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Search Results: 1 - 10 of 3465 matches for " sanning tunneling microscopy "
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Study of β-amyloid adsorption and aggregation on graphite by STM and AFM
Zhigang Wang,Lijun Wan,Chunqing Zhou,Xiaohong Fang,Chen Wang,Chunli Bai
Chinese Science Bulletin , 2003, DOI: 10.1007/BF03183245
Abstract: The scanning tunneling microscopy (STM) and the atomic force microscopy (AFM) have been applied to the direct study of the adsorption and aggregation of β-amyloid(1–42)(Aβ42) on the hydrophobic graphite surface. It was found that Aβ42 were preferentially adsorbed on graphite defects such as the edges. Aβ42 peptides self-assembled into intermediate protofibrils, which in turn self-associated to form fibrils. Usually, two or more fibrils intertwined to form the helical structure. These results will provide an important clue to studying the aggregation process of β-amyloid.
Study of-amyloid adsorption and aggregation on graphite by STM and AFM
Study of β—amyloid adsorption and aggregation on graphite by STM and AFM

WANGZhigang,WANLijun,ZHOUChungqing,FANGXiaohong,WANGChen,BAIChunli
科学通报(英文版) , 2003,
Abstract: The scanning tunneling microscopy (STM) and the atomic force microscopy (AFM) have been applied to the direct study of the adsorption and aggregation of -amyloid(1-42)(A42) on the hydrophobic graphite surface. It was found that A42 were preferentially adsorbed on graphite defects such as the edges. A42 peptides self-assembled into intermediate protofibrils, which in turn self-associated to form fibrils. Usually, two or more fibrils intertwined to form the helical structure. These results will provide an important clue to studying the aggregation proc-ess of -amyloid.
Epitaxial Ge Growth on Si(111) Covered with Ultrathin SiO2 Films  [PDF]
Alexander A. Shklyaev, Konstantin N. Romanyuk, Alexander V. Latyshev
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2013, DOI: 10.4236/jsemat.2013.33027
Abstract:

The epitaxial growth of Ge on Si(111) covered with the 0.3 nm thick SiO2 film is studied by scanning tunneling microscopy. Nanoareas of bare Si in the SiO2 film are prepared by Ge deposition at a temperature in the range of 570℃-650℃ due to the formation of volatile SiO and GeO molecules. The surface morphology of Ge layers grown further at 360℃-500℃ is composed of facets and large flat areas with the Ge(111)-c(2 × 8) reconstruction which is typical of unstrained Ge. Orientations of the facets, which depend on the growth temperature, are identified. The growth at 250℃-300℃ produces continuous epitaxial Ge layers on Si(111). A comparison of the surface morphology of Ge layers grown on bare and SiO2-film covered Si(111) surfaces shows a significantly lower Ge-Si intermixing in the latter case due to a reduction in the lattice strain. The found approach to reduce the strain suggests the opportunity of the thin continuous epitaxial Ge layer formation on Si(111).

Supported TritonX-100 Polyaniline Nano-Porous Electrically Active Film onto Indium-Tin-Oxide Probe for Sensors Application  [PDF]
Raju Khan
Advances in Chemical Engineering and Science (ACES) , 2011, DOI: 10.4236/aces.2011.13021
Abstract: Supported tritonX100 polyaniline nano-porous electrically active film has been fabricated successfully onto indium-tin-oxide conducting probe using electrochemical polymerization process. The doping of TX-100 in the polymeric network of PANI was suggested using cyclic voltammeter, UV-vis spectroscopy, and Fourier Transform Infrared spectroscopy. The change in the surface morphology of PANI thin film due to incorporation of tritonX-100 was investigated using Atomic Forced Microscopy and porosity has been confirmed scanning electron microscopy, respectively. The surface morphology, uniformly disperse hexagonal close packing of TX-100 in PANI matrices due to the incorporation of TX-100 in polymeric network of PANI was confirmed by Atomic Force Microscopy. The electrical conductivity of PANI-TX-100 increases from 1.06 x 10-2 S/cm-1 to 4.95 x 10-2 S/cm-1 as the amount of TX-100 increases during the polymerization. The change in the morphology and electrical conductivity of PANI due to incorporation of TX-100 prove as a promising material for the sensing application.
Reproducible Fabrication of Scanning Tunneling Microscope Tips
Bernal,Rodrigo; ávila,Alba;
Revista de Ingeniería , 2008,
Abstract: reproducible fabrication of scanning tunneling microscope tips is carried out following an electrochemical procedure widely reported. tips are made from 0.5 diameter tungsten wire. controlling fabrication parameters (immersion in the electrochemical solution, current-voltage ranges, duration of the process, among others) we achieve aspect ratios of 0.68 and tip radii of 330 nm in the best case.
Controlled assembly of copper phthalocyanine with 1-iodooctadecane
Shengbin Lei,Chen Wang,Lijun Wan,Chunli Bai
Chinese Science Bulletin , 2003, DOI: 10.1007/BF03183952
Abstract: The binary assembly behavior of 1-iodooctadecane with substituted phthalocyanine (Pc) is studied using the scanning tunneling microscopy (STM). By altering the substituted alkyl groups attached to the phthalocyanine ring, either uniform assembly or phase separation behavior can be observed. It is suggested that the strength of intermolecular interaction between phthalocyanine molecules is the determining factor for the assembly structure.
TOPICAL REVIEW: Active nanocharacterization of nanofunctional materials by scanning tunneling microscopy
Daisuke Fujita and Keisuke Sagisaka
Science and Technology of Advanced Materials , 2008,
Abstract: Recent developments in the application of scanning tunneling microscopy (STM) to nanofabrication and nanocharacterization are reviewed. The main focus of this paper is to outline techniques for depositing and manipulating nanometer-scale structures using STM tips. Firstly, the transfer of STM tip material through the application of voltage pulses is introduced. The highly reproducible fabrication of metallic silver nanodots and nanowires is discussed. The mechanism is thought to be spontaneous point-contact formation caused by field-enhanced diffusion to the apex of the tip. Transfer through the application of z-direction pulses is also introduced. Sub-nanometer displacement pulses along the z-direction form point contacts that can be used for reproducible nanodot deposition. Next, the discovery of the STM structural manipulation of surface phases is discussed. It has been demonstrated that superstructures on Si(001) surfaces can be reverse-manipulated by controlling the injected carriers. Finally, the fabrication of an atomic-scale one-dimensional quantum confinement system by single-atom deposition using a controlled point contact is presented. Because of its combined nanofabrication and nanocharacterization capabilities, STM is a powerful tool for exploring the nanotechnology and nanoscience fields.
Anchoring of a Single Molecular Rotor and Its Array on Metal Surfaces using Molecular Design and Self-Assembly
Li Gao,Shi-Xuan Du,Hong-Jun Gao
International Journal of Molecular Sciences , 2010, DOI: 10.3390/ijms11020656
Abstract: Functionalizing of single molecules on surfaces has manifested great potential for bottom-up construction of complex devices on a molecular scale. We discuss the growth mechanism for the initial layers of polycyclic aromatic hydrocarbons on metal surfaces and we review our recent progress on molecular machines, and present a molecular rotor with a fixed off-center axis formed by chemical bonding. These results represent important advances in molecular-based nanotechnology.
Polymorphism in Self-Assembled Structures of 9-Anthracene Carboxylic Acid on Ag(111)
Chao Lu,Yinying Wei,Erkuang Zhu,Janice E. Reutt-Robey,Bo Xu
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms13066836
Abstract: Surface self-assembly process of 9-anthracene carboxylic acid (AnCA) on Ag(111) was investigated using STM. Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. The two high-density belt phases possess large unit cells on the scale length of 10 nm, which are seldom observed in molecular self-assembled structures. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions, as well as the steric demand from high molecular surface density.
Caracterización del biomineral CaCO3 en algas rojas coralinas (Corallinales) de las costas del Pacífico mexicano
Fragoso, D;Ramírez-Cahero, F;Rodríguez-Galván, A;Hernández-Reyes, R;Heredia, A;Rodríguez, D;Aguilar-Franco, M;Bucio, L;Basiuk, VA;
Ciencias marinas , 2010,
Abstract: coralline red algae assimilate hco3- to precipitate caco3 in their tissues in the form of calcite or aragonite. a characterization of the biomolecular content and the crystalline structure of the biomineral of coralline red algae from the pacific coast of mexico was performed by powder x-ray diffraction (xrd), scanning electron (sem) and tunneling microscopy (stm), and fourier transform infrared spectroscopy (ftir). the preliminary conclusion drawn from the results is that this type of calcite-aragonite biomineral has a very low organic content occluded within the crystals. ftir bands at 2945 and 2889 cm-1 indicate that the most likely organic molecules are carbohydrates; moreover, peptide bond bands (amide i ~1640 and amide ii ~1540 cm-1) were not detected, suggesting that proteins are not related to mineral synthesis or their stabilization. this could be explained if the biomineral is synthesized by a biologically controlled extracellular mineralization process. the xrd study showed two main mineral phases, calcite and aragonite, with very similar structural parameters to the inorganic mineral counterparts. the crystallite shapes, seen by stm, were found as plates and needles with different sizes, between 20 and 100 nm.
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