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Langmuir: the ACS Journal of Surfaces and Colloids

Yuliang Yuan, Weicheng Wang, Jie Yang, Haichao Tang, Zhizhen Ye, Yujia Zeng, Jianguo Lu
Design of new materials with sophisticated nanostructure has been proven to be an efficient strategy to improve their properties in many applications. Herein, we demonstrate the successful combination of high electron conductive materials of NiCo2O4 with the high capacitance materials of MnMoO4 by forming a core-shell nanostructure. The NiCo2O4@MnMoO4 core-shell nanoarrays (CSNAs) electrode possesses high specific capacitance of 4.24 F cm-2 at a current density of 5 mA cm-2, obviously larger than the pristine NiCo2O4 electrode...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Pedro Morgado, Ana Rosa Garcia, Luís F G Martins, Laura M Ilharco, Eduardo J M Filipe
In this work we demonstrate that n-alkanes coil when mixed with perfluoroalkanes, changing their conformational equilibria to more globular states, with a higher number of gauche conformations. The new coiling effect is here observed in fluids governed exclusively by dispersion interactions, contrarily to other examples in which hydrogen bonding and polarity play important roles. FTIR spectra of liquid mixtures of n-hexane and perfluorohexane unambiguously reveal that the population of n-hexane molecules in all-trans conformation reduces from 32% in the pure n-alkane to practically zero...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Shilpi Kushwaha, Arunava Maity, Monalisa Gangopadhyay, Sapna Ravindranathan, Pattuparambil R Rajamohanan, Amitava Das
A unique fluorescence resonance energy transfer (FRET) process is found to be operational in a unilamellar lipid self-assembly in the aqueous phase. A newly synthesized naphthyl based long chain lipid derivative [N-(naphthalene-1-ylmethyl)tetradecane-1-ammonium chloride, 14NA+] forms various self-assembled architectures in the aqueous phase. Controlled changes in lipid concentration lead to a transition of the self-assemblies from micelles to vesicles to rods. In the presence of cucurbit[7]uril (CB7), 14NA+ forms a host-guest [2]pseudorotaxane complex (CB7∋14NA+) and secondary interactions lead to the formation of a lipid bilayer with hydrophobic pockets situated in between the layers...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Nikolaos Galanakis, Karl Patrick Travis
We present a new method of characterizing damage arising from α-recoil cascades in amorphous materials including glasses. The approach taken is topological, yielding information of atom connectivity and utilizing complete sets of orthogonal functions (spherical harmonics and Hermite functions) to compute order parameters. The utility of our new approach is demonstrated by first applying it to models of radiation damaged crystalline zircon, enabling validation against the standard defect counting method (Wigner-Seitz)...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jean-Philippe Michel, Yingxiong Wang, Irena Kiesel, Yuri Gerelli, Veronique Rosilio
The outer membrane (OM) of Gram-negative bacteria is a complex and asymmetric bilayer that antimicrobial peptides must disrupt in order to provoke the cell lysis. The inner and external leaflets of the OM are mainly composed of phospholipids (PL), and lipopolysaccharide (LPS), respectively. Supported lipid bilayers are interesting model systems to mimic the lipid asymmetric scaffold of the OM and determine the quantitative and mechanistic effect of antimicrobial agents, using complementary physicochemical techniques...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jing Zhao, Fei Gao, Sidharam Pundlik Pujari, Han Zuilhof, Andrew Teplyakov
Computationally predicted N 1s core level energies are commonly used to interpret the experimental measurements obtained with X-ray photoelectron spectroscopy. This work compares the application of Koopmans' theorem to core electrons using the B3LYP functional with two commonly used basis sets, analyses the factors relevant to the comparison of the computational with experimental data, and presents several correlations that allow an accurate prediction of the N 1s binding energy. The first correlation is obtained with a series of known nitrogen-containing functional groups on well-characterized organic monolayers...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Thirupathi Ravula, Nathaniel Hardin, Sudheer Ramadugu, Ayyalusamy Ramamoorthy
The development and applications of detergent-free membrane mimetics have been the focus for the high-resolution structural and functional studies on membrane proteins. The introduction of lipid nanodiscs has attracted new attention towards the structural biology of membrane proteins and also enabled biomedical applications. Lipid nanodiscs provide a native lipid bilayer environment similar to the cell membrane surrounded by a belt made up of proteins or peptides. Recent studies have shown that the hydrolyzed form of styrene maleic anhydride copolymer (SMA) has the ability to form lipid nanodiscs and has several advantages over protein or peptide based nanodiscs...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Hyejung Choi, Joong-Jo Kim, Yong-Hwan Mo, Benjaram Mahipal Reddy
Dynamic process in the synthesis of silica nanotubes (SNTs) by utilizing glycyldodecylamide (GDA) as a soft template was thoroughly investigated. The morphological evolution from GDA to SNTs was deeply explored to elucidate the formation mechanism for optimizing the synthesis procedure. Various analytical tools, namely, XRD, FTIR, SEM, TEM, Z-potential, and N2 adsorption/desorption isotherms were employed during the synthesis procedure. The interactive structure of GDA was also investigated using TEM-EDX as a function of aging time...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Mridula Nandi, Binoy Maiti, Kambalapalli Srikanth, Priyadarsi De
Supramolecular host-guest interaction between randomly methylated β-cyclodextrin (RM β-CD) and side-chain phenylalanine (Phe) and Phe-Phe dipeptide based homopolymers has been employed for amplification of fluorescence emission of otherwise weakly fluorescent amino acid Phe. The host-guest complex has been characterized by 1H and 13C NMR spectroscopy, two-dimensional (2D) rotating-frame overhauser spectroscopy (ROESY), FT-IR, UV-visible and fluorescence spectroscopy. To gain insights into the origin of fluorescence in homopolymers, density functional theory (DFT) calculations were performed where phenyl moieties inside the less polar core of β-CD were observed to form π-π coupled complex resulting in enhanced emission...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Shubhi Bansal, Prosenjit Sen
Manipulating droplets of biological fluids in Electrowetting on Dielectric (EWOD) based digital microfluidic platform is a significant challenge due to biofouling and surface contamination. This problem is often addressed by operating in an oil environment. We study an alternate configuration of sessile compound droplets having an aqueous core surrounded by a smaller oil shell. In contrast to conventional EWOD, open digital microfluidic platform enabled by the core-shell configuration will allow electrical, mechanical or optical probes to get unrestricted access to the droplet and thus enabling highly flexible and dynamically reconfigurable lab-on-chip systems...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Dajana Lichtenstein, Thomas Meyer, Linda Böhmert, Sabine Juling, Christoph Fahrenson, Soeren Selve, Andreas F Thünemann, Jan Meijer, Irina Estrela-Lopis, Albert Braeuning, Alfonso Lampen
The elucidation of mechanisms underlying cellular uptake of nanoparticles is an important topic in nanotoxicological research. Most studies dealing with silver nanoparticle uptake provide only qualitative data about internalization efficiency and do not consider nanoparticle-specific dosimetry. Therefore, we performed a comprehensive comparison of the cellular uptake of differently coated silver nanoparticles of comparable size in different human intestinal Caco-2 cell-derived models to cover also the influence of the intestinal mucus barrier and uptake-specialized M-cells...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Juan Pellico, Jesús Ruiz-Cabello, Irene Fernández-Barahona, Lucía Gutiérrez, Ana V Lechuga-Vieco, Jose A Enríquez, M Puerto Morales, Fernando Herranz
Iron oxide nanomaterial is a typical example of a magnetic resonance imaging probe for negative contrast. It has also been shown how this nanomaterial can be synthesized for positive contrast by modification of the composition and size of the core. However, the role of the organic coating in the relaxometric properties is largely unexplored. Here, maghemite nanoparticles with either excellent positive or very good negative contrast performance are obtained by modifying coating thickness while the core is kept unchanged...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
George Kaptay
The conditions of negative surface tension of a binary regular solution is discussed in this paper using the recently re-confirmed Butler equation (Langmuir, 31 (2015) 5796-5804). It is shown that surface tension becomes negative only for solutions with strong repulsion between the components. This repulsion for negative surface tension should be so strong that this phenomenon appears only within a miscibility gap, i.e. in a 2-phase region of macroscopic liquid solutions. Thus, for a macroscopic solution the negative surface tension is possible only in a non-equilibrium state...
September 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Mardochee Reveil, Hsien-Lien Huang, Huang-Ta Chen, Jason Liu, Michael O Thompson, Paulette Clancy
We expose the predominant diffusional pathways for In and As in InAs, as well as dopant Si atoms in InAs, using Nudged Elastic Band calculations in conjunction with accurate Density Functional Theory calculations of the energy of defective systems. Our results show that As is a very fast diuser compared to In and Si for both vacancy-assisted and interstitially mediated mechanisms. Larger indium atoms, on the other hand, are very slow diffusers and strongly prefer to remain on the In sublattice. Silicon also prefers to stay in substitutional sites in the In sublattice, in agreement with the fact that Si is used to create n-doped InAs...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
M Eric Irrgang, Michael Engel, Andrew J Schultz, David A Kofke, Sharon C Glotzer
Hard polyhedra are a natural extension of the hard sphere model for simple fluids, but no general scheme exists for predicting the effect of shape on thermodynamic properties, even in fluids of moderate density. Only the second virial coefficient is known analytically for general convex shapes, so higher order equations of state have been elusive. Here we investigate high-precision state functions in the fluid phase of 14 representative polyhedra with different assembly behaviors. We discuss historic efforts in analytically approximating virial coefficients up to $B_4$ and numerically evaluating them to $B_8$ Using virial coefficients as inputs, we show the convergence properties for four equations of state for hard convex bodies...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Andrew Z Summers, Christopher R Iacovella, Peter T Cummings, Clare McCabe
Chemisorbed monolayer films are known to possess favorable characteristics for nanoscale lubrication of micro- and nanoelectromechanical systems (MEMS/NEMS). Prior studies have shown that the friction observed for monolayer-coated surfaces features a strong dependence on the geometry of contact. Specifically, tip-like geometries have been shown to penetrate into monolayer films, inducing defects in the monolayer chains and leading to plowing mechanisms during shear, which result in higher coefficients of friction (COF) than those observed for planar geometries...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Benjamin J Bucior, German V Kolmakov, JoAnna M Male, Jinchen Liu, De-Li Chen, Prashant Kumar, J Karl Johnson
Single-walled carbon nanotubes (SWNTs) have been shown from both simulations and experiments to have remarkably low resistance to gas and liquid transport. This has been attributed to the remarkably smooth interior surface of pristine SWNTs. However, real SWNTs are known to have various defects that depend on the synthesis method and procedure used to activate the SWNTs. In this paper we study adsorption and transport properties of atomic and molecular gases and fluids in SWNTs having vacancy point defects...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Sara Bonella, Mauro Ferrario, Giovanni Ciccotti
Equilibrium and non-equilibrium molecular dynamics simulations are combined to compute the full set of coefficients that appear in the phenomenological equations describing thermal transport in a binary mixture subject to a constant thermal gradient. The Dynamical Non-Equilibrium Molecular Dynamics approach (D-NEMD) is employed to obtain the microscopic time evolution of the density and temperature fields, together with that of the mass and energy fluxes. D-NEMD enables to study not only the steady state, but also the evolution of the fields during the transient that follows the onset of the thermal gradient, up to the establishment of the steady state...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Md Symon Jahan Sajib, Mohammadreza Samieegohar, Tao Wei, Katherine Shing
Ethylene production plays a key role in the petrochemical industry. The severe operation conditions of ethylene thermal cracking, such as high-temperature and coke-formation, pose challenges for the development of new corrosion-resistant and coking-resistant materials for ethylene reactor radiant coils tubes (RCTs). We investigated the performance of ceramic materials such as silicon carbide (SiC) in severe pyrolysis conditions by using reactive forcefield molecular dynamics (ReaxFF MD) simulation method. Our results indicate that β-SiC surface remains fully stable at 1500 K, whereas increased temperature results in melted interface...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Yun Tian, Xiaofei Xu, Jianzhong Wu
We report an efficient computational procedure for rapid and accurate prediction of the self-diffusivity of gas molecules in nanoporous materials by implementing the transitional-state theory for inter-cage hopping at infinite dilution with the string method in conjunction with the excess-entropy scaling for predicting gas diffusion at finite loadings. The theoretical procedure has been calibrated with molecular dynamics simulations for the diffusion coefficients of methane and hydrogen gases in representative nanoporous materials including metal organic frameworks and zeolites...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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