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排序方式: 共有502条查询结果,搜索用时 31 毫秒
161.
162.
Iwona Rykowska Wiesław Wasiak 《International journal of environmental analytical chemistry》2013,93(15):1466-1476
This paper describes our research on the synthesis of the sorbent with chemically bonded ketoimine groups, and, furthermore, using this sorbent in the SPE technique to extract and preconcentrate trace amounts of metal ions in water samples. Surface characteristics of the sorbent were determined by elemental analysis, NMR spectra for the solid phases (29Si CP MAS NMR), and analysis of pore size distribution of the sorbent and nitrogen adsorption-desorption. The newly proposed sorbent with ketoimine groups was applied for the extraction and preconcentration of trace amounts of Cu (II), Cr (III) and Zn (II) ions from the water from a lake, post-industrial water and purified water unburdened back to the lake. The determination of the transition-metal ions was performed on an emission spectroscope with inductively coupled plasma ICP-OES. For the batch method, the optimum pH range for Cu (II) and Cr (III) extraction was equal to 5, and Zn(II)–to 8. All the metal ions can be desorbed from SPE columns with 10?mL of 0.5?mol?HNO3. The detection limits of the method were found to be 0.7?µg?L?1 for Cu (II), 0.08?µg?L?1 for Cr (III), and 0.2?µg?L?1 for Zn (II), respectively. 相似文献
163.
Zygfryd Smiatacz Iwona Chrzczanowicz Henryk Myszka Paweł Dokurno 《Journal of carbohydrate chemistry》2013,32(6):723-735
Abstract Dimeric methyl (3,4-di-O-acetyl-2-deoxy-2-nitroso-α-d-glucopyranosyl chloride)uronate (1) reacts with nucleophiles such as: ethanol, pyrazole, methyl N-tert-butyloxycarbonyl-L-serinate to give corresponding glycosides. The stereospecifity of the glycosidation reaction depends mainly on the employed nucleophile. The configuration and conformation of the obtained glycosides were established on the basis of 1H NMR and polarimetric data, and additionally the structure of 1-(methyl 3,4-di-O-acetyl-2-deoxy-2-(Z)-hydroxyimino-α-d-arabino-hexopyranosyluronate)pyrazole (6), was supported by X-ray diffraction data. 相似文献
164.
Dr. Iwona Nierengarten Marc Nothisen Dr. David Sigwalt Thomas Biellmann Dr. Michel Holler Dr. Jean‐Serge Remy Dr. Jean‐François Nierengarten 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(51):17552-17558
Dendritic pillar[5]arene derivatives have been efficiently prepared by grafting dendrons with peripheral Boc‐protected amine subunits onto a preconstructed pillar[5]arene scaffold. Upon cleavage of the Boc‐protected groups, water‐soluble pillar[5]arene derivatives with 20 ( 13 ) and 40 ( 14 ) peripheral ammonium groups have been obtained. The capability of these compounds to form stable nanoparticles with plasmid DNA has been demonstrated by gel electrophoresis, transmission electron microscopy (TEM), and dynamic light scattering (DLS) investigations. Transfection efficiencies of the self‐assembled 13 /pCMV‐Luc and 14 /pCMV‐Luc polyplexes have been evaluated in vitro with HeLa cells. The transfection efficiencies found for both compounds are good, and pillar[5]arenes 13 and 14 show very low toxicity if any. 相似文献
165.
Dr. Julien Lieffrig Dr. Olivier Jeannin Arkadiusz Frąckowiak Dr. Iwona Olejniczak Roman Świetlik Dr. Slimane Dahaoui Dr. Emmanuel Aubert Prof. Dr. Enrique Espinosa Dr. Pascale Auban‐Senzier Dr. Marc Fourmigué 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):14804-14813
Charge‐assisted halogen bonding is unambiguously revealed from structural and electronic investigations of a series of isostructural charge‐transfer complexes derived from iodinated tetrathiafulvalene and tetracyanoquinodimethane derivatives, (EDT‐TTFI2)2(TCNQFn), n=0–2, which exhibit variable degrees of ionicity. The iodinated tetrathiafulvalene derivative, EDT‐TTFI2, associates with tetracyanoquinodimethane (TCNQ) and its derivatives of increasing reduction potential (TCNQF, TCNQF2) through highly directional C? I???N≡C halogen‐bond interactions. With the less oxidizing TCNQ acceptor, a neutral and insulating charge‐transfer complex is isolated whereas with the more oxidizing TCNQF2 acceptor, an ionic, highly conducting charge‐transfer salt is found, both of 2:1 stoichiometry and isostructural with the intermediate TCNQF complex, in which a neutral–ionic conversion takes place upon cooling. A correlation between the degree of charge transfer and the C? I???N≡C halogen‐bond strength is established from the comparison of the structures of the three isostructural complexes at temperatures from 300 to 20 K, thus demonstrating the importance of electrostatics in the halogen‐bonding interaction. The neutral–ionic conversion in (EDT‐TTFI2)2(TCNQF) is further investigated through the temperature dependence of its magnetic susceptibility and the stretching modes of the C≡N groups. 相似文献
166.
Iwona Peech Daniel Sibera Piotr Staciwa Urszula Narkiewicz Robert Cormia 《Molecules (Basel, Switzerland)》2020,25(22)
In this work, low-pressure synthesis of carbon spheres from resorcinol and formaldehyde using an autoclave is presented. The influence of reaction time and process temperature as well as the effect of potassium oxalate, an activator, on the morphology and CO2 adsorption properties was studied. The properties of materials produced at pressureless (atmospheric) conditions were compared with those synthesized under higher pressures. The results of this work show that enhanced pressure treatment is not necessary to produce high-quality carbon spheres, and the morphology and porosity of the spheres produced without an activation step at pressureless conditions are not significantly different from those obtained at higher pressures. In addition, CO2 uptake was not affected by elevated pressure synthesis. It was also demonstrated that addition of the activator (potassium oxalate) had much more effect on key properties than the applied pressure treatment. The use of potassium oxalate as an activator caused non-uniform size distribution of spherical particles. Simultaneously higher values of surface area and total pore volumes were reached. A pressure treatment of the carbon materials in the autoclave significantly enhanced the CO2 uptake at 25 °C, but had no effect on it at 0 °C. 相似文献
167.
Determination of Ultratrace Thallium(I) by Anodic Stripping Voltammetry at Bismuth Film Electrodes Following Double Deposition and Stripping Steps
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The double deposition and stripping steps were proposed to increase the sensitivity in anodic stripping voltammetry of thallium(I). Two in situ plated bismuth film electrodes with drastically different surface areas were exploited for the measurements. Thallium was at first deposited at the electrode with a large surface area. As the deposition step at the large electrode was finished, the electrode was moved at a short distance to the small one. The thallium stripped from the large electrode was then accumulated at the second electrode. Taking into account the small volume of space between the electrodes, the concentration of Tl(I) between the electrodes was drastically higher than that in the bulk solution. The deposition step at the second electrode was performed from solution with a higher concentration of Tl(I) therefore the detection limit was lowered. The calibration graph was linear from 5×10?11 to 5×10?9 mol L?1 following deposition time of 300 s at the first and the second electrode. 相似文献
168.
Marek Dobosz Hirokazu Matsumoto Katuo Seta Shigeo Iwasaki 《Optics and Lasers in Engineering》1996,24(1):43-56
Superposition of different-wavelength, multimode- and single-mode laser diode beams is investigated to locate the fringe of zero interference order in a Twyman-Green interferometer. The possibility of central fringe detection using three multimode laser diodes or one single-mode together with a pair of multimode laser diodes is shown. If a single-mode laser diode is applied, a simultaneous fringe-counting technique for displacement measurement is available. The influence of the angle between wavefronts entering the interferometer is analyzed. A repeatability of about 5 nm is shown for surface position determination when using three-beam source. 相似文献
169.
The applicability of silica gels for the application in solid-phase extraction was tested. Silica was modified with ketoimine
groups. Surface characteristics of the modified silica were determined by elemental analysis, NMR spectra of solid phases
(29Si CP MAS NMR), analysis of pore size distribution of the silica support, and nitrogen adsorption-desorption. Newly proposed
sorbents with ketoimine groups were applied in the preconcentration of trace amounts of the Cu (II) ions from lake water,
post-industrial water, and demineralized water unburdened back to the lake.
Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May
2007. 相似文献
170.
Iwona Zięborak-Tomaszkiewicz Ewa Utzig P. Gierycz 《Journal of Thermal Analysis and Calorimetry》2008,91(1):329-332
The heat capacity of gallium nitride has been measured by DSC method using DuPont Thermal Analyst 2100, DSC 951 unit in the
temperature range (300–850 K). The temperature dependence of the heat capacity can be presented in the following form: C
p=32.960+0.162·10−1
T+2360170T
−2-775370000T
−3. 相似文献