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 2015
2013 / 2014 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 4.42
Cited half-life 6.70
Immediacy index 0.79
Eigenfactor 0.21
Article influence 1.16
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

  • Scott C Bukosky · William D Ristenpart
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    ABSTRACT: Micrometer-scale particles suspended in NaCl solutions aggregate laterally near the electrode upon application of a low-frequency (∼100 Hz) field, but the same particles suspended in NaOH solutions are instead observed to separate laterally. The underlying mechanism for the electrolyte dependence remains obscure. Recent work by Woehl et al. (PRX, 2015) revealed that, contrary to previous reports, particles suspended in NaOH solutions indeed aggregate under some conditions while simultaneously exhibiting a distinct bifurcation in average height above the electrode. Here we elaborate on this observation by demonstrating the existence of a critical frequency (∼25 Hz) below which particles in NaOH aggregate laterally and above which they separate. The results indicate that the current demarcation of electrolytes as either aggregating or separating is misleading and that the key role of the electrolyte instead is to set the magnitude of a critical frequency at which particles transition between the two behaviors.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02432
  • Malte Jesper · Milan Alt · Janusz Schinke · Sabina Hillebrandt · Iva Angelova · Valentina Rohnacher · Annemarie Pucci · Uli Lemmer · Wolfram Jaegermann · Wolfgang Kowalsky · Tobias Glaser · Eric Mankel · Robert Lovrincic · Florian Ernst Golling · Manuel Hamburger · Uwe H F Bunz
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    ABSTRACT: In this work we examine small, conjugated molecules bearing a thiol head group as Self Assembled Monolayers (SAM). Functional groups in the SAM-active molecule shift the work function of gold to n-channel semiconductor regimes and improve the wettability of the surface. We examine the effect of the presence of methylene linkers on the orientation of the molecule within the SAM. 3,4,5 Trimethoxythiophenol (TMP-SH) and 3,4,5-trimethoxybenzylthiol (TMP-CH2-SH) were first subjected to computational analysis, predicting work function shifts of -430 and -310 meV. Contact angle measurements show an increase of the wetting envelope compared to that of pristine gold. Infrared (IR) measurements show tilt angles of 22° and 63° respectively with the methylene linked molecule (TMP-CH2-SH) attaining a flatter orientation The actual work function shift as measured with photoemission spectroscopy (XPS/UPS) is even larger, -600 meV and -430 meV, respectively. The contact resistance between gold electrodes and poly[N,N´-bis(2-octyldodecyl)-naphthalene-1,4:5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5´-(2,2´-bithiophene) (Polyera Aktive Ink, "N2200") in n-type OFETs is demonstrated to decrease by three orders of magnitude due to the usage of TMP-SH and TMP-CH2-SH. The effective mobility was enhanced by two orders of magnitude, significantly decreasing the contact resistance to match the mobilities reported for N2200 with optimized electrodes.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02316
  • Derek Y C Chan
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    ABSTRACT: Small metallic particles used in forming nano-structured to impart novel optical, catalytic or tribo-rheological can be modeled as conducting particles with equipotential surfaces that carry a net surface charge. The value of the surface potential will vary with the separation between interacting particles and in the absence of charge transfer or electrochemical reactions across the particle surface, the total charge of each particle must also remain constant. These two physical conditions require the electrostatic boundary condition for metallic nano-particles to satisfy an equipotential whole-of-particle charge conservation constraint that has not been studied previously. This constraint gives rise to a global charge conserved constant potential (CCCP) boundary condition that results in multi-body effects in the electric double layer interaction that are either absent or are very small in the familiar constant potential or constant charge or surface electrochemical equilibrium condition.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02796
  • Joe Brown Grubbs · Rachelle Marie Arnold · Anandi Roy · Karson Brooks · Jenna A Bilbrey · Jing Gao · Jason Locklin
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    ABSTRACT: Surface-initiated ring-opening polymerization (SI-ROP) of polycaprolactone (PCL) and polylactide (PLA) polymer brushes with controlled degradation rates were prepared on oxide substrates. PCL brushes were polymerized from hydroxyl-terminated monolayers utilizing triazabicyclodecene (TBD) as the polymerization catalyst. A consistent brush thickness of 40 nm could be achieved with a reproducible unique crystalline morphology. The organocatalyzed PCL brushes were chain extended using lactide in the presence of zirconium n-butoxide to successfully grow PCL/PLA block copolymer (PCL-b-PLA) brushes with a final thickness of 55 nm. The degradation properties of "grafted from" PCL brush and the PCL-b-PLA brush were compared to "grafted to" PCL brushes, and we observed that the brush density plays a major role in degradation kinetics. Solutions of methanol/water at pH 14 were used to better solvate the brushes and increase the kinetics of degradation. This framework enables a control of degradation that allows for the precise removal of these coatings.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02093
  • Emi Radoslavova Haladjova · Silvia S Halacheva · Vilma Posheva · Ekaterina Peycheva · Veselina Moskova-Doumanova · Tanya Topouzova-Hristova · Jordan Doumanov · Stanislav Miletiev Rangelov
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    ABSTRACT: Comb-like polyethyleneimines with varying degrees of polymerization of both the main and side chains as well as different grafting densities were evaluated as gene delivery vectors. They were able to condense linear and plasmid DNA into nanosized polyplex particles with dimensions and surface potentials in the 130 - 330 nm and -30 - +15 mV ranges, respectively, depending on the amine:phosphate (N/P) ratio. The polyplexes remained stable in aqueous and buffer solutions from several hours up to several days. The moderate colloidal stability was also manifested in relatively broad size distribution (PDI typically above 0.2) and structural polymorphism observed by transmission electron microscopy. Both the neat polymers and polyplexes displayed low cytotoxicity in WISH cells as the relative cell viability was more than 60 %. Experiments with lysosomal fluorescence staining revealed that the internalization pathways and, in turn, transfection efficiency of the polyplex nanoparticles depended on the polymer chain topology. The vector systems based on the polymers of denser structure can be considered as promising systems for gene transfection in eukaryotic cells.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02408
  • Min Nie · Dilhan Kalyon · Frank T Fisher
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    ABSTRACT: The morphology of polymers inside a confined space has raised great interest in recent years. However, polymer crystallization within a one dimensional carbon nanostructure is challenging due to the difficulty of polar solvents carrying polymers to enter a nonpolar graphitic nanotube in bulk solution at normal temperature and pressure. Here we describe a method whereby nylon-11 was crystallized and periodically distributed on the individual graphitic nanocone structure within hollow carbon nanofibers (CNF). Differential scanning calorimetry and X-ray diffraction indicate that the nylon polymer is in the crystalline phase. A mechanism is suggested for the initiation of nanochannel flow in a bulk solvent as a prerequisite condition to achieve the interior polymer crystallization. Selective etching of polymer crystals on the outer wall of CNF indicates both surface tension and viscosity affect the flow within the CNF. This approach provides an opportunity for the interior functionalization of carbon nanotubes and nanofibers for applications in the biomedical, energy and related fields.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02042
  • Scott R Smith · Ryan Seenath · Monika Kulak · Jacek Lipkowski
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    ABSTRACT: Preparation of a nanoparticle modified gold substrate designed for characterization of hydrophilic self-assembled monolayers of 1-thio-β-D-glucose (TG) with electrochemical surface-enhanced Raman spectroscopy (EC-SERS) is presented. Citrate stabilized gold nanoparticles were deposited on a polycrystalline gold electrode and subjected to an electrochemical desorption procedure to completely remove all traces of adsorbed citrate. Complete desorption of citrate was confirmed by recording cyclic voltammetry curves and SERS spectra. The citrate-free nanoparticle modified gold electrode was then incubated in a 1 mg mL-1 aqueous solution of TG for 16 hours prior to being characterized by EC-SERS. The SERS spectra confirmed that at potentials more negative than -0.1V vs SCE thioglucose forms a monolayer in which majority of the molecules preserve their lactol ring structure and only a small fraction of molecules is oxidized. At potentials more positive than -0.1V the oxidation of TG molecules becomes prominent and at potentials more positive than 0.2V vs SCE the monolayer of TG consists chiefly of thiogluconate. The SERS spectra showed that the SAM of TG is well hydrated and hence can be used for hydrophilic modifications of a gold surface.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02767
  • Rebecca Stjernberg Bejhed · Tian Bo · Kristofer Eriksson · Rimantas Brucas · Sven Oscarsson · Mattias Strömberg · Peter Svedlindh · Klas Gunnarsson
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    ABSTRACT: A lab-on-a-chip travelling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micron-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized forming a sandwich-type assay. The MBs were transported across a detection area and the presence of target molecules resulted in immobilization of MBs within this area. Target quantification was accomplished by MB counting on the detection area using an optical microscope. In order to demonstrate the versatility of the microarray, biotinylated anti-avidin was selected as the target protein. In this case avidin functionalized MBs and an avidin functionalized detection area were used. With a total assay time of 1 to 1.5 hours (depending on the labelling approach used), a limit of detection in the attomol range was achieved. Compared to on-chip surface plasmon resonance biodetection systems, our method has a larger dynamic range and is about a factor of 500 times more sensitive. Furthermore, our MB transportation system can operate in any chip-based biosensor platform, thereby significantly improving traditional biosensors.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b01947
  • Signe S Grønborg · Søren Ulstrup · Marco Bianchi · Maciej Dendzik · Charlotte E Sanders · Jeppe V Lauritsen · Philip Hofmann · Jill A Miwa
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    ABSTRACT: We present a method for synthesizing large area epitaxial single-layer MoS2 on the Au(111) surface in ultrahigh vacuum. Using scanning tunneling microscopy and low energy electron diffraction, the evolution of the growth is followed from nanoscale single-layer MoS2 islands to a continuous MoS2 layer. An exceptionally good control over the MoS2 coverage is maintained using an approach based on cycles of Mo evaporation and sulfurization to first nucleate the MoS2 nanoislands and then gradually increase their size. During this growth process the native herringbone reconstruction of Au(111) is lifted as shown by low energy electron diffraction measurements. Within the MoS2 islands, we identify domains rotated by 60° that lead to atomically sharp line defects at domain boundaries. As the MoS2 coverage approaches the limit of a complete single layer, the formation of bilayer MoS2 islands is initiated. Angle-resolved photoemission spectroscopy measurements of both single and bilayer MoS2 samples show a dramatic change in their band structure around the center of the Brillouin zone. Brief exposure to air after removing the MoS2 layer from vacuum is not found to affect its quality.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02533
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    ABSTRACT: In this study we have reported our efforts to address some of the challenges in the detection of miRNAs using water-soluble graphene oxide and DNA nanoassemblies. Purposefully inserting mismatches at specific positions in our DNA (probe) strands shows an increasing specificity against our target miRNA, miR-10b, over miR-10a which varies by only a single nucleotide. This increased specificity came at a loss of signal intensity within the system, but we demonstrated that this could be addressed with the use of DNase I, an endonuclease capable of cleaving the DNA strands of the RNA/DNA heteroduplex and recycling the RNA target to hybridize to another probe strand. As we had previously demonstrated, this enzymatic signal also comes with an inherent activity of the enzyme on the surface adsorbed probe strands. To remove this activity of DNase I and the steady nonspecific increase in the fluorescence signal, without compromising the recovered signal, we attached thermo-responsive PEGMA polymers (poly(ethylene glycol) methyl ether methacrylate) to nGO. This smart polymer is able to shield the probes adsorbed on the nGO surface from the DNase I activity and capable of tuning the detection capacity of the nGO nanoassembly with a thermo-switch at 39 °C. By utilizing probes with multiple mismatches, the DNase I cleavage of the DNA probe strands and the attachment of PEGMA polymers to graphene oxide to block undesired DNase I activity, we were able to detect miR-10b from liquid biopsy mimics and breast cancer cell lines. Overall we have reported our efforts to improve the specificity, increase the sensitivity and eliminate the undesired enzymatic activity of DNase I on surface adsorbed probes for miR-10b detection using water-soluble graphene nanodevices. Even though we have only demonstrated the discrimination of miR-10b from miR-10a, our approach can be extended to other short RNA molecules which differ by a single nucleotide.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02026
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    ABSTRACT: By coating a thin layer of metal, including gold and gold-palladium alloy, of different thickness on the deformed shape memory polymer (SMP) pillars, we manipulate the degree of recovery of the SMP pillars. Pillars of different tilting angles were obtained as a result of balancing the strain recovery energy of the SMP pillars that favor the original straight state and the elastic energy of the metal layers that prefer the bent state. With this selective coating of a metal layer on the tilted pillars, we report a unique anisotropic liquid spreading behavior, where the water droplet is fully pinned in the direction of pillar tilting but advances in the reverse direction. This phenomenon is explained by the interplay of the surface chemistry and topography.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02622
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    ABSTRACT: Hydrogel fibril and crystal formation are related self-assembly processes that provide materials with distinct emergent properties. The relationship between fibril and crystal growth is poorly understood and efforts to engineer controlled hydrogelation vs. crystallization via small molecule self-assembly currently depend on empirical approaches. Herein we report the dynamic transition of self-assembled hydrogel fibrils of a phenylalanine (Phe) derivative, Fmoc-p-nitrophenylalanine (Fmoc-4-NO2-Phe), to crystalline microtubes. As has been shown with other Fmoc-Phe derivatives, Fmoc-4-NO2-Phe spontaneously self-assembles into amyloid-like fibrils that form an entangled hydrogel network when suspended in water. However, Fmoc-4-NO2-Phe fibrils uniquely transform over time into crystalline microtubes. Hydrogel fibrils appear to be a kinetic state with microtube crystals more thermodynamically favored. This dynamic transition from fibril to crystal has enabled a high-resolution structural analysis of the packing orientation of these self-assembled materials. Taking cues from this structural analysis, we demonstrate a rational strategy for stabilization of the kinetic Fmoc-4-NO2-Phe hydrogel fibrils. These results represent significant advances in our understanding of the dynamic nature of self-assembly processes and in our ability to rationally engineer these processes to provide materials with desired emergent properties.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b01953
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    ABSTRACT: We report an investigation of the influence of reversible self-assembly of amphiphilic redox-mediators on interfacial charge transfer at chemically functionalized electrodes. Specifically, we employed (11-ferrocenylundecyl)-trimethylammonium bromide (FTMA) as a model self-assembling redox mediator and alkanethiol-modified gold films as hydrophobic electrodes. By performing cyclic voltammetry (CV, 10 mV/s) in aqueous solutions containing FTMA above its critical micellar concentration (CMC), we measured anodic (Ia) and cathodic (Ic) peak current densities of 18 ± 3 μA/cm2 and 1.1 ± 0.1 μA/cm2, respectively, revealing substantial current rectification (Ia/Ic= 17) at the hydrophobic electrodes. In contrast, hydroxymethyl ferrocene (a non-self-assembling redox mediator) at hydrophobic electrodes and FTMA at bare gold electrodes yielded relatively low levels of rectification (Ia/Ic= 1.7 and 2.3, respectively). Scan-rate dependent measurements revealed Ia of FTMA to arise largely from diffusion of FTMA from bulk solution to the hydrophobic electrode whereas Ic was dominated by adsorbed FTMA, leading to the proposal that current rectification observed with FTMA is mediated by interfacial assemblies of reduced FTMA that block access of oxidized FTMA to the hydrophobic electrode. Support for this proposal was obtained by using atomic force microscopy and quartz crystal microbalance measurements to confirm the existence of interfacial assemblies of reduced FTMA (1.56 ± 0.2 molecules/nm2). Additional characterization of a mixed surfactant system containing FTMA and dodecyltrimethylammonium bromide (DTAB) revealed that interfacial assemblies of DTAB also block access of oxidized FTMA to hydrophobic electrodes; this system exhibited Ia/Ic>80. These results and others reported in this paper suggest that current rectification occurs in this system because oxidized FTMA does not mix with interfacial assemblies of reduced FTMA or DTAB formed at hydrophobic electrodes. More broadly, these results show that self-assembling redox mediators, when combined with chemically functionalized electrodes, offer the basis of new principles for controlling charge transfer at electrode/solution interfaces.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02212
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    ABSTRACT: Physicochemical properties, regulated by various surface modifications, influence the biological performance of materials. The interaction between surface charge and biomolecules is key to understanding the mechanism of surface-tissue integration. The objective of this study was to evaluate the biological response to a nano-scale titanium surface after ultraviolet (UV) irradiation and to analyze the effects via a physicochemical mechanism. The surface characteristics were evaluated by field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, surface profilometry, and contact angle assay. In addition, we applied the zeta-potential, a direct method to measure the electrostatic charge on UV-treated and UV-untreated titanium nanotube surfaces. The effect of the Ti surface on osteoblast-like MG-63 cells was determined by analyzing initial protein and cell early adhesion, morphology, cytoskeletal arrangement, proliferation and focal adhesion. Compared to an anodized titanium nanotube coating, UV irradiation altered the contact angles on the control surface from 51.5º to 6.2° without changing the surface topography or roughness. Furthermore, titanium nanotubes after UV treatment showed a significant reduction in the content of acidic hydroxyl groups and held less negative charge than the anodized coating. With regard to the biological response, along with an enhanced capability to adsorb bovine serum albumin, MG-63 osteoblast-like cells also exhibited a better affinity and activity on the UV-treated material. The results suggest that UV treatment enhances the biocompatibility by reducing the electrostatic repulsion between biomaterials and biomolecules.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b01850
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    ABSTRACT: Liquid-phase transfer of graphene oxide (GO) and reduced graphene oxide (RGO) monolayers is investigated from the perspective of the mechanical properties of these films. Monolayers are assembled in a Langmuir-Blodgett trough and oscillatory barrier measurements are used to characterize the resulting compressive and shear moduli as a function of surface pressure. GO monolayers are shown to develop a significant shear modulus (10-25 mN/m) at relevant surface pressures while RGO monolayers do not. The existence of a shear modulus indicates that GO is acting as a two-dimensional solid driven by strong interaction between the individual GO sheets. The absence of such behavior in RGO is attributed to the decrease in oxygen moieties on the sheet basal plane, permitting RGO sheets to slide across one another with minimum energy dissipation. Knowledge of this two-dimensional solid behavior is exploited to successfully transfer large-area, continuous GO films to hydrophobic Au substrates. The key to successful transfer is the use of shallow-angle dipping designed to minimize tensile stress present during the insertion or extraction of the substrate. A shallow dip angle on hydrophobic Au does not impart a beneficial effect for RGO monolayers, as these monolayers do not behave as two-dimensional solids and do not remain coherent during the transfer process. We hypothesize that this observed correlation between monolayer mechanical properties and continuous film transfer success is more universally applicable across substrate hydrophobicities and could be exploited to control the transfer of films composed of two-dimensional materials.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b01994
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    ABSTRACT: This paper examines the effects of temperature on the micellization and particle charging behavior of the Span surfactant series in an apolar environment. The critical micelle concentrations of each of six surfactants at five temperatures were measured by conductometric techniques. The thermodynamic properties of micellization were calculated using Gibbs-Helmholtz analysis. Magnesia particles were then dispersed in solutions of these surfactants, and their electrophoretic mobilities measured at three temperatures. Preliminary small angle neutron scattering (SANS) experiments were conducted to measure the size of aggregates (referred to as micelles) of three of the surfactants. It was found that for all but one of the surfactants, the critical micelle concentration increased by as much as an order of magnitude across a 40oC range of temperature. One of the surfactants exhibited a decrease in CMC upon increasing temperature, likely due to a de-crystallization of the tails upon micelle formation. The maximum particle mobilities decreased upon increasing temperature due to the increased electrostatic screening by charged micelles at higher temperatures.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02711
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    ABSTRACT: We report on the use of an alkoxyamine (AA) for fabrication of functional micropatterns with complex structures by UV mask lithography. The living character of the polymer surface as well as the vertical spatial control of the repolymerization reaction from few tens of nm to few microns were demonstrated. The impact of the main parameters governing the controlled polymerization and the re-initiation process activated by light or heat was investigated. Micropatterning is shown to be a powerful method to investigate the physico-chemical molecular phenomena. It is possible to control the polymer microstructure thickness from few tens of nm to few μm. In the last section, some applications are provided showing the potential of the AA for generating covalently bonded hydrophilic/hydrophobic micropatterns or luminescent surfaces. This demonstrates the high versatility and interest of this route.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b01681
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    ABSTRACT: The designed coiled coil forming peptides E: (EIAALEK)3 and K: (KIAALKE)3 are known to trigger efficient membrane fusion when they are tethered to lipid vesicles in the form of lipopeptides. Knowledge of their secondary structure is a key element in understanding their role in membrane fusion. Special conditions can be found at the interface of the membrane, where the peptides are confined in close proximity to other peptide molecules as well as to the lipid interface. Consequently, different structural states were proposed for the peptides when tethered to this interface. Due to the multitude of possible states, determining the structure solely on the basis of circular dichroism spectra at a single temperature can be misleading. In addition, it has not yet been possible to unambiguously distinguish between the membrane bound and the coiled-coil state of these peptides by means of infrared spectroscopy due to very similar amide I' bands. Here, the molecular basis of this similarity is investigated by means of site-specific (13)C labeled FTIR spectroscopy. Structural similarities between the membrane interacting helix of K and the homo coiled-coil forming helix of E are shown to cause the similar spectroscopic properties. Furthermore, the peptide structure is investigated using temperature dependent CD and IR spectroscopy and it is shown that the different states can be distinguished by their thermal behavior. It is shown that the two peptides behave fundamentaly different when tethered to the lipid membrane which implies that their role during membrane fusion is different and the mechanism of this process is asymmetric.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02094
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    ABSTRACT: Surface enhanced Raman scattering (SERS) and localized surface plasmon resonance sensing (LSPR) have been applied for a detailed analysis of lipid bilayers at the surface of gold nanorods. The spatial dependence of surface enhancement and the optical effects of the lipid phase transition confirm the presence of a bilayer membrane structure. Deuterated lipids exchanged rapidly between the nanorod surface and lipid vesicles in solution, suggesting a loosely bound, natural membrane structure. However, at a low solution concentration of lipid vesicles, the lipids on the gold nanorod surface convert to a non-bilayer structure, which could impact biological applications of these nanomaterials.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b01203