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1.
The relative enthalpies of melts in the system KF - K2NbF7 were measured by drop-calorimetry at the temperatures 1058, 1140 and 1208 K as a function of composition. Heat capacities
of melted mixtures and enthalpies of mixing were determined using the experimental data. The molar heat capacity of melts
diverges slightly from additivity. The molar enthalpy of mixing of melts shows small negative deviation from ideality which
decreases with decreasing temperature. The thermal effect at mixing was assigned predominantly to association reactions producing
more complex fluoroniobate anions.
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2.
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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3.
Nadezhda Rangelova Lachezar Radev Sanchi Nenkova Isabel M. Miranda Salvado Maria H. Vas Fernandes Michael Herzog 《Central European Journal of Chemistry》2011,9(1):112-118
Methylcellulose (MC) / SiO2 organic / inorganic hybrid materials have been prepared from MC and methyltriethoxysilane or ethyltrimethoxysilane, and characterized
by XRD, FTIR and AFM. XRD showed peak shifts. FTIR shows intermolecular hydrogen bonding between MC and SiO2. AFM depicts surface roughness which depends on the silica precursor and MC content.
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4.
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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5.
Raúl Terrazas Reza Carlos A. Martínez Pérez Claudia A. Rodríguez González Humberto Monreal Romero Perla E. García Casillas 《Central European Journal of Chemistry》2010,8(5):1041-1046
In this work, the synthesis of magnetite nanoparticles by two variant chemical coprecipitation methods that involve reflux
and aging conditions was investigated. The influence of the synthesis conditions on particle size, morphology, magnetic properties
and protein adsorption were studied. The synthesized magnetite nanoparticles showed a spherical shape with an average particle
size directly influenced by the synthesis technique. Particles of average size 27 nm and 200 nm were obtained. When the coprecipitation
method was used without reflux and aging, the smallest particles were obtained. Magnetite nanoparticles obtained from both
methods exhibited a superparamagnetic behavior and their saturation magnetization was particle size dependent. Values of 67
and 78 emu g−1 were obtained for the 27 nm and 200 nm magnetite particles, respectively. The nanoparticles were coated with silica, aminosilane,
and silica-aminosilane shell. The influence of the coating on protein absorption was studied using Bovine Serum Albumin (BSA)
protein.
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6.
Alexander O. Terent’ev Igor B. Krylov Vera A. Vil’ Zhanna Yu. Pastukhova Sergey A. Fastov Gennady I. Nikishin 《Central European Journal of Chemistry》2012,10(2):360-367
It was found that oximes undergo deoximation in the presence of the H2O2aq-HBraq system to form ketones and bromo ketones. This reaction provided the basis for the synthesis of dibromo ketones in yields
varying from 40% to 94%. This method is environmentally friendly, sustainable, and easy to perform. The results of this investigation
extend the potential of the use of oximes for the protection of carbonyl group, thus offering the ability to perform not only
conventional deoximation but also the subsequent bromination of ketones. The reaction is easily scaled up and dibromo ketones
can be prepared in gram amounts.
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7.
8.
Yuriy Tyvanchuk Volodymyr Svitlyk Yaroslav Kalychak 《Central European Journal of Chemistry》2012,10(2):354-359
The polycrystalline Ho4Ni11In20 was obtained by arc-melting of the elements. The subsequent high temperature procedure was used for single crystal growth. Crystal structure of the compound was investigated by X-ray single crystal method: U4Ni11Ga20 type, C 2/m, a = 22.4528(17), b = 4.2947(3), c = 16.5587(13) Å, β = 124.591(5)°, R1 = 0.0276, wR2 = 0.0493 for 1989 independent reflections with [I>2σ(I)].The structure is composed of three-dimensional network from Ni and In atoms in which Ho atoms fill distorted pentagonal channels. Open image in new window 相似文献
9.
Optimum conditions for synthesizing monoclinic and triclinic Mg2B2O5 compounds by high-temperature solid-state reactions were investigated. Mixtures composed of boric acid and magnesium oxide
at MgO:B2O3 mole ratios of 1:0.25, 1:0.5 and 1:1.5 were heated for 1 hour at temperatures between 600–1050°C and the formed phases were
identified by XRD analysis. Monoclinic Mg2B2O5 was formed by heating at 850°C for 4 hours together with minimum amounts of triclinic Mg2B2O5, while triclinic Mg2B2O5 was formed as a single phase at 1050°C for the same reaction time. The products obtained at optimum conditions were subjected
to a series of tests to determine their chemical compositions, particle size distributions, surface area values, IR spectra
and TG/DTA patterns.
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10.
Rayna Bryaskova Nelly Georgieva Dimitar Peshev 《Central European Journal of Chemistry》2010,8(5):1053-1058
Polyvinyl alcohol (PVA) and tetraethoxysilane (TEOS) hybrid materials were prepared by sol-gel methods and tested as matrices
for immobilization of Trichosporon cutaneum R57, capable of removing cadmium and copper ions from aqueous solutions. A kinetic model was applied and the effects of matrix
TEOS content on the copper and cadmium uptake equilibria and rate constants were investigated.
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11.
Renata Farkas Mercedesz Törincsi Pal Kolonits Jenö Fekete Oscar Jimenez Alonso Lajos Novak 《Central European Journal of Chemistry》2010,8(2):300-307
During the diazo-coupling reaction, nucleophilic displacement of a nitro group was also observed. This was the main reaction
(1→7) when the starting amine bore either a chlorine or methoxy group at the para position (1b–c). The newly prepared compounds (7) might serve as convenient building blocks in synthesis of some heterocycles.
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12.
Diamond D5 is the name proposed by Diudea for hyper-diamonds having their rings mostly pentagonal. Within D5, in crystallographic terms: the mtn structure, known in clathrates of type II, several substructures can be defined. In the present work, the structural stability
of such intermediates/fragments appearing in the construction/destruction of D5 net was investigated using molecular dynamics simulation. Calculations were performed using an empirical many-body potential
energy function for hydrocarbons. It has been found that, at normal temperature, the hexagonal hyper-rings are more stable
while at higher temperature, the pentagonal ones are relatively more resistant against heat treatment.
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13.
Radina Kralchevska Maria Milanova Petya Kovacheva Jovo Kolev Georgi Avdeev Dimitar Todorovsky 《Central European Journal of Chemistry》2011,9(6):1027-1038
Microcomposites consisting of TiO2 (or Ce-doped TiO2) and ThO2 (0.5–2% of the TiO2 mass) are produced by sol-gel synthesis of TiO2 in presence of ThO2. X-ray diffraction study reveals the effects of ThO2 (compared to the ThO2-free TiO2, obtained by the same method) on the anatase interplanar distances, crystallites size and phase composition. The photocatalytic
tests in presence of the composites under UV irradiation reveal an increase of the Malachite Green degradation rate constant.
The effect depends on the Th relative content, temperature of annealing of the catalyst and addition of other doping agent.
The highest photocatalytic activity is observed for TiO2 obtained at 550°C and containing 1% ThO2. The composite exhibits activity in dark, also. The presence of Ce4+ ions is not an obligatory requirement for the realization of the ThO2 effect. The reported results suggest that the radioactivity of the Th and/or its decay products is one of the main factors
responsible for the increased photocatalytic activity of TiO2.
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14.
Ramin Ghorbani-Vaghei Seyedeh Mina Malaekehpour 《Central European Journal of Chemistry》2010,8(5):1086-1089
N,N,N,’N’-Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoalkyl
naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.
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15.
Bo?ena Bittner Ewa Janus Eugeniusz Milchert 《Central European Journal of Chemistry》2011,9(1):192-198
A comparative study of the Diels-Alder reactions between cyclopentadiene (1) and dienophiles (2 a–c) in N-hexylpyridinium
bis(trifluoromethylsulfonyl)imide in a temperature range of 20–45°C is reported. The reaction rate constants and activation
energies were calculated. Moreover, the catalytic systems based on N-hexylpyridinium bis(trifluoromethylsulfonyl)imide and
Lewis acids were tested as a reaction media to perform the Diels-Alder reaction. Yb, Y, Mg, Zn triflates and chlorides (0.005
to 0.1 mmol) were used as catalysts. The recycling of catalytic system consisted of YCl3 and ionic liquid was performed.
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16.
Federico Cozzi Gianpiero Adami Pierluigi Barbieri Edoardo Reisenhofer Pietro Apostoli Massimo Bovenzi 《Central European Journal of Chemistry》2010,8(5):1014-1026
PM10 samples were collected during winter and summer seasons at two different sites in the area of Trieste (Italy). The content
of As, Cd, Cr, Mn, Ni, Pb and V in the PM10 samples was determined by inductively coupled plasma-mass spectrometry, with the purpose of evaluating the relevance of PM10 inhalation as a route of human exposure to these elements. The results showed that the ambient air concentration of the aforementioned
elements were below the limits or target values for both sites and season. Site and season-specific correlation analysis was
conducted for the identification of metals with similar origin: very good correlation for the couple Ni-V was found in both
sites and seasons, showing the influence of combustion of heavy oils in PM10 composition. The inter-site and seasonal variability of both PM10 and metal concentrations were examined. A stronger impact by the vehicular traffic on the PM10 and metal concentrations was found for the urban site in both seasons. Because of the great importance of the “Bora” wind
on the local climate, variability of PM10 and toxic elements concentration with wind were analysed, allowing determination of the effect of wind on dilution of the
pollutants for the urban site during both seasons.
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17.
Ali Hassanzadeh Behrang Moazzez Hossein Haghgooie Mohsen Nasseri Mir Maqsood Golzan Hassan Sedghi 《Central European Journal of Chemistry》2008,6(4):651-656
A simple sol-gel process is proposed for synthesizing SnO2 nanopowders utilizing normal propanol and isopropanol mixture instead of just using normal alcohols such as ethanol, propanol
or butanol for Sol preparation. No surfactant was used in this Sol preparation process. The structure of sol is studied by
FT-IR-ATR technique. On altering propanol to isopropanol ratio, three different nanopowders were obtained. X-ray powder diffraction,
high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction pattern (SAED) and BET techniques
were used to characterize prepared powders. Results show that smaller grain size was obtained via altering alcohols ratio.
In addition, Merck commercial SnO2 powder was also used as a reference material for comparing purposes; because it has nanometer scale (ca. 60 nm). HRTEM images
show that obtained nanopowders were polycrystalline and their average diameters fall into the range of 6–80 nm. Finally, the
effect of alkoxide ligand size through sol-gel synthesis on product particle size is discussed.
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18.
Oleksiy V. Grygorovych Oleksiy V. Nevskii Sofia M. Moskalenko Vasyl G. Pivovarenko Andrey O. Doroshenko 《Central European Journal of Chemistry》2010,8(4):766-782
Protolytic interactions in the series of prospective fluorescent ratiometric wide-range pH indicators — structurally rigid
analogs of 2,6-distyrylpyridine — (3E,5E)-3,5-dibenzylidene-8-phenyl-1,2,3,5,6,7-hexahydrodicyclopentano[b,e]pyridine — were
investigated. The pyridine nitrogen atom basicity in these compounds is significantly lower in comparison with that of unsubstituted
heterocycle and 2,6-distyrylpyridine. The photochemical E→Z photoisomerization and the side benzene rings substituents influence
on the acid-base equilibria were studied. The complex multi-stage mechanism of the acid-base interactions of the polysubstituted
compounds was elucidated. The most significant spectral effects were typical to the N,N-dialkylamino substituted compounds
of the investigated series. The widest pH sensitivity interval covering nearly the full range of 0–14 units was demonstrated
for compounds with both proton donor and proton acceptor substituents.
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19.
Karlis Pajuste Aiva Plotniece Kintija Kore Liva Intenberga Brigita Cekavicus Dainis Kaldre Gunars Duburs Arkadij Sobolev 《Central European Journal of Chemistry》2011,9(1):143-148
The synthesis of cationic amphiphilic 1,4-dihydropyridine derivative, potential gene delivery agent is achieved via an efficient multi-step sequence. The key step of this approach is a two-component Hantzsch type cyclisation of 3-oxo-2-[1-phenylmethylidene]-butyric
acid dodecyl ester and 3-amino-but-2-enoic acid dodecyl ester utilising bis(2-hydroxyethyl)ether as a solvent and 1-butyl-4-methylpyridinium
chloride as a catalyst. The 1,4-dihydropyridine derivative with long alkyl ester chains at positions 3 and 5 of the 1,4-DHP
ring — 3,5-bis(dodecyloxycarbonyl)-2,6-dimethyl-4-phenyl-1,4-dihydropyridine was obtained in substantially higher yield with
respect to classical Hantzsch synthesis. Bromination of this compound followed by nucleophilic substitution of bromine with
pyridine gave the desired cationic amphiphilic 1,4-dihydropyridine.
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20.
Thermodynamics and kinetics of adsorption of congo red (CR) on cellulose are studied at 308–328 K. In the used concentration
range of CR, interaction of CR with cellulose is exothermic and CR molecules adsorb chemically on cellulose surface. The effects
of contact time, temperature and initial concentration of CR on kinetics of its adsorption on cellulose were investigated.
The process proceeds according to the pseudo-second-order equation. Initial adsorption rate of adsorption is first-order in
CR and the intraparticle diffusion of CR molecules within cellulose is identified as the main rate-limiting step.
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