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Atomic Force Microscopy Images (atomic + force_microscopy_image)
Selected AbstractsOrganization of Coordination Polymers on Surfaces by Direct SublimationADVANCED MATERIALS, Issue 20 2009Lorena Welte Sublimation and surface reassembly of coordination polymers is achieved due to the reversibility of the coordination bonds. Atomic force microscopy images show linear structures on surfaces, as expected for a 1D coordination polymer [source] Gold electrodes modified with poly(4-aminophenol): incorporation of nitrogenated bases and an oligonucleotidePOLYMER INTERNATIONAL, Issue 4 2008Lucas F Ferreira Abstract BACKGROUND: Investigations of chemical modification of electrode surfaces and immobilization of nitrogenated bases and oligonucleotides are considered essential for the construction of DNA electrochemical nanodevices. Modification of gold electrode surfaces with poly(4-aminophenol) was carried out in order to produce polymers capable of immobilizing purine bases and oligonucleotides. RESULTS: Gold electrodes coated with poly(4-aminophenol) showed improved analytical characteristics and considerably enhanced the electrochemical signals associated with the detection of adenine and guanine by factors of ca 3 and ca 6, respectively, when compared with non-coated gold surfaces. Impedance studies indicated higher charge transfer impedance to modified electrodes containing adenosine monophosphate. Atomic force microscopy images showed that nitrogenated bases have a strong influence over the morphology of the modified electrode surface. It was observed that the modified electrode containing guanine presents globular morphology. CONCLUSION: The modified electrodes increased the amplitude of the current signal of nitrogenated bases when compared to non-coated gold surfaces and produced good response and peaks to the detection of an oligonucleotide. This work presents, for the first time, the electropolymerization of 4-aminophenol on gold electrodes, as well as the detection of nitrogenated bases and an oligonucleotide incorporated on these modified electrodes. Copyright © 2007 Society of Chemical Industry [source] Photoelectron Generation by Photosystem,II Core Complexes Tethered to Gold SurfacesCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 4 2010Michele Vittadello, Prof. Abstract By using a nondestructive, ultrasensitive, fluorescence kinetic technique, we measure in,situ the photochemical energy conversion efficiency and electron transfer kinetics on the acceptor side of histidine-tagged photosystem,II core complexes tethered to gold surfaces. Atomic force microscopy images coupled with Rutherford backscattering spectroscopy measurements further allow us to assess the quality, number of layers, and surface density of the reaction center films. Based on these measurements, we calculate that the theoretical photoelectronic current density available for an ideal monolayer of core complexes is 43,,A,cm,2 at a photon flux density of 2000,,mol,quanta,m,2,s,1 between 365 and 750,nm. While this current density is approximately two orders of magnitude lower than the best organic photovoltaic cells (for an equivalent area), it provides an indication for future improvement strategies. The efficiency could be improved by increasing the optical cross section, by tuning the electron transfer physics between the core complexes and the metal surface, and by developing a multilayer structure, thereby making biomimetic photoelectron devices for hydrogen generation and chemical sensing more viable. [source] Supramolecular Self-Assembly: Self-Assembly of a Donor-Acceptor Dyad Across Multiple Length Scales: Functional Architectures for Organic Electronics (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Mater. More than the sum of its parts: by covalently coupling polycyclic donor and acceptor moieties, Samori and co-workers demonstrate on page 2486 that a donor,acceptor dyad, based on nanographene and perylene, self-assembles into highly ordered supramolecular architectures with nanosegregated coaxial donor and acceptor regions. The cover image features an atomic force microscopy image of mesoscopic ribbons along with the proposed crystallographic arrangement of the constituent molecules. [source] Effect of Molecular Orientation of Epitaxially Grown Platinum(II) Octaethyl Porphyrin Films on the Performance of Field-Effect Transistors,ADVANCED MATERIALS, Issue 9 2003Y.-Y. Noh The molecular alignment of platinum(II) octaethyl porphyrin (PtOEP) crystals evaporated on KBr (see atomic force microscopy image, Figure) can be readily changed from perpendicular to parallel by changing the substrate temperature. The field-effect mobility of transisitors prepared using epitaxially grown PtOEP films aligned perpendicularly to a substrate is 100 times higher than that of those of parallel alignment. [source] The Formation of Ordered Nanoholes in Binary, Chemically Similar, Symmetric Diblock Copolymer Blend Films,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 12 2004Yu Xuan Abstract Summary: Binary symmetric diblock copolymer blends, that is, low-molecular-weight poly(styrene- block -methyl methacrylate) (PS- b -PMMA) and high-molecular-weight poly(styrene- block -methacrylate) (PS- b -PMA), self-assemble on silicon substrates to form structures with highly ordered nanoholes in thin films. As a result of the chemically similar structure of the PMA and the PMMA block, the PMMA chain penetrates through the large PMA block that absorbs preferentially on the polar silicon substrate. This results in the formation of nanoholes in the PS continuous matrix. An atomic force microscopy image of the thin film obtained from the blend of low-molecular-weight PS- b -PMMA and high-molecular-weight PS- b -PMA. The regular array of nanoholes in the films surface is clearly visible. [source] Fabrication of Organized Porphyrin-Nanotube-Attached Heat-Sensitive Polyelectrolyte Capsules,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2006S. Sadasivan Abstract A facile method of connecting fluorescent meso -tetrakis(4-sulfonatophenyl)porphine tetranion nanotubes to polyelectrolyte capsules is developed. Heat-sensitive robust polyelectrolyte capsules consisting of poly(diallyldimethylammonium chloride) and poly(styrene sulfonate) multilayers have been fabricated using the conventional layer-by-layer technique. Supramolecular aggregation of porphyrin monomers to nanotubes is induced in the microenvironment of the capsules by sequential addition of salt and acid. Scanning electron microscopy, transmission electron microscopy, and atomic force microscopy images reveal satellite-like structures consisting of a central capsule core with porphyrin nanotubes emerging radially from the capsule walls. The growth and the distribution of the porphyrin units have been monitored by UV-vis spectroscopy, fluorescence spectroscopy, and confocal laser scanning microscopy. Changing the temperature alters the dimensions and the arrangement of the nanotubes on the capsule walls. Such an attachment of porphyrin tubes onto robust functional capsules should help in developing an artificial light-harvesting system. [source] Low-temperature bitumen stiffness and viscous paraffinic nano- and micro-domains by cryogenic AFM and PDMJOURNAL OF MICROSCOPY, Issue 3 2007J-F. MASSON Summary In an effort to better understand the structure and behaviour of bitumen in low temperature, we describe the first use of cryogenic atomic force microscopy and phase detection microscopy to characterize bitumen nano- and micro-structures. The results were interpreted in light of glass transition temperatures (Tgs) for bitumen fractions. The domains visible by microscopy, the catana, peri and para phases, were attributed to domains rich in asphaltenes, naphthene and polar aromatics, and saturates, respectively. Between ,10°C and ,30°C, atomic force microscopy images revealed topographic features not visible in atomic force microscopy images acquired at room temperature. According to phase detection microscopy and Tgs, the features were assigned to viscous unfrozen saturates. Upon cooling to ,72°C, unfrozen domains of 20,400 nm were observed. These domains were found in the paraphase rich in saturates and in the periphase rich in naphthene aromatics and polar aromatics. The findings indicate that new viscous domains form upon cooling to low temperatures owing to phase segregation, and that some bitumens are never entirely rigid in low temperatures. [source] Cover Picture: Plasma Process.PLASMA PROCESSES AND POLYMERS, Issue 1 2005Polym. Cover: The effect of pressure in the surface modification of poly(ethylene terephthalate) fibers induced by SF6 plasma treatment is shown by atomic force microscopy images of (a) the untreated surface and of the fiber surface after 60 s long SF6 plasma treatment at (b) 0.05 mbar, (b) 0.20 mbar and (c) 0.40 mbar. The RF power was 105W; PET fabrics were plasma-treated at 7.5 cm from the RF antenna. Further details can be found in the Full Paper by R. Barni, C. Riccardi, E. Selli,* M. R. Massafra, B. Marcandalli, F. Orsini, G. Poletti, and L. Meda on page 64. [source] Study of Langmuir,Blodgett phospholipidic films deposited on surface enhanced Raman scattering active gold nanoparticle monolayersBIOPOLYMERS, Issue 4-5 2002S. Bernard Abstract Surface enhanced Raman scattering (SERS) was used to study phospholipid monolayers transferred by the Langmuir,Blodgett (LB) technique to SERS active substrates. These substrates, which were constituted of gold colloidal nanoparticles bound to polysilane films grafted onto glass plates, showed a uniform and homogeneous layer with strong interacting particles as revealed from UV,visible extinction spectra and atomic force microscopy images. Laser excitation at 632.8 nm within the red part of the localized surface plasmon resonance leads to intense and reproducible SERS spectra of trans -1,2-bis(4-pyridyl)ethylene (BPE). From SERS measurements at different pHs it was possible to determine the apparent pKa of BPE adsorbed on gold-coated silanized substrates in the absence and presence of one LB monomolecular layer of phospholipids. These SERS titrations allowed the estimation of the pH at the metal,LB film interface. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 314,318, 2002 [source] On the Rigidity of Polynorbornenes with Dipolar Pendant GroupsCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2006Wei-Yu Lin Abstract A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C-5,6 positions was synthesized by ring-opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod-like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod-like structure. [source] | |||||||||||||||||||||||||