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Force Microscopy Study (force + microscopy_study)
Selected AbstractsPhase Segregation in Thin Films of Conjugated Polyrotaxane, Poly(ethylene oxide) Blends: A Scanning Force Microscopy Study,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007L. Sardone Abstract Scanning force microscopy (SFM) is used to study the surface morphology of spin-coated thin films of the ion-transport polymer poly(ethylene oxide) (PEO) blended with either cyclodextrin (CD)-threaded conjugated polyrotaxanes based on poly(4,4,-diphenylene-vinylene) (PDV), ,-CD,PDV, or their uninsulated PDV analogues. Both the polyrotaxanes and their blends with PEO are of interest as active materials in light-emitting devices. The SFM analysis of the blended films supported on mica and on indium tin oxide (ITO) reveals in both cases a morphology that reflects the substrate topography on the (sub-)micrometer scale and is characterized by an absence of the surface structure that is usually associated with phase segregation. This observation confirms a good miscibility of the two hydrophilic components, when deposited by using spin-coating, as suggested by the luminescence data on devices and thin films. Clear evidence of phase segregation is instead found when blending PEO with a new organic-soluble conjugated polymer such as a silylated poly(fluorene)- alt -poly(para -phenylene) based polyrotaxane (THS,,-CD,PF,PPP). The results obtained are relevant to the understanding of the factors influencing the interfacial and the intermolecular interactions with a view to optimizing the performance of light-emitting diodes, and light-emitting electrochemical cells based on supramolecularly engineered organic polymers. [source] Large-scale, Uniform DNA Network on 11-mercaptoundecanoic Acid Modified Gold (111) Surface: Atomic Force Microscopy StudyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 7 2007Yonghai Song Abstract Large-scale, uniform plasmid deoxyribonucleic acid (DNA) network has been successfully constructed on 11-mercaptoundecanoic acid modified gold (111) surface using a self-assembly technique. The effect of DNA concentration on the characteristics of the DNA network was investigated by atomic force microscopy. It was found that the size of meshes and the height of fibers in the DNA network could be controlled by varying the concentration of DNA with a constant time of assembly of 24 h. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] Compression-Inhibited Pore Formation of Polyelectrolyte Multilayers Containing Weak Polyanions: A Scanning Force Microscopy StudyCHEMPHYSCHEM, Issue 3 2006Bo Wang Abstract Morphological changes of poly(acrylic acid)/poly(diallyldimethylammonium chloride) multilayers induced by low pH were investigated by scanning force microscopy. The weakened interaction between the charged polymer chains in the protonation process is believed to be the reason for this variation. Kinetic studies have shown that during protonation phase separation and dissociation of the multilayers took place successively. The compression of the multilayers, however, caused a transition of the multilayers from a rubbery state to a glassy state. As a result, the closely compacted multilayers lost their sensitivity to pH change. An increase of electrostatic and hydrophobic interactions, can decrease the free energy of the multilayers, and stabilize the films. By compression of the multilayers with a rubber stamp having geometric patterns, films with spatially localized pores were produced. [source] Influence of Molecular Order on the Local Work Function of Nanographene Architectures: A Kelvin-Probe Force Microscopy StudyCHEMPHYSCHEM, Issue 11 2005Vincenzo Palermo Dr. Abstract We report a Kelvin-probe force microscopy (KPFM) investigation on the structural and electronic properties of different submicron-scale supramolecular architectures of a synthetic nanographene, including extended layers, percolated networks and broken patterns grown from solutions at surfaces. This study made it possible to determine the local work function (WF) of the different , -conjugated nanostructures adsorbed on mica with a resolution below 10 nm and 0.05 eV. It revealed that the WF strongly depends on the local molecular order at the surface, in particular on the delocalization of electrons in the , -states, on the molecular orientation at surfaces, on the molecular packing density, on the presence of defects in the film and on the different conformations of the aliphatic peripheral chains that might cover the conjugated core. These results were confirmed by comparing the KPFM-estimated local WF of layers supported on mica, where the molecules are preferentially packed edge-on on the substrate, with the ultraviolet photoelectron spectroscopy microscopically measured WF of layers adsorbed on graphite, where the molecules should tend to assemble face-on at the surface. It appears that local WF studies are of paramount importance for understanding the electronic properties of active organic nanostructures, being therefore fundamental for the building of high-performance organic electronic devices, including field-effect transistors, light-emitting diodes and solar cells. [source] Atomic force microscopy study of living diatoms in ambient conditionsJOURNAL OF MICROSCOPY, Issue 3 2003I. C. Gebeshuber Summary We present the first in vivo study of diatoms using atomic force microscopy (AFM). Three chain-forming, benthic freshwater species ,Eunotia sudetica, Navicula seminulum and a yet unidentified species , are directly imaged while growing on glass slides. Using the AFM, we imaged the topography of the diatom frustules at the nanometre range scale and we determined the thickness of the organic case enveloping the siliceous skeleton of the cell (10 nm). Imaging proved to be stable for several hours, thereby offering the possibility to study long-term dynamic changes, such as biomineralization or cell movement, as they occur. We also focused on the natural adhesives produced by these unicellular organisms to adhere to other cells or the substratum. Most man-made adhesives fail in wet conditions, owing to chemical modification of the adhesive or its substrate. Diatoms produce adhesives that are extremely strong and robust both in fresh- and in seawater environments. Our phase-imaging and force-pulling experiments reveal the characteristics of these natural adhesives that might be of use in designing man-made analogues that function in wet environments. Engineering stable underwater adhesives currently poses a major technical challenge. [source] Atomic force microscopy study of the role of LPS O-antigen on adhesion of E. coliJOURNAL OF MOLECULAR RECOGNITION, Issue 5 2009Joshua Strauss Abstract The O-antigen is a highly variable component of the lipopolysaccharide (LPS) among Escherichia coli strains and is useful for strain identification and assessing virulence. While the O-antigen has been chemically well characterized in terms of sugar composition, physical properties such as O-antigen length of E. coli LPS have not been well studied, even though LPS length is important for determining binding of bacteria to biomolecules and epithelial cells. Atomic force microscopy (AFM) was used to characterize the physicochemical properties of the LPS of eight E. coli strains. Steric repulsion between the AFM tip (silicon nitride) and the E. coli cells was measured and modeled, to determine LPS lengths for three O157 and two O113 E. coli strains, and three control (K12) strains that do not express the O-antigen. For strains with an O-antigen, the LPS lengths ranged from 17,±,10 to 37,±,9,nm, and LPS length was positively correlated with the force of adhesion (Fadh). Longer lengths of LPS may have allowed for more hydrogen bonding between the O-antigen and silanol groups of the AFM silicon nitride tip, which controlled the magnitude of Fadh. For control strains, LPS lengths ranged from 3,±,2 to 5,±,3,nm, and there was no relationship between LPS length and adhesion force between the bacterium and the silicon nitride tip. In the absence of the O-antigen, we attributed Fadh to electrostatic interactions with lipids in the bacterial membrane. Copyright © 2009 John Wiley & Sons, Ltd. [source] Graphite under the magnetic force microscopePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2007T. L. Makarova Abstract In search for magnetically active carbon structures, we have undertaken the magnetic force microscopy study of intrinsic defects at the surface of highly oriented pyrolytic graphite. Most of the observed defects, such as ridges and cleavage edges, are found magnetically inert. However, some of the observed sharp cleavage edges do show magnetic activity , a built-in surface magnetization, which reveals itself as the magnetic force gradient signal sensitive to the polarity of the tip magnetization. These results indicate the existence of a defect related magnetism at room temperature on graphite surface. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||