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Safonova OV Neisius T Ryzhikov A Chenevier B Gaskov AM Labeau M 《Chemical communications (Cambridge, England)》2005,(41):5202-5204
The effect of Pd nanoparticles on the H2 sensitivity of SnO2 thin films was studied in real working conditions using X-ray Absorption Spectroscopy (XAS), electrical conductivity measurements and mass-spectrometry. 相似文献
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Elucidating the Thermal Decomposition of Dimethyl Methylphosphonate by Vacuum Ultraviolet (VUV) Photoionization: Pathways to the PO Radical,a Key Species in Flame‐Retardant Mechanisms 下载免费PDF全文
Shuyu Liang Dr. Patrick Hemberger Dr. N. Matthias Neisius Dr. Andras Bodi Prof. Dr. Hansjörg Grützmacher Prof. Dr. Joelle Levalois‐Grützmacher Dr. Sabyasachi Gaan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1073-1080
The production of phosphoryl species (PO, PO2, HOPO) is believed to be of great importance for efficient flame‐retardant action in the gas phase. We present a detailed investigation of the thermal decomposition of dimethyl methylphosphonate (DMMP) probed by vacuum ultraviolet (VUV) synchrotron radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. This technique provides a snapshot of the thermolysis process and direct evidence of how the reactive phosphoryl species are generated during heat exposure. One of the key findings of this work is that only PO is formed in high concentration upon DMMP decomposition, whereas PO2 is absent. It can be concluded that the formation of PO2 needs an oxidative environment, which is typically the case in a real flame. Based on the identification of products such as methanol, formaldehyde, and PO, as well as the intermediates O?P?CH3, H2C?P?OH, and H2C?P(?O)H, supported by quantum chemical calculations, we were able to describe the predominant pathways that lead to active phosphoryl species during the thermal decomposition of DMMP. 相似文献
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OG Khvostenko ZS Yarullina NM Shishlov VE Rusin 《Rapid communications in mass spectrometry : RCM》1999,13(12):1091-1097
A correlation between the energies of electronic singlet transitions in benzodiazepines and their biological activity, which was revealed earlier by means of negative ion mass spectrometry with resonance electron capture, has been verified with a UV absorption spectroscopy investigation. Also, it has been noted that the energies of electronic singlet transitions in benzodiazepines are close in value to the ionization energies of atoms Cs, Rb, K, Na, Li and Tl, the cations of which are known to play an important role in nerve cell excitation processes. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Fiddy SG Evans J Newton MA Neisius T Tooze RP Oldman R 《Chemical communications (Cambridge, England)》2003,(21):2682-2683
Highly dilute EXAFS characterisation for the elucidation of species involved in Heck chemistry is demonstrated; the major "monomer" species of Herrmann's acetate-bridged phosphapalladadacycle is characterised and species present during the course of a 50 ppm [Pd] Pd(OAc)2/PBu(t)3 catalysed Heck reaction are presented. 相似文献
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Fiddy SG Evans J Neisius T Newton MA Tsoureas N Tulloch AA Danopoulos AA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(13):3652-3659
A study on the Mizoroki-Heck coupling of selected aryl bromides with acrylates catalysed by a series of Pd complexes of bidentate pyridyl-, picolyl-, diphenylphosphinoethyl- and diphenylphosphinomethyl-functionalised N-heterocyclic carbene (NHC) is reported. The observed activity is dependent on the type of solvent and base used and the nature of the "classical" donors of the mixed-donor bidentate ligand and its bite angle. A mechanistic model is presented for the pyridine-functionalised NHC complexes based on an in situ EXAFS study under dilute catalyst conditions (2 mM Pd). The model involves pre-dissociation of the pyridine functionality and oxidative addition of ArBr in the early stages of the reaction, as well as formation of monomeric and dimeric Pd species at the time of substrate conversion. 相似文献
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AM Cardoso SM Alexandre CM Barros AJ Correia NM Nibbering 《Rapid communications in mass spectrometry : RCM》1999,13(19):1885-1888
The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Acinetobacter strain PS12B was isolated from marine sediment and was found to be a good candidate to degrade agar and produce agarase enzyme. The extracellular agarase enzyme from strain PS12B was purified by ammonium sulfate precipitation followed by DEAE-cellulose ion-exchange chromatography. The specific activity of the crude enzyme which was 1.52 U increased to 45.76 U, after two-stage purification, with an enzyme yield of 9.76%. Purified enzyme had a molecular mass of 24 kDa. The optimum pH and temperature for activity of purified agarase were found to be 8.0 and 40 °C, respectively. The Km and Vmax values for agarase were 4.69 mg/ml and 0.5 μmol/min, respectively. Treatment with EDTA reduced the agarase activity by 58% at 5 mM concentration. The enzyme activity was stimulated by the presence of Fe2+, Mn2+, and Ca2+ ions while reducing reagents (β-mercaptoethanol and dithiothreitol, DTT) enhanced its activity by 30–40%. The purified agarase exhibited tolerance to both detergents and organic solvents. Major hydrolysis products of agar were DP4 and also a mixture of longer oligosaccharides DP6 and DP7. The enzyme hydrolysed seaweed (Gracilaria verrucosa) exhibited strong antioxidant activity in vitro. Successful hydrolysis of seaweed indicates the potential use of the enzyme to produce seaweed hydrolysate having health benefits as well as the industrial application like the production of biofuels. 相似文献
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Separate optimized s and p bond functions (BFs) were added to the corresponding Dunning basis sets (11s,6p15s) → (5s,4p13s) for the four hydrides. Properties calculated with these basis sets are quasi-identical to those obtained with conventional polarization functions (dlp). The computer time ratios found are: t(BF)/t(dlp) = for UHF calculations, and for MC SCF calculations. 相似文献