The mechanical and leaching stability of enzymes adsorbed on macroporous carriers is an important issue for the technical applicability of such biocatalysts. Both can considerably benefit from the deposition of silicone coating on the carrier surface. The coating of the immobilized lipase Novozyme 435 (NZ435), as a model enzyme preparation, with different silicone loadings was studied in detail by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as by energy‐dispersive X‐ray spectroscopy (EDX) and BET isotherms, and offers explanations and prerequisites for its stabilizing effects. The deposition of silicone on the poly(methyl methacrylate) (PMMA) carrier was found to form an interpenetrating network composite rather than the anticipated core‐shell structure. The silicone precursors homogeneously wet the carrier surface including all inner pores and gradually fill the complete carrier. In parallel, the surface area of NZ435 decreases from an initial value of 89 m2g−1to 0.2 m2g−1after silicone loading. A visible layer of silicone on the outer surface of the carrier was only observed at a silicone concentration of 54 % w/w and more. Maximum leaching stability corresponds to the formation of this layer. The mechanical stability increases with the amount of deposited silicone. It can be expected that stabilization against leaching and/or mechanical stress by formation of silicone composites can easily be transferred to a whole range of alternative biocatalytic systems. This should considerably advance their general technical applicability and overall implementation of biocatalysts in chemical synthesis.
Transparent coating systems applicable on plastics surfaces by a spray technique are presented. The coatings are based on highly photocatalytically active nanoscaled titania powders, surface modified with silanes containing organic or fluoro-organic side chains. The modification allows for the introduction of the particles in organic inorganic hybrid NANOMER\ coating systems. In the wet film -due to the evaporation of the solvents -a decompatibilisation of the coated particles to the matrix results in a self-organising gradient layer formation with an up-concentration of the active particles at the interface layer between coating and air. After activation by irradiation with artificial or natural UV-light, highly active transparent photocatalytic coatings for a great variety of materials are obtained. D
COMMUNICATIONS dried in vacuo with toluene twice to remove any remaining solvent and water. The dried resin was weighed and used in the screening procedure. The resin-supported ligand (0.02 mmol) was placed in a dried test tube with a rubber septum under an argon atmosphere. Ti(OiPr), (0.1 M in toluene, 200 pL, 0.02 mmol) was added and allowed to stand for 1 h. Subsequently, cyclohexene oxide ( 1 . 0~ in toluene, 200 pL, 0.2 mmol) and TMSCN ( 1 . 0~ In toluene 200 pL, 0.2 mmol) were added, and the reaction was gently agitated for 20 h (4 "C). The reaction was quenched by addition of Et,O ( I .O mL), and the solution forced through a silica gel plug with additional Et,O (1.0 mL). Reaction selectivity was determined by GLC analysis (BE-TADEX 120 chiral column).
Sure diisocyanate (1) exists! Those who believed that of the many conceivable C2N2O2 isomers only cyanogendi‐N‐oxide (1) could be synthesized were mistaken. It is possible to generate diisocyanate by means of matrix‐isolation techniques, to characterize it spectroscopically, and to compile data on its stability. equation image
Structural investigations on six combined liquid-crystalline polymers using the X-ray technique are described. The measurements have allowed a characterization of the liquid-crystalline phases and have led to our first ideas about the phase structures. All mesogenic groups are arranged parallel to each other, the shortest segment in the main-chain or in the side-chain determines the smectic layer spacing. A modified designation for liquid-crystalline phases of high polymers is proposed.
Natürlich gibt es Diisocyanat 1! Wer dachte, von den vielen C2N2O2‐Isomeren gäbe es nur Dicyan‐di‐N‐oxid 2, hat sich geirrt. Mit der Matrixisolationstechnik ist es möglich, Diisocyanat zu erzeugen, spektroskopisch zu identifizieren und Aussagen über seine Stabilität zu machen.
Katalysatoren. Auch wenn strukturell ahnliche Substrate unterschiedliche Reaktivitaten und Selektivitaten aufweisen, kann durch die vorgestellte Screening-Methode jedem Substrat rasch ein geeigneter Ligand zugeordnet werden, ohne dalj notwendigerweise a priori etwas uber den Mechanismus bekannt sein muBte.Unsere Methode weist gegenuber traditionelleren Verfahren zur Entdeckung chiraler Liganden eine Reihe von Vorteilen auf: 1) Die Suche kann auf einem festen Trager durchgefuhrt werden, wodurch der Suchprozelj merklich vereinfacht und die Zahl der verfugbaren Liganden grober wird. 2) Die Methode liefert den am besten geeigneten chiralen Liganden fur ein spezielles Substrat. Nach den oben vorgestellten Ergebnissen konnen sogar strukturell ahnliche meso-Epoxide deutlich unterschiedliche Selektivitatsprofile aufweisen. 3) Wegen der Effizienz der Methode konnen auljerordentlich viele experimentelle Daten in sehr kurzer Zeit gesammelt werden. Es konnen so unerwartete Ergebnisse erhalten werden, ohne Gefahr zu laufen, dalj infolge vorgegebener mechanistischer Vorstellungen wichtige Hinweise ubersehen werden; der AuswahlprozeR beruht statt dessen allein auf qualitativen Befunden uber die Griinde fur Veranderungen der Ligandenstruktur. Die hier beschriebene Methode und Strategie ist somit ein neuer und effizienter Weg fur das Design, die Entdeckung und die Entwicklung neuer asymmetrischer katalytischer Synthesemethoden. ExperimentellesDie Liganden wurden auf WANG-Harz [16] wie bereits beschrieben [l] hergestellt (Advanced ChemTech, Beladung 0.7-0.85 mmolg-I), allerdings wurde der Abspaltungsschritt ausgelassen [I]. Die WANG-Harz/Ligand-Konjugate wurden mit Toluol (10 x 1.0 mL) gewaschen und zweimal jeweils nach Zugabe von Toluol im Vakuum getrocknet, um jegliche Losungsmittel-und Wasserriickstande zu entfernen. Das getrocknete Harz wurde gewogen und im ScreeningprozeD eingesetzt. Der auf den Harztrager aufgebrachte Ligand (0.02 mmol) wurde unter Argon in ein wasserfreies Probenrohrchen gefiillt, das rnit einem Gummiseptum verschlossen wurde. Ti(OiPr), (0.1 M in Toluol, 200 pL, 0.02 mmol) wurde zugegeben und die Losung 1 h stehengelassen. AnschlieDend wurden Cyclohexenoxid (1 . O M in Toluol, 200 pL, 0.02 mmol) und TMSCN (1.0 M in Toluol, 200 pL, 0.02 mmol) zufiigt; die Reaktionsmischung wurde 20h bei 4°C leicht geschiittelt. Die Reaktion wurde durch Zugabe von Et,O (1.0 mL) abgebrochen und die Reaktionsmischung mit weiterem Et,O (1.0 mL) durch eine Kieselgelsaule filtriert. Die Selektivitat der Reaktion wurde gaschromatographisch (BETADEX-120-Saule) bestimmt.
A total of 81 doped and undoped anatase nano-particles were synthesised by a precipitation/co-precipitation process followed by a hydrothermal treatment to obtain increased visible light photocatalytic activity. The screening process was performed utilising a high throughput analysis system based on the photometric monitoring of the photocatalytic degradation of organic dyes (Rhodamine B, Malachite Green, Acid Blue 29). Photocatalytically active coatings were prepared with selected catalysts with high and low rankings from the screening. Degradation experiments with stearic acid could confirm the varying grades of visible light activity as seen in the screening process.
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