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Langmuir: the ACS Journal of Surfaces and Colloids

Matteo Bonomo, Danilo Dini, Andrea Giacomo Marrani
The adsorption of I(-) and I3(-) anions, i.e. the two species constituting the most common redox couple of dye-sensitized solar cells (DSCs), onto the surface of screen-printed nanoporous NiO was studied by means of X-ray photoelectron spectroscopy (XPS). Mesoporous NiO films were deposited on transparent metallic fluorine-doped tin oxide (FTO) and polarized as working electrodes in a three-electrode cell with differently concentrated I(-)/I3(-) electrolytes to simulate the different conditions experienced by the NiO cathodes during the lifecycle of a p-type DSC (p-DSC) at those atomic sites not passivated by the dye...
October 21, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Astha Garg, Charles A Cartier, Kyle J M Bishop, Darrell Velegol
The zeta potential of a particle characterizes its motion in an electric field and is often thought to be negligible at high ionic strength (several moles per liter) due to thinning of the electrical double layer (EDL). Here, we describe zeta potential measurements on polystyrene latex (PSL) particles at monovalent salt concentrations up to saturation (~ 5 M NaCl) using electrophoresis in sinusoidal electric fields and high-speed video microscopy. Our measurements reveal that the zeta potential remains finite at even the highest concentrations...
October 21, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Himanshu Chaudhary, Aditya Iyer, Vinod Subramaniam, Mireille M A E Claessens
Phospholipid vesicles are commonly used to get insight into the mechanism by which oligomers of amyloidogenic proteins damage membranes. Oligomers of the protein α-synuclein (αS) are thought to create pores in phospholipid vesicles containing a high amount of anionic phospholipids but fail to damage vesicle membranes at lower surface charge densities. The current understanding of how αS oligomers damage membranes is thus incomplete. This incomplete understanding may, in part, result from the choice of model membrane systems...
October 21, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Xianyu Song, Shuangliang Zhao, Shenwen Fang, Yongzhang Ma, Ming Duan
The dissipative particle dynamics (DPD) method is used to investigate the adsorption behavior of PEO-PPO-PEO triblock copolymers at the liquid/solid interface. The effect of molecular architecture on the self-assembled monolayer adsorption of PEO-PPO-PEO triblock copolymers on hydrophobic surfaces is elucidated by adsorption process, film properties, adsorption morphologies, respectively. The adsorption thicknesses on hydrophobic surfaces and diffusion coefficient as well as aggregation number of Pluronic copolymers in aqueous solution observed in our simulations agree well with previous experimental and numerical observations...
October 20, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Qiang Zhao, Zhen Lian, Xuedong Gao, Yun Yan, Jianbin Huang
The ability to modulate the amphiphilic aggregation reversibly with external stimuli, especially by light trigger, is of great importance. It makes great contribution to the development of applications by self-assembly. However, most previously described systems are based on specific molecular design and difficultly applied in light-inert aggregations. Here we develop a general and effective approach to control the morphology of amphiphilic aggregates by light, which is suitable for different assemblies such as micelle, vesicle and helix...
October 20, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Nir Kampf, Chunxian Wu, Yilin Wang, Jacob Klein
The surface structure of the trimeric surfactant tri(dodecyldimethylammonioacetoxy)-diethyltriamine trichloride (DTAD) on mica, and the interactions between two such DTAD-coated surfaces were determined using atomic force microscopy and a surface force balance. In an aqueous solution of 3 mM, five times the critical aggregation concentration (CAC), the surfaces are coated with worm-like micelles or hemi-micelles and larger (ca. 80 nm) bilayer vesicles. Repulsive normal interactions between the surfaces indicate a net surface charge and a solution concentration of ions close to that expected from the CAC...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Yuqin Zou, Alex S Walton, Ian A Kinloch, Robert A W Dryfe
A study of the differences between the capacitance of freshly exfoliated highly ordered pyrolytic graphite (HOPG, sample denoted FEG), HOPG aged in air (denoted AAG) and aged in an inert atmosphere (hereafter IAG) is presented in this work. The FEG is found to be more hydrophilic than AAG and IAG since the aqueous electrolyte contact angle (CA) increases from 61.7o to 72.5o and 81.8o after aging in Ar and air, respectively. Electrochemical impedance spectroscopy (EIS) shows the FEG has higher intrinsic capacitance (6...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Nagesh D Patil, Prathamesh G Bange, Rajneesh Bhardwaj, Atul Sharma
Effects of substrate temperature, substrate wettability and particles concentration are experimentally investigated for evaporation of a sessile water droplet containing colloidal particles. Time-varying droplet shapes and temperature of the liquid-gas interface are measured using high-speed visualization and infrared thermography, respectively. The motion of the particles inside the evaporating droplet is qualitatively visualized by an optical microscope and profile of final particle deposit is measured by an optical profilometer...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Nobuo Kimizuka, Nobuhiro Yanai, Masa-Aki Morikawa
Self-assembly of functional molecules into ordered molecular assemblies and fulfillment of potentials unique to their nano-to-mesoscopic structures have been one of the central challenges in chemistry. This Feature Article provides an overview of recent progress in the field of molecular self-assembly with the focus on the triplet-triplet annihilation-based photon upconversion (TTA-UC) and supramolecular storage of photon energy. Based on the integration of molecular self-assembly and photon energy harvesting, triplet energy migration-based TTA-UC has been achieved in varied molecular systems...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Xunzhi Li, Wenchuan Ma, Alexander A Shestopalov
This study describes formation of functional organic monolayers on hard and soft interfaces via a vapor-phase carbene insertion into Si-H and C-H bonds. We demonstrate that functional diazirine molecules can be used to form mono-molecular coatings on silicon, silicon nitride and urethane-acrylate polymers under mild vacuum conditions and exposure to UV light. We investigate the molecular coverage and the long-term stability of the resulting monolayers in air, isopropanol and water. Our results suggest that vapor-phase carbenylation can be used as a complementary technology to the traditional self-assembly, permitting functionalization of various passivated substrates with stable and functional molecular coatings under mild and scalable conditions...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Stephan Ingmar Brückner, Sergii Donets, Arezoo Dianat, Manfred Bobeth, Rafael Gutierrez, Gianaurelio Cuniberti, Eike Brunner
Understanding the molecular interactions between inorganic phases such as silica and organic material is fundamental for chromatographic applications, for tailoring silica-enzyme interactions, and for elucidating the mechanisms of biomineralization. The formation, structure, and properties of the organic/inorganic interface is crucial in this context. Here, we investigate the interaction of selectively (13)C-labeled choline with (29)Si-labeled monosilicic acid/silica at the molecular level. Silica/choline nanocomposites were analyzed by solid-state NMR spectroscopy in combination with extended molecular dynamics (MD) simulations to understand the silica/organic interface...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Jingyu Chen, Bing Yuan, Zhenyu Li, Bin Tang, Akhil Gupta, Sheshanath-Vishwanath Bhosale, Jingliang Li
Co-assembly of molecules can produce materials with improved properties and functionalities. To this end, achieving a molecular level understanding of the interactions governing the co-assembly is essential. In this work, two molecular gelators with significantly different structures and main intermolecular forces for assembly were co-assembled. The elastic moduli of the hybrid gels are more than one order of magnitude higher than those of the gels formed by the individual gelators, showing an obvious synergistic effect...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Ting Yu, Guangnan Zhou, Xia Hu, Shuji Ye
Understanding the transport behavior of the cholesterol molecules within cell membrane is a key challenge in cell biology at present. Here, we applied sum frequency generation vibrational spectroscopy (SFG-VS) to characterize the transport and organization of the cholesterol in different kinds of planar solid-supported lipid bilayers by combining achiral and chiral-sensitive polarization measurements. This method allows us to distinguish cholesterol organizations in the tail to tail, head to tail, head to head, and side-by-side manners...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Yichuan Hu, Bo Liang, Lu Fang, Guanglong Ma, Guang Yang, Qin Zhu, Shengfu Chen, Xuesong Ye
In this work, a versatile fabrication method of coating enzyme-based biosensors with ultra-thin antifouling zwitterionic polymer films to meet the challenge of the long-time stability of sensors in vivo was developed. Electrochemically mediated atom transfer radical polymerization (eATRP) was applied to polymerize zwitterionic sulfobetaine methacrylate (SBMA) monomers on the rough enzyme-absorbed electrode surfaces, meanwhile a refined overall bromination was developed to improve the coverage of polymers on the biosensor surfaces, and maintain the enzyme activity simultaneously for the first time...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Yang Ruan, Yudan Zhu, Yumeng Zhang, Qingwei Gao, Xiaohua Lu, Linghong Lu
Residual Mg2+ could reduce the performance of lithium-ion batteries, but separating Mg2+ and Li+ is difficult because of their similar ionic properties. Inspired by the high selectivity of biological Mg2+ channels, this work investigates the ability of graphene-based nanopores with different diameters (0.789, 1.024 and 1.501 nm) to separate Mg2+ and Li+ under a series of transmembrane voltages using atomistic simulations. We analyzed the spatial distribution of molecules in the pore vicinity, ionic hydration structure properties, and potential of mean force of ions traveling through the nanopores...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Baoying Li, Yihe Zhang, Ruifeng Du, Lin Gan, Xuelian Yu
In this paper, novel types of Bi2S3-Au heterostructures are fabricated through rationally controlling the growth atmosphere. Under argon condition, Au nanoparticles are preferentially deposited onto the tips of Bi2S3 nanorods to form Bi2S3-Au dumbbelled heterostructures. In contrast, due to the etching effect by amine, Au nanoparticles are randomly anchored onto the surface of nanorods to form Bi2S3-Au nanocorns in the presence of oxygen. Furthermore, the size of gold nanoparticles can be controlled through adjusting the concentration of reaction precursors...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Anna L Calkins, Jennifer Yin, Jacenda L Rangel, Madeleine R Landry, Amelia A Fuller, Grace Y Stokes
The first report of a water-soluble peptoid adsorbed to silica monitored by second harmonic generation (SHG) at the liquid/solid interface is presented here. The molecular insights gained from these studies will inform the design and preparation of novel peptoid coatings. Simple 6- and 15-residue peptoids were dissolved in phosphate buffered saline and adsorbed to bare silica surfaces. Equilibrium binding constants and relative surface concentrations of adsorbed peptoids were determined from fits to the Langmuir model...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Hui Yang, Huabo Duan, Xu Wu, Min Wang, Ting Chen, Fanghui Liu, Shizhe Huang, Wei Zhang, Gang Chen, Danfeng Yu, Jinben Wang
The adsorption processes of a geminized amphiphilic polyelectrolyte, comprising double elementary charges and double hydrophobic tails in each repeat unit (denoted as PAGC8), was investigated and characterized by means of quartz crystal microbalance with dissipation (QCM-D), ellipsometry, and atomic force microscopy (AFM). By comparison, the self-assembly behaviors of a traditional polyelectrolyte without hydrophobic chains (denoted as PASC1), and an amphiphilic polyelectrolyte with a single hydrophilic head group and hydrophobic tail in each repeat unit (denoted as PASC8) at the solid/liquid interface, were also investigated in parallel...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Mark J DelloStritto, James David Kubicki, Jorge Osvaldo Sofo
We use ab-initio molecular dynamics simulations to study the effect of ions on the structure and dynamics of the quartz(101)-water interface. We study several IA (Na(+),Rb(+)) and IIA (Mg(2+),Sr(2+)) cations, with Cl(-) as counterion, adsorbed onto acidic, neutral, and basic surface configurations at 300K and 373K. We find that both cations and anions can bond directly to the surface and perturb the local H-bond network. The adsorbed ions promote the formation of intrasurface H-bonds, as shown by vibrational density of states and orientations of the surface silanols...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Anders Sandell, Davide Ragazzon, Andreas Schaefer, Mari Helene Farstad, Anne Borg
We present a dedicated synchrotron radiation photoelectron spectroscopy (SR-PES) study of a photochemical reaction on the surface of rutile TiO2(110). The photoreaction kinetics of carboxylate species (trimethyl acetate, TMA) upon irradiation by UV and soft x-rays were monitored and we show that it is possible to control the reaction rates from UV light and soft x-rays independently. We directly observe Ti4+ → Ti3+ conversion upon irradiation, attributed to electron trapping at Ti sites close to surface OH groups formed by deprotonation of the parent molecule, trimethyl acetic acid (TMAA)...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
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