1,721,038 research outputs found
Reazioni di Diels-Alder ad alta pressione di dieni a struttura paraciclofanica. Applicazione alla sintesi di elicenofani
No full textSmall Molecular Aryl Acetylenes: Chemically Tailoring High-Efficiency Organic Semiconductors for Solar Cells and Field-Effect Transistors
No full textOver the last two decades, ever increasing interest has been focused on -conjugated triple-bond-containing systems, namely, (poly)aryl acetylenes, as a very promising class of semiconducting materials, owing to the availability of flexible/efficient synthetic protocols and the new conception of their conformational and steric advantages. In this review, the major design/synthetic strategies used to obtain molecular aryl acetylene semiconductors are discussed. A brief discussion of their key properties as well as their performance in organic field-effect transistors and photovoltaic cell applications is also included
Production of an innovative film-filter for sun simulators: theoretical analysis.
No full textSun simulators are employed to test the performance of photovoltaic devices according to the standard IEC 61215. Photovoltaic manufacturers need to insert a sun simulator at the end of the PV production chain in order to measure the I-V curve and to evaluate the peak power of PV devices. The sun simulator needs specific lamps to simulate solar spectrum and a specific filter to simulate atmosphere absorbance. Such filter can cost over 6 € per square centimeter. The aim of this work is to develop an alternative filter. In particular, both chemical analysis and spectrophotometric measurements are carried out to evaluate if the Air Mss 1.5 G filter can be replaced by a cheaper material. Preliminary simulations show how specific compounds coated on glass surface can absorb sun spectrum such as the A.M 1,5 filter but with lower costs
AFM as powerful imaging tool for the characterization of polymer supported TBD catalysts
No full textIn the last years the growing interest on the polymer-supported catalysts mainly resides in their use in various synthetic processes to improve work-up procedures as well as to allow the simple and efficient recovery and recycling of the catalytic systems used (1,2). Recent studies have been focused on the polystyrene-immobilized version of the highly representative basic catalyst 1,5,7,-triazabicyclo[4,4,0]dec-5-ene (TBD) to approach its efficient and easy recovery (3), and opening therefore the route towards the greening of industrial synthetic procedures by substituting the use of costly metal catalysts and reducing the waste/cost of chemical production.
In order to design the proper combination of polymeric support and catalyst, it is crucial to investigate the morphology of the polymer network, the polymer porous structure and surface area. Among the different analytical methods commonly used to determine the porosity and the pore distribution in a polymeric support (4-6), the most widely applied are nitrogen/helium absorption (BET analyses) and mercury intrusion porosimetry (MIP). The drawback of these two methods, however, is that it is not possible to determine the total porosity of a sample. Indeed, BET defines only the micropores, while MIP only reveals the mesopores. Further, modifications of the sample may occur during the analyses (5). Currently an increasing interest is directed towards the application of atomic force microscopy (AFM) to determine the pore morphology on polymeric scaffolds, fibers and films (7,8). However, no reports have focused on polymer-immobilized TBD catalysts.
Recently we have undertaken a broad research project with the aim of defining the optimal application method of AFM analysis to determine the morphology of newly synthesized polymer-immobilized TBDs, in which the supports incorporate various percentages and types of cross-linkers (9). This may also allow to optimize the experimental design for the preparation of highly efficient polymer-supported TBD catalysts.
Here we report on first results for a comparative characterization of macroporous divinylbenzene cross-linked polystyrenes (PS) used as supports to immobilize TBD, with an emphasis on investigations through AFM
Salt-Weathered Heritage Sites: A Study On The Effectiveness Of Eco-Friendly Crystallization Inhibitors In The Presence Of Protective Treatments
No full textSynthesis of optically active polycyclic compounds by Diels-Alder reactions of (+)-nopadiene
No full textSynthesis of enantiopure angularly condensed [2.2]paracyclophanes containing five-membered rings
No full textOptically active angularly condensed [2.2]paracyclophanes containing five-membered rings have been synthesized by a two-step approach based on the Diels-Alder cycloaddition of (S)-(+)-4-vinyl[2.2]paracyclophane. Structural analysis by NMR spectroscopy is presented. These helicenophanes containing a cyclopentane ring show extraordinarily high specific rotations. This phenomenon has been discussed in terms of structural modifications caused by the replacement of the benzene unit with a cyclopentane ring. © 2003 Elsevier Science Ltd. All rights reserved
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