This paper investigates theoretically the electronic transmission
spectra of the three terminal pyrene molecular bridge and the
quantum current distribution on each bond by the tight-binding model
based on nonequilibrium Green's function and the quantum current
density approach, in which one π molecular orbital is taken
into account per carbon atom when the energy levels and HOMO-LUMO
gap are obtained. The transmission spectra show that the electronic
transmission of the three terminal pyrene molecular bridge depends
obviously on the incident electronic energy and the pyrene
eigenenergy. The symmetrical and oscillation properties of the
transmission spectra are illustrated. A novel plus-minus energy
switching function is found. The quantum current distribution shows
that the loop currents inside the pyrene are induced, and some bond
currents are much larger than the input and the output currents. The
reasons why the loop currents and the larger bond currents are
induced are the phase difference of the atomic orbits and the
degeneracy of the molecular orbits. The calculations illustrate that
the quantum current distributions are in good agreement with
Kirchhoff quantum current conservation law. 相似文献
Summary: Alternating copolymers between substituted 1,3,5‐triazine (substituent = alkyl or amine) and thiophene or bithiophene are synthesized. The copolymer of amino‐1,3,5‐triazine with thiophene is soluble in organic solvents, transparent in most parts of the visible region, and photoluminescent. The copolymer receives electrochemical n‐doping with an Epc of −2.08 V vs Ag+/Ag and shows a time‐of‐flight electron drift mobility of 2.0 × 10−4 cm2 · V−1 · s−1, which is larger than that of widely used Al(8‐quinolinolato)3.
The first photocontrollable magnetic nanoparticles containing CdS and Prussian blue (PB) have been created using reverse micelles as nanoreactors. Photoinduced electron transfer from CdS to PB in the reverse micelle changed the magnetic properties of the composite nanoparticles from ferromagnetic to paramagnetic. The magnetization in the ferromagnetic region below 4 K was substantially decreased after UV light illumination and could be restored almost to its original level by thermal treatment at room temperature. This novel strategy of designing composite nanoparticles containing photoconductive semiconductors and magnetic materials to create photoswitchable magnetic materials may open many possibilities in the development of magneto-optical devices. 相似文献
5,10,15,20-Tetrakis-3,5-di-tert-butyl-4-oxocyclohexadienylidene porphyrinogen and its di-N-benzylated derivative are solvatochromic dyes capable of binding anionic species. The influence of solvent polarity and hydrogen bonding on their electronic absorption spectra was observed. Hydrogen bonding by the porphyrinogen amine protons of acetone solvent molecules could be observed in the solid state. The acetone solvate of N21N23-dibenzyl-5,10,15,20-tetrakis-3,5-di-tert-butyl-4-oxocyclohexadienylidene porphyrinogen crystallized under anhydrous conditions in the space group P with cell dimensions a = 12.1693(11) A, b = 17.5849(13) A, c = 21.0965(17) A, alpha = 69.870(4) degrees , beta = 78.140(4) degrees , gamma = 82.865(5) degrees . These porphyrinogens are capable of binding a variety of anions and can be used to distinguish fluoride chromogenically from the other halide anions. Solvatochromism was combined with anion binding in an attempt to provide more selective tests for anions. The anion binding properties were investigated using UV/vis spectrophotometry and 1H NMR spectroscopy. 相似文献
Plastic microchips are very promising analytical devices for the high-speed analysis of biological compounds. However, due to its hydrophobicity, their surface strongly interacts with nonpolar analytes or species containing hydrophobic domains, resulting in a significant uncontrolled adsorption on the channel walls. This paper describes the migration of fluorescence-labeled amino acids and proteins using the poly(methyl methacrylate) microchip. A cationic starch derivative significantly decreases the adsorption of analytes on the channel walls. The migration time of the analytes was related to their molecular weight and net charge or pI of the analytes. FITC-BSA migrated within 2 min, and the theoretical plate number of the peak reached 480,000 plates/m. Furthermore, proteins with a wide range of pI values and molecular weights migrated within 1 min using the microchip. 相似文献
Four new plastoquinones were isolated from the methanolic extract of the brown alga, Sargassum micracanthum. Their structures were elucidated based on spectroscopic analysis and chemical conversions from 2-geranylgeranyl-6-methyl-1,4-benzohydroquinone. These plastoquinones exhibited significant antioxidant activities such as an inhibitory effect on lipid peroxidation and a radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH). Some of the new plastoquiones showed cytotoxic activity against cancer cell line. 相似文献
The new coupling reaction of phenacylamines with silylstannane and lithium diisopropylamide (LDA) is reported. The treatment of a phenacylamine iodide 1 with (trimethylsilyl)tributylstannane (Me3SiSnBu3) and cesium fluoride (CsF) gave a dimerization product 2 having no iodine atom. Reaction of 1 with LDA afforded a dimerization product 3 with an iodine atom. The products 2 and 3 were separated to the meso and racemic isomers, respectively. 相似文献
Holographic gratings were in a composite material that comprised a cross-linked polymer with azobenzene side chains and a nematic liquid crystal. Holographic recording was based on the photoinduced alignment of the nematic liquid crystal inside a cell as a result of amplification of the photoreorientation of azobenzene residues. The diffraction efficiency depends on cell thickness and reading angle of the gratings, so this composite material exhibits volume holographic properties with Bragg diffraction. 相似文献