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991.
Jayeon Hong Sangsub Kim Gyurim Park Yongmoon Lee Hyungchae Kim Sungjin Kim Tae-Woo Lee Changsoon Kim Youngmin You 《Chemical science》2021,12(25):8668
Polymer electroluminescence devices producing circularly polarized luminescence (CP PLEDs) have valuable photonic applications. The fabrication of a CP PLED requires a polymer host that provides the appropriate chiral environment around the emitting dopant. However, chemical strategies for the design of chiral polymer hosts remain underdeveloped. We have developed new polymer hosts for CP PLED applications. These polymers were prepared through a free-radical polymerization of 3-vinylcarbazole with a chiral N-alkyl unit. This chiral unit forces the carbazole repeat units to form mutually helical half-sandwich conformers with preferred (P)-helical sense along the polymer main chain. Electronic circular dichroism measurements demonstrate the occurrence of chirality transfer from chiral monomers to achiral monomers during chain growth. The (P)-helical-sense-enriched polymer interacts diastereoselectively with an enantiomeric pair of new phosphorescent (R)- and (S)-dopants. The magnitude of the Kuhn dissymmetry factor (gabs) for the (P)-helically-enriched polymer film doped with the (R)-dopant was found to be one order of magnitude higher than that of the film doped with the (S)-dopant. Photoluminescence dissymmetry factors (gPL) of the order of 10−3 were recorded for the doped films, but the magnitude of diastereomeric enhancement decreased to that of gabs. The chiral polymer host permits faster energy transfer to the phosphorescent dopants than the achiral polymer host. Our photophysical and morphological investigations indicate that the acceleration in the chiral polymer host is due to its longer Förster radius and improved compatibility with the dopants. Finally, multilayer CP PLEDs were fabricated and evaluated. Devices based on the chiral polymer host with the (R)- and (S)-dopants exhibit electroluminescence dissymmetry factors (gEL) of 1.09 × 10−4 and −1.02 × 10−4 at a wavelength of 540 nm, respectively. Although challenges remain in the development of polymer hosts for CP PLEDs, our research demonstrates that chiroptical performances can be amplified by using chiral polymer hosts.Polymer electroluminescence devices producing circularly polarized luminescence (CP PLEDs) have valuable photonic applications. 相似文献
992.
α,β-Unsaturated ketones are important synthetic intermediates because of their versatile reactivities and many syn-thetic applications of them have been reported in the literature.[1] However, only a few methods for the synthesis of (Z)-α,β-unsaturated ketones are available. The palladium catalyzed coupling reactions of alkenyl copper reagents with acid chlorides afforded (Z)-α,β-unsaturated ketones.[2] The phase transfer catalyzed hydroacylation of allenes with carbon monoxide, decacarbonyldimanganese and methyl iodide gave (Z)-α,β-unsaturated ketones in a stereospecific process. 相似文献
993.
Syntheses of quaternary 1-alkyl-3-perfluoroalkyl-4,5-dimethyl-1,2,4-triazolium iodides have led to a variety of new quaternary salts via metathesis reactions. 1,4,5-Trimethyl-3-trifluoro-methyl-1,2,4-triazolium iodide (6) with LiN(SO(2)CF(3))(2), KSO(3)CF(3), AgClO(4), AgBF(4); 1-(3-fluoropropyl)-3-trifluoromethyl-4,5-dimethyl-1,2,4-triazolium iodide (7) with LiN(SO(2)CF(3))(2); and 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium iodide (8) with LiN(SO(2)CF(3))(2), AgClO(4), AgBF(4) gave excellent yields of new thermally stable and relatively low melting quaternary salts. The structure of 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium tetrafluoroborate (11c) was confirmed by single-crystal X-ray analysis. Although the molecular weight of 11c (cation) is 3-fold greater than that of the 3-trifluoromethyl derivative 9d, its melting point is 32 degrees C lower. 相似文献
994.
Yao‐Cheng Shi Su‐Hua Zhang Hong‐Jian Cheng Wei‐Ping Sun 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(9):m407-m410
The title compounds, both [Fe(C5H5)(C15H14NO2)], crystallize with Z′ = 2 in the centrosymmetric space group P. In each compound, there is an intramolecular N—H⋯O=C hydrogen bond, and pairs of intermolecular O—H⋯O=C hydrogen bonds link the molecules into chains, parallel to [10] in the 3‐hydroxy compound and parallel to [10] in the 4‐hydroxy compound. 相似文献
995.
The adsorption of Am(III) (total concentration 10(-9) mol/l) on alumina, silica, and hematite was studied by a batch technique. The effects of pH, ionic strength, and humic substances on the adsorption of Am(III) on alumina and silica were investigated, and the adsorption isotherms of Am(III) on alumina and silica at different pH values were determined. It was found that compared with the adsorption of Am(III) on alumina, the adsorbability of silica on the basis of mass is less, the relative adsorption rate on silica is slower, the sensitivity of adsorption on silica to ionic strength is less, the dependence of adsorption on silica on pH is gentler, and consequently that the adsorption characteristics of Am(III) on alumina and silica are distinctly different. The negative effect of fulvic acid on the adsorption on silica and the positive effect of humic acid on the adsorption on alumina were found. In contrast to the Am(III) adsorption on alumina and silica, a tremendously high adsorbability of Am(III) on hematite was found. The sequence of adsorbabilities of Am(III) on the basis of mass is Fe2O3 > Al2O3 > SiO2. 相似文献
996.
A2Ca[B4O5(OH)4]2·8H2O(A=Rb,Cs)硼氧酸盐复盐的合成与表征 总被引:5,自引:0,他引:5
硼氧酸盐晶体结构复杂,因此出现了许多具有特殊物理性能的晶体功能材料犤1,2犦,尤其是重稀碱金属硼氧酸盐(或复盐),如CsLiB6O10犤3犦、LiRbB4O7犤4犦和CsB3O5(CBO)犤5犦都是非线性光学材料。一些学者对铷、铯的偏硼氧酸盐、四硼氧酸盐和五硼氧酸盐的合成、性质及晶体结构等进行过研究犤6~9犦。硼氧酸盐复盐,大多为碱金属和碱土金属、碱金属和碱金属及碱土金属和碱土金属的硼氧酸盐犤10犦,如自然界存在的钠硼解石狖NaCa犤B5O6(OH)6犦·5H2O狚、硼钠镁石狖Na2Mg犤B6O8(OH)4犦2·6H2O… 相似文献
997.
Sorption of uranyl ions on silica: Effects of contact time, pH, ionic strength, concentration and phosphate 总被引:1,自引:0,他引:1
The sorption of UO2
2+ and phosphate on silica were simultaneously studied. The effect of contact time between the solid phase and aqueous solution, pH and ionic strength on the UO2
2+ sorption in the absence and the presence of phosphate was investigated. The effect of contact time between the solid phase and aqueous solution, pH and ionic strength on the phosphate sorption was investigated too. The isotherms of UO2
2+ and phosphate sorption at different pH values were determined. It was found that as compared with the sorption in the absence of phosphate, the sorption of UO2
2+ on silica in the presence of phosphate is increased at low pH and decreased at high pH; the abruptly increased with increasing pH in the pH range 3-6; the sorption is gradually decreased with increasing pH in the pH range 2-12; the sorption insensitive and the sorption of phosphate is sensitive to ionic strength. 相似文献
998.
Biosurface fabrication using the Fab′ fragment of immunoglobulin (IgG) was carried out by self-assembly (SA) technique. The pepsin-digested monoclonal antibody (Mab) against bovine insulin containing the F(ab′)2 fragment and residual proteins was separated using affinity chromatography and dialysis. To prevent the nonspecific binding of F(ab′)2 onto gold (Au) substrate, the native disulfide bridge was reduced using dithiothreitol (DTT) to convert F(ab′)2 into Fab′, which made the immobilization to be carried out via the native thiol (–SH) group. The fabricated biosurface using SA technique showed the formation of stable thin film through AFM topography. Through the concentration change of DTT and Fab′, the absorption characteristics against the Au surface were investigated using surface plasmon resonance (SPR) with the flow cell. The amount of immobilized antibody fragment and the antigen binding capacity were regulated with respect to the reduction state and concentration of F(ab′)2. Based on the biosurface of the fabricated Fab′, the insulin-detection was carried out by the measurement of SPR. The proposed antibody surface could successfully detect the bovine insulin at the concentration from 100 ng/mL to 10 μg/mL. 相似文献
999.
We recorded dispersed fluorescence (DF) spectra following excitation of the pure bending levels 2(0) (n) and the combination states 1(0) (1)2(0) (n) and 2(0) (n)3(0) (1) in the A 1A"<--X 1A' system of HCF and DCF. Spectra were measured with a 0.3 m spectrograph equipped with a gated intensified charge coupled device (CCD) detector and obtained under jet-cooled conditions using a pulsed discharge source. The DF spectra reveal rich detail concerning the vibrational structure of the X state up to 10 000 cm(-1). For HCF, resonances among the nearly degenerate levels 1(1)2n, 2n+13(1), and 2n+2 produce a polyadlike structure in the spectrum, and the usual effective spectroscopic Hamiltonian (Dunham expansion) poorly reproduces the experimental term energies. In contrast, this Hamiltonian works well for the term energies of DCF. Density functional calculations of the ground state vibrational frequencies were performed; the results are in excellent agreement with the experimentally derived vibrational parameters. The search for perturbations involving the low-lying a 3A" state is described. 相似文献
1000.
Ya Wen TANG Shuang CAO Ling Ling ZHANG Jian Chun BAO Ping ZHOU Tian Hong LU 《中国化学快报》2006,17(12):1623-1626
The performance of the direct formic acid fuel cell (DFAFC) is considerably higher than the direct methanol fuel cell (DMFC) because of some characteristics of formic acid1. For example, formic acid is non-toxic. Formic acid has two orders of magnitude smaller crossover flux through a Nafion membrane than methanol2. In DFAFC, the concentration of formic acid can be as high as 20 mol/L, while the best concentration of methanol in DMFC is only about 2 mol/L3. Thus, the power density of … 相似文献