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  • 更新日期:2018-07-20
  • Xeno Nucleic Acid Nanosensors for Enhanced Stability Against Ion-Induced Perturbations
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Alice J. Gillen, Justyna Kupis-Rozmysłowicz, Carlo Gigli, Nils Schuergers, Ardemis A. Boghossian
    更新日期:2018-07-20
  • Machine Learnt Coarse-Grained Models
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Karteek K. Bejagam, Samrendra Kumar Singh, Yaxin An, Sanket A Deshmukh

    Optimizing force-field (FF) parameters to perform molecular dynamics (MD) simulations is a challenging and time-consuming process. Here, we present a novel force-field (FF) optimization framework that integrates MD simulations with particle swarm optimization (PSO) algorithm and artificial neural network (ANN). This new ANN-assisted-PSO framework was used to develop transferable coarse-grained (CG) models for D2O and DMF, as a proof of concept. The PSO algorithm was used to generate the set of input FF parameters for the MD simulations of the CG models of these solvents, which were optimized to reproduce their experimental properties. Herein, for the first time, a reverse approach was employed for on-the-fly training of the ANN model where results (solvent properties) obtained from the MD simulations and their corresponding FF parameters were used as inputs and outputs, respectively. The ANN model was then required to predict a set of new FF parameters, which were tested for their ability to predict the desired experimental properties. This new framework can be extended to integrate any optimization algorithm with ANN and MD simulations to accelerate the FF development.

    更新日期:2018-07-20
  • Multiple Interacting Collective Modes and Phonon Gap in Phospholipid Membranes
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Giovanna D'Angelo, Valeria Conti Nibali, Ulderico Wanderlingh, Caterina Branca, Alessio De Francesco, Francesco Sacchetti, Caterina Petrillo, Alessandro Paciaroni

    We combine Brillouin neutron scattering measurements with recent Inelastic X-ray Scattering1 to propose a model for the collective dynamics of phospholipid bilayers. Neutron and X-ray spectra were tted by the model response function associated to the Hamiltonian of an interacting-phonon system. This approach allows for a comprehensive and unprecedented picture of the vibrational collective features of phospholipids. At low wavevectors Q, the dispersion relations can be interpreted in term of two acoustic-like modes, one longitudinal and one transverse, plus a dispersionless optic-like mode. The transverse mode of the liquid phase shows a phonon gap that can be linked to a passive transport mechanism through membranes, an interpretation that was proposed in Ref.1. At higher Qs, the interaction of the longitudinal acoustic excitation with the dispersionless mode gives rise to a pattern that is consistent with avoided-crossing behavior. Evidence is found for a slow- to fast-sound transition,similarly to bulk water and other biomolecules

    更新日期:2018-07-20
  • Fully Atomistic Real-Time Simulations of Transient Absorption Spectroscopy
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Franco P. Bonafé, Federico J Hernandez, Bálint Aradi, Thomas Frauenheim, Cristian G. Sanchez

    We have implemented an electron-nuclear real-time propagation scheme for the calculation of transient absorption spectra. When this technique is applied to the study of ultrafast dynamics of Soret-excited zinc(II)-tetraphenylporphyrin in the sub-picosecond time scale, quantum beats in the transient absorption caused by impulsively excited molecular vibrations are observed. The launching mechanism of such vibrations can be regarded as a displacive excitation of the zinc-pyrrole and pyrrole C-C bonds.

    更新日期:2018-07-20
  • Spin-Unrestricted Self-Energy Embedding Theory
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Lan Nguyen Tran, Sergei Iskakov, Dominika Zgid

    We present a new theoretical approach, unrestricted self-energy embedding theory (USEET) that is a Green’s function embedding theory used to study problems in which an open, em- bedded system exchanges electrons with the environment. USEET has a high potential to be used in studies of strongly correlated systems with an odd number of electrons and open shell systems such as transition metal complexes important in inorganic chemistry. In this paper, we show that USEET results agree very well with common quantum chemistry methods while avoiding typical bottlenecks present in these methods.

    更新日期:2018-07-20
  • Identification and Self-Reaction Kinetics of Criegee Intermediates syn-CH3CHOO and CH2OO via High-Resolution Infrared Spectra with a Quantum-Cascade Laser
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Pei-Ling Luo, Yasuki Endo, Yuan-Pern Lee

    The Criegee intermediates, carbonyl oxides produced in ozonolysis of unsaturated hydrocarbons, play important roles in atmospheric chemistry. The two conformers of CH3CHOO exhibit distinct reactivity toward several atmospheric species, but a distinct conformer-specific probe is challenging because ultraviolet and infrared absorption bands of syn- and anti-CH3CHOO overlap at low-resolution. Employing a quantum-cascade laser and a Herriott cell, we recorded the O−O stretching bands of CH2OO and syn-CH3CHOO in region 880−932 cm−1 at resolution 0.0015 cm−1. In addition to completely resolved vibration-rotational lines of CH2OO extending over 50 cm−1, some spectral lines associated with hot bands are identified. Spectral lines solely due to syn-CH3CHOO were also observedidentified. Probing these lines, we determined the rate coefficient for the self-reaction of syn-CH3CHOO to be kself = [1.6(+0.5/−0.6)]×10−10 cm3 molecule−1 s−1, about twice that of CH2OO. The effect of the self-reaction of CH3CHOO should be considered in kinetic measurements.

    更新日期:2018-07-20
  • Conformational Free Energy Changes via an Alchemical Path without Reaction Coordinates
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Peng He, Bin W. Zhang, Shima Arasteh, Lingle Wang, Robert Abel, Ronald M. Levy

    We introduce a novel method called Restrain - Free Energy Perturbation - Release (R-FEP-R) to estimate conformational free energy changes via an alchemical path, which for some conformational landscapes like those associated with cellular signaling proteins in the kinase family is more direct and readily converged than the corresponding free energy changes along the physical path. The R-FEP-R method was developed from the dual topology free energy perturbation method that is widely applied to estimate the binding free energy difference between two ligands. In R-FEP-R, the free energy change between two conformational basins is calculated by free energy perturbations that remove those atoms involved in the conformational change from their initial conformational basin while simultaneously growing them back according to the final conformational basin. Both the initial and final dual topology states are unphysical, but they are designed in a way such that the unphysical contributions to the initial and final partition functions cancel. Compared with other advanced sampling algorithms such as Umbrella Sampling and Metadynamics, the R-FEP-R method does not require pre-determined transition pathways or reaction coordinates that connect the two conformational states. As a first illustration, the R-FEP-R method was applied to calculate the free energy change between conformational basins for alanine dipeptide in solution and for a sidechain in the binding pocket of T4 lysozyme. The results obtained by R-FEP-R agree with the benchmarks very well.

    更新日期:2018-07-20
  • Low q Bicelles are Mixed Micelles
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Tracy Caldwell, Svetlana Baoukina, Ashton T. Brock, Ryan C Oliver, Kyle T. Root, Joanna K. Kreuger, Kerney Jebrell Glover, D. Peter Tieleman, Linda Columbus

    Bicelles are used in many membrane protein studies as they are thought to be more bilayer-like than micelles. We investigated the properties of “isotropic” bi- celles by SANS, SAXS, fluorescence anisotropy, and MD. All data suggest that bicelles with a q-value below 1 deviate from the classic bicelle which contains lipids in the core and detergent in the rim. Thus, not all isotropic bicelles are bilayer-like.

    更新日期:2018-07-20
  • Carbon Nanotubes and Graphene Promote Pyrolysis of Free-Base Phthalocyanine
    J. Phys. Chem. Lett. (IF 8.709) Pub Date : 2018-07-19
    Vladimir A. Basiuk, Lina M. Bolivar-Pineda, Victor Meza-Laguna, Elena V. Rybak-Akimova, Elena Golovataya

    Unsubstituted phthalocyanines (both free-base, H2Pc, and many of its metal complexes) are among the most stable organic compounds. They can sublime without decomposition under reduced pressure and temperatures of up to 550 °C. This property was previously employed to design a novel approach to noncovalent functionalization of pristine single-walled carbon nanotubes (SWNTs) with 3d metal(II) phthalocyanine complexes. However, when we attempted to use the same sublimation protocol to prepare a SWNTs–H2Pc hybrid, an unexpected side effect of partial H2Pc pyrolysis was detected, phthalonitrile being a main decomposition product, under the conditions when H2Pc is supposed to be totally stable. By using density functional theory calculations, we offer an explanation for the thermal behavior of H2Pc based on its covalent attachment to the pentagonal-ring topological defects, which are very common in all graphene-derived carbon nanomaterials and capable of reacting with amines via nucleophilic addition process.

    更新日期:2018-07-20
  • 更新日期:2018-07-20
  • 更新日期:2018-07-20
  • Contact Line Pinning Effects Influence Determination of the Line Tension of Droplets Adsorbed on Substrates
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Hongguang Zhang, Shan Chen, Zhenjiang Guo, Yawei Liu, Fernando Bresme, Xianren Zhang
    更新日期:2018-07-20
  • Predicted Binary Compounds of Tin and Sulfur
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Vu Ngoc Tuoc, Tran Doan Huan
    更新日期:2018-07-20
  • Role of Electrochemical Surface Potential and Irradiation on Garnet-Type Almandine’s Dissolution Kinetics
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Yi-Hsuan Hsiao, Erika Callagon La Plante, N. M. Anoop Krishnan, Howard A. Dobbs, Yann Le Pape, Narayanan Neithalath, Mathieu Bauchy, Jacob Israelachvili, Gaurav Sant
    更新日期:2018-07-20
  • 更新日期:2018-07-20
  • 更新日期:2018-07-20
  • 更新日期:2018-07-20
  • Highly Efficient Mass Production of Boron Nitride Nanosheets via a Borate Nitridation Method
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Taotao Li, Chaowei Li, Yongqing Cai, Junhao Lin, Xiaoyang Long, Liangjie Wang, Yancui Xu, Juan Sun, Lei Tang, Yong-Wei Zhang, Kazu Suenaga, Zheng Liu, Yagang Yao
    更新日期:2018-07-20
  • Computational Design of Two-Dimensional Perovskites with Functional Organic Cations
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Sudeep Maheshwari, Tom J. Savenije, Nicolas Renaud, Ferdinand C. Grozema
    更新日期:2018-07-20
  • Direct Visualization of Oxygen Reaction with Paired Hydroxyl on TiO2(110) Surface at 78 K by Atomic Force Microscopy
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Huan Fei Wen, Quanzhen Zhang, Yuuki Adachi, Masato Miyazaki, Yoshitaka Naitoh, Yan Jun Li, Yasuhiro Sugawara
    更新日期:2018-07-20
  • Thin Film Texture and Optical Properties of Donor:Acceptor Complexes. Diindenoperylene:F6TCNNQ vs Alpha-Sexithiophene:F6TCNNQ
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Giuliano Duva, Linus Pithan, Clemens Zeiser, Berthold Reisz, Johannes Dieterle, Bernd Hofferberth, Paul Beyer, Laura Bogula, Andreas Opitz, Stefan Kowarik, Alexander Hinderhofer, Alexander Gerlach, Frank Schreiber

    In this work two novel donor:acceptor (D:A) complexes, namely diindenoperylene(DIP):1,3,4,5,7,8-hexafluoro-tetracyanonaphthoquinodimethane(F6TCNNQ) and alpha-sexithiophene(6T):F6TCNNQ, are studied. The D:A complexes segregate in form of π-π stacked D:A co-crystals and can be observed by X-ray scattering. The different conformational degrees of freedom of the donor molecules, respectively, seem to affect the thin film crystalline texture and composition of the D:A mixtures significantly. In equimolar mixtures, for DIP:F6TCNNQ the crystallites are mostly uniaxially oriented and homogeneous, whereas for 6T:F6TCNNQ a mostly 3D (isotropic) orientation of the crystallites and coexistence of domains of pristine compounds and D:A complex, respectively, are observed. Using optical absorption spectroscopy we observe for each of the two mixed systems a set of new, strong transitions located in the near-IR range below the gap of the pristine compounds: such transitions are related to charge-transfer (CT) interactions between donor and acceptor. The optical anisotropy of domains of the D:A complexes with associated new electronic states is studied by ellipsometry. We infer that the CT-related transition dipole moment is perpendicular to the respective π-conjugated planes in the D:A complex.

    更新日期:2018-07-20
  • A High Performance Single-Molecule Switch Designed by Changing Parity of Electronic Wavefunctions via Intramolecular Proton Transfer
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Zi-Qun Wang, Ming-Zhi Wei, Mi-Mi Dong, Gui-Chao Hu, Zong-Liang Li, Chuan-Kui Wang, Guang-Ping Zhang

    Molecular switches, as one of functional molecular components, play a vital role in nanoscale logic circuits. Here, effect of intramolecular proton transfer on current of single-molecule devices consisting of a keto or enol molecule sandwiched between two magnetic zigzag graphene nanoribbon (zGNR) electrodes is theoretically investigated. The keto and enol tautomers interconvert into each other by intramolecular proton transfer. The results show that the current of the keto molecular device is hardly observed, whereas that of the enol molecular device is significantly enhanced, demonstrating a high efficient switching effect with the ON/OFF ratio up to 3.4×102. Moreover, spin currents of the device with an enol isomer display giant bipolar rectification with the largest rectification ratio of 1.4×105 when the two zGNR electrodes are antiparallely spin-polarized. The underlying mechanism is attributed to parity matching principle of electronic wavefunctions in the core molecule and zGNR electrodes. The intramolecular proton transfer completely changes the parity of the electronic wavefunctions of the core molecule, and the electron tunneling channels around the Fermi energy are thus largely modified, resulting in a significant ON/OFF switching ratio. This work develops a strategy for designing high performance single-molecule switches.

    更新日期:2018-07-20
  • Mineral- and Ion-Specific Effects at Clay-Water Interfaces : Structure, Diffusion and Hydrodynamics
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Pauline Simonnin, Benoît Noetinger, Carlos Nieto-Draghi, Virginie Marry, Benjamin Rotenberg

    We use molecular dynamics to investigate how the structure, diffusion and hydrodynamic properties of clay interfaces with aqueous solution depends on the nature of the clay, the nature of the counterions and the salt concentration in the solution. Specifically, we study water-filled nanopores between uncharged (pyrophyllite) and charged (montmorillonite and beidellite, with susbtitutions located in the octahedral and tetrahedral layers, respectively) clays, with sodium or cesium as counterions, in the absence and in the presence of added salt. We discuss how the balance between solvation and attraction of the cations to the surface results in various distributions between inner- and outer-sphere complexes and how this influences the dynamics of water near the surface, as well as the hydrodynamic flow in the presence of an external force. In the latter case, the discussion based on mapping the molecular velocity profiles to a continuous description (parabolic Poiseuille flow) shows that the larger effects come from the presence/absence of charge in the mineral, as well as the localization of substitutions within the clay layer. The salt concentration and the nature of the counterions have a comparatively less important impact far from the surface -- even though some differences are observed in its close vicinity, which are not properly captured by the continuous description.

    更新日期:2018-07-20
  • Solvatochromic Response of Carbon Dots : Evidence of Solvent Interaction with Different Types of Emission Centres
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Nabaruna Basu, Debabrata Mandal

    The fluorescence emission of Carbon dots (CDs) of ~ 4 nm diameter were studied in a large number of solvents ranging from the weakly polar 1,4-dioxane to the strongly polar and protic water and formamide. The emission spectra in all solvents comprise of two major components, attributed to two distinct populations of emission centres – the edge-states at the periphery of the sp2-hybridized CD core, and the surface fluorophores. Emission from both these centres are sensitive to solvent polarity and H-bonding capacity, and undergo prominent red-shift with solvent ET(30) polarity parameter, which reveals comparable polar character of these centres and their strong interaction with solvent molecules. However, between these two centres, the emission of surface fluorophores is more drastically quenched at high ET(30) solvents, suggesting the opening up of additional non-radiative relaxation channels. This distinct solvatochromic response of these two emission centres also enables the CDs to perform as ratiometric probes for solvent polarity.

    更新日期:2018-07-20
  • Direct Evidence of Surface Charges in n-Type Al-Doped ZnO
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Dongming Zhou, Peijian Wang, Christopher R Roy, Michael D. Barnes, Kevin R. Kittilstved

    The fundamental properties of electrons in the prototypical n-type oxide nanocrystal, Al3+-doped ZnO, has been studied at both the ensemble and single-particle levels by spectroscopic and electron force microscopic techniques. We developed and implemented a new synthetic methodology that enables the tunable incorporation of Al3+ in the ZnO nanocrystal in an "etching-regrowth-doping" (ERD) strategy in a single-pot reaction. The ensemble-averaged properties and evolution of the Al3+ speciation in ZnO was studied using electronic absorption spectroscopy and powder X-ray diffraction and reveal successful substitution of Al3+ only after implementation of the ERD strategy. Characterization of individual ZnO, surface Al3+-doped ZnO, and internal Al3+-doped ZnO nanocrystals using electrostatic force microscopy reveal strong responses in both the quantity of surface charges and electron polarizabilities, that are dependent on the amount of Al3+ in the ZnO lattice. These results appear to suggest an upper-limit to the electron polarizability exists for Al3+-doped ZnO nanocrystals.

    更新日期:2018-07-20
  • Tip-Functionalized Au@Ag Nanorods as Ultrabright SERS Probes for Bioimaging in Off-Resonance Mode
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Boris N. Khlebtsov, Daniil N. Bratashov, Nikolai G. Khlebtsov

    SERS performance of Au nanorods (AuNRs) can be enhanced by the tip adsorption of Raman molecules (RMs) through anisotropic polymer stabilization or through the embedding of RMs between AuNR cores and Ag shells of AuNR@RM@Ag composite particles. We propose a new strategy to design ultrabright SERS probes composed of high-aspect-ratio AuNRs with anisotropic Ag coatings, with preferred adsorption of RMs to open AuNR tips. Specifically, for 4-nitrobenzenethiol (NBT) concentrations above a threshold value c>ctr, the fabricated Au@NBT@Ag particles had NBT-functionalized open Au tips, as well as anisotropic Ag shells grown on the AuNR sides. The SERS response of these probes with an optimal Ag shell was highest in the off-resonance mode, when the excitation wavelength was far from the plasmon resonance of the Au@NBT@Ag composites. Growing the Ag shell further to completely cover the AuNRs decreased the SERS enhancement. For biocompatibility and stability, the probes were additionally covered with a thin silica layer. Under optimal conditions, the probes demonstrated superstrong and superstable SERS spectra, as compared to those from common SERS tags (AuNRs, nanostars, and Au@Ag NRs) with surface-adsorbed NBT. The excellent SERS performance of the developed ultrabright probes is illustrated by single-particle detection of SERS spectra, Raman imaging of living cells, and deep tissue imaging.

    更新日期:2018-07-20
  • Elucidation of Chemical Species and Reactivity at Methylammonium Lead Iodide and Cesium Tin Bromide Perovskite Surfaces via Orthogonal Reaction Chemistry
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Weiran Gao, Kenneth Zielinski, Benjamin N. Drury, Alexander D Carl, Ronald L. Grimm

    We quantified the chemical species present at and reactivity of the (100) face of single-crystal methylammonium lead iodide, MAPbI3(100), and polycrystalline cesium tin bromide, CsSnBr3. For these ABX3 perovskites, experiments utilized the orthogonal reactivity of the A+-site cation, the B2+-site cation, and the X--site halide anion. Ambient-pressure exposure to BF3 solutions probed the reactivity of interfacial halides. Reactions with p-trifluoromethylanilinium chloride probed the exchange reactivity of the A+-site cation. A complex-forming ligand, 4,4’-bis(trifluoromethyl)-2,2’-bipyridine, probed for interfacial B2+-site cations. Fluorine features in x-ray photoelectron spectroscopy (XPS) quantified reaction outcomes for each solution-phase species. XPS indicated adsorption of BF3 indicating surface-available halide anions on both MAPbI3(100) and on CsSnBr3. Temperature-programmed desorption (TPD) quantified a ~200 kJ mol–1 desorption activation energy from MAPbI3(100) and a ~215 kJ mol–1 desorption energy from CsSnBr3. Adsorption of the fluorinated anilinium cation included no concomitant adsorption of chlorine as revealed by the absence of Cl 2p features within the limits of XPS detection. Within detection limits, the bipyridine ligand demonstrated no adsorption to MAPbI3(100), but adsorption to CsSnBr3. We discuss the present results in the context of interfacial stability, passivation, and reactivity for perovskite-based energy conversion.

    更新日期:2018-07-20
  • Two Dimensional Infrared Spectra of Cationic Dopamine Under Different Electric Fields: Theoretical Studies from the Density Function Theory Anharmonic Potential
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Hai-chao Ren, Jiaonan Yuan, Wei-Sen Xu, Tu-Nan Chen, Guang-Fu Ji, Dong-Qing Wei

    The geometry optimizations and vibrational frequencies of cationic dopamine (DAH+) under different intensity of electric fields (I.E.F.) are investigated using density function theory (DFT)/B3LYP/6-311G (d, p), and two dimensional infrared spectra (2D IR) are pictured based on anharmonic approximation. In spite of some differences, the optimized structural parameters calculated by DFT/B3LYP/6-311G (d, p) can well reproduce the experimental ones. Anharmonic approximation greatly improves the agreement between experimental and calculated fundamental frequencies. This study mainly focuses on the potential energy distributions (P. E. D.) and rotational isomerization of DAH+ under different electric fields. The results showed that there were very strong absorption peaks observed at 3571 cm-1 and 3683 cm-1 for O-H stretching vibrations. The symmetric and asymmetric of C-H stretching vibrations with benzene ring and amidogen, were calculated by anharmonic approximation and observed at 2921 cm-1, 2904 cm-1, 2997 cm-1 and 3007 cm-1, respectively. In addition, strong absorption peaks were also observed at 3266 cm-1, 3313 cm-1 and 3316 cm-1 for N-H stretching vibrations. For C-H stretching vibrations with amidogen, when I.E.F. is rising from -30×10-4 to 20×10-4 a.u. the vibrations of symmetry and asymmetry are coupled. However, the two vibrations were no longer coupled while I.E.F. goes on increasing to 30×10 -4 a.u.; For C-H stretching vibrations with benzene ring, the vibrations of symmetry and asymmetry were uncoupled when I.E.F. are -20×10-4 a.u., -10×10-4 a.u., 0×10-4 a.u. and 30×10-4 a.u. In addition, DAH+ undergoes rotational isomerization only when I.E.F. ranging from -20×10-4 to 10×10-4 a.u.

    更新日期:2018-07-20
  • Intraband Mid-Infrared Transitions in Ag2Se Nanocrystals: Potential and Limitations for Hgfree Low Cost Photodetection
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Junling Qu, Nicolas Goubet, Clément Livache, Bertille Martinez, Dylan Amelot, Charlie Greboval, Audrey Chu, Julien Ramade, Herve Cruguel, Sandrine Ithurria, Mathieu G. Silly, Emmanuel Lhuillier

    Infrared photodetection based on colloidal nanoparticles is a promising path toward low cost devices. However, mid-infrared absorption relies on interband transition in heavy metal based materials, which is a major flaw for the development toward mass market. In the quest of infrared active colloidal materials, we here investigate Ag2Se nanoparticles presenting intraband transition between 3 and 15 µm. With photoemission and infrared spectroscopy, we are able to propose an electronic spectrum of the material in absolute energy scale. We also investigate the origin of doping and demonstrate that it is the result of cation excess under Ag+ form. We demonstrate photoconduction into this material including under resonant excitation of the intraband transition. However, performances are currently quite weak with (i) a slow photoresponse (several seconds), and (ii) some electrochemical instabilities at room temperature.

    更新日期:2018-07-20
  • A Series of Photoswitchable Azobenzene-Containing Metal-Organic Frameworks with Variable Adsorption Switching Effect
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Zhengbang Wang, Kai Müller, Michal Valášek, Sylvain Grosjean, Stefan Brase, Christof Wöll, Marcel Mayor, Lars Heinke

    Nanoporous metal-organic frameworks (MOFs) equipped with light-responsive azobenzene pendant groups present a novel family of smart materials, enabling advanced applications like switchable guest adsorption, membranes with tunable molecular separation factors and photoswitchable proton-conduction. While it is obvious that for small pore sizes steric constraints may prohibit azobenzene switching, guidelines for optimizing the MOF architecture to achieve large switching effects have not yet been established. Here, a series of 5 different photoswitchable azobenzene-containing pillared-layer MOF structures is presented. The switching effect is quantified by the light-induced increase of the uptake amount of butanol as probe molecule. For fast and reproducible measurements, thin well-defined MOF films, referred to as SURMOFs, were used in combination with a quartz crystal microbalance. Although the series com-prises similar MOF structures, the magnitude of the switching effect considerably differs, here by a factor of 5. The up-take data show that, rather than the pore size or the number of azobenzene molecules per pore, the density of azoben-zene per pore volume is crucial. The finding that a large switching effect is reached for a high density of azobenzene moieties per MOF unit cell provides the basis for further applications of photoswitchable MOFs and SURMOFs.

    更新日期:2018-07-20
  • Pressure-Induced Topological Non-Trivial Phase and Tunable Optical Properties in All-Inorganic Halide Perovskites
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Yiran Ying, Xin Luo, Haitao Huang

    Cesium-based all-inorganic halide perovskites CsMX3 (M=Pb, Sn; X=Cl, Br, I) have been considered as an important candidate for highly-efficient, chemically stable optoelectronic devices and solar cells. Pressure can serve as an effective and clean thermodynamic approach to better performance of CsMX3. In this work, we use first-principles density functional theory calculations with both PBE and GW+BSE to systematically study the effects of pressure on the electronic structures, carrier transport and optical properties of cubic phase CsMX3. Our results show that with increasing hydrostatic pressure, the optical band gap red-shifts until the pressure reaches a critical value, above which the band inversion was observed due to the spin-orbit coupling. The resulting non-trivial topological gap blue-shifts with further increasing pressure. This work provides insights into the rational design of experiments to engineer properties of CsMX3 perovskites by applying pressure.

    更新日期:2018-07-20
  • Quantifying the ‘Subtle Interplay’ between Intermolecular and Molecule-Substrate Interactions in Molecular Assembly on Surfaces
    J. Phys. Chem. C (IF 4.484) Pub Date : 2018-07-19
    Thomas W. White, Natalia Martsinovich, Alessandro Troisi, Giovanni Costantini

    The effect of the concurrent action of intermolecular and molecule-substrate interactions on the two-dimensional (2-D) self-assembly of organic molecules on solid surfaces is investigated in a combined experimental and theoretical effort. Scanning tunnelling microscopy measurements of terephthalic acid on the Cu(111) surface, a model system where the interplay between the two interactions is particularly evident, are used to develop a general, simple and computationally inexpensive model that quantitatively accounts for the experimental observations. The model, related to the well-known Frenkel-Kontorova model, offers a comprehensive description of the ‘subtle interplay’ between intermolecular and molecule-substrate interactions and provides a qualitative and quantitative predictive capability in the design and fabrication of 2-D molecular nanostructures at surfaces.

    更新日期:2018-07-20
  • 更新日期:2018-07-20
  • Multiform Sulfur Adsorption Centers and Copper-Terminated Active Sites of Nano-CuS for Efficient Elemental Mercury Capture from Coal Combustion Flue Gas
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Zequn Yang, Hailong Li, Shihao Feng, Pu Li, Chen Liao, Xi Liu, Jiexia Zhao, Jianping Yang, Po-Heng Lee, Kaimin Shih
    更新日期:2018-07-20
  • 更新日期:2018-07-20
  • Structural Analysis of Cellulose-Coated Oil-in-Water Emulsions Fabricated from Molecular Solution
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Sofia Napso, Dmitry M. Rein, Zhendong Fu, Aurel Radulescu, Yachin Cohen
    更新日期:2018-07-20
  • Impact of Glycolipid Hydrophobic Chain Length and Headgroup Size on Self-Assembly and Hydrophobic Guest Release
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Kanaparedu P. C. Sekhar, Harikrishna Adicherla, Rati Ranjan Nayak
    更新日期:2018-07-20
  • Synthesis of Fluorescent and Water-Dispersed Germanium Nanoparticles and Their Cellular Imaging Applications
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Jiali Hu, Qiujun Lu, Cuiyan Wu, Meiling Liu, Haitao Li, Youyu Zhang, Shouzhuo Yao
    更新日期:2018-07-20
  • Structure Dependence of Pyridine and Benzene Derivatives on Interactions with Model Membranes
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Benjamin J. Peters, Cameron Van Cleave, Allison A. Haase, John Peter B. Hough, Keisha A. Giffen-Kent, Gabriel M. Cardiff, Audra G. Sostarecz, Dean C. Crick, Debbie C. Crans
    更新日期:2018-07-20
  • Polymeric Nanoparticles Limit the Collective Migration of Cellular Aggregates
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Grégory Beaune, Usharani Nagarajan, Françoise Brochard-Wyart, Françoise M. Winnik
    更新日期:2018-07-20
  • Morphology Evolution of Stimuli-Responsive Triblock Copolymer Modulated by Polyoxometalates
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Junyan Tan, Dandan Chong, Yue Zhou, Rong Wang, Xinhua Wan, Jie Zhang
    更新日期:2018-07-20
  • Kinetically Stable Triglyceride-Based Nanodroplets and Their Interactions with Lipid-Specific Proteins
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Valerija Vezočnik, Vesna Hodnik, Simona Sitar, Halil I. Okur, Magda Tušek-Žnidarič, Cornelis Lütgebaucks, Kristina Sepčić, Ksenija Kogej, Sylvie Roke, Ema Žagar, Peter Maček
    更新日期:2018-07-20
  • Metal-Organic Gels (MOGs) of Catechol-Based Ligands with Ni(ΙΙ) Acetate for Dye Adsorption
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Yue Hong, Zhiliang Gao, Mengjun Chen, Jingcheng Hao, Shuli Dong

    ABSTRACT: Metal organic gels (MOGs) are a class of supramolecular complexes, which have attracted widespread interest due to the coupled advantages of inorganic and organic building blocks. A new compound terminated with catechol was synthesized. This new compound can be used to coordinate with Ni2+ to form MOGs. These MOGs show favorable viscoelasticity and wormhole shaped porous structures which were confirmed by TEM and SEM images. Taking the benefits of porosity into account, the xerogel could serve as an adsorbent to adsorb dye molecules from the aqueous media. The experimental results indicate that the xerogels possess good adsorption effect both on anionic and cationic dyes. Exhaustive researches have performed on the adsorption kinetic and isotherm, revealing that the adsorption process accords with the pseudo-second-order model and the Langmuir model.

    更新日期:2018-07-20
  • Self-template Etching Synthesis of Urchin-like Fe3O4 Microspheres for Enhanced Heavy Metal Ions Removal
    Langmuir (IF 3.789) Pub Date : 2018-07-19
    Yong Yu, Yang Li, Yongqiang Wang, Bingfang Zou

    Hierachical Fe3O4 microspheres with superparamagnetic property are attractive for their superior structural, water-dispersible and magnetic separation merits. Here self-template etching route was developed to create optimal porous structure in superparamagnetic Fe3O4 microspheres by using the oxalic acid (H2C2O4) as etching agent. A plausible formation mechanism of the urchin-like Fe3O4 microspheres was proposed based on systematic investigation of the etching process, which involved two stages including pore-forming step based on size-selective etching and pore-expanding step based on further etching. The as-synthesized Fe3O4 microspheres exhibited urchin-like structure with specific surface area and pore-size tunable, water-dispersible and superparamagnetic properties. The optimal urchin-like Fe3O4 microspheres demonstrated superior performance including fast magnetic separation and high removal capabilities for the heavy metals ions like Pb2+ (112.8 mg g-1) and Cr(VI) (68.7 mg g-1). This work will shed new light on the synthesis of urchin-like microspheres for superior performance.

    更新日期:2018-07-20
  • Solvent effect on the energetics of Proton Coupled Electron Transfer in Guanine-Cytosine pair in chloroform by mixed explicit and implicit solvation models
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-18
    Lara Martinez-Fernandez, Giacomo Prampolini, Javier Cerezo, Yanli Liu, Fabrizio Santoro, Roberto Improta

    The Watson-Crick hydrogen bonded pair formed by deoxyGuanosine and deoxyCytidine (GC) in chloroform has been analysed by classical Molecular Dynamics simulations, which shows the existence of several fairly stable solute/solvent hydrogen bonds. Time-Dependent Density Functional Theory (TD-DFT) calculations with M052X functional, including solvation effect by a mixed continuum/discrete model, show that solvent stabilizes G →C Charge Transfer excited states (CTGC). The Proton Transfer (PT) processes that can occur in CTGC have been mapped by TD-DFT combining State Specific and Linear Response implementations of the Polarizable Continuum Model. For the first time, the effect of explicit solute/solvent interactions on the PT is considered by studying models containing up to three CHCl3 molecules. Our study shows that PT from the N1 atom of G to the N3 of C is exoergonic also in solution but, at variance with what observed in gas-phase, a stable minimum is predicted for CTGC state in chloroform.

    更新日期:2018-07-19
  • Experimental and theoretical study of the excited-state tautomerism of 6-azauracil in water surroundings
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-18
    Evelin P. Yankov, Rumyana I. Bakalska, Ernst Horkel, Dennis Svatunek, Vassil B. Delchev

    The irradiation of water solution of 6-azauracil showed that one of the photoreactions is the phototautomerization of the oxo tautomer of the compound into the hydroxy tautomer. The photoreaction was identified by a thorough analysis of experimetally obtained UV-spectra and the theoretical spectra simulation of several hydroxy tautomers of the compound. Furthermore we performed DFT level (BLYP/aug-cc-pVDZ) investigations of the mechanism of phototautomerization of the oxo tautomer of 6-azauracil in water surroundings applying PCM. The complete excited-state reaction path of the mechanism was proposed. It was found that the phototautomerization occurs along the 1πσ∗ excited-state reaction path. This reaction path was found to connect the two conical intersections S0/S1 of the H-detachment processes in the oxo and hydroxy tautomers of 6-azauracil.

    更新日期:2018-07-19
  • Resolving the Excited State Relaxation Dynamics of Guanosine Monomers and Hydrogen-Bonded Homodimers in Chloroform Solution
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-18
    Rebecca A. Ingle, Gareth M. Roberts, Katharina Röttger, Hugo J.B. Marroux, Frank D. Sönnichsen, Ming Yang, Łukasz Szyc, Yu Harabuchi, Satoshi Maeda, Friedrich Temps, Andrew J. Orr-Ewing

    The relaxation pathways of silyl-modified guanosine nucleoside monomers (G) and double-hydrogen-bonded homodimers (GG1) are compared in chloroform solution after 260-nm ultraviolet excitation. Transient absorption spectra support two previously reported relaxation pathways for the monomer with time constants of 210 ± 20 fs and 2.6 ± 0.1 ps. These pathways are associated with bifurcated approach to a seam of conical intersections between the excited 1ππ∗ 1La state and the ground electronic state. In the homodimer, an increase in the larger time constant to 18 ± 2 ps is attributed to slower passage through the minimum energy region of the 1ππ∗ state. A further time constant of 70 ± 10 fs indicates wavepacket evolution out of the 1ππ∗ state Franck-Condon region. A slow component of recovery of ground-state GG1 is proposed to result either from relaxation of the product of inter-base electron-driven proton transfer, or from the lowest triplet state (3ππ∗, T1).

    更新日期:2018-07-19
  • Vibronic absorption spectra of the angular fused bisindolo- and biscarbazoloanthracene blue fluorophores for OLED applications
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-18
    Gleb V. Baryshnikov, Dmitry A. Sunchugashev, Rashid R. Valiev, Boris F. Minaev, Hans Ågren

    An in-depth analysis of the vibronic absorption spectra for the recently synthesized blue-fluorescent OLED emitters bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3',4'-h]anthracene has been carried out computationally at the density functional theory level within the Franck-Condon approximation. These molecules are characterized by extended and rich electronic absorption spectra with most absorption bands being of vibronic origin. The first excited singlet state of bis[(1,2)(5,6)]indoloanthracene compound demonstrates a clear observable double-peak vibronic progression for two different active modes in the absorption spectrum, while the S2 state is vibronically inactive. In contrast, for the larger biscarbazolo[3,4-a:3',4'-h]anthracene compound the S0→S2 transition demonstrates well-resolved intense vibronic bands which overlap the less intense progressions of few modes in the S0→S1 transition. We have also found, that even the higher-lying and very intense S0→S4 and S0→S5 transitions for bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3',4'-h]anthracene, respectively, are characterized by clear vibronic progressions in excellent agreement with experimental spectra.

    更新日期:2018-07-19
  • In-situ N-doped Mesoporous Black TiO2 with Enhanced Visible-Light-Driven Photocatalytic Performance
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-18
    Hang Zhang, Yan Zhang, Junwei Yin, Zhenzi Li, Qi Zhu, Zipeng Xing

    In-situ N-doped mesoporous black TiO2 photocatalyst is fabricated by a facile sol-gel method combined with an in-situ solid-state chemical reduction technique, using urea as nitrogen resource. The N-doped mesoporous black TiO2 possesses high surface area of 96 m2 g-1, large pore size of 5.4 nm and narrow band gap of 2.05 eV. Meanwhile, the optical absorption extends to visible light region because of Ti3+ and N co-doping. The N-doped mesoporous black TiO2 exhibits higher photocatalytic activity than that of others under visible light irradiation for photocatalytic degradation of methyl orange (MO) and rhodamine B (RhB), which is up to 93.27% and 93.64%, respectively. The enhancement is ascribed to the synergistic effect of the N and Ti3+ co-doping extending the visible light absorption, the separation efficiency of photogenerated charge carriers, and the mesoporous structure with large surface area offering more surface active sites, which is beneficial for improving the photocatalytic activity.

    更新日期:2018-07-19
  • Linear Absorption Spectra of Solvated Thiouracils Resolved at the Hybrid RASPT2/MM level
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-18
    Artur Nenov, Irene Conti, Rocio Borrego-Varillas, Giulio Cerullo, Marco Garavelli

    On the example of 2-, 4- and 2,4-thiouracil we demonstrate the performance of the RASPT2/RASSCF protocol in reproducing the spectral positions and line shapes of linear absorption spectra that have been recorded in water and documented in this work. Through a QM/MM scheme coupled to a room-temperature Wigner sampling we simulate condensed phase spectra, permitting to compare our results against experiments. We discuss the sensitivity of the simulations to: a) the active space size by pushing the limits beyond the full-valence active spaces; b) the consideration of “dark” nπ∗-states in the state averaging; c) the flavor of RASPT2 technique; d) the basis set. The benchmarking demonstrates that full-π valence active spaces tend to red-shift the absorption band. Increasing the active space rectifies the problem and we obtain near-quantitative agreement between our experiments and calculations. We, furthermore, demonstrate that the choice of RASPT2 flavor has to be made through rigorous benchmarking.

    更新日期:2018-07-19
  • Surface Enhanced Raman Effect on CVD Growth of WS2 Film
    Chem. Phys. Lett. (IF 1.686) Pub Date : 2018-07-18
    Lan Meng, Song Hu, Chaoji Xu, Xiangfu Wang, Heng Li, Xiaohong Yan

    Chemical vapor deposition (CVD) method was used to grow large area and layer controllable WS2 film. Our results show that the as grown WS2 film is an excellent substrate for surface enhanced Raman scattering (SERS). The Raman enhancement effect depends crucially on the layer number of WS2 film: monolayer WS2 offers the strongest Raman signal, and the Raman enhancement effect gradually decreases with the increase in the layer number of WS2. Further analysis indicates that this transition originates from the charge transfer yield between the R6G molecules and the underlying WS2 substrate.

    更新日期:2018-07-19
  • Narrowing the band gap of graphitic carbon nitride sheet by coupling organic moieties: A DFT Approach
    Chem. Phys. Lett. (IF 1.686) Pub Date : 2018-07-18
    Rakesh Dutta, Bishal Dey, Dhruba Jyoti Kalita

    A series of composite materials based on graphitic carbon nitride (g- C 3 N 4 ) sheet were designed and investigated. The g- C 3 N 4 sheet has been coupled with wide gaped organic molecules to reduce the band gap of the composite materials. Out of the five composites, g- C 3 N 4 -A shows excellent optical and electronic properties. In this case, the band gap of g- C 3 N 4 sheet has been reduced from 3.65 to 2.65 eV. Besides, the angle between the g- C 3 N 4 sheet and the organic molecular plane becomes approximately 90 degree, which minimizes the rate of recombination of the electron-hole pair.

    更新日期:2018-07-19
  • Effect of A-site deficiency on investigation of structural, magnetic and magnetocaloric behaviors for (LaSr)-lacunar manganites
    Chem. Phys. Lett. (IF 1.686) Pub Date : 2018-07-18
    J. Makni-Chakroun, R. M'nassri, W. Cheikhrouhou-Koubaa, M. Koubaa, N. Chniba-Boudjada, A. Cheikhrouhou

    We investigated the effect of both lanthanum and strontium deficiencies upon the structural, magnetic and magnetocaloric properties in La0.7Sr0.3MnO3 mixed-valence manganite. Lacunar powder oxides La0.7-x□x Sr0.3MnO3 and La0.7Sr0.3-x□xMnO3 (x=0, 0.01, 0.02 and 0.05), where □is a vacancy, were prepared by the sol–gel technique by sintering at 750°C and 850°C. Our synthetized samples crystallize in a rhomboedrically distorted perovskite structure with space group R-3C. Both these series of samples are ferromagnets and undergo second order paramagnetic–ferromagnetic transition with decreasing temperature. Magnetization measurements versus magnetic applied field at low temperature confirm the ferromagnetic behavior of our lacunars samples. Curie temperature decrease with increasing vacancy content for strontitum-deficient samples, while, its shows a maximum at about x=0.01 (TC=358K) followed by a minimum for x=0.03 (TC=336K) for lanthanum- deficient compounds. All compounds undergo a large magnetocaloric effect and have consequently potential applications in magnetic refrigeration domain around room temperature.

    更新日期:2018-07-19
  • Red-light induced photoreaction of ozone-dimethylamine complex; Matrix-isolation infrared spectra of dimethylamine-N-oxide and N,N-dimethylhydroxylamine
    Chem. Phys. Lett. (IF 1.686) Pub Date : 2018-07-18
    Kentaro Kamata, Nobuyuki Akai, Munetaka Nakata

    Photoreaction of molecular complex composed of ozone and dimethylamine is investigated by matrix-isolation IR and UV-visible spectroscopies. The UV-visible spectrum of the molecular complex isolated in an Ar matrix shows two broad bands in the region between 400 and 700 nm. Upon red-light irradiation (λ ≥ 680 nm), dimethylamine-N-oxide is produced by intermolecular oxygen-atom transfer from O3 to the lone pair on the nitrogen atom of dimethylamine. Dimethylamine-N-oxide isomerizes to N,N-dimethylhydroxylamine by intramolecular hydrogen-atom migration upon the second light irradiation (λ ≥ 385 nm). The both photoproducts are identified by the DFT calculation at the B3LYP/6-31++G(d,p) level.

    更新日期:2018-07-19
  • Chiral separation of methamphetamine racemate using molecularly imprinted sulfonic acid functionalized resin
    J. Colloid Interface Sci. (IF 5.091) Pub Date : 2018-07-18
    Raedah A.S. Alatawi, M. Monier, Nadia H. Elsayed

    In the present study, a sulfonic acid functionalized enantio-selective resinous material was developed for effective chiral separation of (±)-methamphetamine racemate. R-methamphetamine-sulfonamide phenolic derivative was first prepared and fully characterized utilizing instrumental and spectroscopic techniques, then the sulfonamide was implemented in an acid catalyzed condensation copolymerization with phenol and formaldehyde. The resulted resinous material was then exposed to successive alkaline and acidic treatments in order to remove the R-methamphetamine enantiomer out of the resin matrix and obtaining the molecularly imprinted enantio-selective material, which was also investigated by scanning electron microscope, FTIR and XPS spectroscopy. The maximum selective extraction of the R-methamphetamine enantiomer was achieved at pH 7. The adsorption isotherms indicated an adsorption capacity of 233±1 mg/g and followed the well-known Langmuir model. Also, the enantio-separation experiment of the racemic mixture was performed by column technique and both the supernatant loading and the eluant recovery solutions indicated an enantiomeric excess of 80% and 67% related to S- and R-methamphetamine, respectively.

    更新日期:2018-07-19
  • Aggregation behaviour of triphenylphosphonium bolaamphiphiles
    J. Colloid Interface Sci. (IF 5.091) Pub Date : 2018-07-18
    Francesca Ceccacci, Simona Sennato, Edoardo Rossi, Raffaele Proroga, Stefano Sarti, Marco Diociaiuti, Stefano Casciardi, Valentina Mussi, Alessia Ciogli, Federico Bordi, Giovanna Mancini, Cecilia Bombelli

    Hypothesis Bolaamphiphiles are characterized by wide polymorphism of their aggregates, due to the connection of the headgroups that renders their investigation very intriguing in several technological applications. Some bolaamphiphiles displaying the triphenylphosphonium motif (TPP-bolaamphiphiles) were previously explored for their ability in crossing the mitochondrial membranes but their colloidal features, which are crucial for the potential development of an effective drug delivery system, were never investigated. Experiments Single chain TPP-bolaamphiphiles, featuring chains of 12, 16, 20 and 30 methylene units, were synthesized and their aggregation features (Krafft point, cac, dimensions, morphology, stability) were investigated by conductivity, dialysis, transmission electron microscopy, Raman spectroscopy, dynamic and dielectrophoretic laser light scattering measurements. Findings All the TPP-bolaamphiphiles spontaneously self-assemble into vesicles, independently of the chain length. The bolaamphipile with the longest chain forms monodispersed vesicles whereas for the other bolaamphiphiles two distinct populations of vesicles are observed. All vesicles are not equilibrium systems, in particular vesicles formed by the bolaamphiphiles featuring 20 and 30 methylene units result notably stable to dilution thanks to both the tightening of molecular packing at increasing chain length and the progressive reduction of the monomer percentage in U-shaped conformation. These features make these TPP-bolaamphiphiles very attractive as minor components for the development of novel mitochondriotropic liposomes.

    更新日期:2018-07-19
  • Transport and trapping of nanosheets via hydrodynamic forces and curvature-induced capillary quadrupolar interactions
    J. Colloid Interface Sci. (IF 5.091) Pub Date : 2018-07-18
    Timothy J. Lee, Colby F. Lewallen, Daniel J. Bumbarger, Peter J. Yunker, R. Clay Reid, Craig R. Forest

    Hypothesis The manipulation of nanosheets on a fluid-fluid interface remains a significant challenge. At this interface, hydrodynamic forces can be used for long-range transport (>1x capillary length) but are difficult to utilize for accurate and repeatable positioning. While capillary multipole interactions have been used for particle trapping, how these interactions manifest on large but thin objects, i.e., nanosheets, remains an open question. Hence, we posit hydrodynamic forces in conjunction with capillary multipole interactions can be used for nanosheet transport and trapping. Experiments We designed and characterized a fluidic device for transporting and trapping nanosheets on the water-air interface. Analytical models were compared against optical measurements of the nanosheet behavior to investigate capillary multipole interactions. Energy-based modeling and dimensional analysis were used to study trapping stability. Findings Hydrodynamic forces and capillary interactions successfully transported and trapped nanosheets at a designated trapping location with a repeatability of 10% of the nanosheet’s length and 12% of its width (length = 1500 µm, width = 1000 µm) and an accuracy of 20% of their length and width. Additionally, this is the first report that surface tension forces acting upon nanoscale-thick objects manifest as capillary quadrupolar interactions and can be used for precision manipulation of nanosheets.

    更新日期:2018-07-19
  • Ni modified Pd nanoparticles immobilized on hollow nitrogen doped carbon spheres for the simehydrogenation of phenylacetylene
    J. Colloid Interface Sci. (IF 5.091) Pub Date : 2018-07-18
    Wei Wu, Wei Zhang, Yu Long, Jiaheng Qin, He Wen, Jiantai Ma

    In this work, Ni modified Pd nanoparticles immobilized on hollow nitrogen doped carbon spheres were successfully prepared, denoted as Pd/Ni-N/C. The Pd/Ni-N/C showed a moderate catalytic activity for the catalytic reduction of 4-nitrophenol as a model reaction. When applied for the simehydrogenation of phenylacetylene, the Pd/Ni-N/C exhibited a much better catalytic performance than some other Pd-based catalysts. What’s more, the selectivity of styrene could be kept at high levels even when the reaction time was prolonged. The superior catalytic performance may be ascribed to the incorporation of Ni and N species, which were detailedly characterized and contrastively demonstrated. The contained N groups could disperse and stabilize the supported metal nanoparticles. The Pd/Ni-N/C displayed no obvious decrease of catalytic activity and selectivity in the recycling tests, indicating the potential for various industrial applications.

    更新日期:2018-07-19
  • Effects of pyrolysis temperature on the hydrologically relevant porosity of willow biochar
    J. Anal. Appl. Pyrol. (IF 3.468) Pub Date : 2018-07-18
    Jari Hyväluoma, Markus Hannula, Kai Arstila, Hailong Wang, Sampo Kulju, Kimmo Rasa

    Biochar pore space consists of porosity of multiple length scales. In direct water holding applications like water storage for plant water uptake, the main interest is in micrometre-range porosity since these pores are able to store water that is easily available for plants. Gas adsorption measurements which are commonly used to characterize the physical pore structure of biochars are not able to quantify this pore-size range. While pyrogenetic porosity (i.e. pores formed during pyrolysis process) tends to increase with elevated process temperature, it is uncertain whether this change affects the pore space capable to store plant available water. In this study, we characterized biochar porosity with x-ray tomography which provides quantitative information on the micrometer-range porosity. We imaged willow dried at 60 °C and biochar samples pyrolysed in three different temperatures (peak temperatures 308, 384, 489 °C, heating rate 2 °C min-1). Samples were carefully prepared and traced through the experiments, which allowed investigation of porosity development in micrometre size range. Pore space was quantified with image analysis of x-ray tomography images and, in addition, nanoscale porosity was examined with helium ion microscopy. The image analysis results show that initial pore structure of the raw material determines the properties of micrometre-range porosity in the studied temperature range. Thus, considering the pore-size regime relevant to the storage of plant available water, pyrolysis temperature in the studied range does not provide means to optimize the biochar structure. However, these findings do not rule out that process temperature may affect the water retention properties of biochars by modifying the chemical properties of the pore surfaces.

    更新日期:2018-07-19
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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