molecular dynamics simulation study, we find that such influences can be largely temperature dependent in a polymer/single chain nanoparticle composite. At high temperature, the translational diffusion of polymers can be accelerated due to large deformability of nanoparticle surface. While when temperature decreases, nanoparticle surface deformability decreases dramatically and therefore nanoparticles can impose large excess free energy barrier on polymer diffusion. As a consequence, the diffusion of polymers at low temperature can be largely decelerated.
Keywords: Polymer/nanoparticle composite; Polymer diffusion; Soft nanoparticle; Temperature effect;
The normal modes of vibration of benzene from the trajectories of stress tensor eigenvector projection space by Ming Xing Hu; Tianlv Xu; Roya Momen; Alireza Azizi; Steven R. Kirk; Samantha Jenkins (156-161).
Display OmittedA QTAIM and Stress tensor eigenvector projection Uσ space formalism has been used to provide a detailed description of the participation of each of the bonds of the four infrared active normal modes of benzene. Analysis of the maximum Uσ space trajectory projections revealed a mixture of C―C and C―H bonding characteristics. The four infrared active Uσ space trajectories were found to be unique. The normal mode with the highest infrared intensity was the only mode with non-zero maximum Uσ space trajectory projections in the most preferred and least preferred directions for the C―C and C―H bond critical points respectively.
Microscopic diffusion of CO2 in clay nanopores by Hassan Aljama; Jennifer Wilcox (162-166).
Display OmittedNatural gas production from shale in recent years has made a significant impact on the energy sector. It also presents potential opportunities to mitigate global warming by using shale reservoirs for CO2 sequestration. We attempt to understand the microscopic impact of shale on CO2 transport. We utilize equilibrium molecular dynamics (MD) to study the diffusion behavior of CO2 in the clay part of shales. Such microscopic examination can connect micro-scale calculations to macro-scale measurements. Results show that confinement has profound effects on CO2 diffusion. The diffusion coefficient was found to be slightly anisotropic due to the nature of the clay surface.
Keywords: Molecular dynamics; Shale; Clay; Diffusion;
Brain-like manganese monoxide microspheres as anode materials for lithium ion battery by Lian Shen; Yangai Liu (167-171).
Brain-like MnO microspheres were prepared by simple precipitation method following a thermal annealing. MnO with PAN as a binder shows excellent electrochemical performance. It delivers an initial discharge specific capacity of 1332.3 mAh g−1 and an initial reversible specific capacity of 976.1 mAh g−1. It remains at 912.3 mAh g−1 after 30 cycles with a coulombic efficiency of 97.5%. Its outstanding cyclic performance is owing to the effective conductive network of cross-linked PAN that formed during the thermal treatment. The excess capacity is partially ascribed to the interfacial lithium storage between Li2O and Mn which is formed during the conversion reaction. The porous structure also offers some space for lithium storage.Display OmittedBrain-like manganese monoxide (MnO) microspheres were synthesized by simple precipitation method with subsequent heat treatment. MnO with polyacrylonitrile (PAN) as a binder delivers an initial reversible specific capacity of 976.1 mAh g−1 and it remains at 912.3 mAh g−1 after 30 cycles. The excellent cyclic performance is attributed to the effective conductive network of cross-linked PAN that formed during the thermal treatment. FTIR, ex situ XRD and XAS were performed to investigate the excess reversible capacity of MnO. The results show that the excess capacity is partially ascribed to the interfacial lithium storage between nanosized Li2O and Mn which is formed during the conversion reaction. The porous microspheres with large surface area also provide some active sites for lithium storage.
Keywords: Brain-like; MnO; PAN; Lithium ion battery;
Glass transition behavior of ternary disaccharide-ethylene glycol-water solutions by Tongxu Yu; Lishan Zhao; Qiang Wang; Zexian Cao (172-177).
Display OmittedGlass transition behavior of ternary disaccharide-ethylene glycol-water solutions, in reference to that of the binary combinations, has been investigated towards a better understanding of their cryoprotective ability. In water-deficient solutions, the disaccharides, including trehalose, sucrose and maltose, can associate with more than 100 ethylene glycol molecules to form amorphous complex, one order of magnitude larger than the corresponding hydration numbers. In water-rich solutions, a second glass transition emerges with increasing molar fraction of ethylene glycol, indicating the possible synergy of disaccharides and ethylene glycol in vitrification of the ternary aqueous solution.