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1.
Abdülhadi Baykal Yüksel Köseoğlu Mehmet Şenel 《Central European Journal of Chemistry》2007,5(1):169-176
Heating hydrous manganese (II) hydroxide gel at 85 °C for 12 hours produces Mn3O4 nanoparticles. They were characterized by X-ray powder diffraction (XRD) and infrared spectroscopy (FTIR). The particle size
estimated from the SEM and X-ray peak broadening is approximately 32 nm, showing them to be nanocrystalline. EPR measurements
confirm a typical Mn2+signal with a highly resolved hyperfine structure.
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2.
Chockalingam Karunakaran Premkumar Anilkumar 《Central European Journal of Chemistry》2009,7(3):519-523
Oxidation of iodide ion from an air-saturated solution under natural sunlight (900±50 W m−2) on the surfaces of TiO2, ZnO, Fe2O3, MoO3 and CeO2 enhances by 6 to 12-fold on application of a cathodic bias of −0.2 to −0.3 V (vs NHE) to the semiconductors; light, the semiconductor and dissolved oxygen are essential for iodine generation. The semiconductors
under an anodic bias of +0.2 to +0.3 V (vs NHE) fail to oxidize iodide ion from air-saturated solution under sunlight. Under cathodic bias, semiconductor mixtures like
TiO2-ZnO, TiO2-Fe2O3 and ZnO-Fe2O3 show enhanced photocatalytic activity, indicating improved charge separation in oxide mixtures. The mechanism of photocatalysis
under cathodic bias is discussed.
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3.
Relative enthalpies for low-and high-temperature modifications of Na3FeF6 and for the Na3FeF6 melt have been measured by drop calorimetry in the temperature range 723–1318 K. Enthalpy of modification transition at 920
K, δtrans
H(Na3FeF6, 920 K) = (19 ± 3) kJ mol−1 and enthalpy of fusion at the temperature of fusion 1255 K, δfusH(Na3FeF6, 1255 K) = (89 ± 3) kJ mol−1 have been determined from the experimental data. Following heat capacities were obtained for the crystalline phases and for
the melt, respectively: C
p(Na3FeF6, cr, α) = (294 ± 14) J (mol K)−1, for 723 = T/K ≤ 920, C
p(Na3FeF6, cr, β) = (300 ± 11) J (mol K)−1 for 920 ≤ T/K = 1233 and C
p(Na3FeF6, melt) = (275 ± 22) J (mol K)−1 for 1258 ≤ T/K ≤ 1318. The obtained enthalpies indicate that melting of Na3FeF6 proceeds through a continuous series of temperature dependent equilibrium states, likely associated with the production of
a solid solution.
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4.
Various compositions (1−x)BaTiO3 + xPbF2 + xLiF were prepared, shaped to pellets then sintered at 900°C for 2 h in gold sealed tubes. The purity and the symmetry of the
obtained samples were checked by X-ray diffraction. A new solid solution with Ba1−x
Pb
x
(Ti1−x
Li
x
) O3−3x
F3x formula occurs in the composition range 0 ≤ x ≤ 0.20. SEM observations were performed on polished and fractured ceramics. The complex permittivity was measured as a function
of temperature (−120°C ≤ T ≤ 250°C) and frequency (50 Hz ≤ f ≤ 4 × 107 Hz). The dielectric performances are the best for ceramic Ba0.97Pb0.03(Ti0.97Li0.03)O2.91F0.09. The real component ε′, exhibits a maximum of approximately 7500 at the ferroelectric Curie temperature T
C
≈ -18°C, the dielectric losses tan δ value being 0.012. At room temperature, the relaxation frequency f
r
is around 40 MHz for this ceramic. This novel ferroelectric oxifluoride is a promising material for applications, in particular
in the field of Z5U multilayer capacitors.
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5.
Ladislav Kosa Iveta Macková Ivo Proks Ondrej Pritula Ľubomír Smrčok Miroslav Boča Håkan Rundlőf 《Central European Journal of Chemistry》2008,6(1):27-32
Three thermal effects on heating/cooling of K2TaF7 in the temperature interval of 680–800°C were investigated by the DSC method. The values determined for the enthalpy change
of the individual processes are: ΔtransIIHm(K2TaF7; 703°C) = 1.7(2) kJ mol−1, ΔtransIHm(K2TaF7; 746°C) = 19(1) kJ mol−1 and ΔtransIIIHm(K2TaF7; 771°C) = 13(1) kJ mol−1. The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K2TaF7 and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654–794°C.
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6.
Maria Kurzawa Monika Bosacka Elzbieta Filipek Izabella Rychlowska-Himmel 《Central European Journal of Chemistry》2009,7(2):179-183
In the work presented here, the way of obtaining the phase with general formula Co3+1.5xCr2–x(VO4)4 (0 ≤ × < 0.4) is demonstrated. A new phase is detected in CrVO4 - Co3V2O8 that is formed in one of the intersection of the ternary CoO - V2O5 - Cr2O3 system. Monophasic Co3Cr2(VO4)4 (Co3+1.5xCr2−x(VO4)4, where × = 0) was obtained from both a mixture comprising CrVO4 and Co3V2O8 as well as from the mixture of CoV2O6 with CoCr2O4. The Co3+1.5xCr2−x(VO4)4 is isotypic with the those demonstrating the lyonsite-type structure. The temperature of melting for the new compound was
established using the DTA methods.
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7.
Jinzhang Gao Haifeng Fan Wu Yang Xiangli Sun Chongyang Li Xuefeng Mao Jie Wang Rong Wang Zhengping Jia 《Central European Journal of Chemistry》2008,6(4):617-621
A rapid, simple and reliable capillary electrophoresis method for the separation and quantitation of inorganic cations with
indirect UV detection at 214 nm was developed. The electrolyte was: 12 mM imidazole as background absorbance provider; 5 mM
malic acid and 1.0 mM 18-crown-6 ether as complexing agents; and 20% D2O (v/v) to improve ion mobility. The pH was 4.25. The applied voltage was 22 kV at 22°C. Nine ions were completely separated
and determined with correlation coefficients of 0.9979-0.9992. The relative standard deviations (RSD) were less than 0.5%
for migration time and less than 5.2% for peak area (n=8). The detection limits (S/N=3) were from 0.08 mg L−1 (for Na+) to 0.51 mg L−1 (for Cu2+). To assess the reliability atomic absorption (AA) was also used to determine the same samples. Satisfactory results were
obtained for real samples of jasmine tea drink and coconut milk.
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8.
Jinzhang Gao Dongyu Lv Wu Yang Xiaoxia Wei Jie Qu Hua Chen Hongxia Dai Jie Ren 《Central European Journal of Chemistry》2007,5(2):581-589
A convenient and sensitive method for determination of sulfanilamide (SNA) was described based on the Mn(II)-catalyzed oscillating
chemical reaction. Under optimum conditions, a linear relationship existed between the changes of oscillating period or amplitude
and the negative of logarithm of SNA concentration in the range of 4.27 × 10−8 mol ·L−1 ∼ 7.41 × 10−6 mol ·L−1 (RSD, 0.85%) and 9.33 × 10−8 mol ·L−1 ∼ 3.02 × 10−6 mol ·L−1 (RSD, 1.08%), respectively. The lower limit of detection was found to be 2.69 × 10−8 mol ·L−1 and 6.03 × 10−8 mol ·L−1, respectively.
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9.
Tevhide Özkaya Abdulhadi Baykal Muhammet Sadaka Toprak 《Central European Journal of Chemistry》2008,6(3):465-469
Water-soluble Mn3O4 nanocrystals have been prepared through thermal decomposition in a high temperature boiling solvent, 2-pyrrolidone. The final
product was characterized with XRD, SEM, TEM, FTIR and Zeta Potential measurements. Average crystallite size was calculated
as ∼15 nm using XRD peak broadening. TEM analysis revealed spherical nanoparticles with an average diameter of 14±0.4 nm.
FTIR analysis indicated that 2-pyrrolidone coordinates with the Mn3O4 nanocrystals only via O from the carbonyl group, thus confining their growth and protecting their surfaces from interaction
with neighboring particles.
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10.
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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11.
Ksenija R. Kumrić Tatjana M. Trtić-Petrović Ljubiša M. Ignjatović Jožef J. Čomor 《Central European Journal of Chemistry》2008,6(1):65-69
Lutetium has been determined by differential pulse anodic stripping voltammetry in an acidic solution containing Zn-EDTA.
Lutetium (III) ions liberated zinc (II), which was preconcentrated on a hanging mercury drop electrode and stripped anodically,
resulting in peak current linearly dependent on lutetium (III) concentration. Less than 0.4 ng mL−1 lutetium could be detected after a 2 min deposition.
相似文献
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.
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).
相似文献
14.
Mehrorang Ghaedi Ardeshir Shokrollahi Khodabakhsh Niknam Ebrahim Niknam Mustafa Soylak 《Central European Journal of Chemistry》2009,7(1):148-154
A cloud point extraction procedure for the preconcentration of copper, nickel, iron and zinc ions in various samples has been
described. Analyte ions in aqueous phase are complexed with 3-((indolin-3-yl)(phenyl)methyl)indoline (IYPMI) and following
centrifugation quantitatively extracted to the aqueous phase rich in Triton X-114. The surfactant-rich phase was dissolved
in 2.0 mol L−1 HNO3 in methanol prior to metal content determination by flame atomic absorption spectrometry (FAAS). The effects of some parameters
including, the concentrations of IYPMI, Triton X-114 and HNO3, bath temperature, centrifuge rate and time were investigated on the recoveries of analyte ions. At optimum conditions, the
detection limits of (3 SDb m−1) of 1.6, 2.8, 2.1 and 1.1 ng mL−1 for Cu2+, Fe3+, Ni2+ and Zn2+ along with preconcentration factors of 30 and enrichment factor of 48, 39, 34 and 52 for Cu2+, Ni2+, Fe3+ and Zn2+ respectively, were obtained. The proposed cloud point extraction has been successfully applied for the determination of metal
ions in real samples with complicated matrix such as biological, soil and blood samples with high efficiency.
相似文献
15.
Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes 总被引:1,自引:0,他引:1
M. M. Ghoneim E. M. Mabrouk A. M. Hassanein M. A. El-Attar E. A. Hesham 《Central European Journal of Chemistry》2007,5(3):898-911
The electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson
universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry
and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single,
2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction
of the azomethine group-CH=N- to -CH2-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D
0) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested
to follow the sequence: H+, e−, e−, H+. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with
various divalent transition metal ions (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) were determined potentiometrically at room temperature.
相似文献
16.
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.
相似文献
17.
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.
相似文献
18.
Jaromíra Chýlková Renáta Šelešovská-Fadrná Jaroslava Machalíková 《Central European Journal of Chemistry》2007,5(2):479-495
The optimal process of pre-treatment and activation of gold rotating disc electrode (AuRDE) before voltammetric determination
of mercury is proposed. This treatment encompasses polishing of the electrode surface, electrochemical cycling, and activation.
This procedure both increases determination sensitivity as well as improves determination reproducibility. The detection limit
on the working electrode achieved using this approach amounted to 8.26·10−10 mol L−1for direct mercury determination in water solution (applying 200 s running accumulation). The procedure of the quantitative
mercury isolation from complicated sample matrix was developed as well. It provides better selectivity and significant increase
of sensitivity of mercury determination. In case of mercury isolation from one liter of water the detection limit is 6.23·10−11 mol L−1 (analyzing a greater sample volume the determined concentration could be lower).
相似文献
19.
The degradation efficiency of Th-doped TiO2 / TiO2 photocatalysts were investigated under UV and solar light illumination. The model compound chosen for the study was Oryzalin
(OZ). Doping of inner transition metal ion Th was intended to modify the electronic properties of TiO2. The Th-doped TiO2 were synthesized by incorporating 0.02, 0.04, 0.06, and 0.1 atom percentage of Th into the TiO2 lattice by solid-state reaction. The stochiometry of the prepared samples is Ti1−xThxO2, where ‘x’ is the percentage of Th. The samples were characterized by UV-Visible absorption, UV-Visible -Diffused reflectance
spectra, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX) and X-ray Diffraction (XRD). The pore
size and surface area of these samples were studied by Brunauer, Emmett and Teller (BET) adsorption method. It was found that
metal ion doping at various percentage compositions enables a large shift in the absorption band of the TiO2 towards visible light region. This is due to the formation of various mid band gaps at 2.84 eV, 2.804 eV, 2.66 eV, and 2.55
eV. The extent of degradation of the pesticide was followed by UV-Visible spectroscopy and GC-MS methods. Based on the spectral
analysis, the probable degradation reaction mechanism for OZ is proposed. These results indicate that Th-doped TiO2 with the modified electronic properties is a good catalyst under solar light irradiation. But these particles show marginal
variation in rates under UV-illumination. All the photodegradation reactions follow the first order kinetics.
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20.
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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