共查询到20条相似文献,搜索用时 31 毫秒
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.
Phase equilibria established in the PbO - BiVO4 system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed
using DTA and XRD.
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3.
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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4.
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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5.
Silica surface was modified with phenylboronic acid derivatives. The structures of the functionalized supports were characterized
by FT-IR spectroscopy, 13C CP/MAS NMR spectrometry, elemental and thermogravimetric analysis. The solid supports were effectively applied as artificial
receptors for sugars in aqueous solutions. Alizarin Red S. (ARS) was used to detect colour change upon carbohydrate (sugar)
binding. The association constants of the supports studied-ARS complex and the functionalized silica-sugar (glucose) complex
were calculated. The parameters obtained were comparable with those for the phenylboronic acids used for the silica gel modification.
The competitive binding of the functionalized silica surface with ARS and sugar were studied by UV/VIS measurements.
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6.
Zehra Durmus Hüseyin Kavas Abdulhadi Baykal Muhammet S. Toprak 《Central European Journal of Chemistry》2009,7(3):555-559
A novel environmental friendly, room temperature route using an ionic liquid 1-n-butyl-3-methylimidazolium hydroxide ([BMIM]OH)
for the synthesis of Mn3O4 nanoparticles is presented. The product was characterized using Fourier transform infrared spectroscopy, X-ray powder diffraction,
and transmission electron microscopy. Phase purity was confirmed by XRD, and X-ray line profile fitting determined a crystallite
size of 42 ± 11 nm. TEM analysis revealed various morphologies. EPR measurements have indicated the existence of long-range
interactions, due to the wide range of particle sizes and morphologies observed.
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7.
A novel hydroxyamino phosphane was synthesised through the reaction of 2-imidazolidinone with ClPPh2 and subsequently reaction
of the resulting bisphosphino derivative with the Grignard reagent BrMgC5H11. The interaction of the pentyl substituent with one of the two phosphino groups and the structure in solution is shown by
multinuclear NMR-spectroscopy..
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8.
Ghasem Rezanejade Bardajee Farnaz Jafarpour Hamid Samareh Afsari 《Central European Journal of Chemistry》2010,8(2):370-374
In this report, a rapid, efficient and environmental friendly synthesis of 3-carboxycoumarins under ultrasound irradiation
in water media is described. The Knoevenagel condensation of Meldrum’s acid with substituted benzaldehydes in the presence
of zirconium oxide chloride (ZrOCl2·8H2O) and ultrasonic irradiation in water gave the corresponding 3-carboxycoumarins in good to excellent yields.
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9.
Maria M. Milanova Dimitar S. Todorovsky Christo C. Balarew Natalia L. Minkova Katya I. Ivanova 《Central European Journal of Chemistry》2007,5(1):13-19
The cocrystallization of Ce2(SO4)3 and La2(SO4)3 is studied in aqueous and H2SO4 (150 g/dm3) solutions at 25 °C and 64 °C. The effect of the formation of inner sphere sulfate complexes of the type LnSO
4
+
in determining the composition of the equilibrium phases is revealed.
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10.
The reaction mechanism between AlX and HX (X = Br, Cl, and F) have been characterized in detail using DFT as well as the ab initio method. The reaction yielding AlX3 and molecular hydrogen was calculated to be highly exothermic. The present calculations also show that the possible routes
to the trihalides species start more favorable with the primary insertion product AlX2H than with the biadduct AlX(HX)2 one.
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11.
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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12.
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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13.
In the present paper, an off-line preconcentration procedure for the determination of cadmium and lead by flame atomic absorption
spectrometry (FAAS) is proposed. Polyurethane foam (PUF) functionalized with o-aminophenol (o-AP) followed by Pyrazolone (Pyr)
packed in a minicolumn was used as a sorbent material. The metals were retained on the modified PUF, from which it could be
eluted and effectively preconcentrated. The detection limits were 0.072 and 0.016 μg L−1 for Pb and Cd respectively. Enrichment factors were 250 and 319 for lead and cadmium respectively. The procedure has been
applied successfully to metal determination in water samples, fish liver and reference material.
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14.
Lachezar Radev Vladimir Hristov Irena Michailova Bisserka Samuneva 《Central European Journal of Chemistry》2009,7(3):317-321
In this work we present experimental results about synthesis, structure evolution and in vitro bioactivity of new calcium phosphate silicate/wollastonite (CPS/W) glass-ceramics. The samples obtained were synthesized
via polystep sol-gel process with different Ca/P+Si molar ratio (R). The structure of the materials obtained was studied by
XRD, FTIR spectroscopy and SEM. XRD showed the presence of Ca15(PO4)2(SiO4)6, β-CaSiO3 and α-CaSiO3 for the sample with R=1.89 after thermal treatment at 1200°C/2h. The XRD results are in good agreement with FTIR analysis.
SEM denotes that apatite formation can be observed after soaking in simulated body fluid (SBF).
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15.
Oksana Makota Yuriy Trach Roman Leboda Jadwiga Skubiszewska-Zięba 《Central European Journal of Chemistry》2009,7(4):731-738
The catalytic effect of VSi2 on initial stages of the liquid-phase oxidation of cyclooctene by molecular oxygen was studied. The vanadium disilicide influences
on the oxidation process in the presence of hydroperoxide. VSi2 takes part in a radical formation stage by catalysis of hydroperoxide decomposition reaction. The catalyst was investigated
before and after reaction using FTIR spectroscopy. From the data obtained, the kinetic model of the catalytic oxidation process
was proposed and the equation for the reaction rate was derived. The equation has described all observed dependences of reaction
rate on the concentration of reactants and content of catalyst.
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16.
Y. M. Al-Angari M. W. Kadi I. M. Ismail Mohamed. A. Gabal 《Central European Journal of Chemistry》2010,8(2):331-340
In this project, nanocrystalline SnO2 powders were successfully prepared by (a) citrate sol-gel and (b) direct precipitation methods. Powders were characterized
using thermal analysis techniques (DTA-TG-DSC), X-ray powder Diffraction (XRD), surface area (BET) and electrical conductivity
measurements. XRD patterns showed the presence of the cassiterite structure. SnO2 particles, prepared through sol-gel method exhibit crystallite sizes in the range from 3.1 to 22.3 nm when the gel is heat
treated at different temperatures up to 900°C. SnO2 nanocrystallites prepared by the precipitation method are comparatively larger in size. The higher specific surface area
was obtained for the powder prepared using sol-gel method and the obtained average grain size (d) is relatively large compared with that of the average crystallite size. The powders show a semiconducting behavior with
increasing temperature. The higher conductivity obtained for SnO2 prepared by sol-gel method can be attributed to their smaller average crystallite size. XRD of alumina doped powder exhibits
finer particles than pure SnO2. TEM images showed that the particles are spherical in shape and consist of a core of SnO2 surrounded by a coating of alumina. The calculated surface area was found to decrease with temperature increases. Due to
the effective role of Al2O3 additive as a grain growth inhibitor for the matrix grains, the observed surface area for the coated materials are predominantly
higher than for the uncoated materials.
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17.
Petr Bělina Petra Šulcová Miroslav Trojan Pavel Mazurek 《Central European Journal of Chemistry》2007,5(3):706-714
New binary lanthanum-aluminum triphosphates were synthesized by thermal-condensation method from H3PO4, La2O3 and Al(OH)3. These pigments could be potentially used as special inorganic pigments; their corrosion-inhibition properties were widely
studied. Synthesis conditions were determined on the basis of DTA and TG measurements. The products were also characterized
by X-ray diffraction analysis. Physical properties — density by pycnometric method, particle size distribution, oil number
and critical pigment volume concentration (CPVC), pH and specific conductivity of their aqueous extracts were also determined.
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18.
Lakshman S. Gadekar Shivshankar R. Mane Santosh S. Katkar Balasaheb R. Arbad Machhindra K. Lande 《Central European Journal of Chemistry》2009,7(3):550-554
Natural scolecite has been found as an effective catalyst for the one-pot synthesis of 2,4,5-triarylimidazole derivatives
via a three component reaction using benzil or benzoin, aldehydes and ammonium acetate. This method provides several advantages
such as being environmentally benign, reusable, possessing high yields with increased variations of the substituents in the
product and preparative simplicity.
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19.
Gheorghe Roman 《Central European Journal of Chemistry》2012,10(5):1516-1526
Benzimidazole, benzimidazoles diversely substituted at position 2, and 5,6-dimethylbenzimidazole have been alkylated at N
1 with ketonic Mannich bases derived from acetophenones, acetylnaphthalenes, 2-acetylthiophene and 1-tetralone to afford a
series of novel 1-(3-oxopropyl)benzimidazoles. The reduction of these transamination products with NaBH4 in methanol produced the corresponding 1-(3-hydroxypropyl)benzimidazoles in excellent yields.
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20.
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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