Langmuir (Langmuir)

Publisher: American Chemical Society, American Chemical Society

Journal description

Langmuir is devoted to reporting new and original experimental and theoretical research of interest to chemists and chemical physicists in the fields of surface and colloid chemistry. Coverage includes such topics as micelles, visicles, emulsions, gels, surfacants, colloids, crystal growth, nucleation, liquid crystals, imaging spectroscopy, electro-chemistry, biological colloids & interfaces, biopolymers, nanostructures, multicomponent systems, and materials. In addition to these structures, Langmuir also carries articles on theory, simulation, modeling and experimental developments. Along with national award-winning lectures, Langmuir regularly features letters, articles, reviews, commentaries, notes, and special issues.

Current impact factor: 4.46

Impact Factor Rankings

2015 Impact Factor Available summer 2016
2014 Impact Factor 4.457
2013 Impact Factor 4.384
2012 Impact Factor 4.187
2011 Impact Factor 4.186
2010 Impact Factor 4.268
2009 Impact Factor 3.898
2008 Impact Factor 4.097
2007 Impact Factor 4.009
2006 Impact Factor 3.902
2005 Impact Factor 3.705
2004 Impact Factor 3.295
2003 Impact Factor 3.098
2002 Impact Factor 3.248
2001 Impact Factor 2.963
2000 Impact Factor 3.045
1999 Impact Factor 2.937
1998 Impact Factor 2.813
1997 Impact Factor 2.852
1996 Impact Factor 3.47
1995 Impact Factor 3.143
1994 Impact Factor 3.232
1993 Impact Factor 2.628
1992 Impact Factor 2.638

Impact factor over time

Impact factor

Additional details

5-year impact 4.54
Cited half-life 7.20
Immediacy index 0.68
Eigenfactor 0.18
Article influence 1.10
Website Langmuir website
Other titles Langmuir (Online), Langmuir
ISSN 1520-5827
OCLC 39280622
Material type Document, Periodical, Internet resource
Document type Internet Resource, Computer File, Journal / Magazine / Newspaper

Publisher details

American Chemical Society

  • Pre-print
    • Author cannot archive a pre-print version
  • Restrictions
    • Must obtain written permission from Editor
    • Must not violate ACS ethical Guidelines
  • Post-print
    • Author cannot archive a post-print version
  • Restrictions
    • If mandated by funding agency or employer/ institution
    • If mandated to deposit before 12 months, must obtain waiver from Institution/Funding agency or use AuthorChoice
    • 12 months embargo
  • Conditions
    • On author's personal website, pre-print servers, institutional website, institutional repositories or subject repositories
    • Non-Commercial
    • Must be accompanied by set statement (see policy)
    • Must link to publisher version
    • Publisher's version/PDF cannot be used
    • If mandated sooner than 12 months, must obtain waiver from Editors or use AuthorChoice
    • Reviewed on 07/08/2014
  • Classification

Publications in this journal

  • Zhong Zheng · Yihu Song · Ruiquan Yang · Qiang Zheng ·
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    ABSTRACT: Immobilized polymer fractions have been claimed to be of vital importance for sol-gel transitions generally observed in nanoparticle dispersions but remain debate in mechanism and difficulty for prediction. Here we investigate the immobilized layer structures of tri-functionality polyether polyol (PPG) near the surfaces of hydrophilic and hydrophobic fumed silica (FS) nanoparticles to reveal the role of surface chemistry on the molecular dynamics and sol-gel transitions of the dispersions. Using modulated differential scanning calorimetry, we measure the specific heat capacity during glass transition and the enthalpy during cold-crystallization. Comparing with hydrophobic FS that forms a fully immobilized (glassy) layer, we find that hydrophilic FS immobilizes more PPG, forming a partially immobilized outer layer being unable to crystallize next to the inner glassy layer. By correlating the thickness of the glassy layer with half of the minimum spacing between nanoparticles, we directly evidence the percolation of this layer along the nearest neighbor nanoparticles being responsible for the sol-gel transition. Using effective volume fraction including the glassy layer, we successfully construct master curves of relative viscosity of both hydrophilic and hydrophobic FS dispersions, pointing to a common sol-gel transition mechanism mediated by the surface chemistry.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03899
  • Zaure Avazbaeva · Woongmo Sung · Jonggwan Lee · Minh Dinh Phan · Kwanwoo Shin · David Vaknin · Doseok Kim ·
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    ABSTRACT: It has been reported that octadecylamine (ODA) Langmuir monolayer becomes unstable at low pH values with no measurable surface pressure at around pH 3.5, suggesting significant dissolution of the ODA molecule into the subphase solution (Albrecht, Colloids Surf. A 2006, 284-285, 166-174). However, by lowering the pH further, ODA molecules reoccupy the surface, and a full monolayer is recovered at pH 2.5. Using surface sum-frequency spectroscopy and pressure-area isotherms, it is found that the recovered monolayer at very low pH has a larger area per molecule with many gauche defects in the ODA molecules as compared to that at high pH values. This structural change suggests that the reappearance of the monolayer is due to the adsorbed Cl- counterions to the protonated amine groups leading to partial charge neutralization. This proposition is confirmed by intentionally adding monovalent salts (i.e., NaCl, NaBr, or NaI) to the subphase to recover the monolayer at pH 3.5, of which the detailed structure of the monolayer is confirmed by sum frequency spectra and the adsorbed anions by X-ray reflectivity.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03947
  • Rahul Bapusaheb Karyappa · Ankita Naik · Rochish Thaokar ·
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    ABSTRACT: Emulsification using electric fields is an easy alternative to ow-induced drop breakup and the former is reported to be more effective and economical than the latter, especially when the medium phase is poorly conducting or is highly viscous. In-situ emulsification of a coarse water-in-oil emulsion in uniform electric field is studied. We perform a detailed experimental analysis of the effect of applied electric field strength and the duration of applied electric field on the drop size distribution. The average diameter as well as the time for emulsification decreases with an increase in the intensity of the electric field. Moreover a narrow size distribution is observed. An average size of a few microns of the dispersed phase could be achieved. New breakup mechanisms at play in the emulsification process are discussed. Identified mechanisms involve charged lobe disintegration, charged drop breakup, chain formation in which several water droplets are interconnected by thin water bridges, electrospraying and charge transfer and coalescence. The study shows that charged drop disintegration could be the key mechanism of fine emulsification of an initially electrically neutral coarse emulsion.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03188
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    ABSTRACT: A series of eight sodium sulfonic acid surfactants with differently branched tails (four double-chain sulfosuccinates and four triple-chain sulfocarballylates) were studied as charging agents for sterically-stabilized poly(methyl methacrylate) (PMMA) latexes in dodecane. Tail branching was found to have no significant effect on the electrophoretic mobility of the latexes, but the number of tails was found to influence the electrophoretic mobility. Triple-chain, sulfocarballylate surfactants were found to be more effective. Several possible origins of this observation were explored by comparing sodium dioctylsulfosuccinate (AOT1) and sodium trioctylsulfocarballylate (TC1) using identical approaches: the inverse micelle size, the propensity for ion dissociation, the electrical conductivity, the electrokinetic or ζ potential, and contrast-variation small-angle neutron scattering. The most likely origin of the increased ability of TC1 to charge PMMA latexes is a larger number of inverse micelles. These experiments demonstrate a small molecular variation that can be made to influence the ability of surfactants to charge particles in nonpolar solvents, and modifying molecular structure is a promising approach to developing more effective charging agents.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03876
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    ABSTRACT: CD20, expressed on greater than 90% of B-lymphocytic lymphomas, is a target for antibody therapy. Rituximab is a chimeric monoclonal antibody against the protein CD20, allowing it to destroy B cells and to treat lymphoma, leukemia, transplant rejection, and autoimmune disorder. In this work, the binding of Rituximab with self-assembled monolayers (SAM) of peptide mimotopes of CD20 antigen was systematically characterized. Four peptide mimotopes of CD 20 antigen were selected from literature and redesigned to allow their SAM immobilizations on gold electrodes through a peptide linker with cysteine. The bindings of these peptides with Rituximab and control antibodies (Trastuzumab, and Bevacizumab) were characterized by Quartz Crystal Microbalance (QCM). Among the four peptide mimotopes initially selected, the peptide designated as CN-14 (CGSGSGSWPRWLEN) was the most selective and sensitive for Rituximab binding. The CN-14 SAM was further characterized by ellipsometry and atomic force microscopy. The thickness of the CN-14 SAM film was approximately 32 Å and the CN-14 SAM is suggested to be stabilized by a salt bridge of ARG-10 and GLU-13 between CN-14 peptides. The CN-14 salt bridge was evaluated by a series of modifications to the CN-14 peptide sequence and characterized by QCM. The CN-14 amide variant produced a better affinity to Rituximab than that of CN-14 without a significant impact on selectivity. As the GLU residue pKa of CN-14 increased, the affinity of the SAM to Rituximab increased while the selectivity decreased. This was attributed to the weakening of the salt bridge between the CN-14 ARG-10 and GLU-13 at higher pKa values for GLU-13. Our study shows that peptide mimotopes have potential benefit in sensor applications as the peptide-peptide interactions in the SAM could be manipulated by the addition of functional groups to the peptide to influence binding of the target protein.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b02605
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    ABSTRACT: A novel dimethylacrylate 18-membered macrocycle (DMECE), acting as both bifunctional monomer and cross-linker, was designed and synthesized, and thus employed to construct a series of macrocycle-containing amphiphilic hyperbranched polymers (HBPs). The macrocyclic recognition effect between the HBPs and alkali metal ions showed that Na+ was introduced in 1:1 interactive mode, whereas K+ and Rb+ were in 2:1 ratio. Through the formation of the DMECE/K+=2:1 rigid "sandwich" complex of amphiphilic hyperbranched polymers, dimple-shaped aggregates were observed by TEM, SEM and AFM. Moreover, the initial concentration, the nature of solvent, the mode and affinity of the macrocyclic recognition effect as well as the amount of K+, were essential control factors for the formation of dimple-shaped aggregates. Most importantly, the macrocyclic recognition effect endows the reversibility of the dimple-shaped aggregates and the size controllability of its circular opening, which provides a new strategy for design novel macrocycle-containing HBPs and great potential application in the field of capture and release.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03865
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    ABSTRACT: It has been known for almost one hundred years that a lower surface tension can be achieved at the air-water interface by spreading protein from a concentrated solution than by adsorption from an equivalent total bulk concentration. Nevertheless the factors that control this non-equilibrium process have not been fully understood. In the present work, we apply ellipsometry, neutron reflectometry, X-ray reflectometry and Brewster angle microscopy to elaborate the surface loading of human serum albumin in terms of both the macroscopic film morphology and the spreading dynamics. We show that dominant contribution to the surface loading mechanism is the Marangoni diffusion-limited spreading of protein from the bulk of the droplets rather than the direct transfer of their surface films. The films can be spread on a dilute subphase if the concentration of the spreading solution is sufficientabove a threshold; if not this condition is not met dissolution of the protein occurs dominates and only a textured adsorption layer slowly forms. The morphology of the spread protein films comprises an extended 2D network which with regions of less textured material or gapsincreasing coverage becomes more substantial. Further, mechanical cycling of the surface area Lastly, we show that repeated compression/expansion cycles of the spread films anneal the protein network into a membrane that approach constant compressibility and has with increased superior durability. Our work provides a new perspective on an old problem in colloid and interface science. The scope for optimization of the surface loading mechanism in a range of systems leading to its exploitation in deposition-based technologies in the future is discussed.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03349
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    ABSTRACT: The nanoscale topography of adhesive surfaces is known to be an important factor governing cellular behavior. Previous work has shown that surface coatings composed of halloysite nanotubes enhances the adhesion, and therefore capture, of rare target cells such as circulating tumor cells. Here, we demonstrate a unique feature of these coatings in its ability to reduce the adhesion of leukocytes and prevent leukocyte spreading. Surfaces were prepared with coatings of halloysite nanotubes and functionalized for leukocyte adhesion with E-selectin, and the dilution of nanotube concentration revealed a threshold concentration below which cell spreading became comparable with smooth surfaces. Evaluation of surface roughness characteristics determined that the average distance between discrete surface features correlated with adhesion metrics, with a separation distance of approximately 2 μm identified as the critical threshold. Computational modeling of the interaction of leukocytes with halloysite nanotube coated surfaces of varying concentrations demonstrates that the geometry of the cell surface and adhesive counter-surface produce a significantly diminished effective contact area compared to a leukocyte interacting with a smooth surface.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03288
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    ABSTRACT: Oil foams are composed of gas bubbles dispersed in an oil phase. These systems are scarcely studied despite their great potential in diverse fields such as the food and cosmetic industries. Contrary to aqueous foams, the production of oil foams is difficult to achieve due to the inefficiency of surfactant adsorption at oil-air interfaces. Herein, we report a simple way to produce oil foams from oleogels, whose liquid phase is a mixture of sunflower oil and fatty alcohols. The temperature at which the oleogel formed was found to depend on both fatty alcohol chain length and concentration. The air bubbles in the oleogel foam were stabilized by fatty alcohol crystals. Below the melting temperature of the crystals, oleogel foams were stable for months. Upon heating, these ultrastable foams collapsed within a few minutes due to the melting of the crystal particles. The transition between crystal formation and melting was reversible, leading to thermoresponsive non-aqueous foams. The reversible switching between ultrastable and unstable foam depended solely on the temperature of the system. We demonstrate that these oleogel foams can be made to be photoresponsive by using internal heat sources such as carbon black particles, which can absorb UV light and dissipate the absorbed energy as heat. This simple approach for the formulation of responsive oil foams could be easily extended to other oleogel systems and could find a broad range of applications due to the availability of the components in large quantities and at low cost.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03660
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    ABSTRACT: We have calculated the equilibrium shape of the axially symmetric meniscus along which a spherical bubble contacts a flat liquid surface, by analytically integrating the Young-Laplace equation in the presence of gravity, in the limit of large Bond numbers. This method has the advantage that it provides semi-analytical expressions for key geometrical properties of the bubble in terms of the Bond number. Results are in good overall agreement with experimental data and are consistent with fully numerical (Surface Evolver) calculations. In particular, we are able to describe how the bubble shape changes from hemispherical, with a shallow flat bottom, to lenticular, with a deeper, curved bottom, as the Bond number is decreased.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03970
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    ABSTRACT: The current study is aimed at investigating the effect of cationic charge density and hydrophobicity on the antibacterial and hemolytic activities. Two kinds of cationic surfmers, containing single or double hydrophobic tails (octyl chains or benzyl groups), and the corresponding homopolymers, were synthesized. The antimicrobial activity of these candidate antibacterials was studied by microbial growth inhibition assays against E. coli and hemolysis activity was carried out using human red blood cells. It was interestingly found that the homopolymers were much more effective in antibacterial property than their corresponding monomers. Furthermore, the geminized homopolymers have significantly higher antibacterial activity than those of their counterparts but with single amphiphilic side chains in each repeated unit. It was noteworthy that geminized homopolymers, with high positive charge density and moderate hydrophobicity (such as benzyl groups), combine both advantages of efficient antibacterial property and prominently high selectivity. In order to further explain the antibacterial performance of the novel polymer series, the molecular interaction mechanism was proposed according to experimental data which shows that these specimens are likely to kill microbes by disrupting bacterial membranes, leading them unlikely to induce resistance.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03182
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    ABSTRACT: Aromatic Self-Assembled Monolayers (SAMs) are proposed as platforms for development of supramolecular assemblies driven by surface templates. For many applications, electron processing is used to locally reinforce the layer. In order to achieve a better control of the irradiation step, terphenylthiol SAMs are studied here as model aromatic SAMs to investigate chemical transformations induced by electron impact at 50 eV. High Resolution Electron Energy Loss Spectroscopy (HREELS) and Electron Stimulated Desorption (ESD) of neutral fragments measurements are combined to investigate electron-induced chemical transformation of the layer. The decrease of the CH stretching HREELS signature is mainly attributed to dehydrogenation, without noticeable hybridization change of the hydrogenated carbon centers. Its evolution as a function of the irradiation dose gives an estimate of the effective Hydrogen content loss cross section, σ=2.7-4.7×10(-17)cm(2). Electron impact ionization is the major primary mechanism involved, the impact electronic excitation contributing only marginally. Therefore, special attention is given to the contribution of the low-energy secondary electrons to the induced chemistry. The effective cross section related to dissociative secondary electron attachment at 6 eV is estimated to be one order of magnitude smaller. The 1 eV electrons do not induce significant chemical modification for a 2.5 dose excluding their contribution.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b02109
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    ABSTRACT: Controlled delivery of bioactive signaling molecules and drugs is essential for the development of the next generation of tissue regeneration scaffolds. However, these molecules must be delivered from a nonfouling platform, so that the therapeutic role is not masked by the naturally occurring foreign body response. Therefore, the purpose of this study is to characterize the release profiles of three pseudo-drug molecules from a nonfouling polyampholyte hydrogel to gain insight into the potential for this platform to serve as a tissue regeneration scaffold. Hydrogels composed of equimolar concentrations of [2-(acryloyloxy)ethyl] trimethylammonium chloride (TMA) and 2-carboxyethyl acrylate (CAA) monomers were synthesized in the presence of caffeine, methylene blue, or metanil yellow. Then the release of these three molecules was tracked as a function of the hydrogel cross-linker density, the solution pH, and the solution ionic strength. The results suggest that the release of the neutral caffeine molecule is dictated by diffusion alone, while the release of the two charged pseudo-drug molecules are controlled by their interactions with the charged regions of the TMA and CAA monomer subunits. These interactions are clearly impacted by solution pH and ionic strength leading to clear changes in the rate of release and extent of release for metanil yellow and methylene blue. Additionally, an enzyme-linked immunosorbent assay was used to confirm that the TMA:CAA hydrogels retain their nonfouling characteristics following the release of the pseudo-drug molecules. When these results are combined with the literature related to TMA:CAA hydrogels it is concluded that this system represents a promising multi-functional platform for both short-term and long-term delivery of bioactive molecules for tissue regeneration.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03597
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    ABSTRACT: Controlling aggregation of the dual sensitizer-emitter (S-E), zinc tetraphenylporphyrin (ZnTPP), is an important consideration in solid state noncoherent photon upconversion (NCPU) applications. The Langmuir Blodgett (LB) technique is a facile means of preparing ordered assemblies in thin films to study distance-dependent energy transfer processes in S-E systems and was used in this report to control the aggregation of a functionalized ZnTPP on solid substrates. This was achieved by synthetic addition of a short polar tail to one of the pendant phenyl rings in ZnTPP in order to make it surface active. The surface active ZnTPP derivative formed rigid films at the air-water interface and exhibited mean molecular areas consistent with approximately vertically-oriented molecules under appropriate film compression. A red shift in the UV-Vis spectra as well as unquenched fluorescence emission of the LB films indicated formation of well-ordered aggregates. However, NCPU, present in the solution phase, was not observed in the LB films suggesting that NCPU from ZnTPP as dual S-E required not just a controlled aggregation but a specific orientation of the molecules with respect to each other.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03171
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    ABSTRACT: Biocompatible liposomes were used for the first time to study the deintercalation process of a prominent anticancer drug doxorubicin (DOX) from the doxorubicin intercalated DNA (DOX-DNA complex) under controlled experimental condition. The study revealed that the anionic liposomes (DMPG liposomes) appeared to be the most effective to bring in the highest percentage of drug release while the cationic one (DOTAP liposomes) scored the lowest percentage of release. The drug release was primarily attributed to the electrostatic interaction between liposomes and drug molecules. Apart from this interaction, change in the hydrophobicity of medium upon addition of liposomes to DNA-drug solution accompanied by lipoplex formation between DNA and liposomes were also attributed to the observed deintercalation. The CD and the time resolved rotational relaxation studies confirmed that lipoplex formation took place between liposomes and DNA owing to electrostatic interaction. The confocal study revealed that in the post release period, DOX binds with liposomes. The reason behind the binding is electrostatic interaction as well as the unique bilayer structure of liposomes which helps it to act as "hydrophobic sink" for DOX. The study overall highlighted a novel strategy for deintercalation of drug using biocompatible liposomes as the release of the drug can be controlled over a period of time by varying concentration and composition of the liposomes.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03702
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    ABSTRACT: Micropatterns of hydrophilic polymer brushes were prepared by micromolding in capillaries (MIMIC). The polymers are covalently bound to the surfaces by a rapid hetero Diels-Alder reaction, constituting the first example of polymers grafted to surfaces in a defined pattern by MIMIC. The polymers (poly(acrylic acid), poly(hydroxyethyl acrylate) and poly(tetraethyleneglycole acrylate)) ranging in molecular weight from 1500 to 6000 g mol-1) were prepared with narrow dispersities via the reversible addition fragmentation chain transfer (RAFT) process using a highly electron deficient RAFT agent able to react with surface anchored dienes such as cyclopentadiene. We demonstrate that the anchoring method is facile to perform and highly suitable to prepare patterned surfaces which are passivated against biological impact in well-defined areas.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03924
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    ABSTRACT: In this article, we report the formation of nanoring structures on Fe coated substrate and their application in guiding the growth of carbon nanotube (CNT) patterns with hierarchical structures. The formation of nanorings involves the etching of polystyrene (PS) monolayer colloidal crystals (MCCs) under reactive ion etching (RIE), and the redeposition and cross-linkage of the active degradation products at the contact line between the MCCs and the substrate. After washing out the MCCs, insoluble nanorings with hexagonal order on the substrate are developed. The RIE process can control the morphology of the nanorings, as well as the distribution of the Fe element distribution on the substrate, thus continuous Fe layer and separated Fe discs, on the substrate are created on substrate after washing, depending on the etching time and the shield of MCCs. The survived Fe element can work as the catalyst to initiate the in situ growth of aligned CNTs in the following chemical vapor deposition (CVD) process, while the Fe element underneath the nanorings keep inactivity. Eventually, CNT patterns with hierarchical structures are formed. One level originates from the survived Fe layer; the other level is templated from the nanoring structures, which cause the blank area in the CNT bundles.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03886
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    ABSTRACT: The nanoparticles built of bicontinuos lyotropic phases of cubic symmetry are studied within the framework of the Landau-Brazovskii functional that correctly predicts the structure of soft monocrystals and thin films of bicontinuos lyotropic phases. A detailed description of geometry and topology of cubosomes is presented. Such level of description of the internal structure of cubosomes is not easily accessible by experimental techniques. We show that the internal structure of the cubosomes may be extremely rich.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03799
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    ABSTRACT: A molecular simulation study is reported for water desalination through five zeolitic imidazolate framework (ZIF) membranes, namely ZIF-25, -71, -93, -96, and -97. The five ZIFs possess identical rho-topology but differ in functional groups. The rejection of salt (NaCl) is found to be around 97% in ZIF-25, and 100% in the other four ZIFs. The permeance ranges from 27 to 710 kg/(m(2)·h·bar), about one∼two orders of magnitude higher compared with commercial reverse osmosis membranes. Due to a larger aperture size da, ZIF-25, -71, and -96 exhibit a much higher water flux than ZIF-93 and -97; however, the flux in ZIF-25, -71, and -96 is governed by the polarity of functional group rather than da. With the hydrophobic CH3 group, ZIF-25 has the highest flux despite the smallest da among ZIF-25, -71, and -96. The lifetime of hydrogen bonding in ZIF-25 is shorter than that in ZIF-71 and -96. Furthermore, water molecules undergo a fast flushing motion in ZIF-25 but, frequent jumping in ZIF-96 and particularly in ZIF-97. An Arrhenius-type relationship is found between water flux in ZIF-25 and temperature, and the activation energy is predicted to be 6.5 kJ/mol. This simulation study provides a microscopic insight into water desalination in a series of ZIFs, reveals the key factors (aperture size and polarity of functional group) governing water flux, and suggests that ZIF-25 might be an interesting reverse osmosis membrane for high-performance water desalination.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b03593
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    ABSTRACT: We report on the controlled clustering of charged colloidal particles by the adsorption of ionic surfactants, which tunes charge numbers Z of partilces. In particular, we studied the heteroclustering of submicron-sized polystyrene (PS) and silica particles, both of which are negatively charged, by additions of cetylpyridinium chloride (CPC), a cationic surfactant. The surfactant concentration Csurf was selected below the critical micelle concentration. As CPC molecules were adsorbed, Z values of the PS and silica particles decreased, inverting to positive when Csurf exceeded the isoelectric point Ciep. Hydrophobic PS particles exhibited much lower Ciep than hydrophilic silica particles. At Csurfs between their Cieps, the particles were oppositely charged, and clustering was enabled. To explain the clustering behavior, we investigated adsorption isotherms of the CPC and screened-Coulomb-type pair potential. Expected applications of the present findings are the control of colloidal associations and the aggregation of various particle types into heterogeneous colloidal clusters.
    Langmuir 11/2015; DOI:10.1021/acs.langmuir.5b02778