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991.
992.
Cobalt tetraphenylporphyrin (CoTPP) was bond on the side chains of poly(N‐vinylimidazole) (PVI) and immobilized on PVI/SiO2 via axial coordination reactions, respectively, leading to the soluble metalloporphyrin‐functionalized PVI (denoted as CoTPP–PVI) and the particles CoTPP–PVI/SiO2. The above two target products were characterized using spectroscopy methods such as infrared spectrum, electronic absorption spectrum, and fluorescence emission spectrum. And the effects of various factors on the bonding reaction and immobilization reaction of CoTPP were studied in detail. The experimental results show that CoTPP–PVI and CoTPP–PVI/SiO2 can be prepared favorably through axial coordination reaction of CoTPP with the side imidazole groups of PVI and PVI/SiO2. In addition, the soluble CoTPP–PVI has all the spectral characteristics of CoTPP. As compared to CoTPP, the adsorption spectra of CoTPP–PVI exhibit red shift obviously. In the immobilization process of CoTPP on PVI/SiO2, the higher the concentrations of CoTPP and the reaction temperature, the greater the immobilization amount of CoTPP is. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
993.
R. Rodríguez-Mijangos E. Muñoz-Sandoval R. Pérez-Salas M. Barboza-Flores C. Ruíz-Mejía 《辐射效应与固体损伤》2013,168(2):171-179
Abstract Experimental and theoretical study of the F absorption band were carried out in mixed ionic crystals as a function of temperature and molar composition. Both the point-ion and pseudopotential methods of Gourary–Adrian and Bartram–Stoneham–Gash, respectively, have been used to obtain the F band shift effect in KCl1?x Br x mixed crystals with molar fraction x and the temperature T of the crystal. The theoretical values were compared with the experimental ones, and a good agreement between experimental and theoretical calculations has been found. 相似文献
994.
In this paper,potassium dihydrogen phosphate(KDP) crystals were grown in the presence of a series of silicate(SiO32-) impurity concentrations via conventional temperature cooling and rapid growth methods,respectively.It revealed that the SiO32-impurity could lead to the decrease of transmittance at the region of ultraviolet band for pyramidal sectors and slightly increased the transmittance for prismatic sectors.SiO32-could enter into the crystal lattice and create lattice defects,which consequently increased the density of light scatter.The decrease of laser damage threshold was attributed to the lattice defects and the redundant electrons brought by the replacement of SiO32-at the PO43-position. 相似文献
995.
Dr. Tomoyuki Yoshimura Masatoshi Takuwa Keisuke Tomohara Makoto Uyama Dr. Kazuhiro Hayashi Pan Yang Ryuichi Hyakutake Dr. Takahiro Sasamori Prof. Dr. Norihiro Tokitoh Prof. Dr. Takeo Kawabata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(48):15330-15336
β‐Lactams with contiguous tetra‐ and trisubstituted carbon centers were prepared in a highly enantioselective manner through 4‐exo‐trig cyclization of axially chiral enolates generated from readily available α‐amino acids. Use of a weak base (metal carbonate) in a protic solvent (EtOH) is the key to the smooth production of β‐lactams. Use of the weak base is expected to generate the axially chiral enolates in a very low concentration, which undergo intramolecular conjugate addition without suffering intermolecular side reactions. Highly strained β‐lactam enolates thus formed through reversible intramolecular conjugate addition (4‐exo‐trig cyclization) of axially chiral enolates undergo prompt protonation by EtOH in the reaction media (not during the work‐up procedure) to give β‐lactams in up to 97 % ee. 相似文献
996.
Huang YL Lu DY Yu HC Yu JS Hsu CW Kuo TS Lee GH Wang Y Tsai YC 《Angewandte Chemie (International ed. in English)》2012,51(31):7781-7785
Give me five! Terdentate 2,6-diamidopyridyl ligands were used to stabilize the Cr-Cr quintuple bond and have made it possible to isolate and characterize not only the Cr-Cr quintuple-bonded complex, but also the mixed-valent intermediates (Cr(I) and Cr(II)), which are important species in the formation of type?I quintuple-bonded complexes. 相似文献
997.
NaCl:(F2+)AH-type color center laser crystals were prepared by the crystal growth, additional coloration, annealing, and by light aggregation at 290 and 77 K. The formation process of color center in NaCl crystals were investigated, the influence of doped cation and anion ions on the stability and optical properties of color centers is discussed in this paper. 相似文献
998.
999.
Z. Liliental-Weber 《Journal of Crystal Growth》2010,312(18):2599-2606
A short review of the structural perfection of high-pressure grown bulk crystals is given. As-grown undoped and Mg-doped crystals are described. The dependence of defect arrangement and quality of the surface on growth polarity is described. A high perfection of homoepitaxial layers grown on these substrates is shown. However, growth of thick layers by HVPE may lead to the formation of differently arranged dislocations and the formation of low angle grain boundaries associated with cracks. It is shown that the introduction of dopant or growth of mismatched layers on undoped high-pressure substrates may lead to the formation of additional defects. 相似文献
1000.