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101.
本文首次以LB技术将四苯基卟啉铜(CuTPP)分子沉积到高定向热解石墨上,并用STM研究其表面形貌,得到了原子级分辨的CuTPP分子的表面形貌图,结果表明,CuTPP分子具有近似圆状平面结构,分子直径为1.0nm,与理论结果十分吻合,结合STM原理,讨论了有机大分子STM成像的条件。 相似文献
102.
The composites with nano-particles of Ni-Fe alloys dispersed on the nano-layers of expanded graphite (EG) were prepared by the impregnation of EG with ethanol solutions of nickel and iron acetates, followed by drying and reduction in H2. The square nano-particles of Ni-Fe alloys with particle sizes of mainly 20~40 nm were found to be well spread on the layers of EG. The alloy nano-particles exhibited high shielding effectiveness (SE) for electromagnetic radiations at low frequencies due to their high magnetic conductivity. Since EG is electronically conductive and displayed high SE at high frequencies, the composites exhibited good SE at wide range of frequencies. The electric and magnetic conductivities of the composites could be monitored through regulating the loadings of alloy nano-particles on EG, and it was found that the composites with 20%~40% of the alloys exhibited good SE. Specifically, the composite 27%Ni-3%Fe-EG showed the excellent SE from 66 to 110 dB at the frequencies from 300 kHz to 1.5 GHz. 相似文献
103.
We reported in this paper FTIR linear diehroic spectroscopy and anisotropic properties of the nanoparticulate α-Fe_2O_3-stearate alternating Langmuir-Blodgett films (Fe_2O_3-St LB films) a new inorganic-organic quantum superlattice system. A new method fitted to inorganic-organic alternating films is used to study the molecular orientation and discuss the order arrangement of the nanopartieles in the films. The the results show that a configuration of stearate ions bound to the surface of the nano-particles: COO~- group are spherically bound to the surface of the nanoparticles; the hydrocarbon chains are almost perpendicular (31°±5°) to the substrate (7 nm-Fe_2O_3-St LB films). The orientation of hydrocarbon chains and CH_2 scissors vibration show the existence of trans-zigzag planar structure for C—C broken bone of the hy7drocarbon chains, which is related to high-order structure of the alternate films. 相似文献
104.
P. Hazot J. P. Chapel C. Pichot A. Elaissari T. Delair 《Journal of polymer science. Part A, Polymer chemistry》2002,40(11):1808-1817
Monodisperse, thermosensitive poly(N‐ethyl methacrylamide) microgel particles were prepared by the batch precipitation/emulsion polymerization of water‐soluble N‐ethyl methacrylamide and the hydrophobic crosslinker ethylene glycol dimethacrylate initiated by potassium persulfate. Particular attention was paid to the effect of the crosslinker agent on the polymerization process (kinetics, conversion, and water‐soluble oligomer content). Particles were characterized in terms of their size distribution and swelling capacity. A polymerization mechanism for the water‐soluble monomer and non‐water‐soluble crosslinker is proposed and discussed on the basis of a combination of both emulsion and precipitation polymerization processes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1808–1817, 2002 相似文献
105.
Heimark L Shipkova P Greene J Munayyer H Yarosh-Tomaine T DiDomenico B Hare R Pramanik BN 《Journal of mass spectrometry : JMS》2002,37(3):265-269
A liquid chromatography/mass spectrometry (LC/MS) method for separation and characterization of ergosterol biosynthetic precursors was developed to study the effect of Posaconazole on sterol biosynthesis in fungi. Ergosterol biosynthetic precursors were characterized from their electron ionization mass spectra acquired by a normal-phase chromatography, particle beam LC/MS method. Fragment ions resulting from cleavage across the D-ring and an abundant M - 15 fragment ion were diagnostic for methyl substitution at C-4 and C-14. Comparison of the sterol profile in control and treated Candida albicans incubations showed depletion of ergosterol and accumulation of C-4 and C-14 methyl-substituted sterols following treatment with Posaconazole. These C-4 and C-14 methyl sterols are known to be incapable of sustaining cell growth. The results demonstrate that Posaconazole exerts its antifungal activity by inhibition of ergosterol biosynthesis. Furthermore, Posaconazole appears to disrupt ergosterol biosynthesis by inhibition of lanosterol 14alpha-demethylase. 相似文献
106.
A new chemical method is reported for the determination of total fluoride in complex liquids and suspensions, such as fruit juices, urine, serum and blood. It is based on the formation of the A1F radical in a graphite furnace afterin situ oxygen-assisted ashing of the untreated sample. The absorbance of this radical is measured at 227.45 nm. The method is relatively easy to use and provides a low detection limit (14 ng/ml) and reasonable reproducibility (5–10%). 相似文献
107.
本文采用GF-AAS加平台技术,基体改进剂,测定了中药片仔癀,六味地黄丸中铬、铅和镉的含量,铬、铅和镉的线性范围分别为0-0.8ng/mL,0-50ng/mL,0-5ng/mL,回收率分别为102-103%,99-101%,97.5-98%,本方法简便快速、准确。 相似文献
108.
以金属硝酸盐为原料,分别采用高分子前驱体法、柠檬酸盐凝胶法制备了纳米级的Ce-Zr-Ba-O复合氧化物超细粒子,采用X-射线衍射(XRD)、透射电镜(TEM)、BET比表面测定、热重-差热(TG-DTA)技术对催化剂进行了表征,并考察了催化剂的CO氧化活性和热稳定性。实验结果表明,高分子前驱体法和柠檬酸盐凝胶法制备的催化剂粉体都达到了纳米级。两种方法中,高分子前驱体法所制得的催化剂的BET比表面达118.96m2·g-1,CO氧化反应活性较高,同时该方法制得的催化剂分散性好,无团聚,经1000℃高温焙烧后仍基本无烧结、无团聚现象,具有较高的热稳定性。 相似文献
109.
We employ dissipative particle dynamics (DPD) to examine the self‐assembly behavior of A2‐star‐(B‐alt‐C) molecules. We successfully observe various types of hierarchical structure‐within‐structures, such as A‐formed spheres in the matrix formed by B and C alternating layers, hexagonally packed A‐formed cylinders in the matrix with B and C segregated layers, B and C alternating layers‐within‐lamellae, coaxial B and C alternating domains within hexagonally packed BC‐formed cylinders in the A‐matrix, and co‐centric BC‐alternating domains within BC‐formed spheres in the A‐matrix, by increasing the A composition. Generally speaking, the small length‐scale B and C segregated domains are in parallel to the large length‐scale structures. This hierarchical periodicity along the same axis as well as the various characteristic structures, that the A2‐star‐(B‐alt‐C) copolymers display, are quite different from those in A‐block‐(B‐graft‐C) coil‐comb copolymers. Moreover, it is interesting to find that when the copolymer chain length increases, though the hierarchical structure type is maintained, the number of small length‐scale lamellae that can form within the large length‐scale structure increases. These hierarchical structures under various compositions are reported theoretically for the first time in the copolymer systems consisting of the alternating blocks, and are in good agreement with the most recent experimental work by Matsushita and co‐workers (Macromolecules 2007 , 40, 4023). 相似文献
110.
《Electroanalysis》2006,18(1):44-52
The electrochemical oxidation of cobalt(II) at gold, boron‐doped diamond, basal and edge plane pyrolytic graphite, and highly oriented pyrolytic graphite electrodes in aqueous solutions containing NH3 has been studied using cyclic voltammetry, with subsequent chemical and electrochemical processes explained in detail. Furthermore, the electro‐reduction of [Co(NH3)6]3+ in the presence of different electrolytes has also been studied to obtain a better understanding of the oxidation pathway of the Co(II)‐ammine complexes. In aqueous solution the mechanism can be described by the following scheme: 相似文献