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Langmuir: the ACS Journal of Surfaces and Colloids

Zahava Barkay, Edward Bormashenko
Opening of holes in self-supported thin (nano-scaled) water films has been in situ investigated with the environmental scanning electron microscope. Opening of a hole occurs within a two-stage process. At the first stage the rim surrounding a hole is formed, resembling the process which is observed under puncturing of soap bubbles. At the second stage the exponential growth of the hole is observed, with a characteristic time of a dozen of seconds. We explain the exponential kinetics of holes' growth by the balance between inertia (gravity) and viscous dissipation...
April 25, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Ashley Ann Ellsworth, Amy Victoria Walker
Metallized organic layer constructs have a wide range of technological applications. Electroless deposition is an attractive technique by which to deposit metal overlayers because it is inexpensive and can be performed low temperatures compatible with organic materials. Amine borane reducing agents are versatile which are capable of depositing metals, semiconductors and even insulators. We have investigated the role of amine borane reducing agents in the electroless deposition of copper on -CH3, -OH, and -COOH terminated SAMs adsorbed on gold using time-of-flight secondary ion mass spectrometry, optical microscopy and complementary MP2 calculations...
April 25, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Xiaoyan Liu, Karen L Feilberg, Wei Yan, Erling H Stenby, Esben Thormann
An atomic force microscope, employing the colloidal probe technique, was used to study the interactions between six different combinations of silane-functionalized silica surfaces in NaCl and CaCl2 solutions. The surfaces consisted of monolayers of the apolar trimethoxy(octyl)silane, the positively charged (3-aminopropyl)trimethoxysilane, and the negatively charged (3-mercaptopropyl)trimethoxysilane. The interactions between the three symmetric systems, as well as between the three asymmetric combinations of surfaces, were measured and compared to calculated electrical double-layer forces...
April 25, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Yi Zhang, Songcheng Wang, Jiarun Zhou, Ruiyang Zhao, Gregory Benz, Stephane Tcheimou, J Carson Meredith, Sven Holger Behrens
Surfactants can adsorb in fluid-fluid interfaces and lower the interfacial tension. Like surfactants, particles with appropriate wettability can also adsorb in fluid-fluid interfaces. Despite many studies of particle adsorption at fluid interfaces, some confusion persists regarding the ability of (simple, non-amphiphilic) particles to reduce the interfacial tension. In the present work, the interfacial activity of silica nanoparticles at air-water and hexadecane-water interfaces and of ethyl cellulose particles at the interface of water with trimethylolpropane trimethacrylate was analyzed through pendant drop tensiometry...
April 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Chenjing Jin, Jie Han, Fangyuan Chu, Xiaoxia Wang, Rong Guo
Au@Fe3O4@PANI hybrid shells with controllable polyaniline (PANI) coatings as advanced supported catalysts have been fabricated. Specifically, Fe3O4 and Au nanoparticles were assembled on SiO2 templates, followed by conducting polymer PANI coating, leading to the formation of Au@Fe3O4@PANI hybrid shells after the template removal. The resultant supported Au nanocatalysts not only maintain hollow structures but also possess high saturation magnetization (65.46 emu/g). Catalytic tests toward the reduction of 4-nitrophenol in the presence of NaBH4 indicate that PANI and Fe3O4 not only endow high stability and recyclability but also can largely improve the catalytic activity of Au nanoparticles because of their synergetic effects...
April 25, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Pritam Choudhury, Krishnendu Das, Prasanta Kumar Das
The present article delineates the formation of green fluorescent organic nanoparticle through supramolecular aggregation of naphthalene diimide (NDI) based carboxybenzyl protected L-phenylalanine appended bola-amphiphile, NDI-1. The amphiphilic molecule is soluble in DMSO and with gradual addition of water within the DMSO solution, the amphiphile starts to get self-assembled via H-type aggregation to form spherical nanoparticles. These self-assembly of NDI-1 in presence of high amount of water, exhibited aggregation induced emission (AIE) through excimer formation...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jelena Lasio, Alan M Allgeier, Christopher D Chan, J David Londono, Ebrahim Najafi, Francis J Woerner
Hollow silica particles (HSPs) have become the focus of interest in many labs recently, due to their versatility, stemming from the ability to control their size and shape, as well as surface functionalization. Determining the mechanical stability of hollow particles is essential for their use, both in applications in which they need to retain their structure, as well as those in which they need to break down. We have synthesized a series of HSPs (231 nm inner diameter) with increasing wall thickness (7-25 nm), using a template approach...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Benoit Richard, Jean-Luc Lemyre, Anna M Ritcey
Quasi-monodisperse populations of (H3O)Y3F10∙xH2O nanocrystals of varying size are prepared in Igepal-stabilized microemulsions. Correlations between microemulsion composition, micelle hydrodynamic radius and final nanoparticle size are established and shed light on the mechanism of particle size control. Under the conditions considered here, size control appears to be primarily governed by the number of micelles and the quantities of precursor ions. More specifically, the number of NPs formed can be successfully correlated with the number of micelles present and final NP size is, in turn, determined by the number of nuclei and the total amount of material available for nanocrystal formation...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Hiroki Ogawa, Yukihiro Nishikawa, Mikihito Takenaka, Akihiko Fujiwara, Yohei Nakanishi, Yoshinobu Tsujii, Masaki Takata, Toshiji Kanaya
Using grazing-incidence small-angle scattering (GISAXS) with computed tomography (CT), we have reconstructed the spatial distribution of a thin gold (Au) layer buried under a thin poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) layer. Owing to the difference between total reflection angles of Au and PS-b-P2VP, the scattering profiles for Au nanoparticles and self-assembled nanostructures of PS-b-P2VP could be independently obtained by changing the X-ray angle of incidence. Reconstruction of scattering profiles allows to separately characterize spatial distributions in Au and PS-b-P2VP nanostructures...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Silo Meoto, Niall Kent, Michael M Nigra, Marc-Olivier Coppens
Hierarchically structured membranes composed of mesoporous silica embedded inside the channels of anodic alumina (MS-AAM) were synthesized using the aspiration method. Ethanol is shown to have a significant effect on the type and organization of the mesoporous silica phase. Detailed textural analysis revealed that the pore size distribution of the mesoporous silica narrows and the degree of ordering increases, with decreasing ethanol concentration used in the synthesis mixture. The silica mesopores were synthesized with pores as small as 6 nm in diameter, with the channel direction oriented in lamellar, circular and columnar directions, depending on the ethanol content...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Yan Wang, Jianyang Sun, Jiang Li, Xu Zhao
Nanostructured g-C3N4/BiVO4 composite films with enhanced photoelectrochemical performance have been fabricated via the facile electrospinning technique. The g-C3N4 nanosheets could not only form the heterojunctions with BiVO4, but also could prevent the agglomeration of BiVO4, helping to form the nanostructures. The as-prepared g-C3N4/BiVO4 films are with good coverage and well stability. The photoelectrochemical (PEC) performance of the g-C3N4/BiVO4 films are much enhanced compared with that for individual BiVO4 films due to the enhanced electron-hole separation...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Sri Vallabha Deevi, Nachiketa Janardan, Mahesh V Panchagnula
Drops that impact and stick to a surface (splattered drops) commonly show noncircular triple lines. Physical or chemical defects on the surface are known to pin the triple line in this static metastable state. We report an experimental study to relate the defect distribution on a surface to the triple-line microstructure of such drops. Triple lines of an ensemble of splattered drops have been imaged on a range of surfaces varying in wetting properties. Local contact angles have been calculated, and the microscale pinning force distribution has been estimated...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Yong Guo, Bas G P van Ravensteijn, Chris H J Evers, Willem K Kegel
We report the first example of reversible encapsulation of micron-sized particles by oppositely charged submicron smaller colloids. The reversibility of this encapsulation process is regulated by pH-responsive poly(acrylic acid) (PAA) present in solution. The competitive adsorption between the small colloids and the poly(acrylic acid) on the surface of the large colloids plays a key role in the encapsulation behavior of the system. pH offers an experimental knob to tune the electrostatic interactions between the two oppositely charged particle species via regulation of the charge density of the poly(acrylic acid)...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Leonid Rapoport, Matthew Sullivan, Christopher Harrison
We report a novel nucleation method that exploits thermocapillary forces in binary fluids to generate a cloud of bubbles ejected radially from a thermally pulsed wire. The bubbles are nucleated within milliseconds of the extinction of the microsecond pulse and are ejected outward from the wire surface due to the thermocapillary force created by the radial temperature gradient. At low temperatures the surface tension of the vapor-liquid mixture, consisting of ethane-n-octane, increases with increasing temperature, ejecting the bubbles away from the heated wire...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jacqueline S J Tan, Liping Zhang, Freda C H Lim, Daniel W Cheong
The molecular structure of a surfactant molecule is known to have a great effect on the interfacial properties and the type of nanostructures formed. In this work, we have performed molecular dynamics simulations on six isomers of an alkyl benzenesulfonate surfactant to investigate the effect of the degree and position of aromatic substitution on the interfacial properties and on the collapse of the surfactant monolayer at a decane-water interface. The surface pressure of the monolayers was shown to increase with increasing surface coverage, until some of the monolayers become mechanically unstable and form large undulations...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Peng Zhang, Yang Chen, Xiaoyan Yang, Jianzhou Gui, Yi Li, Hailong Peng, Dan Liu, Jieshan Qiu
To improve the photocatalytic activity and photostability of ZnO, a novel cable-like Pt/ZnO@C composite is successfully fabricated by coating a 3-5 nm hydrothermal carbon (HTC) layer on the surface of the Pt nanoparticle-modified ZnO nanowire. After investigating the optical and photoelectrochemical performance in detail, it is found that the Pt/ZnO@C nanocable shows a dual-enhanced migration efficiency for the photoinduced surface electrons, distributing to the modified Pt nanoparticles and the coated HTC layer...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jakob Andersson, Jacqueline J Knobloch, Michael V Perkins, Stephen A Holt, Ingo Köper
Tethered bilayer lipid membranes are versatile solid-supported model membrane systems. Core to these systems is an anchorlipid that covalently links a lipid bilayer to a support. The molecular structure of these lipids can have a significant impact on the properties of the resulting bilayer. Here, the synthesis of anchorlipids containing ester groups in the tethering part is described. The lipids are used to form bilayer membranes, and the resulting structures are compared with membranes formed using conventional anchorlipids or sparsely tethered membranes...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Srinivas Mettu, Joseph D Berry, Raymond Riley Dagastine
Interaction forces between colliding tetradecane drops were measured in the presence of non-ionic surfactant penta-ethylene-glycol-mono-dodecyl-ether (C12E5). The force behavior was measured in the range of pre-micellar compositions of non-ionic surfactant in various salt solutions and was consistent with the presence of a surface charge even though the surfactant was non-ionic in nature. The surface potential of the oil drops was found to decrease with increase in C12E5 concentration. The measured electrophoretic mobilities and zeta potentials of emulsified tetradecane drops also decreased with an increase in C12E5 concentration...
April 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Omkar D Supekar, Mo Zohrabi, Juliet T Gopinath, Victor M Bright
Adaptive optical lenses, based on the electrowetting principle, are being rapidly implemented in many applications such as microscopy, remote sensing, displays, and optical communication. To characterize the response of these electrowetting lenses, the dependence on DC driving voltage functions was investigated in a low viscosity liquid system. Cylindrical lenses with inner diameter 2.45 and 3.95-mm were used to characterize the dynamic behavior of the liquids under DC voltage electrowetting actuation. By increasing the rise time of the input exponential driving voltage, the originally underdamped system response can be damped, enabling a smooth response from the lens...
April 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Irene Adroher-Benítez, Arturo Moncho-Jorda, Joachim Dzubiella
We have theoretically studied the uptake of a non-uniformly charged biomolecule, suitable to represent a globular protein or a drug, by a charged hydrogel carrier in the presence of a 1:1 electrolyte. Based on the analysis of a physical interaction Hamilto- nian including monopolar, dipolar and Born (self-energy) contributions derived from linear electrostatic theory of the unperturbed homogeneous hydrogel, we have identi- fied five different sorption states of the system, from complete repulsion of the molecule to its full sorption deep inside the hydrogel, passing through meta- and stable sur- face adsorption states...
April 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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