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Brewster Angle Microscopy (brewster + angle_microscopy)
Selected AbstractsAligning Single-Walled Carbon Nanotubes By Means Of Langmuir,Blodgett Film Deposition: Optical, Morphological, and Photo-electrochemical StudiesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Gabriele Giancane Abstract An alkoxy-substituted poly(phenylene thiophene) is used in order to suspend single-walled carbon nanotubes in an organic solvent. The suspension is spread on the air,water interface of a Langmuir trough and the floating film is characterized by means of Brewster angle microscopy and UV-visible reflection spectroscopy and the compression isotherm is recorded. The polymer/carbon-nanotube blend is transferred onto different substrates using the Langmuir,Blodgett technique. AFM measurements indicate the formation of globular structures for the samples transferred at low surface-pressure values and a tubular morphology for high-pressure-deposited samples. AFM analysis is repeated on a sample exposed to soft X-rays for about 5,h and a highly organized structure of bundles of carbon nanotubes rises up. Samples with different numbers of layers are transferred onto ITO substrates by means of the Langmuir,Blodgett method and are tested as photocathodes in a photo-electrochemical cell. A Voc of 0.18,V, an Isc of 85.8,mA, FF of 40.0%, and , of (6.23,×,10,3)% are obtained. [source] A laser imaging and neutron reflection investigation into the monolayer behaviour of fatty acids used for taste masking microspheresJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2008Sheng Qi Abstract Fatty acid microspheres have been used for taste masking purposes whereby the drug is preferentially released in the lower gastrointestinal tract, although the mechanisms involved are poorly understood. In this study, we use a combination of surface pressure measurements, Brewster angle microscopy (BAM) and neutron reflectivity measurements to study the phase miscibility and escaping tendency from mixed stearic and palmitic acid films with a view to relating this to drug dissolution behaviour. It was noted that mixed systems showed considerably greater film interaction and instability than those composed of the pure lipid, especially in alkaline media. BAM studies were able to identify a range of phase separated structures for both the pure and mixed systems. Neutron reflectivity studies indicated a marked selective dissolution of palmitic acid into the subphase as a function of time and allowed quantification of the rate of dissolution of this species. It is concluded that the fatty acids are interacting within the monolayer and in addition the palmitic acid is escaping the mixed monolayers and dissolving into the alkali subphase. These findings have strong relevance for understanding the mechanism of drug release from the associated microspheres. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 1864,1877, 2008 [source] Surface characterization and study of Langmuir films of poly(4-vinylpyridine) quaternized with n -alkylbromidePOLYMER INTERNATIONAL, Issue 8 2001Ligia Gargallo Abstract The surface behaviour of poly(4-vinylpyridine)s (P4VP) quaternized with four different alkyl chains (pentyl, hexyl, octyl and decy bromide) were studied. Surface pressure,area isotherms (,,A) at the air,water interface were determined. Depending on the length of the side-chains, the ,,A isotherms show a plateau region. An extensive plateau is observed for n,>,6. The plateau pressures are similar for n,,=,8 and n,,=,10. The monolayers are stable and exhibit hysteresis phenomena. Brewster angle microscopy (BAM) is used to monitor the monolayer topography of the polymer on water subphase. To obtain information about the surface energy (SE) and the degree of hydrophobicity of these systems, we have estimated the critical surface tension, ,c, and the dispersion force and polar contributions to SE, ,D and ,P, respectively, by measurements of the contact angle (CA) of water and bromobenzene on the polymer surface. The results obtained are depend on the length of the alkyl lateral chain of the functionalized polymers. © 2001 Society of Chemical Industry [source] Exploring the interactions of gliadins with model membranes: Effect of confined geometry and interfacesBIOPOLYMERS, Issue 8 2009Amélie Banc Abstract Mechanisms leading to the assembly of wheat storage proteins into proteins bodies within the endoplasmic reticulum (ER) of endosperm cells are unresolved today. In this work, physical chemistry parameters which could be involved in these processes were explored. To model the confined environment of proteins within the ER, the dynamic behavior of ,-gliadins inserted inside lyotropic lamellar phases was studied using FRAP experiments. The evolution of the diffusion coefficient as a function of the lamellar periodicity enabled to propose the hypothesis of an interaction between ,-gliadins and membranes. This interaction was further studied with the help of phospholipid Langmuir monolayers. ,- and ,-gliadins were injected under DMPC and DMPG monolayers and the two-dimensional (2D) systems were studied by Brewster angle microscopy (BAM), polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and surface tension measurements. Results showed that both gliadins adsorbed under phospholipid monolayers, considered as biological membrane models, and formed micrometer-sized domains at equilibrium. However, their thicknesses, probed by reflectance measurements, were different: ,-gliadins aggregates displayed a constant thickness, consistent with a monolayer, while the thickness of ,-gliadins aggregates increased with the quantity of protein injected. These different behaviors could find some explanations in the difference of aminoacid sequence distribution: an alternate repeated - unrepeated domain within ,-gliadin sequence, while one unique repeated domain was present within ,-gliadin sequence. All these findings enabled to propose a model of gliadins self-assembly via a membrane interface and to highlight the predominant role of wheat prolamin repeated domain in the membrane interaction. In the biological context, these results would mean that the repeated domain could be considered as an anchor for the interaction with the ER membrane and a nucleus point for the formation and growth of protein bodies within endosperm cells. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 610,622, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] | |||||||||||||