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1.
Polystyrene/silica, polystyrene–butylacrylate/silica, silylated polystyrene/silica, and silylated polystyrene–butylacrylate/silica hybrid composites were synthesized by the sol–gel method in tetrahydrofuran using HCl as catalyst and tetraethylorthosilicate as the silica precursor. The polymers were characterized by fourier transform infrared (FTIR), nuclear magnetic resonance, and gel permeation chromatography. The sol–gel mixtures were cast on glass plates and dried in air at 30°C for 72 h. The composites were characterized by FTIR, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy analysis. Silica (12.8%) could be incorporated within the silylated polystyrene–butylacrylate matrix while retaining optical transparency. These composites showed better thermal stability and water resistance in comparison to the individual polymers.
相似文献
S. K DoluiEmail: |
2.
O. N. Zefirova L. A. Zasurskaya E. V. Nurieva N. V. Zyk N. S. Zefirov 《Structural chemistry》2007,18(4):461-464
Molecular structure of ethylene acetal of 3-trityloxymethylbicyclo[3.3.1]nonane-2-on-7-ol (3) was determined by X-ray investigation. It was revealed that 3 has endo-endo-configuration and adopt chair-boat-conformation. The distortion of rings was evaluated by calculation of the Zefirov–Palyulin and Cremer–Pople puckering parameters.
Failure of esterification of 3 was rationalized in terms of steric hindrance and intramolecular hydrogen bonding.
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O. N. ZefirovaEmail: |
3.
Larissa S. Fenn Michal Kliman Ablatt Mahsut Sophie R. Zhao John A. McLean 《Analytical and bioanalytical chemistry》2009,394(1):235-244
The conformation space occupied by different classes of biomolecules measured by ion mobility-mass spectrometry (IM-MS) is
described for utility in the characterization of complex biological samples. Although the qualitative separation of different
classes of biomolecules on the basis of structure or collision cross section is known, there is relatively little quantitative
cross-section information available for species apart from peptides. In this report, collision cross sections are measured
for a large suite of biologically salient species, including oligonucleotides (n = 96), carbohydrates (n = 192), and lipids (n = 53), which are compared to reported values for peptides (n = 610). In general, signals for each class are highly correlated, and at a given mass, these correlations result in predicted
collision cross sections that increase in the order oligonucleotides < carbohydrates < peptides < lipids. The specific correlations
are described by logarithmic regressions, which best approximate the theoretical trend of increasing collision cross section
as a function of increasing mass. A statistical treatment of the signals observed within each molecular class suggests that
the breadth of conformation space occupied by each class increases in the order lipids < oligonucleotides < peptides < carbohydrates.
The utility of conformation space analysis in the direct analysis of complex biological samples is described, both in the
context of qualitative molecular class identification and in fine structure examination within a class. The latter is demonstrated
in IM-MS separations of isobaric oligonucleotides, which are interpreted by molecular dynamics simulations.
Figure Potential for performing simultaneous “omics” through the separation of biomolecular classes on the basis of structure and
mass using ion mobility-mass spectrometry
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
John A. McLeanEmail: |
4.
Fatemeh Hashemzadeh M. Mehdi Kashani Motlagh Amir Maghsoudipour 《Journal of Sol-Gel Science and Technology》2009,51(2):169-174
In this work, MnO2 nanostructure powders with different crystalline phases have been successfully prepared by hydrothermal and sol–gel methods.
The obtained products were characterized by XRD and SEM techniques and their crystallographic phases and morphological properties
compared. Results showed that α-MnO2, β-MnO2, and δ-MnO2 nanorods were synthesized by hydrothermal method and γ-MnO2 polymorph was obtained by sol–gel method.
相似文献
Amir MaghsoudipourEmail: |
5.
Kenichiro Todoroki Hidemichi Etoh Hideyuki Yoshida Hitoshi Nohta Masatoshi Yamaguchi 《Analytical and bioanalytical chemistry》2009,394(1):321-327
We have developed a novel pre-column fluorescence derivatization reagent for amines, F-trap pyrene. This reagent comprises
a fluorescent pyrene moiety, an amine-reactive Marshall linker, and a fluorophilic perfluoroalkyl group known as fluorous
tag. When the reagent reacts with aliphatic amines and amino acids to give fluorescent derivatives, the fluorous tag in the
reagent is eliminated simultaneously. Therefore, excess unreacted reagents in the derivatization reaction solution still have
the fluorous tag and could be removed by fluorous solid-phase extraction selectively before high-performance liquid chromatography
(HPLC) analysis. By using this reagent, 13 kinds of aliphatic amine (C2–C16) derivatives can be separated within 40 min by reversed-phase HPLC with gradient elution. In this chromatogram, unreacted
reagents peak at around 28 min, greatly decrease after fluorous solid-phase extraction, and do not interfere with the quantification
of each amine. The detection limits (S/N = 3) for examined aliphatic amines are 3.6–25 fmol per 20 μL injection. We have also applied this reagent successfully to
the amino acid analysis.
相似文献
Kenichiro TodorokiEmail: |
6.
Abstract The synthesis and acid-catalyzed rearrangement of novel thiazolomorphinandienes have been presented. An isomerization was
observed simultaneously with the backbone transformation. An extensive study was performed to determine the major effects
of the isomerization of 2′-alkyl- and aryl-substituted thiazoloapocodeines into 3′-alkyl- and arylisothiazoloapocodeines.
The obtained results provided another practical example of the reversible benzisothiazole–benzothiazole-type isomerization
emphasizing the determining role of the thermal effects in the occurrence of these isomerization products. The obtained experimental
results and the proposed mechanism were in agreement with the calculated DFT data.
Graphical abstract
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Attila SiposEmail: |
7.
Yan Gao Sabrina Reischmann Johannes Huber Tobias Hanke Rudolf Bratschitsch Alfred Leitenstorfer Stefan Mecking 《Colloid and polymer science》2008,286(11):1329-1334
Single semiconductor quantum dots were embedded into polymer particles with diameters below 0.1 μm by an emulsion polymerization
procedure or via a secondary dispersion approach. The photoluminescence properties of the nanocrystals are retained upon encapsulation,
as demonstrated by fluorescence confocal microscopy.
相似文献
Stefan MeckingEmail: |
8.
Nicholas Leventis Amala Dass Naveen Chandrasekaran 《Journal of Solid State Electrochemistry》2007,11(6):727-735
3-Methylthiophene was chosen as a representative conducting polymer precursor, whose electropolymerization proceeds through
the coupling of cation radicals. The density of the solution that contains electrogenerated 3-methylthienyl radicals and early
oligomers is higher than the density of the surrounding solution, and at low (<0.2 M) monomer concentrations the diffusion
layer falls, compromising the electropolymerization current efficiency. Applying a homogeneous magnetic field (3.0 T) perpendicular
to the electrode surface (θ=0°) produces concentration gradient paramagnetic forces (F
∇C) that hold the diffusion layer in contact with the electrode. This gives time for more oligomers to get oxidized and for
more cation radicals to couple so that the current efficiency increases from 0.028 to 0.037 at 0.05 M of monomer concentration,
and from 0.051 to 0.071 at 0.1 M. With the magnetic field parallel to the electrode surface (θ=90°) Lorenz forces causing magnetohydrodynamic convection, in combination with F
∇C forces keeping the flow pattern in contact with the electrode, increase the current efficiency even more, to 0.048 at 0.05 M
of monomer concentration, and to 0.076 at 0.1 M. At higher monomer concentrations (>0.2 M), the rate of radical coupling is
evidently fast enough so that, even in the absence of a magnetic field, no natural convection effects are observed and the
current efficiency (0.7–0.8) is not affected by the magnetic field.
相似文献
Nicholas LeventisEmail: |
9.
René Dybkaer 《Accreditation and quality assurance》2007,12(12):661-663
Terminology within a small laboratory community can be informal without danger of misunderstanding, but communication with
a wider audience and not least in publications, needs unequivocal terms for defined concepts. As an example, the many meanings
of “concentration” are explored to present a systematic nomenclature, including a concept diagram.
相似文献
René Dybkaer |
10.
In the present work, results of the interaction between methanol and oxidized platinum surfaces as studied via transients
of open-circuit potentials are presented. The surface oxidation before the exposure to interaction with 0.5 M methanol was
performed at different polarization times at 1.4 V vs reversible hydrogen electrode (RHE). In spite of the small changes in
the initial oxide content, the increase of the pre-polarization time induces a considerable increase of the time needed for
the oxide consumption during its interaction with methanol. The influence of the identity of the chemisorbing anion on the
transients was also investigated in the following media: 0.1 M HClO4, 0.5 M H2SO4, and 0.5 M H2SO4 + 0.1 mM Cl−. It was observed that the transient time increases with the energy of anion chemisorption and, more importantly, without
a change in the shape of the transient, meaning that free platinum sites are available at the topmost layer all over the transient
and not only in the potential region of small oxide ‘coverage’. The impact of the pre-polarization time and the effect of
anion chemisorption on the transients are rationalized in terms of the presence of surface and subsurface oxygen driven by place exchange.
相似文献
Hamilton VarelaEmail: |
11.
Saad Alshehri John Burgess Colin D. Hubbard Christopher J. Jones Amit K. Das 《Transition Metal Chemistry》2008,33(4):417-420
The kinetics of substitution by alcohols and by aniline at [tris(3,5-dimethylpyrazolyl)hydroborato]molybdenum nitrosyl dihalides in toluene solution at 298.2 K and at atmospheric pressure
are reported and interpreted in terms of an associative mechanism.
相似文献
Colin D. HubbardEmail: |
12.
Renat R. Nazmutdinov Michael D. Bronshtein Dmitrii V. Glukhov Tamara T. Zinkicheva 《Journal of Solid State Electrochemistry》2008,12(4):445-451
Solvent dynamics effects on the electroreduction of [PtCl3(H2O)]− at a mercury electrode are explored in the framework of Sumi–Marcus model using an efficient computational scheme. According
to results of density functional calculations, the second electron transfer step may be regarded as rate controlling. The
nonmonotonous influence of solvent viscosity on the reaction rate is predicted and explained in terms of the saddle point
avoidance. The results of model calculations are employed to interpret experimental data reported earlier in the literature.
相似文献
Renat R. NazmutdinovEmail: |
13.
X-ray structures of Diels–Alder adducts of thiophene with N-methylmaleimide and 2,5-dimethylthiophene with N-phenylmaleimide were determined and compared to literature data. In addition, quantum chemical calculations at various levels
of theory were used to study their molecular and electronic structure. A comparison with experimental results showed that
MP2/6-31G*, HF/6-311+G** and PBE1PBE/6-31G* methods give the most accurate structures.
相似文献
Davor MargetićEmail: |
14.
Stephen L. R. Ellison 《Accreditation and quality assurance》2006,11(3):146-152
The relationship between calibrated range, residual standard deviation and correlation coefficient r is discussed. It is shown that in typical chemical calibration applications with appropriately distributed calibration points (particularly, with range comparable to mean and with approximately even or with ‘successive dilution’ spacing), the linear correlation coefficient has valid application as a routine criterion for acceptable fit if used with due care.
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Stephen L. R. EllisonEmail: Phone: +44-20-8943-7325Fax: +44-20-8943-2767 |
15.
Poly(ethylene oxides), PEO, end-capped with hexadecyl dimethylammonium, HDDMA+, and trimethylammonium hexyldimethylammonium, THA2+, changed distinctly the sol–gel transition of sodium montmorillonite dispersions. In the presence of HDDMA+-PEO 1,500 and 4,000, domains of sol with increased salt tolerance (c
k=550–1,000 mmol NaCl/l) were found at high polymer and low montmorillonite contents. The corresponding PEO of higher molar mass (20,000 and 35,000) led to extended fields of flocs. THA2+-PEO 1,500 formed attractive gels at polymer concentrations >2–5 g/l and montmorillonite contents >0.5%. These gels showed very high yield values. THA2+-PEO of higher molar mass acted as stabilizing agents. The salt tolerance was highest (300–750 mmol/l) in the presence of THA2+-PEO 20,000. The observed sol–gel diagrams reveal the interplay between polymer end-group fixation on the clay mineral particles, polymer conformation, and colloidal stabilization and destabilization mechanisms.
相似文献
G. LagalyEmail: Phone: +49-431-8807445Fax: +49-431-8801608 |
16.
Electrochemical bandgaps of a series of poly-3-<Emphasis Type="Italic">p</Emphasis>-phenylthiophenes
The change of the UV-Vis optical absorption of electropolymerized substituted poly-3-p-X-phenylthiophenes (X = -H, -CH3, -OCH3, -COCH3, -COOC2H5, -NO2) has been followed in situ as a function of applied electrode potential in an electrolyte solution of tetraethylammoniumtetrafluoroborate
Et4NBF4 in acetonitrile. The UV-Vis spectra show features between 300 and 900 nm similar to those observed with many other polythiophenes
having a high degree of conjugation. During stepwise oxidation of the poly-3-p-X-phenylthiophene films, the intensity of the absorption due to the π→π*-transition around 450–566 nm decreases, and a new broad absorption band associated with (bi)polaron states appears around
730–890 nm. On the other hand, during the oxidation (p-doping) of the poly-3-p-X-phenylthiophene films, a blue (hypsochromic) shift is observed for both absorption bands. This is explained by taking into
account that a polymer contains a distribution of chain lengths, and the longest polymer chains (the absorption of which occurs
at lower energies) start to oxidize at the relatively lowest potentials. The electrochemical bandgaps of poly-3-p-X-phenylthiophenes have been estimated based on results of cyclic voltammetry. Bandgaps obtained this way have been found
to be generally higher than optical bandgaps; the actual discrepancy was found to depend on the mode of evaluation.
Dedicated to Piero Zanello on the occasion of his 65th birthday in recognition of his numerous contributions to inorganic
electrochemistry.
相似文献
Rudolf HolzeEmail: |
17.
Daniela Aiello Luca Malfatti Tongjit Kidchob Rosario Aiello Flaviano Testa Iolinda Aiello Mauro Ghedini Massimo La Deda Tonino Martino Maria Casula Plinio Innocenzi 《Journal of Sol-Gel Science and Technology》2008,47(3):283-289
Highly fluorescent materials have been prepared by incorporation of a zinc complex in mesoporous silica thin films with ordered
pore structure. The zinc complex has been introduced into the mesoporous materials via impregnation in an ethanol solution.
The incorporation into the films has been monitored by UV–Vis, Fourier transform infrared spectroscopy and spectroscopic ellipsometry.
After 18 h of immersion in the doping solution the films showed strong blue emission, increase in the refractive index. Leaching
experiments performed by immersing the samples in ethanol or tetrahydrofuran have shown that the chromophore is retained in
the porous matrix.
相似文献
Plinio InnocenziEmail: |
18.
The relation between particle size and the optical and electrochemical behavior of nanocrystalline ZnO was studied on materials
prepared by the thermal decomposition of zinc peroxide. The formation of zinc oxide starts at 180°C and yields particles of
characteristic size bigger than 10 nm. Smaller particles (r∼2–5 nm) may be prepared at reduced pressure and at a temperature of 150°C. The particle radius of synthesized nanocrystals
increases proportionally to synthesis temperature. Regardless of actual particle size, synthesized ZnO samples show cationic
disorder, with Zn distributed between 2b and 2a sites. The fraction of “octahedrally” coordinated Zn in 2a position decreases with increasing synthesis temperature. Zn disorder causes a narrowing of band gap, which results in the
“red shift” of the absorption edge in the UV–Vis spectra of prepared samples with respect to bulk ZnO. The effect of the disorder
on the band gap width is partially compensated by quantum size effects when the characteristic particle size drops below 5 nm.
A decrease in particle size results in an asymmetric shift of valence and conduction band edges, which can be assigned to
uneven effective masses of electrons and holes in nanocrystalline ZnO. Prepared nanocrystalline samples were (photo)electrochemically
active; their activity, however, decreases with particle size.
相似文献
Petr KrtilEmail: |
19.
Jerzy Zak Mieczyslaw Lapkowski Stephane Guillerez Gerard Bidan 《Journal of Solid State Electrochemistry》2006,10(3):134-139
An existence of a new, stable oligomer state of the solid film is reported, which is produced under electrochemical conditions.
In this state, a formal charge exchanged in the redox process is about one-half of electron per oligomer molecule. The procedure,
which allows controlling precisely the amount of oligomer on the electrode surface, is proposed that together with the coulometric
evaluation of the electric charge provides the number of electrons involved in a redox process. This is demonstrated for a
case of α-monochloro-substituted regioregular sexi (3-octylthiophene) oligomer (6OTCl). The electrochemical results are discussed
together with UV–Vis–NIR spectroelectrochemical data obtained for both solution and solid phase that support the proposed
interpretation.
相似文献
Mieczyslaw LapkowskiEmail: |
20.
S. Vatsadze M. Al-Anber W. R. Thiel H. Lang R. Holze 《Journal of Solid State Electrochemistry》2005,9(11):764-777
Reduction potentials for the first electron transfer to a broad selection of nitrogen containing bi- and polydentate molecules
considered as potential ligands have been determined. Results are compared with data obtained with semiempirical and UV-Vis
spectroscopic data. Close correlations for the investigated molecules are observed. Systematic differences in properties of
molecules with and without the keto moiety can be explained by invoking molecular orbital and surface interaction arguments.
Similar structural arguments can be used to explain the behaviour of 2,4,6-tripyridin-2–yl[1,3,5]triazine. UV-Vis data match
closely those derived from HOMO-LUMO calculations for these molecules.
相似文献
R. HolzeEmail: |