7 results
Search Results
Now showing 1 - 7 of 7
- ItemNaphtalenediimide-based donor-acceptor copolymer prepared by chain-growth catalyst-transfer polycondensation: Evaluation of electron-transporting properties and application in printed polymer transistors(London [u.a.] : Royal Society of Chemistry, 2014) Schmidt, G.C.; Höft, D.; Haase, K.; Hübler, A.C.; Karpov, E.; Tkachov, R.; Stamm, M.; Kiriy, A.; Haidu, F.; Zahn, D.R.T.; Yan, H.; Facchetti, A.The semiconducting properties of a bithiophene-naphthalene diimide copolymer (PNDIT2) prepared by Ni-catalyzed chain-growth polycondensation (P1) and commercially available N2200 synthesized by Pd-catalyzed step-growth polycondensation were compared. Both polymers show similar electron mobility of ∼0.2 cm2 V-1 s-1, as measured in top-gate OFETs with Au source/drain electrodes. It is noteworthy that the new synthesis has several technological advantages compared to traditional Stille polycondensation, as it proceeds rapidly at room temperature and does not involve toxic tin-based monomers. Furthermore, a step forward to fully printed polymeric devices was achieved. To this end, transistors with PEDOT:PSS source/drain electrodes were fabricated on plastic foils by means of mass printing technologies in a roll-to-roll printing press. Surface treatment of the printed electrodes with PEIE, which reduces the work function of PEDOT:PSS, was essential to lower the threshold voltage and achieve high electron mobility. Fully polymeric P1 and N2200-based OFETs achieved average linear and saturation FET mobilities of >0.08 cm2 V-1 s-1. Hence, the performance of n-type, plastic OFET devices prepared in ambient laboratory conditions approaches those achieved by more sophisticated and expensive technologies, utilizing gold electrodes and time/energy consuming thermal annealing and lithographic steps.
- ItemNickel-Catalyzed Carbonylative Synthesis of Functionalized Alkyl Iodides(Amsterdam : Elsevier B.V., 2018) Peng, J.-B.; Wu, F.-P.; Xu, C.; Qi, X.; Ying, J.; Wu, X.-F.Chemistry; Catalysis; Organic Synthesis © 2018 The Author(s)Functionalized alkyl iodides are important compounds in organic chemistry and biology. In this communication, we developed an interesting nickel-catalyzed carbonylative synthesis of functionalized alkyl iodides from aryl iodides and ethers. With Mo(CO)6 as the solid CO source, both cyclic and acyclic ethers were activated, which is also a challenging topic in organic synthesis. Functionalized alkyl iodides were prepared in moderate to excellent yields with outstanding functional group tolerance. Besides the high value of the obtained products, all the atoms from the starting materials were incorporated in the final products and the reaction had high atom efficiency as well.
- ItemPolymeric monolithic materials: Syntheses, properties, functionalization and applications(Amsterdam : Elsevier, 2007) Buchmeiser, M.R.The synthetic particularities for the synthesis of polymer-based monolithic materials are summarized. In this context, monoliths prepared via thermal-, UV- or electron-beam triggered free radical polymerization, controlled TEMPO-mediated radical polymerization, polyaddition, polycondensation as well as living ring-opening metathesis polymerization (ROMP) will be covered. Particular attention is devoted to the aspects of controlling pore sizes, pore volumes and pore size distributions as well as functionalization of these supports. Finally, selected, recent applications in separation science, (bio-) catalysis and chip technology will be summarized. © 2007 Elsevier Ltd. All rights reserved.
- ItemPoisoning of bubble propelled catalytic micromotors: The chemical environment matters(Cambridge [u.a.] : Royal Society of Chemistry, 2013) Zhao, G.; Sanchez, S.; Schmidt, O.G.; Pumera, M.Self-propelled catalytic microjets have attracted considerable attention in recent years and these devices have exhibited the ability to move in complex media. The mechanism of propulsion is via the Pt catalysed decomposition of H2O2 and it is understood that the Pt surface is highly susceptible to poisoning by sulphur-containing molecules. Here, we show that important extracellular thiols as well as basic organic molecules can significantly hamper the motion of catalytic microjet engines. This is due to two different mechanisms: (i) molecules such as dimethyl sulfoxide can quench the hydroxyl radicals produced at Pt surfaces and reduce the amount of oxygen gas generated and (ii) molecules containing -SH, -SSR, and -SCH3 moieties can poison the catalytically active platinum surface, inhibiting the motion of the jet engines. It is essential that the presence of such molecules in the environment be taken into consideration for future design and operation of catalytic microjet engines. We show this effect on catalytic micromotors prepared by both rolled-up and electrodeposition approaches, demonstrating that such poisoning is universal for Pt catalyzed micromotors. We believe that our findings will contribute significantly to this field to develop alternative systems or catalysts for self-propulsion when practical applications in the real environment are considered.
- ItemFaceting and metal-exchange catalysis in (010) β-Ga2O3 thin films homoepitaxially grown by plasma-assisted molecular beam epitaxy(New York : American Institute of Physics, 2018) Mazzolini, P.; Vogt, P.; Schewski, R.; Wouters, C.; Albrecht, M.; Bierwagen, OliverWe here present an experimental study on (010)-oriented -Ga2O3 thin films homoepitaxially grown by plasma assisted molecular beam epitaxy. We study the effect of substrate treatments (i.e., O-plasma and Ga-etching) and several deposition parameters (i.e., growth temperature and metal-to-oxygen flux ratio) on the resulting Ga2O3 surface morphology and growth rate. In situ and ex-situ characterizations identified the formation of (110) and (¯110)-facets on the nominally oriented (010) surface induced by the Ga-etching of the substrate and by several growth conditions, suggesting (110) to be a stable (yet unexplored) substrate orientation. Moreover, we demonstrate how metal-exchange catalysis enabled by an additional In-flux significantly increases the growth rate (>threefold increment) of monoclinic Ga2O3 at high growth temperatures, while maintaining a low surface roughness (rms < 0.5 nm) and preventing the incorporation of In into the deposited layer. This study gives important indications for obtaining device-quality thin films and opens up the possibility to enhance the growth rate in -Ga2O3 homoepitaxy on different surfaces [e.g., (100) and (001)] via molecular beam epitaxy.
- ItemDirect catalytic conversion of cellulose to liquid straight-chain alkanes(Cambridge : Royal Society of Chemistry, 2014) Op de Beeck, Beau; Dusselier, Michiel; Geboers, Jan; Holsbeek, Jensen; Morré, Eline; Oswald, Steffen; Giebeler, Lars; Sels, Bert F.High yields of liquid straight-chain alkanes were obtained directly from cellulosic feedstock in a one-pot biphasic catalytic system. The catalytic reaction proceeds at elevated temperatures under hydrogen pressure in the presence of tungstosilicic acid, dissolved in the aqueous phase, and modified Ru/C, suspended in the organic phase. Tungstosilicic acid is primarily responsible for cellulose hydrolysis and dehydration steps, while the modified Ru/C selectively hydrogenates intermediates en route to the liquid alkanes. Under optimal conditions, microcrystalline cellulose is converted to 82% n-decane-soluble products, mainly n-hexane, within a few hours, with a minimum formation of gaseous and char products. The dominant route to the liquid alkanes proceeds via 5-hydroxymethylfurfural (HMF), whereas the more common pathway via sorbitol appears to be less efficient. High liquid alkane yields were possible through (i) selective conversion of cellulose to glucose and further to HMF by gradually heating the reactor, (ii) a proper hydrothermal modification of commercial Ru/C to tune its chemoselectivity to furan hydrogenation rather than glucose hydrogenation, and (iii) the use of a biphasic reaction system with optimal partitioning of the intermediates and catalytic reactions. The catalytic system is capable of converting subsequent batches of fresh cellulose, enabling accumulation of the liquid alkanes in the organic phase during subsequent runs. Its robustness is illustrated in the conversion of the raw (soft)wood sawdust.
- ItemHomopolymerization of ethylene, 1-hexene, styrene and copolymerization of styrene with 1,3-cyclohexadiene using (η5- tetramethylcyclopentadienyl)dimethylsilyl(N-Ar')amido-TiCl2/MAO (Ar'=6-(2-(diethylboryl)phenyl)pyrid-2-yl, biphen-3-yl)(Basel : MDPI AG, 2011) Camadanli, S.; Decker, U.; Kühnel, C.; Reinhardt, I.; Buchmeiser, M.R.The propensity of a half-sandwich (η55- tetramethylcyclopentadienyl) dimethylsilylamido TiIV-based catalyst bearing an auxiliary diethylboryl-protected pyridyl moiety (Ti-8), activated by methylaluminoxane (MAO) to homopolymerize α-olefins such as ethylene, 1-hexene and styrene as well as to copolymerize styrene with 1,3-cyclohexadiene is described. The reactivity of Ti-8 was investigated in comparison to a 6-(2-(diethylboryl)phenyl)pyrid-2-yl-free analogue (Ti-3).