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
    ​ white

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Encapsulated bacteria usually exhibit strong resistance to a wide-range of sterilisation methods, and are often virulent. Early detection of encapsulation can be crucial in microbial pathology. This work demonstrates a fast and sensitive method for the detection of encapsulated bacterial cells. Nanoindentation force measurements were used to confirm the presence of deliquescent bacterial capsules surrounding bacterial cells. Force/distance approach curves contained characteristic linear - non-linear - linear domains, indicating co-compression of the capsular layer and cell, indentation of the capsule and compression of the cell alone. This is a sensitive method for the detection and verification of the encapsulation status of bacterial cells. Given that this method was successful in detecting the nanomechanical properties of two different layers of cell material, i.e. distinguishing between the capsule and the remainder of the cell, further development may potentially lead to the ability to analyse even thinner cellular layers, e.g. lipid bilayers.
    Langmuir 10/2015; DOI:10.1021/acs.langmuir.5b02546
  • [Show abstract] [Hide abstract]
    ABSTRACT: Viscoelastic property measurements made at the solid-liquid interface are key to characterizing materials for a variety of biological and industrial applications. Further, nanostructured materials require nanoscale measurements. Here, material loss tangents (tan δ) were extracted from confounding liquid effects in nanoscale contact resonance force microscopy (CR-FM), an atomic force microscope based technique for observing mechanical properties of surfaces. Obtaining reliable CR-FM viscoelastic measurements in liquid is complicated by two effects. First, in liquid, spurious signals arise during cantilever excitation. Second, it is challenging to separate changes to cantilever behavior due to the sample from changes due to environmental damping and added mass effects. We overcame these challenges by applying photothermal cantilever excitation in multiple resonance modes and a predictive model for the hydrodynamic effects. We demonstrated quantitative, nanoscale viscoelastic CR-FM measurements of polymers at the solid-liquid interface. The technique is demonstrated on a point-by-point basis on polymer samples and while imaging in contact mode on a fixed plant cell wall. Values of tan δ for measurements made in water agreed with the values for measurements in air for some experimental conditions on polystyrene and for all examined conditions on polypropylene.
    Langmuir 10/2015; DOI:10.1021/acs.langmuir.5b02860
  • [Show abstract] [Hide abstract]
    ABSTRACT: Temperature-responsive properties of surface-attached poly(N-isopropylacrylamide) (PNIPAM) network films with well-controlled chemistry are investigated. The synthesis consists in crosslinking and grafting preformed and ene-reactive polymer chains through thiol-ene click chemistry. The formation of surface-attached and crosslinked polymer films has the advantage of being well-controlled without any caution of no-oxygen atmosphere or addition of initiators. PNIPAM hydrogel films with same crosslinks density are synthesized on a wide range of thickness, from nanometers to micrometers. The swelling-collapse transition with temperature is studied by using ellipsometry, neutron reflectivity and atomic force microscopy as complementary surface probing techniques. Sharp and high amplitude temperature-induced phase transition is observed for all submicrometric PNIPAM hydrogel films. For temperature above LCST, surface-attached PNIPAM hydrogels collapse similarly but without complete expulsion of water. For temperature below LCST, the swelling of PNIPAM hydrogels depends on the film thickness. It is shown that the swelling is strongly affected by the surface attachment for ultrathin films below approximately 150 nm. For thicker films above 150 nm (to micrometers), surface-attached polymer networks with same crosslinks density swell equally. The density profile of the hydrogel films in the direction normal to the substrate is confronted with in-plane topography of the free surface. It results that the free interface width is much larger than the roughness of the hydrogel film, suggesting pendant chains at the free surface.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02948
  • [Show abstract] [Hide abstract]
    ABSTRACT: As surfactants for preparation of non-aqueous microcapsule dispersions by the emulsion solvent evaporation method, three copolymers composed of stearyl methacrylate (SMA) and glycidyl methacrylate (GMA) with different monomer sequences (i.e., random, block, and block-random) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Despite having the same comonomer composition, the copolymers exhibited different functionality as surfactants for creating emulsions with respective dispersed and continuous phases consisting of methanol and isoparaffin solvent. The optimal monomer sequence for the surfactant was determined based on the droplet sizes and the stabilities of the emulsions created using these copolymers. The block-random copolymer led to an emulsion with better stability than obtained using the random copolymer and a smaller droplet size than achieved with the block copolymer. Modification of the epoxy group of the GMA unit by diethanolamine (DEA) further decreased the droplet size, leading to higher stability of the emulsion. The DEA-modified block-random copolymer gave rise to non-aqueous microcapsule dispersions after evaporation of methanol from the emulsions containing colored dyes in their dispersed phases. These dispersions exhibited high stability and the particle sizes were small enough for application to the inkjet printing process.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02358
  • [Show abstract] [Hide abstract]
    ABSTRACT: We investigated the pH-dependent properties of multilayered films made of chitosan (CHI) and alginate (ALG) and focused on their post-assembly response to different pH environments usingquartz crystal microbalance with dissipation monitoring (QCM-D), swelling studies, zeta potential measurements and dynamic mechanical analysis (DMA). In an acidic environment, the multilayers presented lower dissipation values and, consequently, higher moduli when compared with the values obtained for the pH used during the assembly (5.5). When the multilayers were exposed to alkaline environments the opposite behavior occurred. These results were further corroborated with the ability of this multilayered system to exhibit a reversible swelling-deswelling behavior within the pH range from 3 to 9. The changes of the physicochemical properties of the multilayer system were gradual and different from the ones of individual solubilized polyelectrolytes. This behavior is related to electrostatic interactions between the ionizable groups combined with hydrogen-bonding and hydrophobic interactions. Beyond the pH range of 3-9 the multilayers were stabilized by genipin cross-linking. The multilayered films also became more rigid while preserving the pH-responsiveness conferred by the ionizable moieties of the polyelectrolytes. This work demonstrates the versatility and feasibility of LbL methodology to generate inherently pH stimuli-responsive nanostructured films. Surface functionalization using pH-repsonsiveness endows abilities for several biomedical applications such as drug delivery, diagnostics, microfluidics, biosensing or biomimetic implantable membranes.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02478
  • [Show abstract] [Hide abstract]
    ABSTRACT: Electrically actuated transport dynamics of colloidal droplets, on a hydrophobic dielectric film covering an array of electrodes, is studied here. Specifically, the effects of the size and electrical properties (zeta-potential) of the colloidal particles on such transport characteristics are investigated. For the colloidal droplets, the application of an electrical voltage leads to additional attenuation of the local dielectric-droplet interfacial tension. This is due to the electrically triggered colloidal particle adsorption at the dielectric-droplet interface, in the immediate vicinity of the droplet three-phase contact line (TPCL). The extent of interfacial particle adsorption, and hence, the extent of the consequential reduction in the interfacial tension, is dictated by the combined effects of the three-phase contact line spreading, particle size, the interfacial electrostatic interaction between the colloidal particles (if charged) and the charged dielectric surface above the activated electrode, and the interparticle electrostatic repulsion. The electrical driving force of varying magnitude, stemming from this altered solid-liquid interfacial tension gradient, culminates in different droplet transport velocity and droplet transfer frequency, for different colloidal droplets. We substantiate the inferences from our experimental results by a quasi-steady state force balance model for colloidal droplet transport. We believe that the present work will provide an accurate framework for determining the optimal design and operational parameters for digital microfluidic chips handling colloidal droplets, as encountered in a plethora of applications.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b01941
  • [Show abstract] [Hide abstract]
    ABSTRACT: Single-molecule force spectroscopy measurements of a DNA duplex comprising an artificial metal-mediated base pair are reported. The measurements reveal that DNA duplexes comprising one central imidazole:imidazole mispair rupture at lower forces than a related duplex with canonical base pairs only. In contrast, DNA duplexes with one central imidazole-Ag+-imidazole base pair (formed by the addition of Ag+ to the aforementioned duplex with the mispair) rupture at higher forces. These measurements indicate for the first time that the increase in thermal stability of a nucleic acid duplex that is observed upon the formation of a metal-mediated base pair is accompanied by a concomitant mechanical stabilization. In fact, the mechanical stabilization even exceeds the thermal one. This result indicates that nucleic acids with metal-mediated base pairs should be ideal building blocks for rigid functionalized DNA nano-objects.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b03183
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recently, it turned out that nano-structured reaction media containing highly inert solvents as tetrahydrothiophen-1,1-dioxid (sulfolane) are needed in strongly oxidizing or reductive reactions. Due to their ability of solubilizing polar and nonpolar solvents with a large nano-structured interface in particular microemulsions provide such interesting reaction media. Starting from the pseudo-ternary microemulsion H2O - n-octane - C12E4/C12E5 (polyoxyethylene n-alkylether) water was successively replaced by the highly inert tetrahydrothiophen-1,1-dioxid (sulfolane). We found that an increasing sulfolane content drives the system beyond the tricritical point. Replacing the already long chain surfactants C12E4 and C12E5 by a mixture of the even longer chain surfactants C18E6 and C18E8 we were able to prepare non-aqueous sulfolane-microemulsions for the very first time. We also teach how in a second step the phase behavior of the hydrophilic sulfolane - n-octane - C18E8 system can be tuned at constant temperature (as required by the reaction conditions) by addition of the hydrophobic cosurfactant 1-octanol (C8E0). The change in curvature by adding 1-octanol is demonstrated measuring the size of reverse micelles by DLS exhibiting radii which vary from at least 8 nm to 16 nm suitable sizes for inverse nano-reaction vessels.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02529
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mineral deposition within living cells relies on control over the distribution and availability of precursors as well as the location and rates of nucleation and growth. This control is provided in large part by biomolecular chelators, which bind precursors and regulate their availability, and compartmentalization within specialized mineralizing vesicles. Biomimetic mineralization in self-assembled lipid vesicles is an attractive means of studying the mineralization process, but has proven challenging due to vesicle heterogeneity in lamellarity, contents and size across a population, difficulties encapsulating high and uniform precursor concentrations, and the need to transport reagents across an intact lipid bilayer membrane. Here we report the use of liposome-stabilized all-aqueous emulsion droplets as simple artificial mineralizing vesicles (AMVs). These biomimetic microreactors allow entry of precursors while retaining a protein catalyst by equilibrium partitioning between internal and external polymer-rich phases. Small molecule chelators with intermediate binding affinity were employed to control Ca2+ availability during CaCO3 mineralization, providing protection against liposome aggregation while allowing CaCO3 formation. Mineral deposition was limited to the AMV interior, due to localized production of CO32- by compartmentalized urease. Particle formation was uniform across the entire population of AMVs, with multiple submicrometer amorphous CaCO3 particles produced in each one. The all-aqueous emulsion-based approach to biomimetic giant mineral deposition vesicles introduced here should be adaptable for enzyme-catalyzed synthesis of a wide variety of materials, by varying the metal ion, enzyme, and/or chelator.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02754
  • [Show abstract] [Hide abstract]
    ABSTRACT: An original protocol of simultaneous surface modification and transfer from aqueous to organic phases of anatase TiO2 nanoparticles (NPs) using alkylphosphonic acids (PAs) is studied. The influence of the solvent, the nature and concentration of the PA, and the size, concentration, and aggregation state of the TiO2 NPs was investigated. Complete transfer was observed for linear alkyl chains (5, 8, 12, and 18 C atoms), even at very high sol concentrations. After transfer, the grafted NPs were characterized by (31)P solid-state MAS NMR. The dispersion state of NPs before and after phase transfer was monitored by dynamic light scattering (DLS). Small-angle neutron scattering (SANS) was used to characterize the structure of PA-grafted NPs in the organic solvent. Using a quantitative core-shell model cross-checked under different contrast conditions, it is found that the primary particles making up the NPs are homogeneously grafted with a solvated PA-layer. The nanometric thickness of the latter is shown to increase with the length of the linear carbon chain of the PA, independent of the size of the primary TiO2 NP. Interestingly, a reversible temperature-dependent aggregation was evidenced visually for C18PA, and confirmed by DLS and SANS: heating the sample induces the breakup of aggregates, which reassemble upon cooling. Finally, in the case of NPs agglomerated by playing with the pH or the salt concentration of the sols, the phase transfer with PA is capable of redispersing the agglomerates. This new and highly versatile method of NP surface modification with PAs and simultaneous transfer is thus well suited for obtaining well-dispersed grafted NPs.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02833
  • [Show abstract] [Hide abstract]
    ABSTRACT: The spreading of axisymmetric viscoplastic droplets extruded slowly on glass surfaces is studied experimentally using shadowgraphy and swept-field confocal microscopy. Shadowgraphy provides measurements of the evolving position of the free surface; the microscopy furnishes vertical profiles of the radial velocity using Particle Image Velocimetry (PIV) with neutrally buoyant tracers seeded in the fluid. Experiments were conducted for two complex fluids: aqueous solutions of Carbopol and xanthan gum. On untreated glass surfaces PIV demonstrates that both fluids suffer a significant amount of effective slip. The experiments were repeated on glass that had been treated to feature positive surface charges, thereby promoting adhesion between the negatively charged polymeric constituents of the fluids and the glass surface. The Carbopol and xanthan gum droplets spread more slowly on the treated surface and to a smaller radial distance. PIV demonstrated that this reduced spreading was associated with a substantial reduction in slip. For Carbopol, the effective slip could be eliminated entirely to within the precision of the PIV measurements; the reduction in slip was less effective for xanthan gum, with a weak slip velocity remaining noticeable.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02353
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we have devised a new approach to measure the critical pressure that a liquid marble can withstand. A liquid marble is gradually squeezed under a mechanical compression applied by two parallel plates. It ruptures at a sufficiently large applied pressure. Combining the force measurement and the high speed imaging, we can determine the critical pressure that ruptures the liquid marble. This critical pressure, which reflects the mechanical robustness of liquid marbles, depends on the type and size of the stabilizing particles as well as the chemical nature of the liquid droplet. By investigating the surface of the liquid marble, we attribute its rupture under the critical pressure to the low surface coverage of particles when highly stretched. Moreover, the applied pressure can be reflected by the inner Laplace pressure of the liquid marble considering the squeezing test is a quasi-static process. By analyzing the Laplace pressure upon rupture of the liquid marble, we predict the dependence of the critical pressure on the size of the liquid marble, which agrees well with experimental results.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02792
  • [Show abstract] [Hide abstract]
    ABSTRACT: For the first time we report a new fabrication for manipulating the ferromagnetic property of molecular magnets by forming wormlike micelles in a magnetic-ionic-liquid (mag-IL) complexes. The ferromagnetism of the mag-IL complexes was enhanced 4 times because of the formation of wormlike micelles, interpreting a new evidence of the essence of magnetism generation in molecular level. The characteristics like morphology and magnetic properties of the wormlike micelle gel were investigated in detail by cryogenic transmission electron microscopy (Cryo-TEM), rheological measurements, circular dichroism (CD), FT-IR spectra and superconducting quantum interference device method (SQUID). An explanation of ferromagnetism elevation from the view of the molecular (ionic) distribution is also given. For the changes of the magnetic properties (ferromagnetism elevation) in the wormlike micelle systems, the ability of CTAFe in magnetizing AzoNa4 (or AzoH4) can be ascribed to an interplay of the magnetic [FeCl3Br]- ions both in the Stern layer and in the cores of the wormlike micelles. Formation of colloidal aggregates, i.e. wormlike micelles provides a new strategy to tune the magnetic properties of novel molecular magnets.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b03148
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study we explore the fundamental aspects of Pickering emulsions stabilized by oppositely charged particles. Using oppositely charged latex particles as a model system, Pickering emulsions with good long term stability can be obtained without the need for any electrolyte. The effects of parameters like oil to water ratio, mixed particle composition and pH on emulsion type and stability are explored and linked to the behavior of the aqueous particle dispersion prior to emulsification. The particle composition is found to affect the formation of emulsions, viz. stable emulsions were obtained close to a particle number ratio of 1:1 and no emulsion was formed with either positive or negatively charged particles alone. The emulsions in particle mixtures exhibited phase inversion from oil-in-water to water-in-oil beyond an oil volume fraction of 0.8. Morphological features of emulsion droplets in terms of particle arrangement on the droplets are discussed.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02443
  • [Show abstract] [Hide abstract]
    ABSTRACT: Interparticle forces govern the mechanical behavior of granular matter and direct the hierarchical assembling of nanoparticles into supramolecular structures. Understanding how these forces change under different ambient conditions would directly benefit industrial-scale nanoparticle process units such as filtering or fluidization. Here we rationalize and quantify the contributions of dispersion, capillary and solvation forces between hydrophilic TiO2 nanoparticles with sub-10nm diameter and show that the humidity dependence of the interparticle forces is governed by a delicate interplay between the structure of adsorbed water layers and the surface roughness. All-atom molecular dynamics modelling supported by force-spectroscopy experiments reveal an unexpected decrease of the contact forces at increasing humidity for nearly spherical particles, while the forces between rough particles are insensitive to strong humidity changes. Our results also frame the limits of applicability of discrete solvation and continuum capillary theories in a regime where interparticle forces are dominated by the molecular nature of surface adsorbates.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02989
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we study silicon nanowire synthesis via one-step metal-assisted chemical etching (MACE) on micro-structured silicon surfaces with periodic pillar/cavity array. It is found that hydrogen gas produced from the initial anodic reaction can be trapped inside cavities and between pillars, which serves as a mask to prevent local etching, and leads to the formation of patterned vertically aligned nanowire array. A simple model is presented to demonstrate that such bubble entrapment is due to the significant adhesion energy barrier, which is a function of pillar/cavity geometry, contact angle and nanowire length to be etched. The bubble entrapment can be efficiently removed when extra energy is introduced by sonication to overcome this energy barrier, resulting in nanowire growth in all exposed surfaces. This bubble-regulated MACE process on micro-structured surfaces can be used to fabricate nanowire arrays with desired morphologies.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b03056
  • [Show abstract] [Hide abstract]
    ABSTRACT: The surface and bulk properties of bola-type dicarboxylic acid (sebacic acid, SA) and zwitterionic surfactant tetradecyldimethylamine oxide (C14DMAO) mixtures in aqueous solutions were studied. Surface tension measurements indicate pronounced synergistic effect between SA and C14DMAO. In bulk aqueous solutions, rich phase behavior was observed with varied SA-to-C14DMAO ratio () and total surfactant concentration. Typically at  = 0.5, a novel pseudo-gemini surfactant (C14-S-C14 ) forms driven by electrostatic interaction and hydrogen bonding. The C14-S-C14/H2O system exhibits rich phase behavior induced by transition of aggregates. With increasing concentration of C14-S-C14, one can observe a viscous L1 phase, an L1/Lα two-phase region where a birefringent Lα phase is on the top of an L1 phase, a single Lα phase and finally a mixture of Lα phase and precipitate. Microstructures formed in the Lα phases were determined by freeze-fracture transmission electron microscopy (FF-TEM) and cryogenic-transmission electron microscopy (cryo-TEM) observations. Polymorphic aggregation behavior was observed with the formation of a variety of bilayer structures including uni-lamellar vesicles, onions, open and hyper-branched bilayers. Rheological measurements showed that the Lα phases are viscoelastic and sensitive to temperature where a quick loss of the viscoelasticity was observed at elevated temperature.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02491
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the side chain type liquid crystalline (LC) polymers, the main chain rigidity significantly affects the LC structure and properties. We show herein a relevant new effect regarding the orientation of side chain mesogenic groups of LC polymers in a thin film state. A subtle change in the main chain structure, i. e., polyacrylate and polymethacrylate, leads to a clear alternation of mesogens in the homeotropic and planar modes, respectively. This orientational discrimination is triggered from the free surface region (film-air interface) as revealed by surface micropatterning via inkjet printing.
    Langmuir 09/2015; DOI:10.1021/acs.langmuir.5b02442