Home About us Contact
|
Home About us Contact | ||
|
|
||
Atomic Force (atomic + force)
Terms modified by Atomic Force Selected AbstractsTopological and Electron-Transfer Properties of Yeast Cytochrome c Adsorbed on Bare Gold ElectrodesCHEMPHYSCHEM, Issue 11 2003Beatrice Bonanni Dr. Abstract The redox metalloprotein yeast cytochrome c was directly self-chemisorbed on "bare" gold electrodes through the free sulfur-containing group Cys102. Topological, spectroscopic, and electron transfer properties of the immobilised molecules were investigated by in situ scanning probe microscopy and cyclic voltammetry. Atomic force and scanning tunnelling microscopy revealed individual protein molecules adsorbed on the gold substrate, with no evidence of aggregates. The adsorbed proteins appear to be firmly bound to gold and display dimensions in good agreement with crystallographic data. Cyclic voltammetric analysis showed that up to 84,% of the electrode surface is functionalised with electroactive proteins whose measured redox midpoint potential is in good agreement with the formal potential. Our results clearly indicate that this variant of cytochrome c is adsorbed on bare gold electrodes with preservation of morphological properties and redox functionality. [source] Influence of Treatment Conditions on the Chemical Oxidative Activity of H2SO4/H2O2 Mixtures for Modulating the Topography of Titanium,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Fabio Variola Abstract Host-tissue integration of medical implants is governed by their surface properties. The capacity to rationally design the surface physico-chemical cues of implantable materials is thus a fundamental prerequisite to confer enhanced biocompatibility. Our previous work demonstrated that different cellular processes are elicited by the nanotexture generated on titanium (cpTi) and Ti6Al4V alloy by chemical oxidation with a H2SO4/H2O2 mixture. Here, we illustrate that by varying the etching parameters such as temperature, concentration, and treatment time, we can create a variety of surface features on titanium which are expected to impact its biological response. The modified submicron and nanotextured surfaces were characterized by scanning electron (SEM) and atomic force (AFM) microscopies. Contact angle measurements revealed the higher hydrophilicity of the modified surfaces compared to untreated samples and Fourier transform infrared spectroscopy (FT-IR) established that the etching generated a TiO2 layer with a thickness in the 40,60,nm range. [source] Structural Evolution of Self-Assembling Nanohybrid Thin Films from Functionalized Urea Precursors,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007I. Karatchevtseva Abstract Hybrid organic-inorganic thin films exhibiting patterned structuring on the nanometer scale have been prepared through the controlled hydrolysis-condensation of enantiomerically pure chiral urea-based silyl compounds. The thin films are obtained by spin-coating of sols obtained via acid- or base-catalyzed hydrolytic condensation of these molecular precursors. A self-templating process is demonstrated via atomic force and transmission electron microscopy, showing the formation of nanometer size aggregates consisting of interconnected spherulates under acidic condition and of assembled fibers under basic conditions. [source] Palladium Nanowire from Precursor Nanowire: Crystal-to-Crystal Transformation via In,Situ Reduction by Polymer Matrix,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007S. Porel Abstract Precursor nanowires of potassium palladium(II) chloride crystallized inside a poly(vinyl alcohol) film are reduced to palladium nanowires by the polymer itself under mild thermal annealing. The chemical reaction occurring in situ inside the polymer film, including byproduct formation, is investigated through electronic absorption and X-ray photoelectron spectroscopy together with atomic force and electron microscopy. The overall process can be described as a novel case of crystal-to-crystal transformation at the nanoscopic level. Optical limiting characteristics of the nanowire-embedded polymer film are explored. The fabrication procedure developed, involving chemistry inside a polymer matrix mediated by the polymer, opens up a convenient route to the fabrication of free-standing metal nanowire-embedded thin films. [source] Soluble Graphene: Soluble Graphene: Generation of Aqueous Graphene Solutions Aided by a Perylenebisimide-Based Bolaamphiphile (Adv. Mater.ADVANCED MATERIALS, Issue 42 200942/2009) Single-layer graphene (SLG) can be deposited onto Si/SiO2 substrates from aqueous dispersions using a scalable and quick detergent-based method that takes advantage of the availability and low cost of graphite as a feedstock, report Andreas Hirsch and co-workers on p. 4265. The deposits were analyzed using absorption and Raman spectroscopy and atomic force and optical microscopy. Evaluation of the two-phonon defect-induced Raman peak of individual particles on the substrate was then used to confirm exfoliation into graphene monolayers. [source] Soluble Graphene: Generation of Aqueous Graphene Solutions Aided by a Perylenebisimide-Based BolaamphiphileADVANCED MATERIALS, Issue 42 2009Jan M. Englert Single-layer graphene (SLG) is deposited onto Si/SiO2 substrates from aqueous dispersions using a scalable and quick detergent-based method (see figure). The deposits are analyzed using absorption and Raman spectroscopy and atomic force and optical microscopy. Evaluation of the two-phonon defect-induced Raman peak of individual particles on the substrate is used to confirm exfoliation into graphene monolayers. [source] Threading dislocations in domain-matching epitaxial films of ZnOJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2007W.-R. Liu The structures of high-quality ZnO epitaxial films grown by pulsed-laser deposition on sapphire (0001) without an oxygen gas flow were investigated by X-ray diffraction and transmission electron microscopy. The great disparity of X-ray diffraction line widths between the normal and in-plane reflections reveals the specific threading dislocation geometry of ZnO. Most threading dislocations are pure edge dislocations. From a combination of scattering and microscopic results, it is found that threading dislocations are not uniformly distributed in the ZnO films, but the films consist of columnar epitaxial cores surrounded by annular regions of edge threading dislocations in large density. The local surface morphology and capacitance signal obtained from atomic force and scanning capacitance microscopes indicate that the aggregation of threading dislocations leads to high interface traps at the annular regions. [source] Phenomenological description of domain recording in ferroelectric semiconductors by using atomic force microscopyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2005Anna N. Morozovska Abstract The equilibrium sizes of domains caused by the electric field of the atomic force microscope tip in ferroelectric semicon-ductor crystals have been calculated. The domain was consi-dered as a prolate semi-ellipsoid with rather thin domain walls. For the first time we modified the Landauer model al-lowing for semiconductor properties of the sample and the surface energy of the domain butt. The free carriers inside the crystal lead to the formation of a screening layer around the domain, which partially shields its interior from the depolari-zation field. The obtained dependence of domain radius on applied voltage is in a good quantitative agreement with the ones of submicron ferroelectric domains recorded by high-voltage atomic force and scanning probe microscopy in LiNbO3, BaTiO3 and RbTiOPO4 crystals. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Degradation of Structural and Optical Properties of InGaN/GaN Multiple Quantum Wells with Increasing Number of WellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003S. Pereira Abstract We compare the structural and spectral properties of two multi quantum wells (MQWs), grown by metal organic chemical vapour deposition under the same nominal conditions, with a different number of periods. The MQWs, each with 20% InN and containing 8 and 18 wells, respectively, grew on-axis and coherent to GaN, as revealed by X-ray diffraction reciprocal space mapping (RSM) analysis. Comparison of the asymmetrical (105) RSMs indicates an overall structural deterioration and greater well-barrier intermixing for the MQW with the larger number of wells. Moreover, the composition of the MQWs was depth-profiled by grazing incidence Rutherford backscattering spectrometry (RBS). RBS further evidences strong intermixing in the 18-well heterostructure. The deleterious effects of intermixing on the emission spectrum are revealed by low temperature photoluminescence spectroscopy. Despite similar peak emission energies (,E < 45 meV) the 8-well structure shows a more symmetric and narrow peak (FWHM , 100 meV) in comparison with that of the 18-well sample (FWHM , 170 meV). Surface analyses by atomic force and scanning electron microscopy show an increased density, size and depth of V-pit defects on the 18-well structure. These results suggest that dislocations and pitting result from a larger elastic strain energy accumulated in the thicker MQW stack and are a fundamental intermixing mechanism for InGaN/GaN MQWs. [source] Revision of pyrrhotite structures within a common superspace modelACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2007Zunbeltz Izaola The structure of pyrrhotite (Fe1,,,xS with 0.05 ,x, 0.125) has been reinvestigated in the framework of the superspace formalism. A common model with a centrosymmetric superspace group is proposed for the whole family. The atomic domains in the internal space representing the Fe atoms are parametrized as crenel functions that fulfil the closeness condition. The proposed model explains the x -dependent space groups observed and the basic features of the structures reported up to now. Our model yields for any x value a well defined ordered distribution of Fe vacancies in contrast to some of the structural models proposed in the literature. A new (3,+,1)-dimensional refinement of Fe0.91S using the deposited dataset [Yamamoto & Nakazawa (1982). Acta Cryst. A38, 79,86] has been performed as a benchmark of the model. The consistency of the proposed superspace symmetry and its validity for other compositions has been further checked by means of ab initio calculations of both atomic forces and equilibrium atomic positions in non-relaxed and relaxed structures, respectively. [source] | ||||||||||||||||