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Langmuir: the ACS Journal of Surfaces and Colloids

Dayong Chen, Zhiwei Sun, Thomas P Russell, Lihua Jin
The co-assembly kinetics of graphene oxide (GO) nanosheets and diblock copolymers at the water/toluene interface is probed by tracking the dynamic interfacial tension using pendant drop tensiometry. The diblock copolymer significantly enhances the surfactancy of the GO nanosheets at the interface. It is found that diblock copolymers rapidly adsorb to the water/toluene interface and enhance the adsorption affinity of GO nanosheets to the interface. The continuous adsorption of GO at the interface leads to a random loose packing state, at which the adsorbed GO and diblock copolymers start to form an elastic film...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
David G Moore, Jonathan V A Brignoli, Patrick Alberto Rühs, André R Studart
Microcapsules with organic-inorganic hybrid shells can be used as functionally-responsive delivery systems that are attractive for a broad range of applications. Hybrid-shell microcapsules have often been synthesized by the assembly of solid inorganic nanoparticles and polymers. Efforts to extend this approach to microfluidic emulsification have been hampered by problems with clogging and flow instabilities when utilizing dispersions of solid particles. In this work, hybrid shell microcapsules are synthesized through the reaction of liquid precursors, eliminating the use of solid dispersions...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Xuye Lang, Lingling Zhu, Yingning Gao, Ian Wheeldon
Understanding the chemical and physical interactions at the interface of protein surfaces and inorganic crystals has important implications in the advancement of immobilized enzyme catalysis. Recently, enzyme-inorganic hybrid complexes have been demonstrated as effective materials for enzyme-immobilization. The precipitation of phosphate nanocrystals in the presence of enzymes creates enzyme-Cu3(PO4)2-3H2O particles with high surface-to-volume ratios, enhanced activity, and increased stability. Here, we begin to develop a mechanistic understanding of enzyme loading in such complexes...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Michael David Clark, Kenneth R Morris, Maria Silvina Tomassone
We present a novel simulation-based investigation of the nucleation of nanodroplets from solution and from vapor. Nucleation is difficult to measure or model accurately, and predicting when nucleation should occur remains an open problem. Of specific interest is the "metastable limit", the observed concentration at which nucleation occurs spontaneously, which cannot currently be estimated a priori. To investigate the nucleation process, we employ Gauge Cell Monte Carlo simulations to target spontaneous nucleation and measure thermodynamic properties of the system at nucleation...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Siddhartha Varma, Lionel Bureau, Delphine Débarre
No abstract text is available yet for this article.
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Huan-Pu Chang, En-De Chu, Yu-Ting Yeh, Yueh-Chun Wu, Fang-Yuh Lo, Wei-Hua Wang, Ming-Yau Chern, Hsiang-Chih Chiu
Oxygen vacancy is the most studied point defect and has been found to significantly influence the physical properties of zinc oxide (ZnO). By using atomic force microscopy (AFM), we show that the frictional properties on the ZnO surface at the nanoscale greatly depend on the amount of oxygen vacancies present in the surface layer and the ambient humidity. The photocatalytic effect (PCE) is used to qualitatively control the amount of oxygen vacancies in the surface layer of ZnO and reversibly switch the surface wettability between hydrophobic and superhydrophilic states...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Aleksander Cholewinski, Fut K Yang, Boxin Zhao
Modifying hydrogels with catechol functionality is a promising approach for improving their mechanical and interfacial properties in water, particularly in biological environments. However, the effects of this modification on hydrogels' contact behavior with soft tissues are not well-studied due to the complexity of hydrogels and lack of suitable techniques to probe this behavior. In addition, modification can alter the mechanical properties of hydrogels, resulting in consequences for adhesive strength as well...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Ekanem E Ekanem, Zilin Zhang, Goran T Vladisavljević
Patchy and patchy Janus particles composed of poly(dl-lactic acid) (PLA) and polycaprolactone (PCL) regions were produced with a controlled size, patchiness, composition, and shape anisotropy by microfluidic emulsification and solvent evaporation. Isotropic particles composed of PCL patches embedded in the PLA matrix were produced from relatively small drops with a diameter of 14-25 μm because of the fast solvent extraction as a result of high interfacial area of the particles. Anisotropic patchy Janus particles were formed from large drops, 100-250 μm in diameter...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Siyi Ming, Gang Chen, Jiahao He, Yudi Kuang, Yu Liu, Ruiqiang Tao, Honglong Ning, Penghui Zhu, Yingyao Liu, Zhiqiang Fang
A viable solution toward "green" optoelectronics is rooted in our ability to fabricate optoelectronics on transparent nanofibrillated cellulose (NFC) film substrates. However, the flammability of transparent NFC film poses a severe fire hazard in optoelectronic devices. Despite many efforts toward enhancing the fire-retardant features of transparent NFC film, making NFC film fire-retardant while maintaining its high transparency (≥90%) remains an ambitious objective. Herein, we combine NFC with NFC-dispersed monolayer clay nanoplatelets as a fire retardant to prepare highly transparent NFC-monolayer clay nanoplatelet hybrid films with a superb self-extinguishing behavior...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jerzy Włoch, Artur P Terzyk, Marek Wiśniewski, Piotr Kowalczyk
The new molecular dynamics simulation results showing the influence of the edge carbon surface atoms on the wettability of a highly oriented pyrolytic graphite (HOPG) surface with water nanodroplets are reported. The conditions for the occurrence of the Wenzel effect are discussed, and the Cassie-to-Wenzel transition (CTWT) mechanism in the nanoscale is explored. This transition is detected by the application of a new procedure showing that the CTWT point shifts toward larger values of carbon-oxygen potential well depth with the decrease in the HOPG side angle...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Somasri Hazra, Tapati Dutta, Shantanu Das, Sujata Tarafdar
Desiccation crack formation is affected by the presence of electric fields. We show here that the field effect not only is at work while the power supply is on but also leaves a memory even after switching off. The time required for the first appearance of cracks is shown to depend on the voltage of the field as well as the time duration of exposure. We model the system as a leaky capacitor described by a fractional order derivative in the constitutive equation. This gives a good fit to experimental data and explains the memory effect...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Amirfarrokh Farzaneh, Robert F DeJaco, Lindsay Ohlin, Allan Holmgren, J Ilja Siepmann, Mattias Grahn
A promising route for sustainable 1-butanol (butanol) production is ABE (acetone, butanol, ethanol) fermentation. However, recovery of the products is challenging because of the low concentrations obtained in the aqueous solution, thus hampering large-scale production of biobutanol. Membrane and adsorbent-based technologies using hydrophobic zeolites are interesting alternatives to traditional separation techniques (e.g., distillation) for energy-efficient separation of butanol from aqueous mixtures. To maximize the butanol over water selectivity of the material, it is important to reduce the number of hydrophilic adsorption sites...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Daniel Bahamon, Lourdes F Vega
Adsorption on activated carbons of five pharmaceutical molecules (ibuprofen, diclofenac, naproxen, paracetamol, and amoxicillin) in aqueous mixtures has been investigated by molecular simulations using the Grand Canonical Monte Carlo (GCMC) method. A virtual nanoporous carbon model based on polyaromatic units with defects and polar-oxygenated sites was used for this purpose. The simulation results show excellent agreement with available experimental data. The adsorption capacities of the carbons for the five drugs were quite different and were linked, essentially, to their molecular dimensions and atom affinities...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Liangxu Xie, Kwong-Yu Chan, Nick Quirke
Canonical molecular dynamics simulations are performed to investigate the behavior of single-chain and multiple-chain poly(ethylene glycol) (PEG) contained within a cubic framework spanned by polyethylene (PE) chains. This simple model is the first of its kind to study the chemical physics of polymer-threaded organic frameworks, which are materials with potential applications in catalysis and separation processes. For a single-chain 9-mer, 14-mer, and 18-mer in a small framework, the PEG will interact strongly with the framework and assume a more linear geometry chain with an increased radius of gyration Rg compared to that of a large framework...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Hong-Wei Yang, C Robert Kao, Akitsu Shigetou
The evolution of surface chemical structures of polyimide induced by Ar fast atom beam (Ar-FAB) bombardment and vacuum ultraviolet (VUV) irradiation was investigated using X-ray photoelectron spectroscopy (XPS) to clarify the activated sites for low-temperature hybrid bonding. These sites in molecular chains are considered corresponding to the bonding sites. They affect interfacial properties. Therefore, such analyses are necessary to optimize the processing parameters in different surface-modification methods...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Stéphane Isabettini, Sarah Massabni, Joachim Kohlbrecher, Lukas D Schuler, Peter Walde, Marina Sturm, Erich J Windhab, Peter Fischer, Simon Kuster
Cholesterol (Chol-OH) and its conjugates are powerful molecules for engineering the physicochemical and magnetic properties of phospholipid bilayers in bicelles. Introduction of aminocholesterol (3β-amino-5-cholestene, Chol-NH2) in bicelles composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the thulium-ion-chelating phospholipid 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA/Tm(3+)) results in unprecedented high magnetic alignments by selectively tuning the magnetic susceptibility Δχ of the bilayer...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Siddarth A Vasudevan, Astrid Rauh, Lorenzo Barbera, Matthias Karg, Lucio Isa
Colloidal particles are extensively used to assemble materials from bulk suspensions or after adsorption and confinement at fluid interfaces (e.g., oil-water interfaces). Interestingly, and often underestimated, optimizing interactions for bulk assembly may not lead to the same behavior at fluid interfaces. In this work, we compare model composite nanoparticles with a silica core coated with a poly-N-isopropylacrylamide hydrogel shell in bulk aqueous suspensions and after adsorption at an oil-water interface...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Eric Detmar, Simin Yazdi Nezhad, Ulrich K Deiters
Extensive Monte Carlo simulations were performed for (neon + krypton) mixtures for temperatures between 200 K and 600 K and pressures up to 1 GPa, using Lennard-Jones potentials to describe the intermolecular interactions. The residual entropies were obtained via Widom's insertion method, as well as via an integration technique. At high pressures, the residual entropy is, to a very good approximation, a linear function of λa(-1), which is the reciprocal value of the average Monte Carlo displacement parameter that gives the acceptance ratio a for translational moves...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Hsiu-Yu Yu, Zahera Jabeen, David M Eckmann, Portonovo S Ayyaswamy, Ravi Radhakrishnan
We have studied the microstructure of a flow-driven hardsphere suspension inside a cylinder using dynamical density functional theory and Monte Carlo simulations. In order to be representative of various physical conditions that may prevail in experiments, we investigate the problem using both the grand canonical ($\mu VT$) ensemble and the canonical ($NVT$) ensemble. In both ensembles, the hydrodynamic effect on the suspension mediated by the presence of the confining wall is implemented in a mean-field fashion by incorporating the thermodynamic work done by the inertial lift force on the particle given the average flow field...
August 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Dirk Müter, Gernot Rother, Henry Bock, Martin Schoen, Gerhard H Findenegg
Adsorption and aggregation of nonionic surfactants at oxide surfaces has been studied extensively in the past, but only for concentrations below and near the critical micelle concentration. Here we report an adsorption study of a short-chain surfactant (C6E3) in porous silica glass of different pore sizes (7.5 to 50 nm), covering a wide composition range up to 50 wt.-% in a temperature range from 20°C to the LCST. Aggregative adsorption is observed at low concentrations, but the excess concentration of C6E3 in the pores decreases and approaches zero at higher bulk concentrations...
August 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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