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Synthesis Time (synthesis + time)
Kinds of Synthesis Time Selected AbstractsLazy Solid Texture SynthesisCOMPUTER GRAPHICS FORUM, Issue 4 2008Yue Dong Abstract Existing solid texture synthesis algorithms generate a full volume of color content from a set of 2D example images. We introduce a new algorithm with the unique ability to restrict synthesis to a subset of the voxels, while enforcing spatial determinism. This is especially useful when texturing objects, since only a thick layer around the surface needs to be synthesized. A major difficulty lies in reducing the dependency chain of neighborhood matching, so that each voxel only depends on a small number of other voxels. Our key idea is to synthesize a volume from a set of pre-computed 3D candidates, each being a triple of interleaved 2D neighborhoods. We present an efficient algorithm to carefully select in a pre-process only those candidates forming consistent triples. This significantly reduces the search space during subsequent synthesis. The result is a new parallel, spatially deterministic solid texture synthesis algorithm which runs efficiently on the GPU. Our approach generates high resolution solid textures on surfaces within seconds. Memory usage and synthesis time only depend on the output textured surface area. The GPU implementation of our method rapidly synthesizes new textures for the surfaces appearing when interactively breaking or cutting objects. [source] Highly Enantioselective Synthesis of No-Carrier-Added 6-[18F]Fluoro- L -dopa by Chiral Phase-Transfer AlkylationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2004Christian Lemaire Abstract [18F]Fluoro- L -dopa, an important radiopharmaceutical for positron emission tomography (PET), has been synthesized using a phase-transfer alkylation reaction. A chiral quaternary ammonium salt derived from a Cinchona alkaloid served as phase-transfer catalyst for the enantioselective alkylation of a glycine derivative. The active methylene group of this Schiff-base substrate was deprotonated with cesium hydroxide and rapidly alkylated by the 2-[18F]fluoro-4,5-dimethoxybenzyl halide (X = Br, I). The reaction proceeded with high yield (> 90%) at 0 °C or room temperature in various solvents such as toluene or dichloromethane. Preparation of the [18F]alkylating agent on a solid support was developed. After labelling, the labeled [18F]fluoroveratraldehyde was trapped on a tC18 cartridge and then converted on the cartridge into the corresponding benzyl halide derivatives by addition of aqueous sodium borohydride and gaseous hydrobromic or -iodic acid. Hydrolysis and purification by preparative HPLC made 6-[18F]fluoro- L -dopa ready for human injection in a 25,30% decay-corrected radiochemical yield in a synthesis time of 100 min. The product was found to be chemically, radiochemically and enantiomerically pure (ee > 95%). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] MEL-type Pure-Silica Zeolite Nanocrystals Prepared by an Evaporation-Assisted Two-Stage Synthesis Method as Ultra-Low- k Materials,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2008Yan Liu Abstract A MEL-type pure-silica zeolite (PSZ), prepared by spin-on of nanoparticle suspensions, has been shown to be a promising ultra-low-dielectric-constant (k) material because of its high mechanical strength, hydrophobicity, and chemical stability. In our previous works, a two-stage synthesis method was used to synthesize a MEL-zeolite nanoparticle suspension, in which both nanocrystal yield and particle size of the zeolite suspension increased with increasing synthesis time. For instance, at a crystal yield of 63%, the particle size is 80,nm, which has proved to be too large because it introduces a number of problems for the spin-on films, including large surface roughness, surface striations, and large mesopores. In the current study, the two-stage synthesis method is modified into an evaporation-assisted two-stage method by adding a solvent-evaporation process between the two thermal-treatment steps. The modified method can yield much smaller particle sizes (e.g., 14,vs. 80,nm) while maintaining the same nanocrystal yields as the two-stage synthesis. Furthermore, the nanoparticle suspensions from the evaporation-assisted two-stage synthesis show a bimodal particle size distribution. The primary nanoparticles are around 14,nm in size and are stable in the final suspension with 60% solvent evaporation. The factors that affect nanocrystal synthesis are discussed, including the concentration, pH value, and viscosity. Spin-on films prepared by using suspensions synthesized this way have no striations and improved elastic modulus (9.67,±,1.48,GPa vs. 7.82,±,1.30,GPa), as well as a similar k value (1.91,±,0.09 vs. 1.89,±,0.08) to the previous two-stage synthesized films. [source] Synthesis and Optical Properties of Europium-Doped ZnS: Long-Lasting Phosphorescence from Aligned Nanowires,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2005C. Cheng Abstract Quasi-aligned Eu2+ -doped wurtzite ZnS nanowires on Au-coated Si wafers have been successfully synthesized by a vapor deposition method under a weakly reducing atmosphere. Compared with the undoped counterpart, incorporation of the dopant gives a modulated composition and crystal structure, which leads to a preferred growth of the nanowires along the [010] direction and a high density of defects in the nanowire hosts. The ion doping causes intense fluorescence and persistent phosphorescence in ZnS nanowires. The dopant Eu2+ ions form an isoelectronic acceptor level and yield a high density of bound excitons, which contribute to the appearance of the radiative recombination emission of the bound excitons and resonant Raman scattering at higher pumping intensity. Co-dopant Cl, ions can serve not only as donors, producing a donor,acceptor pair transition with the Eu2+ acceptor level, but can also form trap levels together with other defects, capture the photoionization electrons of Eu2+, and yield long-lasting (about 4,min), green phosphorescence. With decreasing synthesis time, the existence of more surface states in the nanowires forms a higher density of trap centers and changes the crystal-field strength around Eu2+. As a result, not only have an enhanced Eu2+ 4f65d1,4f7 intra-ion transition and a prolonged afterglow time been more effectively observed (by decreasing the nanowires' diameters), but also the Eu2+ related emissions are shifted to shorter wavelengths. [source] Radiosynthesis of 13N-labeled thalidomide using no-carrier-added [13N]NH3JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2010Katsushi Kumata Abstract Recent studies revealed that thalidomide (1) has unique and broad pharmacological effects on multi-targets although the application of 1 in therapy is still controversial. In this study, we synthesized nitrogen-13-labeled thalidomide ([13N]1) as a potential positron emission tomography (PET) probe using no-carrier-added [13N]NH3 as a labeling agent. By use of an automated system, [13N]1 was prepared by reacting N -phthaloylglutamic anhydride (2) with [13N]NH3, following by cyclization with carbonyldiimidazole in a radiochemical yield of 56±12% (based on [11N]NH3, corrected for decay) and specific activity of 49±24,GBq/µmol at the end of synthesis (EOS). At EOS, 570,780,MBq (n=7) of [13N]1 was obtained at a beam current of 15,µA after 15,min proton bombardment with a synthesis time of 14,min from the end of bombardment. Using a small animal PET scanner, preliminary biodistribution of [13N]1 in mice was examined. Copyright © 2010 John Wiley & Sons, Ltd. [source] HPLC methods for the purification of [11C]-labelled radiopharmaceuticals: reversal of the retention order of products and precursorsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 5 2009Szabolcs Lehel Abstract Preparative HPLC methods have been developed for a number of [11C]-methylated PET tracers, which enable elution of the labelled compounds prior to their precursors, thus reducing the overall synthesis time and avoiding contamination of the final product with precusor. This reversal of retention order has been achieved for [11C]DASB, [11C]raclopride, [11C]FLB 457, [11C]carfentanil, and 2-fluoro-[N -methyl- 11C]apomorphine, enabling collection of the purified radiopharmaceuticals from the HPLC system after 5,7,min. Furthermore, by using ethanol as the organic modifier, residual solvent analysis prior to human injection could be avoided and three of the radiopharmaceuticals could be injected directly following simple dilution and sterile filtration. Copyright © 2009 John Wiley & Sons, Ltd. [source] Radiosynthesis of [11C]ximelagatran via palladium catalyzed [11C]cyanationJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2008Anu J. Airaksinen Abstract N -hydroxyamidines (amidoximes) may be used in prodrug technology in improving oral bioavailability of drugs containing amidino functional groups. In the body, amidoximes are reduced quickly to amidines by enzymes that are present in several organs. Ximelagatran is a benzamidoxime and ethyl ester prodrug of melagatran, which is a thrombin inhibitor. Our aim was to develop a fast and efficient labeling route for the synthesis of [11C]ximelagatran ([11C]3) with a label in a metabolically stable position. [11C]3 was synthesized via a two-step synthesis sequence, starting from palladium catalyzed [11C]cyanation of its corresponding bromide precursor (2-[2-(4-bromo-benzylcarbamoyl)-azetidin-1-yl]-1-cyclohexyl-2-oxo-ethyl amino-acetic acid ethyl ester) (1), followed by a reaction with hydroxylamine. [11C]3 was synthesized with 27±17% total overall decay corrected yield (specific radioactivity of 2360±165,Ci/mmol at EOS), with a total synthesis time of 45,min. A fast and efficient labeling route for the synthesis of [11C]3 was developed. Copyright © 2008 John Wiley & Sons, Ltd. [source] 4-[18F]fluorophenyl ureas via carbamate-4-nitrophenyl esters and 4-[18F]fluoroaniline,JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 12 2006Sebastian Olma Abstract Four different no carrier added (n.c.a.) 4-[18F]fluorophenylurea derivatives are synthesized as model compounds via two alternative routes. In both cases carbamate-4-nitrophenylesters are used as intermediates. Either n.c.a. 4-[18F]fluoroaniline reacts with carbamates of several amines, or the carbamate of n.c.a. 4-[18F]fluoroaniline is formed at first and an amine is added subsequently to yield the urea derivative. The choice of the appropriate way of reaction depends on the possibilities of precursor synthesis. The radiochemical yields reach up to 80% after 50 min of synthesis time while no radiochemical by-products can be determined. These high yields were possible due to an optimized preparation of n.c.a. 4-[18F]fluoroaniline with a radiochemical yield of up to 90%. From the various ways of its radiosynthesis, the substitution with n.c.a. [18F]fluoride on dinitrobenzene is chosen, using phosphorous acid and palladium black for reduction of the second nitro group. Copyright © 2006 John Wiley & Sons, Ltd. [source] Synthesis of 2-[(2-chloro-2,-[18F]fluoroethyl)amino]-2H-1,3,2-oxazaphosphorinane-2-oxide (18F-fluorocyclophosphamide), a potential tracer for breast tumor prognostic imaging with PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 9 2005Goran Lacan Abstract A fluorine-18 labeled analog of the widely used chemotherapeutic agent cyclophosphamide was synthesized as a tracer for prognostic imaging with positron emission tomography. 2-[(2-Chloro-2,-[18F]fluoroethyl)amino]-2H-1,3,2-oxazaphosphorinane-2-oxide (18F-fluorocyclophosphamide), was prepared by direct halogen exchange reaction from the parent cyclophosphamide. In small-scale syntheses, radiochemical yields of up to 4.9% and specific activities of 960 Ci/mmol were achieved in a total synthesis time of 60,75 min. The [18F]-labeled cyclophosphamide analog with radioactive purity >99% and chemical purity >96% was suitable for in vivo (microPET imaging) and ex vivo studies of a murine model of human breast tumors. Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthesis and preliminary in vivo evaluation of 4-[18F]fluoro- N -{2-[4-(6-trifluoromethylpyridin-2-yl)piperazin-1-yl]ethyl}benzamide, a potential PET radioligand for the 5-HT1A receptorJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 9 2004M. Vandecapelle Abstract 4-Fluoro- N -{2-[4-(6-trifluoromethylpyridin-2-yl)piperazin-1-yl]ethyl}benzamide is a full 5-HT1A agonist with high affinity (pKi=9.3), selectivity and a c log P of 3.045. The corresponding PET radioligand 4-[18F]fluoro- N -{2-[4-(6-trifluoromethylpyridin-2-yl)piperazin-1-yl]ethyl}benzamide was synthesized by nucleophilic aromatic substitution on the nitro precursor. The fluorinating agent K[18F]F/Kryptofix 2.2.2 was both dried (9 min, 700 W) and incorporated in the precursor (5 min, 700 W) using a commercially available microwave oven. In a total synthesis time of 60 min, an overall radiochemical yield of 18% (SD=5, n=7, EOS) was obtained. Radiochemical purity was always higher than 99% and specific activity always higher than 81.4 GBq/µmol (2.2 Ci/µmol). Initial brain uptake in mice was 2.19% ID (5.47% ID/g, 2 min) but decreased rapidly (0.17% ID, 0.45% ID/g (60 min)). During the first 20 min p.i., radioactivity concentration of the brain was significantly higher than that of blood demonstrating good brain entry of the tracer. Copyright © 2004 John Wiley & Sons, Ltd. [source] A general method for the fluorine-18 labelling of fluoroquinolone antibioticsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 8 2003Oliver Langer Abstract Fluoroquinolones are an important class of antibiotic agents with a broad spectrum of antibacterial activity. Labelling of fluoroquinolones with fluorine-18 is of interest for the performance of pharmacokinetic measurements and the visualization of bacterial infections in humans with positron emission tomography. A two-step radiosynthetic pathway to prepare fluorine-18-labelled ciprofloxacin (1-cyclopropyl-6-[18F]fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-quinoline-3-carboxylic acid) has previously been developed. In the present work this approach was applied to the preparation of the structurally related compounds [18F]norfloxacin (1-ethyl-6-[18F]fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-quinoline-3-carboxylic acid) and [18F]pefloxacin (1-ethyl-6-[18F]fluoro-1,4-dihydro-7-(4-methyl-1-piperazinyl)-4-oxo-quinoline-3-carboxylic acid). The first step of the radiosynthesis consisted of a 18F for 19F exchange reaction on a 7-chloro-substituted precursor molecule, followed by coupling reactions with the amines piperazine or 1-methylpiperazine. Starting from 51,58 GBq of [18F]fluoride 1.9,2.0 GBq of [18F]norfloxacin or [18F]pefloxacin, ready for intravenous injection, could be obtained in a synthesis time of 130 min (3.5,3.8% overall radiochemical yield). Moreover, the preparation of [18F]levofloxacin ((-)-(S)-9-[18F]fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylicacid) was attempted but failed to afford the desired product in practical amounts. Copyright © 2003 John Wiley & Sons, Ltd. [source] Preparation of 4-[11C]methylmetaraminol, a potential PET tracer for assessment of myocardial sympathetic innervationJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2003Oliver Langer Abstract The false adrenergic neurotransmitter [11C]meta -hydroxyephedrine ([11C]HED) is currently the PET tracer of choice for assessment of myocardial sympathetic innervation. The molecule is metabolised in the 4-position of the aromatic ring. The resulting radiolabelled metabolites need to be measured in order to obtain an arterial input function. Our aim was the development of a PET tracer with an increased metabolic stability relative to [11C]HED. We selected 4-methylmetaraminol as a candidate molecule for radiolabelling with 11C (t1/2 20.4 min). Our radiosynthetic approach towards 4-[11C]methylmetaraminol involved a palladium-catalyzed cross-coupling reaction of a protected 4-trimethylstannyl derivative of metaraminol with [11C]methyl iodide followed by removal of the protective groups. 4-[11C]methylmetaraminol was obtained in a final decay-corrected radiochemical yield of 20,25% within a synthesis time of 60,80 min. The specific radioactivity at the end of the synthesis ranged from 18,37 to GBq/,mol. The unlabelled reference molecule, 4-methylmetaraminol, was prepared in a 5-step synthesis starting from metaraminol. A biological evaluation of 4-[11C]methylmetaraminol is in progress and the results will be reported elsewhere. Copyright © 2002 John Wiley & Sons, Ltd. [source] Critical evaluation of the chemical standardization procedure for measuring gastric emptying of solidsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2002P. Goethals Abstract The purpose of this study was to evaluate the baking process of yolk spiked with octanoate to measure gastric emptying rate of solids. [1- 11C]octanoate was produced by the reaction of [11C]CO2 with heptyl magnesium bromide in tetrahydrofuran (THF), followed by purification with HPLC. The decay corrected radiochemical yield ranged from 24 to 38% (5.9,9.8 GBq EOS, synthesis time: 25 min; specific radioactivity ,90 GBq ,mol,1). To check the evaporation of [1- 11C]octanoate during the baking process of yolk, [1- 11C]octanoate or potassium [1- 11C]octanoate, respectively, was added. An important fraction of the acid evaporated while for the potassium [1- 11C]octanoate <10% disappeared. Conclusion: potassium (1- 13C)octanoate is a better tracer than (1- 13C) octanoate to study gastroenterological phenomena. Copyright © 2002 John Wiley & Sons, Ltd. [source] Synthesis of MMP inhibitor radiotracers [11C]methyl-CGS 27023A and its analogs, new potential PET breast cancer imaging agentsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 6 2002Xiangshu Fei Abstract [11C]Methyl-CGS 27023A (1a) and its analogs [11C]methyl-2-picolyl-CGS 27023A (1b), [11C]methyl-benzyl-CGS 27023A (1c), [11C]methyl-2-nitro-CGS 27023A (1d), [11C]methyl-3-nitro-CGS 27023A (1e), and [11C]methyl-4-nitro-CGS 27023A (1f), novel radiolabeled matrix metalloproteinase (MMP) inhibitors, have been synthesized for evaluation as new potential positron emission tomography (PET) breast cancer imaging agents. The appropriate precursors for radiolabeling were obtained in four to five steps from starting material amino acid D -valine with moderate to excellent chemical yields. Precursors were labeled by [11C]methyl triflate through 11C,O-methylation method at the aminohydroxyl position under basic conditions and isolated by solid-phase extraction (SPE) purification to produce pure target compounds in 40,60% radiochemical yields (decay corrected to end of bombardment), in 20,25 min synthesis time. Copyright © 2002 John Wiley & Sons, Ltd. [source] Novel synthesis of [1- 11C], -vinyl- , -aminobutyric acid ([1,11C]GVG) for pharmacokinetic studies of addiction treatmentJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 3 2002Zongren Zhang Abstract , -Vinyl- , -aminobutyric acid (GVG, Vigabatrin®), a suicide inhibitor of GABA-transaminase (GABA-T), has been suggested as a new drug for the treatment of substance abuse. In order to better understand its pharmacokinetics and potential side effects, we have developed a radiosynthesis of carbon-11 (t1/2=20 min) labeled GVG for positron emission tomographic (PET) studies. We report here a novel synthetic strategy to prepare the precursor and to efficiently label GVG with C-11. 5-Bromo-3-(carbobenzyloxy)amino-1-pentene was synthesized in five steps from homoserine lactone, including reduction and methylenation. This was used in a one-pot, two-step radiosynthesis. Displacement of bromide with no-carrier-added [11C]cyanide followed by acid hydrolysis afforded [1- 11C]GVG with decay corrected radiochemical yields of 27±9% (n=6, not optimized) with respect to [11C]cyanide in a synthesis time of 45 min. Copyright © 2002 John Wiley & Sons, Ltd. [source] Precursor synthesis and radiolabelling of [11C]ADAM: a potential radioligand for the serotonin transporter exploration by PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2001Johnny VERCOUILLIE Abstract The serotoninergic system is involved in a variety of neurological and psychiatric disorders. Exploration of the serotonin transporters (5-HTT) in living human brain by PET would be of great value for better understanding, diagnosis and therapeutic follow up of these diseases. In order to obtain a selective radioligand to explore the 5-HTT by PET we report the synthesis of [11C]N,N-dimethyl-2-(2-amino-4-iodophenylthio)-benzylamine ([11C]ADAM). The precursor for labelling N-demethyl ADAM, was obtained in five steps using 2,5-dibromonitrobenzene and 2-thio-N-methylbenzamide as starting material. [11C]ADAM was synthesised by N-alkylation of the precursor using [11C]methyl iodide in DMF. The incorporation yield of [11C]methyl iodide was in the range of 50 to 70%. Finally [11C]ADAM was obtained in 30 minutes synthesis time including HPLC and with a radiochemical purity better than 99%. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of [N -methyl- 11C]mianserin: a tetracyclic, atypical antidepressantJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2001K. Marthi Abstract As part of our program to develop PET tracers for investigating monoaminergic processes in the brain, mianserin, a tetracyclic, atypical antidepressant, was selected as a candidate for labelling with 11C for in vivo evaluation. [N -methyl- 11C]Mianserin was produced by the alkylation of N -desmethyl mianserin with [11C]methyl iodide followed by HPLC purification and formulation. [N -methyl- 11C]Mianserin was obtained with a radiochemical purity >93% in a 16% decay corrected radiochemical yield. For a typical production starting with 40 GBq [11C]CO2, 1.9 GBq [N -methyl- 11C]mianserin was obtained as a formulated solution in a synthesis time of 35 min (counted from EOB). Copyright © 2001 John Wiley & Sons, Ltd. [source] Resin comparison and fast automated stepwise conventional synthesis of human SDF-1,JOURNAL OF PEPTIDE SCIENCE, Issue 12 2008Hirendra Patel Abstract Human SDF-1, contains 68 amino acids and is a member of the chemokine family of peptides. This long peptide was synthesized stepwise using classical conditions in 101 h. The reaction times were then reduced to deprotection times of 2 × 2 min and coupling times of 2 × 2.5 min, resulting in a total synthesis time of 22 h. The effect of different resins, resin substitutions and deprotection reagents on the crude peptide purities was compared. A small portion of crude peptide was purified using an RP-HPLC column and the mass of the final product was confirmed with MALDI-TOF mass spectrometry. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source] Formation of ZSM-22 Zeolite Catalytic Particles by Fusion of Elementary NanorodsCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2007Kazuaki Hayasaka Abstract An ZSM-22 aluminosilicate zeolite was synthesized using the hydrothermal gel method at 150,°C. Products obtained after different synthesis times were characterized using various techniques and catalytic testing. Massive formation of ZSM-22 nanocrystals occurs after only a short synthesis time, appearing as isolated rods with a cross section of 12±4,nm. Nanorods have aluminum enriched at their external surface. Later in the crystallization process nanorods align and fuse sideways, whereby the external surface is systematically converted into an internal micropore surface. The formation of aluminum bearing micropores by the joining of nanorod surfaces is responsible for the enhanced catalytic activity. For this, the zeolite synthesis of nanoscale crystallites is ineffective for enhancing catalytic activity. [source] One-pot synthesis of [11C]ureas via triphenylphosphiniminesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2006Erica W. van Tilburg Abstract A series of 11C-labeled ureas was prepared using a rapid and efficient one-pot procedure. First, the intermediate [11C]phenylisocyanate was formed with phenyltriphenylphosphinimine and [11C]CO2. A range of amines was then reacted with the [11C]phenylisocyanate yielding the [11C]urea derivatives in short synthesis times. This easy-to-handle method circumvents disadvantages of known procedures and generates the possibility to prepare other kinds of 11C-labeled compounds using a variety of phenylphosphinimines in combination with different nucleophiles. The presented approach is an alternative to the use of established methods in 11C-labeling chemistry. Copyright © 2006 John Wiley & Sons, Ltd. [source] Formation of ZSM-22 Zeolite Catalytic Particles by Fusion of Elementary NanorodsCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2007Kazuaki Hayasaka Abstract An ZSM-22 aluminosilicate zeolite was synthesized using the hydrothermal gel method at 150,°C. Products obtained after different synthesis times were characterized using various techniques and catalytic testing. Massive formation of ZSM-22 nanocrystals occurs after only a short synthesis time, appearing as isolated rods with a cross section of 12±4,nm. Nanorods have aluminum enriched at their external surface. Later in the crystallization process nanorods align and fuse sideways, whereby the external surface is systematically converted into an internal micropore surface. The formation of aluminum bearing micropores by the joining of nanorod surfaces is responsible for the enhanced catalytic activity. For this, the zeolite synthesis of nanoscale crystallites is ineffective for enhancing catalytic activity. [source] | ||||||||||