Chemical Physics Letters (v.664, #C)
Editorial Board (IFC).
Harmonic spectral modulation of an optical frequency comb to control the ultracold molecules formation by Svetlana A. Malinovskaya; Gengyuan Liu (1-4).
Display OmittedA method for creation of ultracold molecules by stepwise adiabatic passage from the Feshbach state to the fundamentally ground state using an optical frequency comb is presented within a semiclassical multilevel model. The sine modulation of the spectral phase of the comb leads to the creation of a quasi-dark dressed state. An insignificant population of the excited state manifold in this dark state provides an efficient way of mitigating decoherence in the system. In contrast, the cosine modulation does not lead to the quasi-dark state formation. The results demonstrate the importance of the parity of the spectral chirp in quantum control.
Potential energy landscapes of tetragonal pyramid molecules by Yuichiro Yoshida; Hirofumi Sato; John W.R. Morgan; David J. Wales (5-9).
Display OmittedHiraoka et al. have developed a self-assembling system referred to as a nanocube (Hiraoka et al., 2008). In the present contribution a coarse-grained model for this system is analysed, focusing on how the potential energy landscape for self-assembly is related to the geometry of the building blocks. We find that six molecules assemble to form various clusters, with cubic and sheet structures the most stable. The relative stability is determined by the geometry of the building blocks.
Keywords: Self-assembly; Potential energy surface;
Micro-structuring the surface reactivity of a borosilicate glass via thermal poling by A. Lepicard; T. Cardinal; E. Fargin; F. Adamietz; V. Rodriguez; K. Richardson; M. Dussauze (10-15).
Display OmittedThermal poling was proven successful to induce second order nonlinear properties and concurrent modification of composition, structure and chemical reactivity in glasses. With current efforts to reduce devices sizes in components employing such attributes, means to control changes at the micrometer scale are needed. We present a micro-imprinting poling process to locally tailor surface properties of a glass. Measurements using infrared, Raman and second harmonic generation microscopies confirm that changes in glass structure associated with an induced static electric field are responsible for the enhanced surface reactivity that is successfully controlled at the micrometer scale.
Keywords: Thermal poling; Surface reactivity; Micro-patterning;
Self-assembly of micelles in organic solutions of lecithin and bile salt: Mesoscale computer simulation by A. Markina; V. Ivanov; P. Komarov; A. Khokhlov; S.-H. Tung (16-22).
Display OmittedWe propose a coarse-grained model for studying the effects of adding bile salt to lecithin organosols by means of computer simulation. This model allows us to reveal the mechanisms of experimentally observed increasing of viscosity upon increasing the bile salt concentration. We show that increasing the bile salt to lecithin molar ratio induces the growth of elongated micelles of ellipsoidal and cylindrical shape due to incorporation of disklike bile salt molecules. These wormlike micelles can entangle into transient network displaying perceptible viscoelastic properties.
Keywords: Mesoscale computer simulations; Biological surfactants; Self-assembly; Wormlike micelles;
Electrochemical performances of asymmetric super capacitor fabricated by one-dimensional CoMoO4 nanostructure by Yunxuan Zhao; Fei Teng; Zailun Liu; Qian Du; Jingjing Xu; Yiran Teng (23-28).
A flexible asymmetric super capacitor is fabricated by CoMoO4 nanorods.Display OmittedWe have prepared the CoMoO4 nanorods (NR) electrode with a specific capacitance (89.5 F g− 1) at a current density of 1 mA cm−2. Moreover, the asymmetric supercapacitor (ASC) has been fabricated by using CoMoO4 NR as positive electrode and activated carbon (AC) as negative electrode. At a power density of 80 mW cm−3, the ASC can deliver an energy density of 0.226 mW h cm−3 in the voltage range of 0–1.6 V. In addition, the CoMoO4 NR-based ASC device still remains a high energy density (84.07%) after 5000 cycles, demonstrating that one-dimensional nanostructures could be promising to achieve the high-energy-density materials.
Keywords: CoMoO4 nanorods; Energy density; Asymmetric supercapacitor (ASC);
Low-temperature controllable preparation of vertically standing graphene sheets on indium tin oxide glass and their field emission properties by Fei Zou; Haitao Zhou; Ning Yu; Zhaohui Yao; Fei Liu; Chengmin Shen (29-32).
Display OmittedVertically standing graphene sheets (VSGs) were successfully grown on indium tin oxide (ITO) glass through plasma enhanced chemical vapor deposition system. The lateral size of the graphene sheets was evidently affected by the growth temperature. The VSGs with smaller sheet size were obtained at 600 °C than at 500 °C. The dependence of the field-emission behavior of VSGs grown on ITO glass (VSGs/ITO) on the sheet size was investigated. The VSGs/ITO films with smaller sheet size possessed a higher field-enhancement factor and a lower turn-on field, which was proposed to be attributed to more field-emission sites and better electrical conductivity.
Keywords: CVD; Scanning electron microscopy; Glass; Electrical properties; Vertically standing graphene;
Understanding the light-emitting mechanism of an X-shape organic thermally activated delayed fluorescence molecule: First-principles study by Jianzhong Fan; Lei Cai; Lili Lin; Chuankui Wang (33-38).
Display OmittedThe light-emitting mechanism of an X-shape organic thermally activated delayed fluorescent molecule is investigated based on first-principles calculations. It is found that there are two stable configurations for the ACRSA molecule, and that the molecule with conformer A is nonluminous. Further, the excited states dynamics of conformer B is studied. The normal modes analysis of the reorganization energy indicates that the non-radiation process of the first singlet excited state (S1) mainly comes from the out-of-plane vibration with low frequencies. Besides, calculations of energy levels of excited states demonstrate that the up-conversion happens between the S1 and T1 states.
Ultrafast photophysical studies of a multicomponent sunscreen: Oxybenzone–titanium dioxide mixtures by Lewis A. Baker; Lucy C. Grosvenor; Michael N.R. Ashfold; Vasilios G. Stavros (39-43).
Display OmittedRecent studies of the sunscreen constituent oxybenzone have suggested that the dominant mechanism underlying the efficient photoprotection it offers relies on an initial ultrafast enol → keto tautomerisation, followed by nonadiabatic transfer to the ground electronic state. Subsequent collisions with the solvent bath then reform the original enol-tautomer. Utilising femtosecond transient electronic absorption spectroscopy we explore the dissipation of electronic excitation energy in oxybenzone in the presence of titanium dioxide, a widely used, and complementary sunscreen component. We find the relaxation dynamics of this popular organic filter are unaltered by the presence of this favoured inorganic scatterer and the overall dynamics can be described by the additive contribution of the individual constituents. The combination of the two components provides broadband photoprotective properties justifying the widely used organic filter and inorganic scatterer mixtures in commercial sunscreen products.
Keywords: Oxybenzone; Titanium dioxide; Sunscreens; Transient absorption spectroscopy; Ultrafast photochemistry; Solution phase;
Structural study of lysozyme in two ionic liquids at cryogenic temperature by Yukihiro Yoshimura; Takahiro Takekiyo; Takahiro Mori (44-49).
Display OmittedWe have investigated the structure and activity of chicken egg-white lysozyme in aqueous solutions of two typical ionic liquids, 1-butyl-3-methylimidazolium chloride and ethylammonium nitrate, at cryogenic temperature. An increase in structural disorder due to the unfolding and a decrease in the α-helical structure of lysozyme were noticeable upon glass formation. However, a decrease in the structural stability after cooling was less than that before cooling. The secondary and tertiary structures showed good reversibility upon cooling to 77 K and then reverting back to ambient temperature. We discussed an influence of a cooling upon the structure in aqueous ionic liquid solutions.
Keywords: Lysozyme; Higher order structure; Enzyme activity; Ionic liquids; Low temperature; Optical spectroscopy;
How to distinguish various components of the SHG signal recorded from the solid/liquid interface? by Pierre-Marie Gassin; Gaelle Martin-Gassin; Benedicte Prelot; Jerzy Zajac (50-55).
Display OmittedSecond harmonic generation (SHG) may be an important tool to probe buried solid/liquid interfaces because of its inherent surface sensitivity. A detailed interpretation of dye adsorption onto Si-SiO2 wafer is not straightforward because both adsorbent and adsorbate contribute to the overall SHG signal. The polarization resolved SHG analysis points out that the adsorbent and adsorbate contributions are out of phase by π/2 in the present system. The surface nonlinear susceptibility χ(2) represents thus a complex tensor in which its real part is related to the adsorbent contribution and its imaginary part to the adsorbate one.
Keywords: Second harmonic generation; Malachite green dye; Dyes adsorption; Molecular orientation; Solid/Liquid interface;
Excited-state symmetry breaking of linear quadrupolar chromophores: A transient absorption study by Nadia Dozova; Lionel Ventelon; Guillaume Clermont; Mireille Blanchard-Desce; Pascal Plaza (56-62).
Display OmittedThe photophysical properties of two highly symmetrical quadrupolar chromophores were studied by both steady-state and transient absorption spectroscopy. Their excited-state behavior is dominated by the solvent-induced Stokes shift of the stimulated-emission band. The origin of this shift is attributed to symmetry breaking that confers a non-vanishing dipole moment to the excited state of both compounds. This dipole moment is large and constant in DMSO, whereas symmetry breaking appears significantly slower and leading to smaller excited-state dipole in toluene. Time-dependant increase of the excited-state dipole moment induced by weak solvation is proposed to explain the results in toluene.
Cholinergic inhibitors replace thioflavin-T from acetylcholinesterase binding pocket: A potential fluorescence based molecular switch by Mullah Muhaiminul Islam; Sivaprasad Mitra (63-69).
Display OmittedThe fluorescence intensity of acetylcholinesterase (AChE) bound thioflavin-T (ThT) is found to decrease regularly in presence of cholinergic inhibitors. The quenching phenomenon is not consistent with typical Stern-Volmer mechanism and can be explained on the basis of dynamic replacement of the probe from AChE gorge into the bulk aqueous medium. The resulting modulation in steady state intensity and/or time-dependent fluorescence depolarization forms the basis of a molecular switch between ThT and inhibitors, which can be correlated with AChE inhibition activity of the drugs.
Keywords: Acetylcholinesterase (AChE) inhibitors; Thioflavin-T (ThT); Fluorescence anisotropy; Quenching; Molecular switch;
Density functional analysis of gaseous molecules adsorbed on metal ion/defective nano-sheet graphene by Jin-Pei Deng; Wen-Hua Chuang; Chin-Kuen Tai; Hsien-Chang Kao; Jiunn-Hung Pan; Bo-Cheng Wang (70-72).
Display OmittedDensity functional theory was applied to calculate the adsorption property of metal/hexa-vacancy defective graphene (denoted as HDG-M, M: Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) with O- and N-dopants. We investigate the adsorption properties of these complexes between gaseous molecules and HDG-M. Our results show that HDG-Cu has a high selectivity for O2, but HDG-Fe has a good ability to capture many gases such as CO, NO and O2. Our calculations could provide useful information for designing new graphene-based adsorbents to remove undesired gases, which may poison the metal catalysts in reaction processes.
Keywords: Defective graphene; Gas adsorption; Metal complexes;
Cr-doping effects on unoccupied d-band electronic structure of TiO2 by K. Wojtaszek; K. Tyrala; J. Czapla-Masztafiak; J. Sa; J. Szlachetko (73-76).
Display OmittedResonant X-ray emission spectroscopy (RXES) was applied to probe the electronic states above Fermi level for Cr-doped anatase TiO2. The results reveal doping-induced electronic band on low energy side of unoccupied electronic states. The experimental RXES data in combination with theoretical simulations allowed distinguishing electronic state changes on both, d-localized and d-delocalized orbitals of Cr-doped anatase TiO2. The detailed information on unoccupied electronic states is crucial in order to correlate enhanced light absorption properties with catalytic activity of the material.
Temperature effects in static and dynamic polarizabilities from distinct generalized gradient approximation exchange-correlation functionals by Javier Carmona-Espíndola; José L. Gázquez; Alberto Vela; S.B. Trickey (77-82).
Display OmittedTo demonstrate that there are specific temperature effects in the description of static and dynamic polarizabilities which arise from generalized gradient approximation exchange-correlation functionals that obey distinctive asymptotic constraints, we present calculations for a test set of small molecules, at the experimental geometry, at the optimized ground-state geometry, and at the Born-Oppenheimer molecular dynamics geometries that arise from simulating a temperature of 300 K. The results indicate that a functional with the correct asymptotic potential (CAP) provides a better description at room temperature than does a GGA functional with an exponentially decaying exchange potential such as PBE.
Keywords: Density functional theory; Exchange-correlation functional; Exchange potential asymptotic behavior; Polarizabilities; Hyperpolarizabilities; Molecular dynamics;
Productivity and order versus the superficial behavior of the prox reaction on a copper-ceria catalyst Monte Carlo simulations by Joaquín Cortés; Eliana Valencia; Paulo Araya (83-88).
The graphs show an example of reaction order in the case of CO for the production of CO2 that correlates with the competition between the superficial CO and H species during the catalytic process. (a) CO2 production as a function of CCO with fixed H2 and O2 concentrations CH2 = 0.5, CO2 = 0.005 at 515 K; 15% Cu (○); 100% Cu (●). (b) Surface coverage θi as a function of CO concentration, CCO, for the same temperature, CH2, and CO2 as in (a) and 15% Cu θCuCO (□) θCuH (■).Display OmittedMonte Carlo simulations for the productivity and order of the PROX/copper-ceria catalyst reaction with different superficial %Cu are made. The results are correlated with the behavior of the different surface species (CO, H, O, OH, vacancies) during the process. Among other results, an inversion is seen of the production of CO2 with respect to that of H2O with the increase of %Cu, a positive order for CO2 with at low CCO, and with CO2 if it is low, a positive order for H2O with CO2 only if %Cu is high, and zero order with CH2 in all cases.
Keywords: Monte Carlo simulations; PROX reaction; Copper-ceria catalyst;
Thermosensitive polymer-modified gold nanoparticles with sensitive fluorescent properties by Chunhua Luo; Qiujing Dong; Meijuan Qian; Hong Zhang (89-95).
Display OmittedTwo types of thermosensitive polymer-modified gold nanoparticles (GNPs), P(DMAM-co-MADMAC)-modified GNPs (GNPs@PDM) and P(NIPAM-co-MADMAC)-modified GNPs (GNPs@PNM), are fabricated by the “grafting through” polymerization technique. The as-prepared GNPs are characterized by UV–vis, TEM, XPS, TGA, FT-IR and 1H NMR spectroscopy. The thermosensitivity and fluorescence of the GNPs are investigated. It is found that all GNPs aqueous solutions but GNPs@PDM1 exhibit thermosensitivity originated from thermosensitive polymer chains and sensitive fluorescence from the dimethylaminochalcone group. The lower critical solution temperature (LCST) of the GNPs decreases with the increasing content of MADMAC unit in the GNPs. The GNPs aqueous solution shows weak fluorescence after the temperature increases from 25 °C to 45 °C, or after β-cyclodextrin (β-CD) is added. Furthermore, it exhibits strong fluorescence when the solvent is changed to ethanol or chloroform, and the fluorescent wavelength undergoes a blue shift from ethanol to chloroform.
Keywords: Gold nanoparticles; Thermosensitive polymers; Sensitive fluorescence;
(10, 10) Single walled carbon nanotube consisted of chemisorbed oxygen atoms as a promising supercapacitor electrode material: A first principles study by Ehsan Targholi; Masoumeh Molaei; S. Morteza Mousavi-Khoshdel (96-100).
Display OmittedThe effects of atomic oxygen chemisorption on the electronic structures and quantum capacitance of (10, 10) CNT have been studied in this article. The results indicated that the chemisorption on bonds aligned with nanotube axis is more favorable than other position. The most efficient configuration for enhancing quantum capacitance is the nanotube with oxygen atoms chemisorbed on axial bonds. Specifically, in water stability range, the quantum capacitance of (10, 10) CNT before and after chemisorption of six oxygen atoms (aligned with nanotube axis) were found to be 222.6 (anode) −117.6 (cathode) and 306.9 (anode) −217.2 (cathode) F/g, respectively.
Keywords: Quantum capacitance; Supercapacitors; Chemisorption; Ab-initio study;
Theoretical analysis of structural diversity of covalent organic framework: Stacking isomer structures thermodynamics and kinetics by Taku Hayashi; Yuh Hijikata; Alister Page; Donglin Jiang; Stephan Irle (101-107).
Display OmittedCovalent organic frameworks (COFs) have attracted much interest due to their utility as functional materials. Unfortunately, experimental synthesis struggles with low single crystallinity of COFs. We have theoretically investigated isomer structures of a representative two-dimensional COF for both monolayer and three-dimensional stacking orders. We show that rotations of p-phenylene rings are common in monolayers, however, affect the global stacking order substantially. We also discuss the discrepancy between powder X-ray diffraction patterns corresponding to the structures predicted by our calculations and those experimentally observed. The discrepancy demonstrates the importance of dynamics in the self-assembly process of COF organic components.
Protein dynamics and thermodynamics crossover at 10 °C: Different roles of hydration at hydrophilic and hydrophobic groups by Yuan Chong; Alfred Kleinhammes; Yue Wu (108-113).
Display OmittedWater at hydrophilic and hydrophobic groups interact differently with proteins. Particularly, hydration properties at hydrophobic groups undergo qualitative changes as temperature decreases below 10 °C. The influence of such interfacial changes on protein dynamics and thermodynamics remains largely unexplored. Here, nanosecond to microsecond protein dynamics and the free energy, enthalpy, and entropy of protein hydration are investigated by in-situ NMR as a function of hydration level and temperature. A crossover at 10 °C in protein dynamics and thermodynamics is revealed. The influence of water at hydrophilic groups shows little temperature dependence, whereas water at hydrophobic groups has stronger effect above 10 °C.
Keywords: Protein hydration; Hydrophilic and hydrophobic groups; Temperature effect; In-situ NMR; Protein dynamics and thermodynamics;
Path integral centroid molecular dynamics simulation of para-hydrogen sandwiched by graphene sheets by Yuki Minamino; Kenichi Kinugawa (114-119).
Path integral centroid molecular dynamics simulations were carried out to reveal static and dynamic properties of para-hydrogen molecules sandwiched by two graphene sheets at 17 K. A characteristic mode of 140 cm−1 arising from perpendicular motion of the molecules adsorbed onto the graphene sheets was found out for liquid-like para- hydrogen in sandwiched interstice.Display OmittedThe carbon-hydrogen composite systems of para-hydrogen (p-H2) sandwiched by a couple of graphene sheets have been investigated by means of path integral centroid molecular dynamics simulations at 17 K. It has been shown that sandwiched hydrogen is liquid-like but p-H2 molecules are preferably adsorbed onto the graphene sheets because of attractive graphene-hydrogen interaction. The diffusion coefficient of p-H2 molecules in the direction parallel to the graphene sheets is comparable to that in pure liquid p-H2. There exists a characteristic mode of 140 cm−1 of the p-H2 molecules, attributed to adsorption-binding motion perpendicular to the graphene sheets.
Keywords: Para-hydrogen; Graphene; Graphite; Adsorption; Physisorption; Path integral centroid molecular dynamics; Quantum dynamics;
Computing the position-spread tensor in the CAS-SCF formalism II: Spin partition by Ahmad W. Huran; Thierry Leininger; Gian Luigi Bendazzoli; Stefano Evangelisti (120-126).
Display OmittedThe Spin-Partitioned (SP) Total Position-Spread (TPS) tensor provides finer insights that supplement the information conveyed in the Spin-Summed (SS) TPS. The calculation of the SP-TPS has been implemented in the MOLPRO code for CAS-SCF wavefunctions allowing the study of electron (de) localization in relatively large molecular systems where the FCI treatment is rather unfeasible. An illustrative example considering one-dimensional Be wires is given as an application of the formalism.
Keywords: Electrons (de)localization; Localization tensor; Total position-spread; Spin partitioned TPS; CAS-SCF; MOLPRO;
Post-oxidation treated graphene quantum dots as a fluorescent probe for sensitive detection of copper ions by Yan Li; Xinqian Liu; Qiyao Li; Juan Ge; Hui Liu; Sen Li; Lifeng Wang; Jun Wang; Ning Ma (127-132).
Display OmittedGraphene quantum dots (GQDs) have been an ideal probe for copper ions detection due to its excellent optical properties, low toxicity and biocompatibility. However, most of GQDs prepared by present methods have low oxidation degree, which could hinder the complexation between copper ions and oxygen functional groups on the surface of GQDs. Therefore, we proposed a universal, mild and in situ post-treated approach for modifying GQDs obtained by any methods, which will increase the oxidation degree of GQDs without any other affect and its influence on the responsivity of copper ions.
Keywords: Graphene quantum dots; Post-oxidation treatment; Fluorescent sensor; Copper ions detection;
Optimal experiment design: Link between the concentration and the accuracy of estimation of aggregation parameters by Vladislav P. Evstigneev; Irina S. Pashkova; Viktor V. Kostjukov; Adrian A. Hernandez Santiago; Maxim P. Evstigneev (133-137).
Display OmittedThe principal condition for optimal experiment design, required for getting reasonable error for equilibrium aggregation constant, K, determination is obtained. This condition states that the selected concentration range for performing titration experiment should be inversely proportional to the expected value of K. As a consequence, the choice of physico-chemical methods for determination of aggregation parameters must obey this condition.
Keywords: Aggregation; Linear polymerization; Indefinite aggregation model; Experiment design;
Characterization of the [18.42]0+ – X 1Σ+ (0, 0) band of tantalum nitride, TaN by Timothy Steimle; Damian L. Kokkin; Yongrak Kim; Richard J. Mawhorter; Colan Linton (138-142).
Display OmittedHigh resolution laser-induced fluorescence (LIF) spectra of the [18.42]0+ − X 1Σ+ (0, 0) band of tantalum nitride, TaN, near 543 nm, have been recorded and analyzed field-free and in the presence of a static electric field. The nuclear electric quadrupole hyperfine structure due to 181Ta(I = 7/2) was resolved and analysis of the field-free spectrum yielded nuclear electric quadrupole coupling constants, eQq 0, of −0.24025(75) cm−1 and −0.05755(76) cm−1 for the X 1Σ+ and [18.42]0+ states, respectively. The Stark tuning of the R(0) and P(1) lines was analyzed to determine the magnitude of the molecular frame electric dipole moments, | μ → el | , of 3.33(4) D and 4.48(3) D for the X 1Σ+ and [18.42]0+ states, respectively. The | μ → el | and eQq 0 values are discussed in terms of predicted molecular orbitals for the X 1Σ+ and [18.42]0+ states.
Excess electron states in fluid methane: Density-functional versus Lanczos approaches by Fernan Saiz; Nick Quirke; Leonardo Bernasconi; David Cubero (143-148).
Display OmittedWe compare density-functional theory (DFT) electronic structure calculations at the hybrid B3LYP level for fluid methane with experiments and a pseudo-potential Lanczos method. We generate fluid configurations from classical/ab initio molecular dynamics and use DFT to determine one-particle orbital and total energies. Our results show that DFT predicts excess electron energies that qualitatively agree with experiments over a density range, provided these values are determined from total energy differences between charged and neutral systems. By contrast, orbital energies of the lowest unoccupied state of the N-electron system provide qualitatively incorrect excess electron energies as a function of the fluid density.
First-principle based modeling of urea decomposition kinetics in aqueous solutions by André Nicolle; Stefania Cagnina; Theodorus de Bruin (149-153).
Display OmittedThis study aims at validating a multi-scale modeling methodology based on an implicit solvent model for urea thermal decomposition pathways in aqueous solutions. The influence of the number of cooperative water molecules on kinetics was highlighted. The obtained kinetic model is able to accurately reproduce urea decomposition in aqueous phase under a variety of experimental conditions from different research groups. The model also highlights the competition between HNCO desorption to gas phase and hydrolysis in aqueous phase, which may influence SCR depollution process operation.
Keywords: Urea; Decomposition; Multiscale modeling; Kinetics; Ab initio; Water cooperation;
Utilization of surface Plasmon resonance band of silver nanoparticles for determination of critical micelle concentration of cationic surfactants by Jamil K. Salem; Issa M. El-Nahhal; Bassam A. Najri; Talaat M. Hammad (154-158).
Display OmittedWe have utilized surface Plasmon resonance (SPR) band sensitivity to surfactant concentration to investigate the critical micelle concentration (cmc) of CTAB, HY and CPB. The process is based upon an in situ formation of silver nanoparticles (AgNPs) through the reduction of silver ions (Ag+) by diethylene triamine (DETA) at 25 °C. In the presence of cationic surfactants, Ag+ ions can be reduced to AgNPs in a few minutes, accompanied by changes in intensity and wavelength of the SPR band. The spectral shifts of SPR band and the change of color have been used to determine CMC values of cationic surfactants.
Keywords: Silver nanoparticles; Cationic surfactants; Critical micelle concentration; Surface Plasmon resonance; Colorimetric;
Breakdown of 1D water wires inside charged carbon nanotubes by Shashank Pant (159-166).
Display OmittedUsing molecular dynamics approach we investigated the structure and dynamics of water confined inside pristine and charged 6,6 carbon nanotubes (CNTs). This study reports the breakdown of 1D water wires and the emergence of triangular faced water on incorporating charges in 6,6 CNTs. Incorporation of charges results in high potential barriers to flipping of water molecules due to the formation of large number of hydrogen bonds. The PMF analyses show the presence of ∼2 kcal/mol barrier for the movement of water inside pristine CNT and almost negligible barrier in charged CNTs.
Highly efficient visible-light photocatalytic performance based on novel AgI/g-C3N4 composite photocatalysts by Chunsheng Lei; Meng Pi; Xiaofeng Zhu; Pengfei Xia; Yingqing Guo; Fenge Zhang (167-172).
Display OmittedA novel AgI/g-C3N4 composite photocatalysts with enhanced visible-light photocatalytic pollutants degradation activity were synthesized by a facile ultrasonication-precipitation method. The composite photocatalysts were characterized by XRD, FESEM, FTIR, XPS, DRS and basic test. The results proved that the AgI/g-C3N4 composite photocatalysts exhibit excellent photocatalytic performance and favorable stability towards Methylene blue (MB) degradation in aqueous solution under visible light (λ > 420 nm). Approximately 97.5% of MB was degraded after 1 h of irradiation using the best catalyst. Superior stability was also achieved in the cyclic runs, indicating that the as-prepared composite photocatalyst has potential application for treatment of organic-dye-contaminated wastewaters.
Keywords: Pohotocatalysis; AgI/g-C3N4; Ultrasonication-precipitation; Methylene blue; Degradation;
Proton impact charge transfer on hydantoin – Prebiotic implications by Marie-Christine Bacchus-Montabonel (173-177).
Display OmittedFormation and destruction of prebiotic compounds in astrophysical environments is a major issue in reactions concerning the origin of life. Detection of hydantoin in laboratory irradiation of interstellar ice analogues has confirmed evidence of this prebiotic compound and its stability to UV radiation or collisions may be crucial. Considering the different astrophysical environments, we have investigated theoretically proton-induced collisions with hydantoin in a wide energy range, from eV in the interstellar medium, up to keV for processes involving solar wind or supernovae shock-waves protons. Results are compared to previous investigations and qualitative trends on damage under spatial radiations are suggested.
Keywords: Hydantoin; Prebiotic compounds; Charge transfer processes; Ion-biomolecule collisions; Ab-initio molecular calculations;
Coloration of tyrosine by organic-semiconductor interfacial charge-transfer transitions by Jun-ichi Fujisawa; Natsumi Kikuchi; Minoru Hanaya (178-183).
Display OmittedL-tyrosine (Tyr) plays a crucial role as a proteinogenic amino acid and also as a precursor to several neurotransmitters and hormones. Here we demonstrate coloration of Tyr based on organic-semiconductor interfacial charge-transfer (ICT) transitions. The ICT transitions from Tyr to TiO2 are induced by the chemisorption of Tyr on TiO2 surfaces via the hydroxy group of the phenol moiety. Because other amino acids possess no chemical group to induce ICT transitions, this coloration method enables to detect Tyr selectively without drastic structural change in contrast to the conventional coloration methods.
High-temperature unimolecular decomposition of ethyl propionate by Binod Raj Giri; Mohammed AlAbbad; Aamir Farooq (184-190).
Display OmittedThis work reports rate coefficients of the thermal unimolecular decomposition reaction of ethyl propionate (EP) behind reflected shock waves over the temperature range of 976–1300 K and pressures of 825–1875 Torr. The reaction progress was monitored by detecting C2H4 near 10.532 μm using CO2 gas laser absorption. In addition, G3//MP2/aug-cc-pVDZ and master equation calculations were performed to assess the pressure- and temperature-dependence of the reaction. Our calculations revealed that C2H4 elimination occurs via a six-centered retro-ene transition state. Our measured rate data are close to the high-pressure limit and showed no discernable temperature fall off.
Keywords: Ethyl propionate; Shock tube; Unimolecular decomposition; Retro-ene elimination;
Parallel implementation of approximate atomistic models of the AMOEBA polarizable model by Omar Demerdash; Teresa Head-Gordon (191-198).
Display OmittedIn this work we present a replicated data hybrid OpenMP/MPI implementation of a hierarchical progression of approximate classical polarizable models that yields speedups of up to ∼10 compared to the standard OpenMP implementation of the exact parent AMOEBA polarizable model. In addition, our parallel implementation exhibits reasonable weak and strong scaling. The resulting parallel software will prove useful for those who are interested in how molecular properties converge in the condensed phase with respect to the MBE, it provides a fruitful test bed for exploring different electrostatic embedding schemes, and offers an interesting possibility for future exascale computing paradigms.
Free energy of adsorption of supported lipid bilayers from molecular dynamics simulation by M. Schneemilch; N. Quirke (199-204).
Display OmittedA novel method is presented for the calculation of adhesion energies of lipid bilayers on solid surfaces from molecular dynamics simulation. We illustrate the method with a fully atomistic model comprising a gold surface and an adsorbed lipid bilayer. We use our technique to scale the lipid-surface interactions to reproduce the experimental value for adsorption of DMPC bilayers on gold surfaces. Finally we estimate the entropic contribution to the free energy change on adsorption of the bilayer.
Night-time atmospheric degradation of a series of butyl methacrylates by Mariano A. Teruel; Rocío S. Pérez López; Ian Barnes; María B. Blanco (205-212).
Display OmittedRate coefficients for the reactions of NO3 with n-butyl methacrylate (k1), iso-butyl methacrylate (k2) and tert-butyl methacrylate (k3) have been determined at 298 K and atmospheric pressure using the relative rate method. The following rate coefficients (×10−15 cm3 molecule−1 s−1) were obtained for the first time: k1 = (5.5 ± 2.6), k2 = (5.8 ± 2.8) and k3 = (5.6 ± 2.5).The NO3 reactions of these compounds could contribute to the removal of NOx and as NOy reservoirs. The potential importance for the tropospheric nitrogen budget of these reactions is discussed and atmospheric lifetimes for the butyl esters are calculated.
Keywords: n-Butyl methacrylate; iso-Butyl methacrylate; tert-Butyl methacrylate; NO3 radicals; Rate coefficients; Mechanisms; Tropospheric chemistry;
Changing electrical properties of PEDOT:PSS by incorporating with dimethyl sulfoxide by Yow-Jon Lin; Jhe-You Lee; Shang-Min Chen (213-218).
Display OmittedThe effect of incorporation of dimethyl sulfoxide (DMSO) into poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on the electrical conductivity is investigated. It is shown that the values of the carrier mobility and the carrier density increase significantly for PEDOT:PSS films with DMSO addition. The high carrier mobility of PEDOT:PSS samples with the addition of DMSO is attributed to a combined effect of the modification of the electron-phonon coupling and a change in the value of the PSS-to-PEDOT ratio. The high carrier density of PEDOT:PSS samples with DMSO addition is attributed to a high affinity of DMSO for water.
Keywords: Thin films; Polymer; Electrical properties; Carrier mobility;
Facile synthesis of size tunable Fe3O4 nanoparticles in bisolvent system by Zhuanzhuan Huang; Kelu Wu; Qiao-He Yu; Yi-Yan Wang; Jiayi Xing; Tian-Long Xia (219-225).
Display OmittedMagnetic nanoparticle clusters with magnetization of about 80 emu/g and tunable size between 55 and 500 nm were synthesized through a bisolvent solvothermal process in the presence of ethylene glycol (EG) and diethylene glycol (DEG), triethylene glycol (TEG) or 1,2-propanediol (PG) with polyethylene glycol (PEG) or hexadecyltrimethyl ammonium bromide (CTAB) as surfactant. It was found that the volume ratio of EG to the other polyol played an important role in controlling the size and morphology of Fe3O4. Effect of the concentration of Ferric chloride hexahydrate (FeCl3·6H2O) and original reactants on controlling the size of Fe3O4 particles was also discussed.
Keywords: Fe3O4 cluster; Binary solvent; Magnetic materials; X-ray diffraction; SEM;
Analytic method for sputtering yield calculation in nanoislands by J.C. Jiménez-Sáez; A.M.C. Pérez-Martín; J.J. Jiménez-Rodríguez (226-232).
Display OmittedA theoretical approach based on the well-known work of Sigmund to explain the sputtering of surfaces covered with nanoclusters is developed. Predictions of this approach are compared with molecular dynamics results of bombardment of a periodical array of Co nanoislands deposited on a Cu(0 0 1) substrate with 1-keV argon ions. Sputtering yield is analyzed distinguishing among particles leaving the target across the nanoisland surface and across the flat substrate surface without nanoparticle above, and the sum of both. Results consider the dependence on two factors: the spacing among nanoislands and the nanoisland height.
Keywords: Sputtering; Nanoislands; Ion bombardment;
Site-specific recoil-induced effects on inner-shell photoionization of linear triatomic molecules: N 1 s photoelectron spectra of N 2 O by Yu.S. Krivosenko; A.A. Pavlychev (233-236).
Display OmittedWe investigate hard X-ray ionization of linear triatomic molecules accenting recoil-induced effects on the dynamics of molecular frame. This dynamics is studied within the two-springs and harmonic approximations. The mode-channel relationship connecting the excitations of vibrational, rotational and translational degrees of freedom with the Σ → Σ and Σ → Π photoionization channels is applied to compute the N 1 s - 1 photoelectron spectra of molecular N 2 O for various photon energies. The distinct ionized-site- and molecular-orientation-specific changes in the vibration structure of the 1 s photoelectron lines of terminal and central nitrogen atoms are revealed and discussed.
Keywords: HAXPES; Photoelectron-induced recoil; Small molecules; Inner-shell photoionization dynamics; N 2 O ;
Synchrotron threshold photoelectron photoion coincidence spectroscopy of radicals produced in a pyrolysis source: The methyl radical by Yupeng Zhu; Xiangkun Wu; Xiaofeng Tang; Zuoying Wen; Fuyi Liu; Xiaoguo Zhou; Weijun Zhang (237-241).
Display OmittedWe present here a flash pyrolysis source coupled with a threshold photoelectron photoion coincidence (TPEPICO) spectrometer and vacuum ultraviolet synchrotron radiation to investigate the spectroscopy and photochemistry of free radicals. The radicals are produced from pyrolysis in a heated silicon carbide tube, and the TPEPICO scheme provides a strategy to obtain pure spectra of the radicals without contamination from other byproducts. As a representative example, the methyl radical was studied, and its threshold photoelectron spectrum shows a series of umbrella vibrational transitions. The adiabatic ionization energy of the methyl radical was determined to be 9.84 ± 0.01 eV.
Keywords: Methyl radical; Flash pyrolysis; Threshold photoelectron spectroscopy; PEPICO; Vacuum ultraviolet; Photoionization;
Displacement of Cl substituent in chlorofluorotoluene in corona discharge by Sang Youl Chae; Manho Lim; Sang Kuk Lee (242-245).
Display OmittedThe precursor 2-chloro-6-fluorotoluene can produce the 2-chloro-6-fluorobenzyl radical in corona discharge, together with the 2-fluorobenzyl radical which could be generated by the displacement of Cl with H of methyl group. In order to identify the reaction mechanism, two precursors, 2-chloro-6-fluorotoluene and 2-chloro-6-fluorobenzyl chloride were employed to observe the vibronic emission spectra from the corona discharge with a large amount of inert carrier gas He. By comparing the spectra observed, we are able to propose the displacement mechanism of Cl, in which methyl group is believed to play an important role in the process, which is discussed in terms of bond dissociation energies.
Keywords: Displacement mechanism; Spectroscopy; Corona discharge; 2-Chloro-6-fluorobenzyl radical; 2-Chloro-6-fluorotoluene; Bond dissociation energy;