1,720,985 research outputs found
Anchoring and reactivity of calixarenes and rotaxanes on semiconductor and metal surfaces, studied by XPS, AFM and electrochemistry
Full text linkRedox-active monolayers on silicon as prototypical hybrid materials for molecular memories
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Role of the extent of π-electron conjugation in visible-light assisted molecular self-assembling on Si(111) surfaces
No full textStructural electronic study via XPS and TEM of sub-nanometric gold particles protected by calixarenes
No full textIn the last years, substituted ferrocenes have been investigated as active redox molecules,
able to tune the response of a functionalized electrode (especially gold and silicon) on which they are adsorbed, due to their attractive electrochemical characteristics: fast electron-transfer rate, low oxidation potential, and two stable redox states [1]. Ferrocene derivatives present also the advantage of a facile tunability of their redox potential via substitution of one or more H atoms of the cyclopentadyenil (Cp) ring with distinct functional groups.
We present the results of an experimental and theoretical investigation on pure ethyl-, vinyl and ethynylferrocene in the gas phase by means of NEXAFS at the C K-edge, and XPS of the C 1s region, and by DFT calculations. Such a combination probes both the state of charge of the C atoms of the substituent group of the three molecules, and the extent of conjugation of the C-C arm with the Cp ring. A reliable assignment of the characteristic NEXAFS features associated to double and triple C-C bond of the lateral substituents of such closely related molecules may offer the fingerprint of the preservation or loss of the unsaturation in the anchoring arm upon its reaction with a surface, as well as shed light on the reaction mechanism for the surface anchoring on Si with different recipes, which is an actively investigated, yet still open, issue
Probing the role of related ring substituents over the electronic structure of ferrocene via synchrotron radiation photoabsorption and photoemission
No full textA mechanistic explanation of the peculiar amphiphobic properties of hybrid organic-inorganic coatings by combining XPS characterization and DFT modeling
No full textWe report a combined X-ray photoelectron spectros- copy and theoretical modeling analysis of hybrid functional coatings constituted by fluorinated alkylsilane monolayers covalently grafted on a nanostructured ceramic oxide (Al2O3) thin film deposited on aluminum alloy substrates. Such engineered surfaces, bearing hybrid coatings obtained via a classic sol−gel route, have been previously shown to possess amphiphobic behavior (superhydrophobicity plus oleophobicity) and excellent durability, even under simulated severe working environments. Starting from XPS, SEM, and contact angle results and analysis, and combining it with DFT results, the present investigation offers a first mechanistic explanation at a molecular level of the peculiar properties of the hybrid organic−inorganic coating in terms of composition and surface structural arrangements. Theoretical modeling shows that the active fluorinated moiety is strongly anchored on the alumina sites with single Si-O-Al bridges and that the residual valence of Si is saturated by Si− O−Si bonds which form a reticulation with two vicinal fluoroalkylsilanes. The resulting hybrid coating consists of stable rows of fluorinated alkyl chains in reciprocal contact, which form well-ordered and packed monolayers
Calix[4]arene receptors and rotaxanes on Si(100) and Cu surfaces: synthesis and characterization
No full textPhotoemission study of ferrocenes: insights into the electronic structure of Si-based hybrid materials
Full text linkWe present here the results of synchrotron radiation-excited UV-photoemission investigation and DFT calculations on vinylferrocene (VFC), a redox molecule suitable for applications in molecular electronics. A detailed assignment is discussed of the valence photoelectron spectra (UPS), which provides new data on the electronic structure and offers a partial re-interpretation of previous assignments on VFC based on theoretical and experimental evidences. Furthermore, the present results can allow for a meaningful comparison of photoemission results from the corresponding hybrid obtained by covalently attaching VFC to Si oriented surfaces. © 2008 IOP Publishing Ltd
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