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Langmuir: the ACS Journal of Surfaces and Colloids

Siddarth Ayakulangara Vasudevan, Astrid Rauh, Martin Kroger, Matthias Karg, Lucio Isa
We investigate the conformation, position, and dynamics of core-shell nanoparticles (CSNPs) composed of a silica core encapsulated in a cross-linked poly-N-isopropylacrylamide shell at a water-oil interface for a systematic range of core sizes and shell thicknesses. We first present a free-energy model that we use to predict the CSNP wetting behavior at the interface as a function of its geometrical and compositional properties in the bulk phases, which gives good agreement with our experimental data. Remarkably, upon knowledge of the polymer shell deformability, the equilibrium particle position relative to the interface plane, an often elusive experimental quantity, can be extracted by measuring its radial dimensions after adsorption...
November 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Joseph Pazzi, Melissa Xu, Anand Bala Subramaniam
Lamellar phospholipid stacks on cellulose paper vesiculate to form cell-like giant unilamellar vesicles (GUVs) in aqueous solutions. The sizes and yields of the GUVs that result and their relationship to the properties of the cellulose fibers are unknown. Here, we report the characteristics of GUVs produced on four different cellulose substrates, three disordered porous media consisting of randomly entangled cellulose fibers (high-purity cellulose filter papers of different effective porosities), and an ordered network of weaved cellulose fibers (cotton fabric)...
November 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Christoffer Dam Florentsen, Ann-Katrine Vransø West, Helena Maria D Danielsen, Szabolcs Semsey, Poul Martin Bendix, Lene B Oddershede
Novel RNA-based technologies provide an avenue of possibilities to control the regulation of gene expression in cells. To realize the full potential of small interfering RNA (siRNA)-based therapy, efficient delivery vehicles and novel strategies for triggering release from carrier vehicles have to be developed. Gold nanoparticles (AuNPs) with sizes of ∼50-150 nm have the ability to accumulate in tumor tissue and can be transported across the membrane by endocytosis. Therefore, a laser-controlled oligonucleotide release from such particles is of particular interest...
November 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Mian Wang, Jens O M Karlsson, Alptekin Aksan
In this article, we explored the effects of cooling rate, dimethyl sulfoxide (DMSO) concentration, and thawing protocol on the post-thaw viability of frozen human white blood cells (WBCs). Different cooling rates (1, 2, 5, 10, 20, and 50 °C/min) at two DMSO concentrations (5 and 10% v/v) were tested as the samples were cooled to -120 °C. Frozen samples were thawed following either a fast (100 °C/min) or slow (2 °C/min) warming protocol applied in either a single stage or in two stages interrupted by a 6 min hold at -40, -50, -60, -70, or -80 °C...
November 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Run Li, Marisol Ripoll, Naveen Reddy, Jan K G Dhont, Ruben Dierick, Zeger Hens, Christian Clasen
Linear flow dichroism is shown to be a powerful tool to characterize the hydrodynamic dimensions of extremely small nonspherical colloids in solution. Dispersions of prolate and oblate quantum dots (QDs) are employed to investigate the validity of flow dichroism as a characterization tool. Shape-anisotropic QDs are important from an application perspective, where it is necessary to have a good knowledge of their hydrodynamic dimensions to predict and control their orientation during solution processing. Flow dichroism quantifies the tumbling motion of QDs in shear flow by optical means, which provides a characteristic signature of the particle shape, hydrodynamic friction, and size distribution...
November 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Aparna Saraf, Shweta Sharma, Shilpee Sachar
This work reports the physicochemical behavior of antibiotic drug sulfamethoxazole (SMX) in the presence of different surfactants, viz., cetyl trimethyl ammonium bromide (CTAB), dodecyl trimethyl ammonium bromide, didodecyl dimethyl ammonium bromide, sodium dodecyl sulfate, sodium deoxycholate, Tween 80, and Tween 20. The drug-surfactant systems were studied by UV-visible and fluorescence spectroscopies to assess the binding constants ( Kb ), partition coefficient ( Kx ), free energy of partition (Δ Gp ), aggregation number ( Nagg ), and quenching constant ( KSV )...
November 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Ryan J Gasvoda, Scott Wang, Dennis M Hausmann, Eric A Hudson, Sumit Agarwal
The reaction mechanism of propanoyl chloride (C2 H5 COCl) with -SiOH-terminated SiO2 films was studied using in situ surface infrared spectroscopy. We show that this surface functionalization reaction is temperature dependent. At 230 °C, C2 H5 COCl reacts with isolated surface -SiOH groups to form the expected ester linkage. Surprisingly, as the temperature is lowered to 70 °C, the ketone groups are transformed into the enol tautomer, but if the temperature is increased back to the starting exposure temperature of 230 °C, the ketone tautomer is not recovered, indicating that the enol form is thermally stable over a wide range of temperatures...
November 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Sajan D George, Santhosh Chidangil, Deepak Mathur
Recent work is summarized that shows how microbubbles may have potential utility in biomedical situations as (i) highly localized generators of intense whitelight in an aqueous environment, (ii) disruptors of matter in aqueous solution, (iii) essential precursors in laser-writing structures on substrates on which biological cells can be spatially aligned, and (iv) mediators in fabrication of hierarchical nano-structures that enhance signals in biological Raman spectroscopy. Indeed, microbubbles generated upon laser irradiation of surfaces have many more ramifications than originally thought, with implications in laser modification of surfaces producing either hydrophilicity or hydrophobicity...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Ekaterina Razuvaeva, Alevtina Kulebyakina, Dmitry R Streltsov, Artem V Bakirov, Roman Kamyshinsky, Nikita Miсhailovich Kuznetsov, Sergei N Chvalun, Eleonora V Shtykova
Effect of the hydrophobic block length in di- (PLLAx-b-PEO113, x = 64, 166, 418) and triblock (PLLAy-b-PEO91-b-PLLAy, y = 30, 52, 120) copolymers of L-lactic acid and ethylene oxide on the structure of micelles prepared by dialysis was studied by wide- and small-angle X-ray scattering in diluted aqueous solution, dynamic light scattering, transmission electron microscopy, atomic force microscopy and force spectroscopy. It was found that the size of the crystalline PLLA core is weakly dependent on the PLLA block length...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Tatsunori Sakamaki, Yoshihiro Inutsuka, Kosuke Igata, Keiko Higaki, Norifumi L Yamada, Yuji Higaki, Atsushi Takahara
The ion-specific hydration states of zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropane sulfonate) (PMAPS) brushes in various aqueous solutions were investigated by neutron reflectivity (NR) and atomic force microscopy (AFM). The asymmetric hydration state of the PMAPS brushes was verified from the NR scattering-length density profiles, while the variation in their swollen thickness was complementary determined from AFM topographic images. The extent of swelling and the dimensions of swollen chain structure in the PMAPS brushes were dependent on the ion species and salt concentration in the solutions...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
You Yong, Mingyu Qiao, Alan Chiu, Stephanie Fuchs, Qingsheng Liu, Yehudah Pardo, Randy Worobo, Zheng Liu, Minglin Ma
Reducing biofouling while increasing lubricity of inserted medical catheters is highly desirable to improve their comfort, safety, and long-term use. We report here a simple method to create thin (~30 μm) conformal lubricating hydrogel coatings on catheters. The key to this method is a three-step process including Shape-forming, Gradient cross-linking and Swell-peeling (we term this method as SGS). First, we took advantage of the fast gelation of agar to form a hydrogel layer conformal to catheters; then we performed a surface-bound UV crosslinking of acrylamide mixed in agar in open air, purposely allowing gradual oxygen inhibition of free radicals to generate a gradient of crosslinking density across the hydrogel layer; and finally we swelled the hydrogel to let the non-crosslinked/loosely attached hydrogel fall off, leaving behind a surface-bound, thin and mostly uniform hydrogel coating...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Tristan D Clemons, Ruhani Singh, Anabel Sorolla, Nutan Chaudhari, Alysia Hubbard, K Swaminathan Iyer
The role of nanoparticles in cancer medicine is vast with debate still surrounding the distinction between therapeutic efficacy of actively targeted nanoparticles versus passively targeted systems for drug delivery. While it is commonly accepted that methodologies that result in homing high concentration of drug loaded nanoparticles to the tumour is beneficial, the role of intracellular trafficking of these nanoparticles in dictating the overall therapeutic outcome remains unresolved. Herein we demonstrate that the therapeutic outcome of drug loaded nanoparticles is governed beyond simply enabling nanoparticle internalization in cells...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Pascal Bertsch, Michael Diener, Jozef Adamcik, Nathalie Scheuble, Thomas Geue, Raffaele Mezzenga, Peter Fischer
Nanocrystalline cellulose (NCC) is a promising biological nanoparticle for the stabilization of fluid interfaces, which is however poorly understood due to the inability to form controlled NCC interfacial layers. Herein we present parameters that allow the adsorption of unmodified NCC at the air-water (A/W) interface. Initial NCC adsorption is limited by diffusion, followed by monolayer saturation and decrease in surface tension at the time scale of hours. These results confirm current hypotheses of a Pickering stabilization...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Florent Pourcin, Clement Reynaud, Miriam Carlberg, Judikael Le Rouzo, David Duché, Jean-Jacques Simon, Ludovic Escoubas, Rose-Marie Sauvage, Gérard Berginc, Olivier Margeat, Jorg Ackermann
Plasmonic nanocomposites based on metal nanoparticles embedded in dielectric polymer matrixes combine tunability in plasmonic resonance with simplicity of solution processing. Use of shaped nanoparticles in such nanocomposites is of high interest due to their localized surface plasmon resonances that can lead to novel optical features. Here, we present nanocomposites based on silver nanocubes embedded in poly(vinyl-pyrrolidon) with varying volume fraction of nanocubes. We demonstrate that the dominant absorption of the dipole resonance shows a strong red shift with increasing volume fraction of the silver nanocubes due to plasmonic coupling...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Jun-Jie Huang, Xu-Bin Xiao, Yu-Jie Li
Coalescence-induced droplet jumping from a round hydrophobic fiber was studied by phase-field-based hybrid lattice-Boltzmann finite-difference simulations in which the interface dynamics is handled by the finite-difference solution of the Cahn-Hilliard equation and the hydrodynamics is handled by the lattice-Boltzmann method. It was found that at a small Ohnesorge number of O(0.01), several different outcomes, including normal jumping at a positive velocity, jumping with a negative velocity, jumping after wrapping the fiber, and oscillating on the fiber, may occur after droplet coalescence, depending on the wettability of the fiber and the droplet-to-fiber radius ratio...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Akito Fujita, Kei Kobayashi, Hirofumi Yamada
Hydration structures play crucial roles in a wide variety of chemical and biological phenomena. However, the key factors that determine the hydration structure remain an open question. Most recent studies have focused on the electrostatic interactions between the surface charges and dipoles of the water molecules, which are determined by the atomic/ionic species of the outermost solid surface, as the dominating factor. The number of studies on the correlation between the hydration structure and the atomic-scale surface corrugation has been limited...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Masaki Hanzawa, Hidekazu Oohinata, Shin-Ichi Kawano, Masaaki Akamatsu, Kenichi Sakai, Hideki Sakai
Adsorption of triblock Pluronic surfactants bearing poly(ethylene oxide) (PEO) chains of different lengths, L-62 (5 EO groups on each end), L-64 (13 EO groups on each end), and F-68 (79 EO groups on each end), on silica has been characterized using atomic force microscopy (AFM). The solvent used herein was a mixture of ethylene carbonate (EC) and propylene carbonate (PC). The three Pluronic surfactants were dissolved in the mixed solvent, with the PEO chain acting as a solvophilic group and the poly(propylene oxide) (PPO) chain acting as a solvophobic group...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Qingxian Jin, Shuyu Chen, Hejin Jiang, Yuan Wang, Li Zhang, Minghua Liu
We designed glutamide-derived amphiphilic Schiff bases containing three different aldehyde moieties for the fabrication of circularly polarized luminescence (CPL) emitting materials. Upon self-assembly in acetonitrile, Schiff bases featuring 4-(dimethylamino)-2-hydroxylbenzaldehyde and 1-hydroxy-2-naphthaldehyde groups form supramolecular gels with twist and fiber structures, respectively, whereas Schiff bases featuring 2-hydroxy-1-naphthaldehyde groups form precipitation with flake structures. Although emission and circular dichroism signals can be detected from the supramolecular gels formed by amphiphilic Schiff bases, none of them exhibits a circularly polarized luminescence (CPL)...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Sai Adapa, Dhananjay R Swamy, Samhitha Kancharla, Swastik Pradhan, Ateeque Malani
Understanding solid-water(vapor) interfacial systems is relevant for both industrial and academic scenarios for their presence in wide areas ranging from tribology to geochemistry. Using grand canonical Monte Carlo simulations, we have investigated the role of monovalent (lithium, Li+ ; sodium, Na+ ; and potassium, K+ ) and divalent (magnesium, Mg2+ ; calcium, Ca2+ ) cations on the structure and adsorption behavior of water on mica surface. The water density adjacent to the surface exhibits (a) oscillations due to hydration of surface cations (interfacial layer), (b) followed by a thick liquidlike layer...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Kanaparedu P C Sekhar, Rati Ranjan Nayak
Biosourced surfactants are endeavored as a green alternative to biosurfactants and petrochemical surfactants having industrial utilization. Nine glycolipids with headgroup and chain length variation were derived from renewable resources like vegetable oils, carbohydrates, and amino acids. The concentration-dependent interfacial activity, foamability, wetting power, emulsification power, and solubilization capacities of glycolipids were investigated to provide a structure-activity relationship. Later, the metal flotation and emulsification experiments were performed...
November 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
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