共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
peri-Acenes have shown great potential for use as functional materials because of their open-shell singlet biradical character. However, only a limited number of peri-acene derivatives larger than peri-tetracene have been synthesized to date, presumably owing to the low stability of the target compounds in addition to the complicated synthesis scheme. Here, a very simple synthesis route for the tetrabenzo[a,f,j,o]perylene (TBP) structure enables the development of highly stable peri-tetracene analogues. Despite a high degree of singlet biradical character, the compounds with four substituents at the zigzag edge show a remarkable stability in solution under ambient conditions, which is better than that of acene derivatives with a closed-shell electronic configuration. The crystal structures of the TBP derivatives were obtained for the first time; these are valuable to understand the relationship between the structure and biradical character of peri-acenes. The application of peri-acenes in electronic devices should also be investigated. Therefore, the semiconducting properties of the TBP derivative were investigated by fabricating the field-effect transistors.Highly stable peri-tetracene analogues with a high degree of singlet biradical character were synthesized in a very simple route, and their crystal structures and semiconducting properties were investigated. 相似文献
3.
Membrane transport characteristics of ultrafine capillaries 总被引:6,自引:0,他引:6
4.
M. G. Demidova A. I. Bulavchenko T. Yu. Podlipskaya A. I. Boronin L. S. Kibis V. I. Zaikovskii 《Russian Journal of Inorganic Chemistry》2011,56(8):1199-1207
We have developed methods for the synthesis and coagulation of ultrafine silver powders in the water-Triton N-42-decane inverted-micellar
system. Varying AgNO3 concentration (1–5 mol/L), the type of reducing agent (hydrazine or potassium borohydride), and the coagulation method (spontaneous
or induced by acetone or water addition) allowed us to select the parameters that provide powders containing about 98% silver
and having particle sizes of 15–80 nm. We propose methodology for characterizing ultrafine silver powders comprising the determination
of the total and surface composition and the charge state of impurities using atomic absorption spectroscopy (AAS), atomic
emission spectroscopy (AES), microanalysis, FTIR spectroscopy, and X-ray photoelectron spectroscopy. The impurity composition
of the nanomaterial is found to depend on the type of reducing agent, the synthesis parameters, and coagulation conditions. 相似文献
5.
《Ceramurgia International》1979,5(4):148-154
Coprecipitation from water solution of chlorides was used to obtain yttria-stabilized zirconia powders. It was shown that precalcination processing of the coprecipitated gel greatly affects the microstructure of the resultant powder as well as its cold compaction behaviour and hence its sinterability. Relative densities of +98% theoretical have been achieved at sintering temperature as low as 1300°C. 相似文献
6.
7.
8.
V. G. Sevastyanov E. P. Simonenko D. V. Sevastyanov N. P. Simonenko V. L. Stolyarova S. I. Lopatin N. T. Kuznetsov 《Russian Journal of Inorganic Chemistry》2013,58(1):1-8
Ultrafine Nd2Hf2O7 powders with the pyrochlore structure are prepared by self-propagating hightemperature synthesis (in the Pechini version). The elemental and phase composition of the powder are studied. Microstructure is studied by scanning electron microscopy. BET specific surface areas are determined. Thermal behavior is studied by TGA/DSC/DTA up to 1473 K. The sintering kinetics of as-synthesized Nd2Hf2O7 powder at various temperatures is studied. Nd2Hf2O7 vaporization in the range 2400–2600 K is studied by Knudsen effusion/mass spectrometry, and the thermodynamic characteristics of this compound are determined. 相似文献
9.
10.
11.
Physicochemical properties of ultrafine copper-containing powders synthesized by cathode reduction 总被引:1,自引:0,他引:1
S. A. Chulovskaya S. A. Lilin V. I. Parfenyuk G. V. Girichev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(2):264-267
Copper-containing ultrafine (nanosized) powders were synthesized from solutions of copper dichloride in the water-isopropanol binary solvent by electrochemical reduction. Particles were analyzed using a transmission electron microscope. A combination of thermal analysis with mass spectrometry made it possible to determine the composition of the cathode deposit obtained. 相似文献
12.
Computational study of structure,electronic, and microscopic charge transport properties of small conjugated diketopyrrolopyrrole‐thiophene molecules
下载免费PDF全文
![点击此处可从《International journal of quantum chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Maria V. Makarova Sergey G. Semenov Olga A. Guskova 《International journal of quantum chemistry》2016,116(20):1459-1466
π‐Conjugated small molecules containing diketopyrrolopyrrole (DPP) and thiophene moieties represent a modern class of functional materials that exhibit promising charge transport properties and therefore have great potential as building blocks of active elements of electronic devices. As a starting point of this computational study, the molecular structure, electronic characteristics, and reorganization energies associated with electron or hole transfer are considered. Prediction of molecular crystal packing is followed by the calculation of couplings between adjacent molecules and detection of the effective charge transfer pathways. Finally, the rates of charge transfer process are evaluated. The obtained results shed light not only on the properties of materials containing low‐molecular species but also serve as a benchmark for further classical force‐field simulations of DPP‐based polymers. 相似文献
13.
The molecular and electronic structures and electron transport characteristics of a Co complex are investigated using first principles calculations. The Co complex belongs to the D(2d) point group, and its two ligands are perpendicular to each other. The central atom Co forms a distorted octahedron with six donor N atoms. In a low oxidation state, the bond length between Co and pyrrole nitrogen, 1.849 A, is much shorter than the distance between Co and pyridine nitrogen, 2.168 A, while, in a high oxidation state, the bond length differences between Co and pyrrole nitrogen, 1.814 A, and between Co and pyridine nitrogen, 1.990 A, are not as large as those in the Co2+ complex. The HOMO energy of the low oxidation state is very close to the Fermi level of bulk Au, allowing hole creation in the molecule. On the other hand, the LUMO energy of the high oxidation state is close to the Au Fermi level, allowing a low barrier for electron injection from the Au cathode to the molecule. These structural characteristics make the Co complex a good hole-conduction molecule. The density of states, transmission probability, and I-V characteristics are evaluated using the Green function approach. 相似文献
14.
B Purushothaman SR Parkin MJ Kendrick D David JW Ward L Yu N Stingelin OD Jurchescu O Ostroverkhova JE Anthony 《Chemical communications (Cambridge, England)》2012,48(66):8261-8263
Acenes larger than pentacene are predicted to possess enticing electronic properties, but are insoluble and prone to rapid decomposition. Utilizing a combination of functionalization strategies, we present stable, solution-processable hexacenes and an evaluation of their hole and electron transport properties. 相似文献
15.
Christian Melzer Martin Brinkmann Victor V Krasnikov Georges Hadziioannou 《Chemphyschem》2005,6(11):2376-2382
We investigated various thin-film morphologies of vacuum-deposited highly luminescent 2,5-di-n-octyloxy-1,4-bis[4'-(styryl)styryl]benzene (Ooct-OPV5) in a typical light-emitting-diode device structure. Important modifications in the thin-film morphology and structure were obtained by changing the substrate temperature in the range 23-90 degrees C. Structural analysis by X-ray and electron diffraction provided clear evidence for polymorphism in evaporated thin films of Ooct-OPV5. Concomitantly, the hole mobility in the corresponding devices was determined by transient electroluminescence measurements. We demonstrate that the substrate temperature T(sub) is a key parameter that controls the hole mobility of the devices. Increasing T(sub) between 23 and 84 degrees C results in a progressive increase of the zero-field hole mobility from 10(-6) to 10(-4) cm(2) V(-1) s(-1). The increase in hole mobility is correlated to the average grain size in the thin films. In addition, we give evidence for the existence of a peculiar growth mode in the bulk crystal structure of Ooct-OPV5, whereby the (a,b) and (b,c) planes can grow in a homoepitaxial manner. 相似文献
16.
E. N. Lysenko A. P. Surzhikov S. P. Zhuravkov V. A. Vlasov A. V. Pustovalov N. A. Yavorovsky 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1447-1452
The oxidation kinetics of ultrafine metallic iron powder to hematite (α-Fe2O3) up to temperatures 800 °C were studied in air using non-isothermal and isothermal thermogravimetric (TG) analysis. The powders with average particles size of 90, 200, and 350 nm were made by the electric explosion of wire. It was observed that the reactivity of the iron powder is increased with the decreasing particle size of powder. The experimental TG curves clearly suggest a multi-step process for the oxidation, and therefore a model-fitting kinetic analysis based on multivariate non-linear regressions was conducted. The complex reaction can be best described with a three-step reaction scheme consisting of two concurrent and one parallel reaction step. In one reaction pathway Fe is oxidized to α-Fe2O3. The other pathway is described by the oxidation of Fe to magnetite (Fe3O4). At higher temperatures the formed Fe3O4 is further oxidized in a α-Fe2O3. It is established that the best fitting three-step mechanism employed a branching set of n-order equations for each step. 相似文献
17.
18.
A simple method was developed to prepare highly water-soluble nanocrystal powders of magnetic iron oxides with different oxidation degree from magnetite (Fe(3)O(4)) to maghemite (γ-Fe(2)O(3)) coated with gluconic acid (GLA). X-ray diffraction and transmission electron microscopy measurements show that the products have a narrow size distribution, and the cores are inverse spinel iron oxides and completely crystallized. Vibrating sample magnetometry measurements reveal that all the samples exhibit superparamagnetic behavior at room temperature. Fourier transform infrared (FTIR) and Raman spectra were used to identify the products. It is shown that GLA molecules are immobilized on the nanoparticle surface by chemical bonding and the carboxyl is asymmetrically bound to the surface iron atom, and the vacancies in the γ-Fe(2)O(3) cores are disordered. Compared with FTIR, Raman spectrum analysis is a rapid, simple, and accurate method for identifying inverse spinel iron oxides. The chemical stability and the high solubility of the products are explained in terms of the proposed coordination modes of the surface iron atom with GLA. 相似文献
19.
Imahori H Umeyama T Kurotobi K Takano Y 《Chemical communications (Cambridge, England)》2012,48(34):4032-4045
Large π-conjugated compounds are promising building blocks for organic thin-film electronics such as organic light-emitting diodes, organic field-effect transistors, and organic photovoltaics. Utilization of porphyrins and phthalocyanines for this purpose is highly fascinating because of their excellent electric, photophysical, and electrochemical properties as well as intense self-assembling abilities arising from π-π stacking interactions. This paper focuses on fundamental aspects of self-assembled structures that have been obtained from porphyrin and phthalocyanine building blocks and more complex composites for photoinduced charge separation and charge transport toward the potential applications to organic thin-film electronics. 相似文献
20.
Koh SE Delley B Medvedeva JE Facchetti A Freeman AJ Marks TJ Ratner MA 《The journal of physical chemistry. B》2006,110(48):24361-24370
Density-functional theory (DFT) is employed to investigate the structural, electronic, and transport properties of several isomeric fluoroarene-oligothiophene-based semiconductors. Three oligothiophene systems varying in the perfluoroarene group positions within the molecule are studied to understand the electronic structure leading to the observed mobility values and to the n- or p-type behavior in these structures. Analyses of both intermolecular interactions in dimers and extended interactions in crystalline structures afford considerable insight into the electronic properties and carrier mobilities of these materials, as well as the polarity of the charge carriers. From the calculated carrier effective masses, we find that sterically governed molecular planarity plays a crucial role in the transport properties of these semiconductors. Our calculations correlate well with experimentally obtained geometries, highest-occupied molecular orbital (HOMO)/lowest-unoccupied molecular orbital (LUMO) energies, and the experimental carrier mobility trends among the systems investigated. 相似文献