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1.
Thin films of silicon oxynitride have largely replaced pure silicon oxide films as gate and tunnel oxide films in modern technology due to their superior properties in terms of efficiency as boron barrier, resistance to electrical stress and high dielectric strength. A single chamber system for plasma enhanced chemical vapor deposition was employed to deposit different films of SiOxNyHz with 0.85 < x < 1.91. All films were previously characterized by Rutherford back-scattering and infrared spectroscopy to determine the stoichiometry and the presence of various bonding configurations of constituent atoms. We used X-ray reflectivity to determine the electron density profile across the depth, and we showed that the top layer is densified. Moreover, grazing incidence small-angle X-ray scattering was used to study inhomogeneities (clustering) in the films, and it is shown that plate-like inhomogeneities exist in the top and sphere-like particles at the bottom part of the film. Their shape and size depend on the stoichiometry of the films. 相似文献
2.
A. F. Pronin J. Kovač R. Kada V. G. Kharchenko 《Chemistry of Heterocyclic Compounds》1979,15(12):1279-1283
The a complexes of furan, thiophene, pyrrole, pyridine, and benzene with the hydride ion were calculated by the MINDO/3 method. The affinities of the indicated aromatic rings and a number of substituted furans for the H– ion were estimated. It is shown that the relative magnitude of the affinity correlates qualitatively with the experimental data on the relative rates of the reaction of the examined compounds with nucleophilic reagents. The following order of increasing reactivities of unsubstituted aromatic rings was obtained: pyrrole相似文献
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Tanja Brezo-Borjan Zorica Stojanovi Zvonimir Suturovi Jovana Kos Sneana Kravi Ana urovi 《Monatshefte für Chemie / Chemical Monthly》2020,151(3):285-291
A new electroanalytical method for vitamin B1 determination, based on adsorptive chronopotentiometric stripping analysis and non-specific adsorption onto mercury film electrode, was developed and validated. Stripping chronopotentiograms showed a single well-defined oxidation wave corresponding to vitamin B1 at about − 0.43 V in citrate buffer pH 6.0. The most important experimental factors affecting the monitored electroanalytical response of vitamin B1 were investigated and optimised. Under the optimal experimental conditions, linear response of vitamin B1 was obtained in the concentration range of 5–50 mg dm−3, with the achieved limit of detection of 1.64 mg dm−3, and the limit of quantitation of 4.97 mg dm−3. A mean recovery of 97.1% and relative standard deviations of 3.75% were achieved. The developed electrochemical procedure was successfully applied for the determination of vitamin B1 in pharmaceutical products. The results of the proposed method were in good agreement with those obtained by parallel HPLC analyses, confirming an accuracy of the developed method. 相似文献
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Enisa Selimović Tatjana Vulović Biljana Petrović Živadin D. Bugarčić Jovana Bogojeski 《Transition Metal Chemistry》2013,38(6):635-640
The kinetics of the complex formation reactions of two [(TL tBu)PtCl]+ and [Pt(tpdm)Cl]+ complexes (TL tBu = 2,6-bis[(1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine and tpdm = terpyridinedimethane) with N-donor ligands, l-histidine (L-His), inosine (Ino), inosine-5′-monophosphate (5′-IMP) and guanosine-5′-monophosphate (5′-GMP), were studied. All reactions were studied under pseudo-first-order conditions as a function of nucleophile concentration and temperature in aqueous 0.1 M NaClO4 solution in the presence of 10 mM NaCl using variable-temperature Uv–Vis spectrophotometry. The order of reactivity of the studied ligands is L-His > Ino > 5′-GMP > 5′-IMP. This order of reactivity is in relation to their electronic properties and structures. The mechanism of the substitution reactions is associative in nature as supported by the negative entropy of activation. 相似文献
7.
Superbasic Alkyl‐Substituted Bisphosphazene Proton Sponges: Synthesis,Structural Features,Thermodynamic and Kinetic Basicity,Nucleophilicity and Coordination Chemistry
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8.
Constrained‐Geometry Bisphosphazides Derived from 1,8‐Diazidonaphthalene: Synthesis,Spectroscopic Characteristics,Structural Features,and Theoretical Investigations
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Julius F. Kögel Nuri C. Abacılar Felicia Weber Dr. Benjamin Oelkers Dr. Klaus Harms Dr. Borislav Kovačević Prof. Dr. Jörg Sundermeyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):5994-6009
Investigations on the Staudinger reaction between 1,8‐diazidonaphthalene and phosphorous(III) building blocks, a key step in the synthesis of superbasic bisphosphazene proton sponges, yielded a set of bisphosphazides with a constrained geometry 1,8‐disubstituted naphthalene backbone. This compound class has attracted our interest not only due to their surprisingly high stability, but in particular because of their theoretically predicted basicity in the range of their bisphosphazene analogues that can be referred to the constrained geometry interaction of two highly basic nitrogen atoms. Eleven new bisphosphazides bearing simple P‐amino groups as well as P‐guanidino substituents, azaphosphatrane moieties, P2 building blocks, or chiral P‐amino substituents derived from L ‐proline are presented. They were studied concerning their spectroscopic properties and partly also their chromophoric and structural features. In the case of the pyrrolidino‐substituted TPPN(2N2) (TPPN=1,8‐bis(trispyrrolidinophosphazenyl)naphthalene), the stepwise nitrogen elimination is investigated theoretically and experimentally, which led to the isolation and structural characterization of TPPN(1N2) bearing a phosphazide and a phosphazene functionality in one molecule. Attempts to protonate the obtained bisphosphazides and to prove the computationally predicted pKBH+ values through NMR titration reactions resulted in their decay, which again was rationalized by theoretical calculations. Altogether we present the so far most extensive spectroscopic, structural and theoretical investigation of constrained geometry bisphosphazides and their Brønsted and Lewis basic properties. 相似文献
9.
Dr. Kang Cheng Lars I. van der Wal Dr. Hideto Yoshida Jogchum Oenema Dr. Justine Harmel Dr. Zhaorong Zhang Dr. Glenn Sunley Dr. Jovana Zečević Prof. Krijn P. de Jong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(9):3620-3628
Improving product selectivity by controlling the spatial organization of functional sites at the nanoscale is a critical challenge in bifunctional catalysis. We present a series of composite bifunctional catalysts consisting of one-dimensional zeolites (ZSM-22 and mordenite) and a γ-alumina binder, with platinum particles controllably deposited either on the alumina binder or inside the zeolite crystals. The hydroisomerization of n-heptane demonstrates that the catalysts with platinum particles on the binder, which separates platinum and acid sites at the nanoscale, leads to a higher yield of desired isomers than catalysts with platinum particles inside the zeolite crystals. Platinum particles within the zeolite crystals impose pronounced diffusion limitations on reaction intermediates, which leads to secondary cracking reactions, especially for catalysts with narrow micropores or large zeolite crystals. These findings extend the understanding of the “intimacy criterion” for the rational design of bifunctional catalysts for the conversion of low-molecular-weight reactants. 相似文献
10.
ngela Liberal ngela Fernandes Nikolaos Polyzos Spyridon A. Petropoulos Maria Inês Dias Jos Pinela Jovana Petrovi Marina Sokovi Isabel C.F.R. Ferreira Lillian Barros 《Molecules (Basel, Switzerland)》2020,25(23)
Petroselinum crispum Mill., Fuss., is a culinary vegetable used as an aromatic herb that garnishes and flavours a great variety of dishes. In the present study, the chemical profiles and bioactivities of leaf samples from 25 cultivars (three types: plain- and curly-leafed and turnip-rooted) from this species were assessed. Seven phenolic compounds were identified in all the varieties, including apigenin and kaempherol derivates. Apigenin-O-pentoside-O-hexoside was the major compound in all the tested parsley types (20, 22 and 13 mg/g of extract, respectively) and responsible for its excellent antioxidant activity, also investigated in this study. Antimicrobial activities were also explored, and the results revealed a good bioactivity against specific tested pathogens, such as bacteria and fungi. In conclusion, the leaves of all the types of P. crispum are a good source of natural bioactive compounds that confer health benefits, and thus, they should be part of a balanced and diversified diet. 相似文献