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Littérature scientifique sur le sujet « Surface electronic propertie »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "Surface electronic propertie"

Terebinska, M. I., O. I. Tkachuk, A. M. Datsyuk, O. V. Filonenko et V. V. Lobanov. « Electronic structure of complexes of oligomers of 3,4-ethylene-dietoxythiophene with polystyrlesulphonic acid ». Surface 13(28) (30 décembre 2021) : 84–93. http://dx.doi.org/10.15407/surface.2021.13.084.

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By the method of density functional theory (B3LYP, 6-31G **) the electronic structures of poly 3,4-ethylenedioxythiophene containing 12 links in charge states 0, +1, +2, +3 and +4 were calculated. It is shown that the oligomer of 12 units is sufficient to reflect the properties of the conductive polymer. To estimate the probability of electron density movement along the polymer chain, the width of the energy gap between NOMO and LUMO was calculated. It is shown that the molecules of oligomers EDOT and SS do not remain parallel to each other after polymerization, but rather, with increasing chain length, the latter gradually bends around the anionic unit SS; the charge distribution in the EDOT and SS oligomer complexes indicates the presence of two separated polarons at the two ends of the chain, and the asymmetry in the charge distribution also implies the presence of a curved spiral structure of the formed complex.

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Karpenko, O. S., V. V. Lobanov et M. T. Kartel. « C1s core-level binding energy shift dependence from carbon atoms position in graphenenanoflakes C96 and polycyclic aromatic hydrocarbon C96H24 : a dft study ». SURFACE 14(29) (30 décembre 2022) : 63–77. http://dx.doi.org/10.15407/surface.2022.14.063.

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The hexagon-shape graphene nanoflakes (GNFs) limited by zigzag edges only (with doubly and triply coordinated atoms) have unique increased reactivity. Despite the high systems symmetry (D6h) the Carbon atoms in GNFs occupy non-equivalent positions. Can such physical and chemical characteristics of GNFs, which depend of the atom position in the cluster, definition? This characteristic together with the simplicity of its calculation makes it possible to predict the properties of nanoflakes obtained from GNFs by introducing single and multiatomic vacancies into them or by replacing Carbon atoms with electron withdrawing and electron donating atoms. This characteristic includes the C1s core-level binding energy shifts, the maxima of which characterize the C atoms of a certain type. The proposed work is devoted to quantum chemical calculations of the electronic density of states (DOS) of pristine hexagon-shape GNF C96 (multiplicity, M=5), their saturated counterpart –polycyclic aromatic hydrocarbon(PAH) C96H24 (M=1) and their derivatives with one and two single vacancies in the ground electronic state (GES). All calculations were performed using the density functional theory (DFT) method with the involvement of the valence-split basis set 6-31G (d,p). Systems with open shells were considered using the UB3LYP exchange-correlation functional. The obtained spectra were fitted using Gaussian curve fitting program to determine the binding energy for each peak. The Gaussian function distribution of the theoretically calculated C1s core-level binding energy shifts of GNFs testified the presence of six peaks, each of which refers to a certain type of Carbon atoms. The C1s peak with the highest binding energy (-285.57 eV) is caused by contributions from the doubly coordinated edge cyclic chain (ECC) Carbon atoms. The C1s orbitals of the central hexagon (CHex) atoms and the first cyclic chain (FCC) atoms form delocalized molecular orbitals (MOs) in different parts of the cluster. The analogous spectrum of PAH C96H24 is slightly shifted to the region of lower binding energies and contains only two well-defined peaks. The peak with a higher binding energy (-284.36 eV) is generated by the 1s states of the CHex atoms and the atoms of the FCC, which are bounded to the CHex atoms. The electronic DOS difference in C1s core-level spectra of GNF C96 (M=5) and their saturated counterpart PAH C96H24 is established due to the presence of two weakly bounded π-systems in GNF and common conjugated system in PAH. The electronic DOS of defect-containing cluster C96-1(1) (M=3) (one CHex atom has been removed from the C96nanoflake) is generated by the C1s core-level atoms of the second cyclic chain (SCC), which are located at the different distances from the center of the nanoflake. The peak of the lowest intensity (-284.63 eV) appears in the spectrum as a reflection of the appearance of doubly coordinated Carbon atoms surrounding the single vacancy in the C96-1(1) nanoflake. The analysis of the electronic DOS of the C1s core-level spectrum of the C96-2(1) nanoflakeis shown, that doubly coordinated Carbon atoms, concentrated around two single vacancies, are essentially non-equivalent. If the MO with the lowest binding energy is localized on two of them – the MO with the highest binding energy is localized on the third atoms (one around each single vacancy). The electronic C1s core-level DOS spectrum of defect-containing molecular systems with one C96-1(1)H24 and two C96‑2(1)H24 single vacancies are similar to the analogous spectrum of PAH C96H24. In the first of them – one additional maximum appears due to C1s atoms surrounding the single vacancy. In the second – there are two additional maxima, each of which is generated by C1s core-level atoms adjacent to individual vacancies.

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Kang, Jianxiong, Yanni An, Jiwei Xue, Xiao Ma, Jiuzhou Li, Fanfan Chen, Sen Wang, He Wan, Chonghui Zhang et Xianzhong Bu. « Density Functional Theory Study of the Electronic Structures of Galena ». Processes 11, n^o 2 (17 février 2023) : 619. http://dx.doi.org/10.3390/pr11020619.

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In this study, the electronic structure of the galena surface was investigated using the first-principle calculation. The results of band structure, density of states, Mulliken population distribution, and frontier orbital analysis showed that galena was the p-type semiconductor of the direct band gap. During the formation of galena crystals, the 3p orbital of the S and the 6p orbital of the Pb played a primary role. Additionally, S atoms in galena quickly lose electrons and are oxidized, while Pb readily reacts with anions. The results of surface structure and electronic properties, such as surface relaxation, surface state energy levels, electronic density of states, and atomic charge distribution showed that the electronics in the 6p orbital of the Pb are transferred to the 3p orbital of the S in galena crystal. They caused the change of atomic valence states in lattice surfaces. The total electron number of the outermost surface layer was also higher than the bulk, giving the galena surface the properties of electron enrichment. This research is of great significance for developing new galena flotation reagents and for further in-depth exploration of the adsorption of reagents on the galena surface.

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Strelko, V. V., et Yu I. Gorlov. « Influence of electronic states of nanographs in carbon microcrystallines on surface chemistry of activated charcoal varieties ». Surface 13(28) (30 décembre 2021) : 15–38. http://dx.doi.org/10.15407/surface.2021.13.015.

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In this paper, the nature of the chemical activity of pyrolyzed nanostructured carbon materials (PNCM), in particular active carbon (AC), in reactions of electron transfer considered from a single position, reflecting the priority role of paramagnetic centers and edge defunctionaled carbon atoms of carbon microcristallites (CMC) due to pyrolysis of precursors. Clusters in the form of polycyclic aromatic hydrocarbons with open (OES) and closed (CES) electronic shells containing terminal hydrogen atoms (or their vacancies) and different terminal functional groups depending on specific model reactions of radical recombination, combination, replacement and elimination were used to model of nanographenes (NG) and CM. Quantum-chemical calculations of molecular models of NG and CMC and heat effects of model reactions were performed in frames of the density functional theory (DFT) using extended valence-splitted basis 6-31G(d) with full geometry optimization of concrete molecules, ions, radicals and NG models. The energies of boundary orbitals were calculated by means of the restricted Hartry-Fock method for objects with closed (RHF) and open (ROHF) electronic shells. The total energies of small negative ions (HOO-, HO-) and anion-radical О2•‾) were given as the sum of calculated total energies of these compounds and their experimental electron affinities. The estimation of probability of considered chemical transformations was carried out on the base on the well-known Bell-Evans-Polyani principle about the inverse correlation of the thermal effects of reactions and its activation energies. It is shown that the energy gap ΔЕ (energy difference of boundary orbitals levels) in simulated nanographens should depend on a number of factors: the periphery structure of models, its size and shape, the number and nature of various structural defects, electronic states of NG. When considering possible chemical transformations on the AC surface, rectangular models of NG were used, for which the simple classification by type and number of edge structural elements of the carbon lattice was proposed. Quantum chemical calculations of molecular models of NG and CNC and the energy of model reactions in frames of DTF showed that the chemisorption of free radicals (3O2 and N•O), as recombination at free radical centers (FRC), should occur with significant heat effects. Such calculations give reason to believe that FRC play an important role in formation of the functional cover on the periphery of NG in CMC of studied materials. On the base of of cluster models of active carbon with OES new ideas about possible reactions mechanisms of radical-anion О2•‾ formation and decomposition of hydrogen peroxide on the surface of active carbon are offered. Explanation of increased activity of AC reduced by hydrogen in H2O2 decomposition is given. It is shown that these PNCM models, as first of all AC, allow to adequately describe their semiconductor nature and acid-base properties of such materials.

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Tshwane, David M., et Rosinah Modiba. « Surface Properties of Ti₂AlV (100) and (110) Surfaces Using First-Principle Calculations ». MATEC Web of Conferences 370 (2022) : 09005. http://dx.doi.org/10.1051/matecconf/202237009005.

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Ti2AlV alloys are commonly employed as structural materials in electronics, metallurgy, and other industries because of their outstanding properties. Knowledge about their surface properties is lacking and limited at the atomic level. In this work, structural, electronic, and stabilities of Ti2AlV surfaces were investigated using the density functional theory approach. This study also looked at the surface energies and work functions of various surfaces. According to our findings, it was found that the (110) surface is thermodynamically stable with lower surface energy than the (100) surface. It was discovered that the surface energy increases with regard to the thickness of the surface slab. Furthermore, the work function of the (110) surface was found to be increasing than that of the (100) surface. Moreover, the work function was found to increase with increasing number of layers in both surfaces. The partial and total density of states of Ti2AlV (100) and (110) were also studied. It was also found that the Fermi level lies at the minimum curve in the TDOS graphs for the Ti2AlV (110) surface while lies at the maximum in (100) surface.

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Dief, Essam M., Anton P. Le Brun, Simone Ciampi et Nadim Darwish. « Spontaneous Grafting of OH-Terminated Molecules on Si−H Surfaces via Si–O–C Covalent Bonding ». Surfaces 4, n^o 1 (5 mars 2021) : 81–88. http://dx.doi.org/10.3390/surfaces4010010.

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The surface functionalization of oxide-free hydrogen-terminated silicon (Si−H) enables predictably tuning its electronic properties, by incorporating tailored functionality for applications such as photovoltaics, biosensing and molecular electronics devices. Most of the available chemical functionalization approaches require an external radical initiator, such as UV light, heat or chemical reagents. Here, we report forming organic monolayers on Si–H surfaces using molecules comprising terminal alcohol (–OH) groups. Self-assembled monolayer (SAM) formation is spontaneous, requires no external stimuli–and yields Si–O–C covalently bound monolayers. The SAMs were characterized by X-ray photoelectron spectroscopy (XPS) to determine the chemical bonding, by X-ray reflectometry (XRR) to determine the monolayers thicknesses on the surface and by atomic force microscopy (AFM) to probe surface topography and surface roughness. The redox activity and the electrochemical properties of the SAMs were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The availability and the ease of incorporating OH groups in organic molecules, makes this spontaneous grafting as a reliable method to attach molecules to Si surfaces in applications ranging from sensing to molecular electronics where incorporating radical initiator setups is not accessible.

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Sun, Jing-Bo, Jian-Gang Yao, Jiang Meng, Shuping Li, Yong Jiang et Jigang Wang. « Surface energies and electronic properties of intermetallic compound B2-AgMg ». Modern Physics Letters B 33, n^o 08 (20 mars 2019) : 1950097. http://dx.doi.org/10.1142/s0217984919500970.

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A new method was used to predict the surface energies of three low-index surfaces for intermetallic compound B2-AgMg. The results show that Ag-terminal and Mg-terminal are the two kinds of surface models for (1 0 0) and (1 1 1) surfaces which are non-stoichiometry. (1 1 0) surface has only one surface terminal, which is stoichiometry, and the smallest surface energy (about [Formula: see text] in three low-index surfaces. The surface energies are related to the chemical potential of Ag and Mg atoms for (1 0 0) and (1 1 1) surfaces, but it is of no concern to this factor for stoichiometry (1 1 0) surface. Analysis of electronic properties is coincident with the calculated surface energies.

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Kim, Jeong Won, Jae Myung Seo et Sehun Kim. « Surface electronic properties of ». Surface Science 351, n^o 1-3 (mai 1996) : L239—L244. http://dx.doi.org/10.1016/0039-6028(95)01344-x.

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Serrano-Garcia, William, Irene Bonadies, Sylvia W. Thomas et Vincenzo Guarino. « New Insights to Design Electrospun Fibers with Tunable Electrical Conductive–Semiconductive Properties ». Sensors 23, n^o 3 (1 février 2023) : 1606. http://dx.doi.org/10.3390/s23031606.

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Fiber electronics, such as those produced by the electrospinning technique, have an extensive range of applications including electrode surfaces for batteries and sensors, energy storage, electromagnetic interference shielding, antistatic coatings, catalysts, drug delivery, tissue engineering, and smart textiles. New composite materials and blends from conductive–semiconductive polymers (C-SPs) offer high surface area-to-volume ratios with electrical tunability, making them suitable for use in fields including electronics, biofiltration, tissue engineering, biosensors, and “green polymers”. These materials and structures show great potential for embedded-electronics tissue engineering, active drug delivery, and smart biosensing due to their electronic transport behavior and mechanical flexibility with effective biocompatibility. Doping, processing methods, and morphologies can significantly impact the properties and performance of C-SPs and their composites. This review provides an overview of the current literature on the processing of C-SPs as nanomaterials and nanofibrous structures, mainly emphasizing the electroactive properties that make these structures suitable for various applications.

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Grinko, А. M., А. V. Brichka, О. М. Bakalinska et М. Т. Каrtel. « Application of nano cerium oxide in solid oxide fuel cells ». Surface 12(27) (30 décembre 2020) : 231–50. http://dx.doi.org/10.15407/surface.2020.12.231.

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This review is analyzed the state of modern literature on the nanoceria based materials application as components for solid oxide fuel cells. The principle of operation of fuel cells, their classification and the difference in the constructions of fuel cells are described. The unique redox properties of nanosized cerium oxide make this material promising for application as components for solid oxide fuel cells (SOFC). Because of high ionic conductivity, high coefficient of thermal expansion and low activation energy at relatively low temperatures, cerium-containing materials are widely used as a solid electrolyte. On the surface of nanosized CeO2 there many surface defects (which is determined by the concentration of oxygen vacancies) that lead to the electronic conductivity increases even at temperatures (300 - 700 °C). The concentration of surface defects can be increased by doping the surface of nanoceria by divalent and trivalent cations. The ionic and electrical properties of the obtained nanocomposites dependent from synthesis methods, ionic radii and concentration of doping cations. It is explained the effect of the transition in the size of cerium oxide particles in the nanoscale region on the concentration of surface defects and defects in the sample structure. Particular attention is paid to the effect of doping nanosized CeO2 by transition metal cations and lanthanides on the characteristics of the obtained material, namely, on the increase of concentration of surface defects due to the increase of oxygen vacancies. It is established that nanosized cerium oxide is used for the development and implementation of the main components of SOFC: electrolyte, anode and cathode. Advantages of using solid electrolytes based on nanosized cerium oxide over the classical electrolytes are listed. It was shown that doping of cerium oxide by double and triple cations lead to increase the ionic conductivity and reduces the activation energy and has a positive effect on its characteristics as a SOFC electrolyte. Composites, based on nanoscaled cerium oxide, are actively developed and studied for use as electrodes of solid oxide fuel cells. Cerium-containing anodes are resistant to the deposition of carbon and fuel impurities, increase the catalytic activity of solid oxide fuel cells, and compatible with other components. Nanosized cerium oxide particles are sprayed onto the cathode to prevent the cathode from interacting with the electrolyte. The prospects for the use of cerium-containing materials for the conversion of chemical energy of fuel into electrical energy are analyzed.

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Thèses sur le sujet "Surface electronic propertie"

ACHILLI, SIMONA. « Spectral properties of adsorbates on metal surfaces via the embedding method ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/10827.

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Adsorbates on metal surfaces have attracted recently the scientific interest both from a fundamental point of view (quantum confinement) and in perspective of application in technology. In particular the electronic properties of such reduced symmetry systems are strictly related to their low dimensionality. An accurate theoretical description of their spectral properties has necessarily to deal with the absence of periodicity that characterizes these systems in one (thin films) or more (adatoms) directions. The embedding method allows to overcome this drawback considering a really infinite system both on vacuum and bulk side. In this thesis the ab initio spectral properties of single adatoms (alkali-metal atom and Ba) on Cu(111) and thin overlayers (K/Cu(111), Bi/Cu(100), O/Fe(100)) are analyzed, also in comparison with experimental results. The capabilities of the theoretical method adopted allow to evidence the role of the substrate band structure on the adsorbates induced electronic states. In particular the aspects related to the resonant charge transfer from the adsorbate's states to the bulk continuum are analyzed. This process represents an elastic decay channel for the surface electronic states and contributes to the elastic lifetime, that we can estimate according to the description of a continuous substrate band structure. The results presented for single adatoms evidence the blockade effect that a surface projected energy gap of the substrate produces on the resonant charge transfer. On the other hand the results relative to the overlayer allows to analyze the complex hybridization mechanism between surface features and substrate states in different points of the surface Brillouin zone. In addition the theoretical description of the electronic properties of overlayers on metal surfaces is devoted in this thesis also to the simulation of experimental findings, namely STM and STS images and photoemission spectra, showing the predictive character of the theoretical approach used.

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Lau, Chi Hian. « Chemical, electronic and electrochemical properties of diamond thin films ». Thesis, University of Oxford, 2002. http://ora.ox.ac.uk/objects/uuid:53a0886c-14ad-431a-975d-0ecca8fc8968.

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Diamond is of interest as an advanced functional material, since the extreme physical properties of diamond, suggests it is ideally suited to a range of new demanding applications. In this context, the thesis explores basic surface chemical properties of diamond thin films, along with electrochemical, electronic and electron emission processes involving this material. New experiments are reported concerning the nature of surface conductivity on diamond. Measurements clearly show that the conductivity only arises if a hydrogenated diamond surface is exposed to water vapour, in the presence of chemical species capable of acting as electron acceptors. The conduction properties of surface conductive diamond in aqueous solution are also studied, and the first detailed electrochemical investigations of this material are described. Comparative electrochemical studies of nanocrystalline and boron-doped diamond have been performed. Investigations of electrode stability, and the accessible "potential window" are described, as well as the behaviour of a range of 'redox' systems, including transition metal complexes, metal deposition/stripping, and bio-related organic species. Significant differences between the behaviour of nanodiamond and microcrystalline boron-doped material are observed. A range of surface chemical and threshold photoemission studies of diamond thin films are reported. The results indicate that quantum photoyields (QPYs) are insensitive to the diamond "quality", although the wavelength selectivity is dependent on it. The adsorption of oxygen strongly reduces the QPY, although this only occurs slowly in the presence of O₂ because of a low reactive sticking probability. Much more rapid uptake of oxygen and consequent reduction of photoyield is observed in the presence of atomic O or electronically excited dioxygen O₂*. The presence of alkali metals on the diamond surface increases the QPY, and reduces the sensitivity of the QPY to surface oxygen. Significant differences between the surface chemical properties of Li, and other adsorbed akali metals (K and Cs) are observed.

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Plachinda, Pavel. « Electronic Properties and Structure of Functionalized Graphene ». PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/585.

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The trend over the last 50 years of down-scaling the silicon transistor to achieve faster computations has led to doubling of the number of transistors and computation speed over about every two years. However, this trend cannot be maintained due to the fundamental limitations of silicon as the main material for the semiconducting industry. Therefore, there is an active search for exploration of alternate materials. Among the possible candidates that can may [sic] be able to replace silicon is graphene which has recently gained the most attention. Unique properties of graphene include exceedingly high carrier mobility, tunable band gap, huge optical density of a monolayer, anomalous quantum Hall effect, and many others. To be suitable for microelectronic applications the material should be semiconductive, i.e. have a non-zero band gap. Pristine graphene is a semimetal, but by the virtue of doping the graphene surface with different molecules and radicals a band gap can be opened. Because the electronic properties of all materials are intimately related to their atomic structure, characterization of molecular and electronic structure of functionalizing groups is of high interest. The ab-inito (from the first principles) calculations provide a unique opportunity to study the influence of the dopants and thus allow exploration of the physical phenomena in functionalized graphene structures. This ability paves the road to probe the properties based on the intuitive structural information only. A great advantage of this approach lies in the opportunity for quick screening of various atomic structures. We conducted a series of ab-inito investigations of graphene functionalized with covalently and hapticly bound groups, and demonstrated possible practical usage of functionalized graphene for microelectronic and optical applications. This investigation showed that it is possible [to] produce band gaps in graphene (i.e., produce semiconducting graphene) of about 1 eV, without degrading the carrier mobility. This was archived by considering the influence of those adducts on electronic band structure and conductivity properties.

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Scenev, Vitalij. « Electronic properties of graphene and other carbon-based hybrid materials for flexible electronics ». Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2014. http://dx.doi.org/10.18452/17069.

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In dieser Arbeit wurden einerseits die elektronischen Eigenschaften von Graphenen und andererseits die Verwendung von Graphenen und Kohlenstoff-basierten Hybridmaterialien als transparente Elektroden untersucht. Entsprechend ist der erste, umfangreichere Teil der Arbeit Grundlagen-orientiert und fokussiert auf die elektrostatische Wechselwirkung zwischen Graphen und dem Substrat Glimmer. Der zweite, kleinere Teil befasst sich mit der Entwicklung leitfähiger Tinten auf der Basis von Graphenen und anderen Kohlenstoff-basierten Hybridmaterialien für Anwendungen in der druckbaren Elektronik, insbesondere für die Herstellung transparenter Elektroden. Graphen auf Glimmer ist ein sehr wohldefiniertes System, in dem das Graphen über mehrere Quadratmikrometer atomar flach ist. Schichtdickenabhängige Variationen des Oberflächenpotentials von einzel- und mehrlagigen Graphenen auf Glimmer wurden mittels Kelvin Probe Rasterkraftmikroskopie untersucht. Damit konnte die elektrostatische Abschirmlänge von Graphen auf Glimmer bestimmt werden. Lokale Variationen des Oberflächenpotentials innerhalb einer Graphenlage, verursacht durch eingeschlossene Wasserschichten zwischen Graphen und Glimmer, wurden mit Rasterkraftmikroskopie, elektrostatischer Rasterkraftmikroskopie und der Raman-Spektroskopie untersucht. Dies ermöglichte es, die Dotierung von Graphen durch eingeschlossene Wasserschichten zu quantifizieren. Außerdem wurde gezeigt, dass Graphen auf molekular modifiziertem Glimmer lokal auf der Nano-Skala dehnbar ist. Dabei wurde der Glimmer durch das Aufbringen von dendronisierten Polymeren verschiedener Generationen auf Nanometer-Skala modifiziert. Dies eröffnet neue Möglichkeiten, die lokalen elektronischen Eigenschaften von Graphen durch Dehnung zu kontrollieren.Schließlich wurden Kohlenstoff-basierte leitfähige Tinten hergestellt, daraus transparente Elektroden hergestellt, und die Formulierungen der Tinten für das Drucken auf Plastiksubstrate optimiert.
This work focusses on the electronic properties of graphene on the one hand, and on the application of graphenes and other carbon-based hybrid materials for transparent electrodes on the other hand. Accordingly, the first part of the work, which is the larger one, is of fundamental nature and focusses on the electronic interaction between graphene and mica as a substrate. The second, smaller part deals with the design of novel conductive inks based on graphene and other carbon-based hybrid materials for applications in printed electronics, in particular for the production of transparent electrodes. Graphene on mica is a very well defined system, which provides atomically flat graphene extending over several square micrometers. Layer-dependent surface potential variations of single and few layered graphenes on mica were probed with Kelvin Probe Force Microscopy. This allowed to estimate the screening length of graphene on mica. Local variations of the surface electrostatic potential above single layer graphene, originating from confined fluid interfacial monolayers of water between the mica and the graphene, were monitored with Scanning Force Microscopy, Electrostatic Scanning Force Microscopy and Raman spectroscopy. This allowed to quantify the doping of graphene by the confined water layers. Exfoliation of graphene onto adsorbed nanostructures on mica allowed to control the strain of graphene at the nano-scale. Nanostructuring was achieved by first coating mica with submonolayers of dendronized polymers of different generations and subsequently depositing graphene. This approach provides new opportunities for the control of the electronic properties of graphene by strain.Finally, novel conducting carbon-based inks were designed and transparent electrodes were fabricated therefrom. The formulations of the inks were optimized for printing on plastic substrates.

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Feng, Yongjia. « First principles studies of transition metal surfaces : the effect of an external field on surface electronic properties and surface energetics / ». View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202003%20FENG.

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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 106-110). Also available in electronic version. Access restricted to campus users.

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Bolton, Timothy S. « Electronic properties of surface nanofeatures on zinc oxide ». Connect to resource, 2010. http://hdl.handle.net/1811/45011.

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Gennard, Steven John. « Electronic structure properties of metal oxide surfaces ». Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400570.

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Evans, Martin Peter. « Surface structural and electronic properties of Sc and Dy ». Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318253.

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Price, Nicola Jane. « Self-assembled monolayers : electronic properties at the interface ». Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260276.

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Regoutz, Anna. « Structural and electronic properties of metal oxides ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6f425890-b211-4b35-b438-b8de18f7ae64.

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Metal oxides are of immense technological importance. Their wide variety of structural and electronic characteristics leads to a flexibility unrivalled by other groups of materials. However, there is still much debate about the fundamental properties of some of the most widely used oxides, including TiO₂ and In₂O₃. This work presents high quality, in-depth characterisation of these two oxides in pure and doped form, including soft and hard X-ray photoelectron spectroscopy and X-ray diffraction. Bulk samples as well as thin film samples were prepared analysed. For the preparation of thin films a high quality sol-gel dip-coating method was developed, which resulted in epitaxial films. In more detail the organisation of the thesis is as follows: Chapter 1 provides an introduction to key ideas related to metal oxides and presents the metal oxides investigated in this thesis, In₂O₃, Ga₂O₃, Tl₂O₃, TiO₂, and SnO₂. Chapter 2 presents background information and Chapter 3 gives the practical details of the experimental techniques employed. Chapters 4 presents reciprocal space maps of MBE-grown In₂O₃ thin films and nanorods on YSZ substrates. Chapters 5 and 6 investigate the doping of In₂O₃ bulk samples with gallium and thallium and introduce a range of solid state characterisation techniques. Chapter 7 describes the development of a dip-coating sol-gel method for the growth of thin films of TiO₂ and shows 3D reciprocal space maps of the resulting films. Chapter 8 concerns hard x-ray photoelectron spectroscopy of undoped and Sn-doped TiO₂. Chapter 9 interconnects previous chapters by presenting 2D reciprocal space maps of nano structured epitaxial samples of In₂O₃ grown by the newly developed sol-gel based method. Chapter 10 concludes this thesis with a summary of the results.

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Livres sur le sujet "Surface electronic propertie"

Electronic Properties of Surfaces. London : Taylor and Francis, 2017.

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1945-, Gonis Antonios, Stocks G. M. 1943-, North Atlantic Treaty Organization. Scientific Affairs Division. et NATO Advanced Study Institute on Surfaces and Interfaces (1991 : Porto Karras, Chalkidikē, Greece), dir. Equilibrium structure and properties of surfaces and interfaces. New York : Plenum, 1992.

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Bloor, D. Polydiacetylenes : Synthesis, Structure and Electronic Properties. Dordrecht : Springer Netherlands, 1985.

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T, Grahn H., dir. Semiconductor superlattices : Growth and electronic properties. Singapore : World Scientific, 1995.

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Salaneck, W. R. Conjugated polymer surfaces and interfaces : Electronic and chemical structure of interfaces for polymer light emitting devices. Cambridge : Cambridge University Press, 1996.

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Hummel, Rolf E. Electronic Properties of Materials : An Introduction for Engineers. Berlin, Heidelberg : Springer Berlin Heidelberg, 1985.

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Lay, Guy. Semiconductor Interfaces : Formation and Properties. Berlin, Heidelberg : Springer Berlin Heidelberg, 1987.

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Cremer, Till. Ionic Liquid Bulk and Interface Properties : Electronic Interaction, Molecular Orientation and Growth Characteristics. Heidelberg : Springer International Publishing, 2013.

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Schlenker, Claire. Low-Dimensional Electronic Properties of Molybdenum Bronzes and Oxides. Dordrecht : Springer Netherlands, 1990.

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Bushby, Richard J. Liquid Crystalline Semiconductors : Materials, properties and applications. Dordrecht : Springer Netherlands, 2013.

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Chapitres de livres sur le sujet "Surface electronic propertie"

Shikler, R. « Electronic Surface Properties of Semiconductor Surfaces and Interfaces ». Dans Kelvin Probe Force Microscopy, 101–15. Berlin, Heidelberg : Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-22566-6_6.

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Møller, P. J., et F. Grønlund. « Electron Beams in Surface Analysis ». Dans Understanding Molecular Properties, 251–58. Dordrecht : Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3781-9_15.

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Bar, G., S. N. Magonov, H. J. Cantow, T. Greczmiel et G. Kossmehl. « Characterization of the Polythiophene Surface by Scanning Tunneling Microscopy ». Dans Electronic Properties of Polymers, 379–83. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-84705-9_70.

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Berger, C., E. H. Conrad et W. A. de Heer. « Electronic transport properties of epigraphene ». Dans Physics of Solid Surfaces, 716–22. Berlin, Heidelberg : Springer Berlin Heidelberg, 2018. http://dx.doi.org/10.1007/978-3-662-53908-8_168.

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Pate, B. B. « Surfaces and Interfaces of Diamond ». Dans Diamond : Electronic Properties and Applications, 31–60. Boston, MA : Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-2257-7_2.

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Salama, I. A., N. R. Quick et A. Kar. « Laser Surface Modification of Electronic Properties in Wide Band Gap Materials ». Dans Surface Engineering, 111–24. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118788325.ch12.

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Samarin, Sergey, Oleg Artamonov et Jim Williams. « New Experimental Technique for Studying Electron-Electron Interaction, Electron Correlation, Mechanism of Electron Emission and Electronic Properties of Surfaces ». Dans Spin-Polarized Two-Electron Spectroscopy of Surfaces, 5–86. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-00657-0_2.

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Riley, J. D., R. Leckey, Y. Cai, X. Zhang et J. Con Foo. « Electronic Properties of Semiconductor Surfaces and Fermi Surface Studies Using Photoelectron Spectroscopy ». Dans Surface Science, 76–88. Berlin, Heidelberg : Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-80281-2_7.

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Pfnür, H. « Metallic Nanowires on the Atomic Scale : Correlation Between Structure, Electronic Properties, and Electronic Transport ». Dans Nanophenomena at Surfaces, 205–18. Berlin, Heidelberg : Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-16510-8_9.

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Turek, Ilja, Václav Drchal, Josef Kudrnovský, Mojmír Šob et Peter Weinberger. « Magnetic Properties ». Dans Electronic Structure of Disordered Alloys, Surfaces and Interfaces, 225–57. Boston, MA : Springer US, 1997. http://dx.doi.org/10.1007/978-1-4615-6255-9_8.

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Actes de conférences sur le sujet "Surface electronic propertie"

Fei, Haosheng, Xicheng Ai, Li Han, Ruijuan Nie et Zhenhua Hu. « Surface Effect On The Nonlinear Optical Properties Of Transition Metal-Oxode Microcrystallites ». Dans Nonlinear Optics. Washington, D.C. : Optica Publishing Group, 1992. http://dx.doi.org/10.1364/nlo.1992.we15.

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The size dependent modifications of the optical and electronic properties of microcrystallites have attracted considerable attention recently[1-4]. As the diameter of the microcrystallite approaches its corresponding exciton Bohr diameter, its electronic and optical properties start to change because of the quantum confinement effect, dielectric effect and the effect of the surface[5]. For microcrystallites in such a small size regime, a large percentage of the atomes is on or near the surfaces. The existence of this vast interface between the microcrystallite and the surrounding medium can have a profound effect on the nonlinear optical properties of the microcrystallites. For the first time, we studied the nonlinear optical properties of translation metal-oxide microcrystallites by coating the surface with a layer of organic polar molecule(DBS etc.), and found that the change of the surface environment could alter the optical properties greatly. For Fe2O3 as example, (1) the absorption incresed toward the high energy side, (2) the laser induced luminescence intensity decreased by 2 orders in magnitude, and on the contrary, the Raman signal of the surface was enhanced greatly, (3) the saturable absorption phenomenon disappeared, (4) larger third order susceptibility and faster excited state relaxation were obtained compared with uncoated Fe2O3 microcrystallite. These phenomena are the results of the change of the electronic structure caused by the quantum confinement effect and the effect of the surface, unlike semiconductor microcrystallites in which the delocalized Wannier excitons can be influenced greatly by the quantum confinement effect (such as PbS microcrystallite). Transition metal oxide microcrystallite has more complicated electronic structure in which localized d electrons influence its electronic and optical properties greatly[6], and the small diameter Frenkel exciton in such material was effected little by the quantum confinement effect, therefore, the exciton structure could not be abserved in the absorption spectrum. But the size of the transition metal oxide microcrystallites influence their electronic structure strongly. For Fe2O3 as example, the energy structure can be quantitatively shown as the Figure (at the end of the paper), in which a is d-d transition, b represents charge transfer, c is orbital promotion and d is interband transitions. As the size of the microcrystallite decreases, the 3d and 4sp state couples increasingly, and the 3d-4sp (orbital promotion) state contribution increases correspondingly. To some extend, the d electrons and the Frenkel exciton will be delocalized, and the excited electron-hole pair can be ionized and scattered to the surface rapidly. In particular, when the surface was coated with a layer of organic polar molecule, the 3d-4sp state interaction was enhanced greatly under the strong polar interaction of the surface, and some 3d-4sp hydride state will exist, thus the d electrons and the Frenkel exciton will became more delocalization, and the laser induced electron-hole pairs interect and scatter to the surface very fast, so the surface delocalization state generate, accumulate and relax very rapidly and the electron-electron coherence effect[7] is enhanced greatly. Such changes not only increased the nonlinear response, but also resulted in shorter lifetime and stronger nonraditive process.

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Mandich, M. L., et W. D. Reents. « Electronic and Chemical Properties of Small Silicon Clusters ». Dans Microphysics of Surfaces, Beams, and Adsorbates. Washington, D.C. : Optica Publishing Group, 1989. http://dx.doi.org/10.1364/msba.1989.wd1.

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Plasma assisted chemical vapor deposition of silicon films from silanes is widely used in the fabrication of silicon devices. A fundamental understanding of the mechanisms responsible for film growth would have considerable utility in the optimization of processing parameters. Reactive silicon surfaces sites and gas phase ion chemistry are believed to have important roles in the film growth process. Yet, the natures of such surface species and chemistry are highly uncertain. The trend towards increasing subminiaturization of silicon devices also demands a solution to the deleterious formation of silicon dust during film deposition.

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Yablonovitch, Eli, et T. Gmitter. « Chemical Synthesis of Ideal Electronic Surfaces on Silicon and Other Semiconductors ». Dans Microphysics of Surfaces, Beams, and Adsorbates. Washington, D.C. : Optica Publishing Group, 1987. http://dx.doi.org/10.1364/msba.1987.ma2.

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In the past decade semiconductor surface science has successfully studied the electronic structure and reconstructions of totally bare semiconductor surfaces. Recently experimentalists have begun to assume a more active role1,2 in modifying surface chemical structures to passivate the surface, i.e., to render the surface states electronically inactive. We can expect that this work will evolve more and more toward the artificial synthesis of surface chemical-bonding structres with desired physical properties. From the point of view of electronics, it is desirable to covalently satisfy all surface bonds, thereby shifting the surface states out of the band gap and into the valence and conduction bands.

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Stéphan, O. « Surface Plasmon Coupling in Nanotubes ». Dans STRUCTURAL AND ELECTRONIC PROPERTIES OF MOLECULAR NANOSTRUCTURES : XVI International Winterschool on Electronic Properties of Novel Materials. AIP, 2002. http://dx.doi.org/10.1063/1.1514134.

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Marrian, Christie R. K. « Electron Beam Nanolithography ». Dans Microphysics of Surfaces : Nanoscale Processing. Washington, D.C. : Optica Publishing Group, 1995. http://dx.doi.org/10.1364/msnp.1995.mthb1.

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Motivated by trends in the microelectronics industry and the quest to investigate electronic and material properties in the quantum effect size regime, there is a strong drive to understand and overcome the limits of the processing required for microfabrication. At the beginning of the next century, the precision required in feature sizes for microelectronics manufacturing is projected to be close to 10 nm, i.e. about 25 atomic diameters. Still smaller feature sizes are needed for nanoelectronic device research. For example, to observe effects such as lateral resonant tunneling and coulomb blockade at close to room temperature, feature sizes below 10 nm are necessary. Central to any fabrication scheme for these dimensions is a lithographic step where a pattern is defined in a radiation sensitive material, commonly called the resist, and then replicated into the substrate to define a structure or device. Due to the availability of equipment and knowledge base, the preferred means for defining the smallest possible structures involves the use of a focused high energy beam of electrons.

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Ogawa, S., et H. Petek. « Hot-electron dynamics at Cu surfaces ». Dans International Conference on Ultrafast Phenomena. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.fe.47.

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Dynamics of electrons in solids is important to many phenomena such as optical, electrical, magnetical, and chemical properties of matter. Direct measurements of electron-electron (e-e) scattering rates provide critical tests for many body theories. Recent developments in ultrafast laser technology make it possible to probe directly femtosecond phenomena such as e-e scattering in metals. As a consequence of a large cross section for electron scattering hot-electon lifetimes in metals are in femtosecond regime, and until recently the scattering rate could only be evaluated by indirect measurements of heat and electrical transport properties. Two-photon time-resolved photoemission (TPTRP) measures the direct change of hot-electron population as a function of time. So far, this technique has been applied to direct measurement of electron relaxation by electron-phonon scattering in polycrystalline Au[1], hot electron thermalization by e-e scattering in Cu(100)[2], and image potential state decay on Ag(100) and Ag(111) surfaces[3]. With higher time resolution(<10fs) we have been able to resolve coherent component in hot-electron decay due to optical dephasing from the slower population decay rates of hot-electrons at Cu(100) and Cu(110) surfaces[4]. Here we report the results on Cu(100), Cu(110) and Cu(111) surfaces and compare them with Fermi liquid theory.

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Gonçalves, Paulo André, et F. Javier García de Abajo. « Quantum surface-response in nanoplasmonics probed by electron spectroscopies ». Dans Photonic and Phononic Properties of Engineered Nanostructures XII, sous la direction de Ali Adibi, Shawn-Yu Lin et Axel Scherer. SPIE, 2022. http://dx.doi.org/10.1117/12.2609060.

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Seneta, M. Ya, R. M. Peleshchak et S. K. Guba. « Influence of the surface acoustic wave on the electron states of adsorbed semiconductor surface ». Dans 2017 IEEE 7th International Conference "Nanomaterials : Application & Properties" (NAP). IEEE, 2017. http://dx.doi.org/10.1109/nap.2017.8190159.

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Siegle, V. « Coupling of Surface Acoustic Waves to Single Walled Carbon Nanotubes ». Dans ELECTRONIC PROPERTIES OF NOVEL NANOSTRUCTURES : XIX International Winterschool/Euroconference on Electronic Properties of Novel Materials. AIP, 2005. http://dx.doi.org/10.1063/1.2103930.

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Kutner, Wlodzimierz. « Preparation, surface characteristics and electrochemical properties of electrophoretically deposited C60 films ». Dans ELECTRONIC PROPERTIES OF NOVEL NANOSTRUCTURES : XIX International Winterschool/Euroconference on Electronic Properties of Novel Materials. AIP, 2005. http://dx.doi.org/10.1063/1.2103810.

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Rapports d'organisations sur le sujet "Surface electronic propertie"

Hope-Weeks, L., G. Foxx et B. Taylor. Towards Applications of Quantum Dots : Surface Modification and Novel Electronic Properties. Office of Scientific and Technical Information (OSTI), avril 2003. http://dx.doi.org/10.2172/15006452.

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Walters, G. K., et F. B. Dunning. Application of spin-sensitive electron spectroscopies to investigations of electronic and magnetic properties of solid surfaces and epitaxial systems. Office of Scientific and Technical Information (OSTI), juin 1992. http://dx.doi.org/10.2172/7113541.

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Barrow, Jason A. Investigations of the Electronic Properties and Surface Structures of Aluminium-Rich Quasicrystalline Alloys. Office of Scientific and Technical Information (OSTI), janvier 2003. http://dx.doi.org/10.2172/816443.

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Walters, G. K., et F. B. Dunning. Application of spin-sensitive electron spectroscopies to investigations of electronic and magnetic properties of solid surfaces and epitaxial systems. Progress report, 1 November 1993--31 October 1994. Office of Scientific and Technical Information (OSTI), mai 1994. http://dx.doi.org/10.2172/10156526.

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Walters, G. K., et F. B. Dunning. Application of spin-sensitive electron spectroscopies to investigations of electronic and magnetic properties of solid surfaces and epitaxial systems. Progress report, 1 November 1992--31 October 1993. Office of Scientific and Technical Information (OSTI), avril 1993. http://dx.doi.org/10.2172/10156589.

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Walters, G. K., et F. B. Dunning. Application of spin-sensitive electron spectroscopies to investigations of electronic and magnetic properties of solid surfaces and epitaxial systems. Progress report, 1 November 1991--31 October 1992. Office of Scientific and Technical Information (OSTI), juin 1992. http://dx.doi.org/10.2172/10166548.

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Bowen, Kit H. Measuring Complementary Electronic Structure Properties of both Deposited and Gas Phase Clusters using STM, UPS, and PES : Size-Selected Clusters on Surfaces. Office of Scientific and Technical Information (OSTI), mars 2014. http://dx.doi.org/10.2172/1122129.

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Engel, Bernard, Yael Edan, James Simon, Hanoch Pasternak et Shimon Edelman. Neural Networks for Quality Sorting of Agricultural Produce. United States Department of Agriculture, juillet 1996. http://dx.doi.org/10.32747/1996.7613033.bard.

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The objectives of this project were to develop procedures and models, based on neural networks, for quality sorting of agricultural produce. Two research teams, one in Purdue University and the other in Israel, coordinated their research efforts on different aspects of each objective utilizing both melons and tomatoes as case studies. At Purdue: An expert system was developed to measure variances in human grading. Data were acquired from eight sensors: vision, two firmness sensors (destructive and nondestructive), chlorophyll from fluorescence, color sensor, electronic sniffer for odor detection, refractometer and a scale (mass). Data were analyzed and provided input for five classification models. Chlorophyll from fluorescence was found to give the best estimation for ripeness stage while the combination of machine vision and firmness from impact performed best for quality sorting. A new algorithm was developed to estimate and minimize training size for supervised classification. A new criteria was established to choose a training set such that a recurrent auto-associative memory neural network is stabilized. Moreover, this method provides for rapid and accurate updating of the classifier over growing seasons, production environments and cultivars. Different classification approaches (parametric and non-parametric) for grading were examined. Statistical methods were found to be as accurate as neural networks in grading. Classification models by voting did not enhance the classification significantly. A hybrid model that incorporated heuristic rules and either a numerical classifier or neural network was found to be superior in classification accuracy with half the required processing of solely the numerical classifier or neural network. In Israel: A multi-sensing approach utilizing non-destructive sensors was developed. Shape, color, stem identification, surface defects and bruises were measured using a color image processing system. Flavor parameters (sugar, acidity, volatiles) and ripeness were measured using a near-infrared system and an electronic sniffer. Mechanical properties were measured using three sensors: drop impact, resonance frequency and cyclic deformation. Classification algorithms for quality sorting of fruit based on multi-sensory data were developed and implemented. The algorithms included a dynamic artificial neural network, a back propagation neural network and multiple linear regression. Results indicated that classification based on multiple sensors may be applied in real-time sorting and can improve overall classification. Advanced image processing algorithms were developed for shape determination, bruise and stem identification and general color and color homogeneity. An unsupervised method was developed to extract necessary vision features. The primary advantage of the algorithms developed is their ability to learn to determine the visual quality of almost any fruit or vegetable with no need for specific modification and no a-priori knowledge. Moreover, since there is no assumption as to the type of blemish to be characterized, the algorithm is capable of distinguishing between stems and bruises. This enables sorting of fruit without knowing the fruits' orientation. A new algorithm for on-line clustering of data was developed. The algorithm's adaptability is designed to overcome some of the difficulties encountered when incrementally clustering sparse data and preserves information even with memory constraints. Large quantities of data (many images) of high dimensionality (due to multiple sensors) and new information arriving incrementally (a function of the temporal dynamics of any natural process) can now be processed. Furhermore, since the learning is done on-line, it can be implemented in real-time. The methodology developed was tested to determine external quality of tomatoes based on visual information. An improved model for color sorting which is stable and does not require recalibration for each season was developed for color determination. Excellent classification results were obtained for both color and firmness classification. Results indicted that maturity classification can be obtained using a drop-impact and a vision sensor in order to predict the storability and marketing of harvested fruits. In conclusion: We have been able to define quantitatively the critical parameters in the quality sorting and grading of both fresh market cantaloupes and tomatoes. We have been able to accomplish this using nondestructive measurements and in a manner consistent with expert human grading and in accordance with market acceptance. This research constructed and used large databases of both commodities, for comparative evaluation and optimization of expert system, statistical and/or neural network models. The models developed in this research were successfully tested, and should be applicable to a wide range of other fruits and vegetables. These findings are valuable for the development of on-line grading and sorting of agricultural produce through the incorporation of multiple measurement inputs that rapidly define quality in an automated manner, and in a manner consistent with the human graders and inspectors.

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Shomer, Ilan, Louise Wicker, Uzi Merin et William L. Kerr. Interactions of Cloud Proteins, Pectins and Pectinesterases in Flocculation of Citrus Cloud. United States Department of Agriculture, février 2002. http://dx.doi.org/10.32747/2002.7580669.bard.

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The overall objective was to understand the cloud flocculation of citrus juice by characterization of the interactions between proteins and pectins, and to determine the role of PE isozymes in catalyzing this phenomenon. Specific objectives were to: 1. identify/characterize cloud-proteins in relation to their coagulable properties and affinity to pectins; 2. to determine structural changes of PME and other proteins induced by cation/pectin interactions; 3. localize cloud proteins, PME and bound protein/pectates in unheated and pasteurized juices; 4. to create "sensitized" pectins and determine their effect on clarification. The original objectives were not changed but the methods and approach were modified due to specific research requirements. Two i postulates were: 1. there is a specific interaction of cloud proteins with de-esterified regions of ! pectin and this contributes to cloud loss; 2. isozymes of pectin-methyl-esterase (PME) vary in efficiency to create sensitized pectins. The appearance of citrus fruit juice is an important quality factor and is determined by the color and turbidity that .are conferred by the suspended particles, i.e., by the cloud and its homogeneity. Under some circumstances the cloud tend to flocculate and the juice clarifies. The accepted approach to explain the clarification is based on pectin demethoxylation by PME that promotes formation of Ca-pectate. Therefore, the juice includes immediate heat-inactivation upon ~ squeezing. Protein coagulation also promotes cloud instability of citrus fruit extracts. However, the clarification mechanism is not fully understood. Information accumulated from several laboratories indicates that clarification is a more complex process than can be explained by a single mechanism. The increasing trend to consume natural-fresh juice emphasizing the importance of the knowledge to assure homogeneity of fresh juice. The research included complementary directions: Conditions that induce cloud-instability of natural- juice [IL]. Evaluate purification schemes of protein [USA]. Identifications of proteins, pectin and neutral sugars ([IL]; Structure of the cloud components using light and electron microscopy and immuno-labeling of PME, high-methoxyl-pectin (HMP) and low-methoxyl-pectin (LMP); Molecular weight of calcium sensitized pectins [US]; Evaluation of the products of PME activity [US]. Fractions and size distribution and cloud components [IL-US]. The optimal pH activity of PME is 7 and the flocculation pH of the cloud is 3-4. Thus, the c roles of PME, proteins and pectins in the cloud instability, were studied in pH ranges of 2- 7. The experiments led to establish firstly repeatable simulate conditions for cloud instability [IL]. Thermostable PME (TS-PE) known to induce cloud instability, but also thermolabile forms of PME (TL-PE) caused clarification, most likely due to the formation and dissolution of inactive :. PE-pectin complexes and displacement of a protective colloid from the cloud surface [US]. Furthermore, elimination of non-PME protein increases TS-PE activity, indicating that non-PME proteins moderate PME activity [US]. Other experiments Concomitantly with the study of the PME activity but promotes the association of cloud-proteins to pectin. Adjusting of the juice pH to f 7 retains the cloud stability and re-adjusting of the pH to 40% DE reacts to immuno-labeling in the cloud fragments, whereas

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