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Langmuir: the ACS Journal of Surfaces and Colloids

Mitchell Miller, Miaoqi Chu, Binhua Lin, Wei Bu, Pulak Dutta
When lanthanide ions are present in the aqueous subphase of a floating monolayer (Langmuir film), the ions attracted to the interface will in many cases form commensurate and/or incommensurate two-dimensional structures. These lattices depend not only on the molecules forming the monolayer, but also on the atomic number of the lanthanide, with a sudden change between the lattice formed by lighter ions and that formed by heavier ions under a given monolayer. Since there are few other relevant differences between the lanthanides, we attribute the Z-dependent 'transition' to the number of water molecules associated with each ion...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Daniel A McCurry, Ryan C Bailey
Nanopores, and nanoporous materials in general, are interesting for applications in chemical and biomolecular transport as pore sizes are on the same scale as the dimension of many (bio)chemical species. Many studies have focused on either single pores or small arrays of cylindrical pores, which are convenient in terms of their amenability towards computational modeling of transport phenomenon. However, the limited overall porosity may inhibit transport flux as well as the eventual implementation of these materials as active separation elements...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Samantha L Nania, Scott K Shaw
We report experimental observations of a developing fluid-solid interface by examining acetophenone films of varying thicknesses, supported on solid silver substrates. A dynamic wetting technique provides experimental control of fluid film thickness as a function of rotational velocity. Ellipsometry and infrared reflection absorption spectroscopy data are analyzed to provide absolute film thickness and details of the changing chemical environment for varying film thickness. This data is compared to theoretical models that predict fluid film thicknesses based on physical-chemical properties of the acetophenone/silver pair...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Pawilai Chinwangso, Han Ju Lee, Andrew C Jamison, Maria D Marquez, Chul Soon Park, T Randall Lee
Organic thin-films on gold were prepared from a set of new, custom-designed bidentate alkanethiols possessing a mixture of normal alkane and methoxy-terminated tri(ethyleneglycol) chains. The new unsymmetrical spiroalkanedithiol adsorbates were of the form [CH3O(CH2CH2O)3(CH2)5]-[CH3(CH2)n+1]C[CH2SH]2 where n = 3 and 14; designated EG3C7-C7 and EG3C7-C18, respectively. Their corresponding self-assembled monolayers (SAMs) on gold were characterized and compared with monothiol SAMs derived from an analogous normal alkanethiol (C18SH) and an alkanethiol terminated with an oligo(ethylene glycol) (OEG) moiety (i...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Tomoko Kure, Hiromi Sakai
A hemoglobin vesicle (Hb-V) is an artificial oxygen carrier encapsulating a highly concentrated hemoglobin solution (40 g/dL) in a liposome. The in vivo safety and efficacy of Hb-V suspension as a transfusion alternative and structural stability during storage have been studied extensively. Because the intra-liposomal Hb aqueous solution can possess colloid osmotic pressure (COP, 200-300 Torr), which is much higher than that of blood plasma (20-25 Torr), a question arises of whether the lipid membrane senses the transmembrane difference in COP...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Drew Marquardt, Frederick A Heberle, Tatiana Miti, Barbara Eicher, Erwin London, John Katsaras, Georg Pabst
We measured the transbilayer diffusion of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in large unilamellar vesicles in both the gel (Lβ') and fluid (Lα) phases. The choline resonance of headgroup-protiated DPPC exchanged into the outer leaflet of headgroup-deuterated DPPC-d13 vesicles was monitored using (1)H NMR spectroscopy coupled with the addition of a paramagnetic shift reagent. This allowed us to distinguish between the inner and outer leaflet DPPC, and determine the flip-flop rate as a function of temperature...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
James Kruczek, See-Wing Chiu, Eric Jakobsson, Sagar A Pandit
Interactions of monovalent salts with lipid membranes are explored with molecular dynamics (MD) simulations. The simulations included the monovalent ions Na(+) and K(+), for their importance in physiology, Li(+) for its small size and importance in several medical conditions including bipolar disorder, and Rb(+) for its large size. All simulations included Cl(-) as counterions. One bilayer was simulated without salt as a control. Palmitoyl oleoyl phosphatidylcholine (POPC) bilayers experienced reductions in area per lipid with the addition of salt; the smaller the ion the smaller the area, with the exception of Li(+)...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Manuel J S Farias, Carlos Busó-Rogero, Francisco J Vidal-Iglesias, José Solla-Gullón, Giuseppe A Camara, Juan M Feliu
The knowledge about how CO occupies and detaches from specific surface sites on well-structured Pt surfaces provides outstanding information on both dynamics/mobility of COads and oxidation of this molecule under electrochemical conditions. This work reports how the potentiostatic growth of different coverage CO adlayers evolves with time on both cubic and octahedral Pt nanoparticles in acidic medium. Data suggest that during the growth of the CO adlayer, COads molecules slightly shift toward low coordination sites only on octahedral Pt nanoparticles, so that these undercoordinated sites are the first filled on octahedral Pt nanoparticles...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Xudong Yu, Xiaoting Ge, Lijun Geng, Haichuang Lan, Jujie Ren, Yajuan Li, Tao Yi
In this work, two naphthalimide-based compounds, 1a and 1b, have been designed and synthesized. Both compounds can form stable two-component gels in n-propanol or n-butanol upon addition of α-cyclodextrin (α-CD) followed by sonication at room temperature. Interestingly, the 1a/α-CD gel is thixotropic and very sensitive to water. Addition of a small amount of water induces rapid gel collapse, allowing further development of the gel as a visual relative humidity sensor. Specificity of the sensor has been confirmed using several approaches, such as scanning electron microscopy and fluorescence, Fourier transform infrared, and (1)H NMR spectroscopy experiments...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Maria Lopez, Sue Ellen Evangelista, Melissa Morales, Sunghee Lee
A deeper understanding of unassisted passive transport processes can better delineate basic lipid dynamics in biological membranes. A droplet interface bilayer (DIB) is made by contacting two aqueous droplets covered with a lipid monolayer, and has increasingly been employed as a model artificial biological membrane. In this study, we have investigated the effect of acyl chain structure of amphiphilic monoglycerides on the osmotic permeability of water across DIB membranes composed of these monoglycerides, where the acyl chain length (C14-C24), number of double bonds (1-4), and the position of double bond are varied systematically along the acyl chains...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Andrew Kozbial, Charlie Trouba, Haitao Liu, Lei Li
Elucidating the intrinsic water wettability of the graphitic surface has increasingly attracted research interests, triggered by the recent finding that the well-established hydrophobicity of graphitic surfaces actually results from airborne hydrocarbon contamination. Currently, static water contact angle (WCA) is often used to characterize the intrinsic water wettability of graphitic surfaces. In the current paper, we show that because of the existence of defects, static WCA does not necessarily characterize the intrinsic water wettability...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Natsumi Amano, Mitsuru Takahashi, Hiroaki Uchiyama, Hiromitsu Kozuka
Anatase thin films were prepared on various plastic substrates by our recently developed sol-gel transfer technique. Polycarbonate (PC), poly(methyl methacrylate) (PMMA), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polyether ether ketone (PEEK), and polyvinylidene chloride (PVDC) were employed as plastic substrates. A Si(100) substrate was first coated with a polyimide (PI)/polyvinylpyrrolidone (PVP) mixture layer, and an alkoxide-derived titania gel film was deposited on it by spin-coating...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Mariko Miyachi, Shu Ikehira, Daiki Nishiori, Yoshinori Yamanoi, Masato Yamada, Masako Iwai, Tatsuya Tomo, Suleyman I Allakhverdiev, Hiroshi Nishihara
Photosystem II (PSII) modified gold electrodes were prepared by the deposition of PSII reconstituted with platinum nanoparticles (PtNPs) on Au electrodes. PtNPs modified with 1-[15-(3,5,6-trimethyl-1,4-benzoquinone-2-yl)]pentadecyl disulfide ((TMQ(CH2)15S)2) were incorporated into the QB site of PSII isolated from the thermophilic cyanobacterium, Thermosynechococcus elongatus. The reconstitution was confirmed by QA-reoxidation measurements. PSII reconstituted with PtNPs was deposited and integrated on a Au(111) surface modified with 4,4'-biphenyldithiol...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Noga Fridman-Bishop, Viatcheslav Freger
Polymeric membranes are widely used for salt removal, but mechanism of ion permeation is still insufficiently understood. Here we analyze ion transport and scaling in polymers relevant to desalination (dense aromatic polyamide Nomex and cellulose acetate, CA) using impedance spectroscopy (EIS), focusing on the effects of the salt type, concentration and pH. The results highlight the role of proton uptake in ion permeation. For Nomex the exceptionally high affinity to proton results in a power-low dependence of conductivity on salt concentrations with an unusual exponent 1/2...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Syuji Fujii, Emiko Mouri, Ko Akiyama, Saori Nakayama, Kyohei Uda, Yoshinobu Nakamura, Hideki Matsuoka
pH-Sensitive adsorption of polymer particles bearing poly[2-(dimethylamino)ethyl methacrylate] hairs at the air-water interface was investigated using a surface tensiometer, a Langmuir-Blodgett trough and an X-ray reflectometer. We clarified that the particles adsorb at the interface at basic pH; by contrast, at acidic pH, a small number of particles are adsorbed, whereas the majority are dispersed in the water phase. X-ray reflectometry analysis revealed that a particle monolayer was formed at the air-water interface, which packed densely under increasing surface pressure, as determined by the electron density profile change...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Joanna Witos, Giacomo Russo, Suvi-Katriina Ruokonen, Susanne K Wiedmer
Owing to their unique properties and unlimited structural combinations, the ubiquitous use of ionic liquids (ILs) is steadily increasing. The objective of the present work is to shed light onto the effects of amidinium- and phosphonium-based ILs on phospholipid vesicles using a nanoplasmonic sensing measurement technique. A new and relatively simple method was developed for the immobilization of large unilamellar vesicles on two different hydrophilic surfaces composed of titanium dioxide and silicon nitride nanolayers...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Tomohiro G Noguchi, Yasutaka Iwashita, Yasuyuki Kimura
Amphiphilic Janus particles (AJP), composed of hydrophilic and hydrophobic hemispheres, are one of the simplest anisotropic colloids, and they exhibit higher surface activities than particles with homogeneous surface properties. Consequently, a ternary system of AJP, water, and oil can form extremely stable Pickering emulsions, with internal structures that depend on the Janus structure of the particles and the system composition. However, the detail of these structures has not been fully explored, especially for the composition range where the amount of the minority liquid phase and AJP are comparable, where one would expect the Janus characteristics to be directly reflected...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jia-Yu Li, Yang Liu, Qun-Wei Shu, Jia-Man Liang, Fang Zhang, Xian-Ping Chen, Xiao-Yan Deng, Mark T Swihart, Ke-Jun Tan
Blue luminescent carbon dots (CDs) with a high photoluminescence (PL) quantum yield (48.3 ± 5.3%) were prepared by the one-pot hydrothermal reaction of citric acid with poly(ethylenimine) (PEI). The CDs display bright PL, narrow emission spectra, pH-dependent PL intensity, high photostability, and up-converted luminescence. The CDs exhibit a quenching of both down- and up-conversion PL in the presence of morin and thus serve as useful probes for morin detection. Both down- and up-conversion measurements allow the quantification of concentrations from 0 to 300 μmol/L with a detection limit of 0...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Yun Tian, Jianzhong Wu
Heat of adsorption is a basic thermodynamic property extensively used not only for understanding thermal effects and heat management in industrial gas storage and separation processes but also for development and validation of adsorption models and materials force fields. Despite a long history of theoretical studies and a vast experimental literature, controversies often arise in the thermodynamic analysis of heat effects due to various assumptions used to describe gas adsorption and inconsistencies between direct calorimetric measurements and isosteric heat obtained from various adsorption isotherms...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Minh T Lam, Paul A FitzGerald, Gregory G Warr
The phase behavior and self-assembly structures of a series of amphiphilic diblock co-oligomers comprising an ionizable hydrophilic block (5 to 10 units of acrylic acid) and a hydrophobic block (5 to 20 units of n-butyl acrylate, t-butyl acrylate, or ethyl acrylate), synthesized by RAFT polymerization, have been examined by polarizing optical microscopy and small-angle X-ray scattering (SAXS). Self-assembled structure and lyotropic phase stability in these systems is highly responsive to the degree of ionization of the acrylic acid hydrophilic block (i...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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