共查询到20条相似文献,搜索用时 31 毫秒
1.
Abdülhadi Baykal Nermin Kasapoğlu Yüksel Köseoğlu Ali Cemil Başaran Hüseyin Kavas Muhammet S. Toprak 《Central European Journal of Chemistry》2008,6(1):125-130
A series of Ni-doped cobalt ferrites NixCo1−xFe2O4 (x = 0.0, 0.4, 0.6, 0.8, and 1.0) were prepared using microwave-induced combustion. Nickel, cobalt, and ferric nitrates were
used as starting materials and glycine as fuel. The influence of Ni content on the lattice parameter, stretching vibrations,
and magnetization was studied. XRD, FTIR, and SEM were used for structure, composition, and morphology investigation. A porous
network structure was observed with average particle size 60–67 nm. All samples had a cubic spinel structure. The unit cell
parameter “a” decreases linearly with nickel concentration due to the smaller ionic radius of nickel. Magnetization measurements
showed that coercivity decreased as Ni content increased; it increased with decreasing temperature.
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2.
The effect of calcium substitution on the afterglow of tetrastrontium aluminate phosphors (Sr4Al14O25:Eu2+, Dy3+) was investigated. A series of (Sr1-xCax)O⊎nAl2O3:Eu2+(1%), Dy3+(0.5%), with variation of calcium content (x = 0 − 1), were synthesized by a high temperature solid state reaction in a reducing
atmosphere. The photoluminescence, persistent luminescence (afterglow), and lumen equivalents of these materials were studied
and compared. It turned out that the afterglow properties of the phosphors were strongly dependent on the Sr/Ca ratio. As
the Ca content increased, a phase transition and blue shift in emission spectra were observed.
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3.
This paper reports on the results concerning the sol-gel preparation and characterization of Sr-substituted perovskite lanthanum
cobaltates La1−xSrxCoO3−δ (x = 0.0, 0.25, 0.5 and 0.75). The metal ions, generated by dissolving starting materials in diluted acetic acid were complexed
by 1,2-ethanediol to obtain the precursors for the non-substituted and Sr-substituted LaCoO3. The influence of the synthesis temperature, heating time and the amount of substituent on the phase purity of La1−xSrxCoO3−δ were investigated. The phase transformations, composition and micro-structural features in the gels and polycrystalline samples
were studied by thermal analysis (TG/DTA), infrared spectroscopy (IR), powder X-ray diffraction analysis (XRD) and scanning
electron microscopy (SEM).
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4.
Nikolai N. Kolesnikov Elena B. Borisenko Dmitrii N. Borisenko Boris A. Gnesin 《Central European Journal of Chemistry》2011,9(4):619-623
In the present study newly produced semiconductor ceramic nanopowder materials made of CdTe and Cd1−xZnxTe (CZT) are considered. Common features and differences in microstructures, phase transformations, grain growth and properties
of the ceramic materials of the binary and ternary compositions are studied.
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5.
Violeta D. Kassabova-Zhetcheva Lilyana P. Pavlova Bisserka I. Samuneva Zara P. Cherkezova-Zheleva Ivan G. Mitov Mikhail T. Mikhov 《Central European Journal of Chemistry》2007,5(1):107-117
Structural and magnetic properties of Mg
x
Zn1−x
Fe2O4 powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mg
x
Zn1−x
Fe2O4 (x=0.1–0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns
of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes
from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely
small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to
explain quadruple doublets. The quadruple splitting at “shells” is bigger than those at “cores” whereas the isomer shifts
remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones.
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6.
Nermin Kasapoglu Bahar Birsöz Abdülhadi Baykal Yüksel Köseoglu Muhammet S. Toprak 《Central European Journal of Chemistry》2007,5(2):570-580
A series of Ni doped cobalt ferrite compounds with the formula Ni
χ
Co1−χ
Fe2O4 where x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 were prepared using a hydrothermal method and subsequently sintered/annealed at 600
°C for 3 h. The influence of the Ni content on the lattice parameter, a, stretching vibration and the magnetization of specimens were subsequently studied. XRD and FTIR were used to investigate
structure and composition variations. All samples were found to have a cubic spinel structure. SEM was used to study morphological
variations. The results indicate that the average particle sizes are between 30–35 nm with a narrow size distribution along
with nanocrystals forming of regular octahedrons. A decrease in the peak to peak line width and increase in resonance field
with increasing Ni content were observed from ESR measurements. Based on ESR results, a core-shell type of formation was proposed
where the core is made up of undoped CoFe2O4 and the shell is Ni2+ doped CoFe2O4.
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7.
Nitin A. Mirgane Sandip B. Kotwal Anil V. Karnik 《Central European Journal of Chemistry》2010,8(2):356-360
Ionic liquids (IL) are gaining importance as green solvents. Imidazolium ionic liquid [bmim]+[Cl]−, an environmentally benign solvent, was found to promote the Diels-Alder reaction between anthrone and maleimides at room
temperature with excellent yields. The ionic liquid played a dual role as solvent and catalyst.
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8.
Mohamed R. Shehate Mohamed M. Shoukry Mona S. Ragab 《Central European Journal of Chemistry》2012,10(4):1253-1261
The Pd(DMPA)Cl2 complex, where DMPA = N,N-dimethylaminoproylamine, was synthesized and characterized. The stoichiometry and stability constants of the complexes formed between various dicarboxylic acids and [Pd(DMPA)(H2O)2]2+ were investigated. The effect of solvent dielectric constant, chloride ion concentration of the medium and temperature on the stability constant of the cyclobutanedicaroxylic acid (CBDCA) complex was investigated. The equilibrium constants for the displacement of coordinated CBDCA by inosine, taken as an example of DNA constituents, were calculated. The results are expected to contribute to the chemistry of antitumour agents. 相似文献
9.
Mónica Díaz-Pérez Manuel Aboal-Somoza Pilar Bermejo-Barrera Adela Bermejo-Barrera 《Central European Journal of Chemistry》2008,6(4):520-525
Preliminary results of development of a direct and fast method of determination of antimony in samples of tap water using
GFAAS are presented. The found levels of antimony were lower than permitted for human consumption. A mixture of Pd and Mg(NO3)2 (concentrations in the injected solution: 8.6 μg mL−1 and 5.8 μg mL−1 respectively) was used as the chemical modifier. The pyrolysis and atomization temperatures were 1000 and 1700°C, respectively
and the mean analytical recovery 98.2%.
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10.
Dispersive liquid-liquid microextraction and liquid chromatographic determination of pentachlorophenol in water 总被引:1,自引:0,他引:1
Khalil Farhadi Mir A. Farajzadeh Amir A. Matin Paria Hashemi 《Central European Journal of Chemistry》2009,7(3):369-374
A simple and sensitive dispersive liquid-liquid microextraction method for extraction and preconcentration of pentachlorophenol
(PCP) in water samples is presented. After adjusting the sample pH to 3, extraction was performed in the presence of 1% W/V
sodium chloride by injecting 1 mL acetone as disperser solvent containing 15 μL tetrachloroethylene as extraction solvent.
The proposed DLLME method was followed by HPLC-DAD for determination of PCP. It has good linearity (0.994) with wide linear
dynamic range (0.1–1000 μg L−1) and low detection limit (0.03 μg L−1), which makes it suitable for determination of PCP in water samples.
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11.
Studies of dissociative reduction processes of electrochromic WO3−x films were conducted to: (i) evaluate their utility for electroetching and (ii) determine their fundamental mechanistic features
to reduce or eliminate their occurrence in normal optical switching and modulation operation of WO3−x films. We have found that while the small intercalating cations stabilize WO3−x structure, the large nonintercalating surfactant cations (Et4N+, CtMe3N+) contribute to the dissociative reduction. While these cations do not affect WO3−x structure of anodically protected films (E > 0.2 V), they cause surface lattice polarization on electron injection to the conduction band of WO3−x at lower electrode potentials, in the absence of intercalating cations. We have found that this process is limited to the
surface and no structural damage occurs to the underlying film. The mechanistic aspects of the process have been discussed
on the basis of experimental voltammetric and electrochemical quartz crystal nanogravimetric (EQCN) measurements and ab initio quantum mechanical calculations.
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12.
The triplet excited state properties and photosensitization mechanisms of indigo were investigated based on density functional
theory calculations. The solvent effects on the photosensitization mechanisms of indigo have also been considered. The thermodynamic
feasibility of the possible 1O2 and O2·−-photogeneration pathways by triplet excited state indigo in different solvents was explored, in order to gain some deeper
insights into the photosensitization characters of the dye.
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13.
Aleksandra Prichodko Kristina Jonusaite Vida Vickackaite 《Central European Journal of Chemistry》2009,7(3):285-290
A hollow fibre liquid phase microextraction for gas chromatographic determination of some p-hydroxybenzoic acid esters has
been developed. Chlorobenzene containing tetradecane as internal standard was used for the extraction. Optimized extraction
was carried out at room temperature for 40 min in the presence of 0.4 g mL−1 NaCl in the sample solution. Calibration was linear up to 30 mg L−1. Correlation coefficients were 0.996–0.998. Enrichment factors were 21, 95 and 154, and detection limits were 0.20, 0.03
and 0.01 μg mL−1 for methylparaben, ethylparaben and propylparaben, respectively. Reproducibility was acceptable with relative standard deviations
up to 11.7%. The technique was tested for water and urine analysis.
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14.
Joanna Kurczewska Radosław Pankiewicz Grzegorz Schroeder 《Central European Journal of Chemistry》2012,10(5):1452-1458
Silica surface was modified with quaternary ammonium salts to give three matrices of different chain length. The synthesized supports were characterized by elemental analysis and infrared spectroscopy, as well as scanning electron microscopy and semi-empirical parametric method 5. Their exchange capacities for ClO4 −, F−, NO3 − and CH3COO− ions were investigated by conductometric titration. The amount of exchanged chloride ions from the matrix was studied for different initial anions concentration. The functionalized silica gel showed very good ability of perchlorate ions exchange from the water solution in room temperature. The anion-exchange properties were also studied in comparison to different number of reactive sites in the matrices. The increased number of chloride at the silica surface took effect on increased ability of ClO4 − anion exchange 相似文献
15.
Jinzhang Gao Jing Liu Jie Ren Xiuli Niu Yingying Zhang Wu Yang 《Central European Journal of Chemistry》2009,7(3):298-302
This paper described the determination of p-nitroaniline in a double organic substrate oscillating system of tartrate-acetone-Mn2+-KBrO3-H2SO4. Under the optimum conditions, temperature was chosen as a control parameter to design the bifurcation point and proposed
a convenient method for determination of p-nitroaniline. Results showed that the system consisting of 3.5 mL 0.06 mol L−1 tartrate, 4.0 mL 0.7 mol L−1 H2SO4, 1.5 mL 1.5×10−4 mol L−1 MnSO4, 4.0 mL 0.4 mol L−1 acetone and 7.0 mL 0.05 mol L−1 KBrO3 was very sensitive to the surrounding at 33.5°C. A good linear relationship between the potential difference and the negative
logarithm concentration of p-nitroaniline was obtained to be in the range of 2.50×10−7∼3.75×10−5 mol L−1 with a lower detection limit of 2.50×10−8 mol L−1.
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16.
Oztekin Algul Asiye Meric Serpil Polat N. Didem Yuksek Mehmet S. Serin 《Central European Journal of Chemistry》2009,7(3):337-342
Comparative studies were performed on a series of 2,4-di and 2,3,4-trisubstituted benzimidazo[1,2-a]pyrimidines, which were
synthesized with conventional and microwave heating methods. In microwave irradiation method, approximately, 95–97.5% of the
reaction time was increased and 1–45% yield increase was obtained. All compounds were able to inhibit the growth of the screened
microorganisms in vitro with MIC values between 3.9–250 μg mL−1. The highest activity was expressed by compound IIId (2,4-diphenyl-benzo[4,5]imidazo[1,2-a] pyrimidine), which has the MIC
value of 3.9 μg mL−1 and 31.2 μg mL-1 for Penicillium natatum ATCC 24791 and E. faecalis ATCC 29212, respectively.
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17.
Dmitriy A. Golovko Virender K. Sharma Olga. V. Pavlova Elena. A. Belyanovskaya Igor. D. Golovko Victoria. I. Suprunovich Radek Zboril 《Central European Journal of Chemistry》2011,9(5):808-812
A new amperometric titration method was developed for quantitative determination of ferrate(VI) (FeVIO4
2−) in the 7.06×10−5−5.73×10−3 M concentration range. Chromium(III) hydroxide solution was used as the titrant. The diffusion current (Id) had a linear
relationship with the concentration of ferrate(VI) and slopes were dependent on the concentration of NaOH. The amperometric
titration could detect a lower concentration of ferrate(VI) than could potentiometric and colorimetric titrations. The method
was applied successfully to determine concentrations of ferrate(VI), generated electrochemically, in strong alkaline solutions.
相似文献
18.
Abdulhadi Baykal Hüseyin Kavas Zehra Durmu? Mine Demir Sinan Kazan Ramazan Topkaya Muhammet S. Toprak 《Central European Journal of Chemistry》2010,8(3):633-638
We report on the synthesis of Mn3O4 nanoparticles (NPs) using a novel sonochemical method without requiring any pH adjustment. Synthesized material was identified
as tetragonal hausmannite crystal structure model of Mn3O4 from XRD analysis. Crystallite size was estimated from x-ray line profile fitting to be 17±5 nm. FTIR analysis revealed stretching
vibrations of metal ions in tetrahedral and octahedral coordination confirming the crystal structure. TEM analysis revealed
a dominantly cubic morphology of NPs with an average size of ∼20 nm. Magnetic evaluation revealed a blocking temperature,
T
B of 40 K above which the material behaves paramagnetic. Asymmetric coercive field is attributed to the interaction between
ferromagnetic Mn3O4 and antiferromagnetic Mn oxide at the surface of nanoparticles.
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19.
Jinzhang Gao Yingying Zhang Jie Ren Ming Li Wu Yang 《Central European Journal of Chemistry》2010,8(3):602-606
A sensitive and convenient method for the determination of trace europium ions using an oscillating chemical reaction involving
Ce(IV) - KBrO3 - acetone - oxalic acid - H2SO4 was proposed. The results indicated that the changes in oscillating period (T) was linearly proportional to the negative
logarithmic concentration of Eu3+ (-log C) in the range of 1.41 × 10−8 ˜ 1.41 × 10−4 mol L−1 (r = 0.9982) with a detection limit of 1.04 × 10−9 mol L−1. The recoveries were limited to the range of 99.5% to 100.8%. Under the same conditions, other rare earth ions did not interfere
with the determination of Eu3+. In addition, a perturbation mechanism was also discussed briefly.
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20.
Azza A. Shoukry Mohamed M. Shoukry Mohamed N. Hafez 《Central European Journal of Chemistry》2010,8(4):797-805
The kinetics of base hydrolysis of glycine, histidine, and methionine methyl esters in the presence of [Pd(pip)(H2O)2]2+ complex, where pip is piperazine, is studied in aqueous solutions, at T = 25°C, and I = 0.1 mol dm−3. The rate of ester hydrolysis for glycine methyl ester is studied at different temperature and dioxane/water solutions of
different compositions. The kinetic data are fit under the assumption that the hydrolysis proceeds in one step. The activation
parameters for the base hydrolysis of the complexes are evaluated
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