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51.
Xiaoyan Liu Karen L. Feilberg Wei Yan Erling H. Stenby 《Journal of Dispersion Science and Technology》2013,34(11):1611-1617
AbstractIn this study, the atomic force microscopy colloidal probe technique was employed to investigate the interaction between apolar, basic and acidic model oil probes and a calcite surface in solutions containing different concentrations of NaCl, CaCl2 and Na2SO4. In the presence of SO42?, hydration and structural forces were observed between apolar model oil probes and a calcite surface on approach. Relatively low adhesion forces were observed between the basic model oil probes and the calcite surface, while higher adhesion forces were observed between the acidic model oil probes and the calcite surface. Furthermore, the adhesion forces between the basic model oil probes and the calcite surface significantly increased in the presence of SO42?, while the adhesion force between the acidic model oil probes and the calcite surface decreased in the presence of Ca2+ or SO42?. The differences in the adhesion forces are related to electrostatic attraction and ion bridging forces between the model oil probes and the calcite surface. 相似文献
52.
Paul Becher Suzanne E. Trifiletti Pamela C. Petty 《Journal of Dispersion Science and Technology》2013,34(1):53-66
Isotherms for the adsorption of sodium dodecyl benzene sulfonate, sodium POE (4) nonyl phenol sulfate, and POE (25) nonyl phenol, on the hydrophobic crystalline herbicides atrazine and cyanazine were determined. Anionic surfactants were measured at 5°, 25°, and 50° C; the nonionic surfactant at 25° C only. Low degrees of surface coverage were observed; in only one case (atra-zine/NaDBS) was monolayer coverage approached. On the other hand, adsorption was accompanied by a significant increase in negative zeta potential. Although DLVO calculations suggest that this adsorption should lead to stable aggregates, these are of such size that gravitational effects overpower the DLVO terms. 相似文献
53.
A sonic spray ionization (SSI) interface for liquid chromatography-mass spectrometry (LC-MS) analysis was optimized for analysis of 2-[(1R)-3-[bis(1-methylethyl)amino]-1-phenylpropyl]-4-methyl-phenol (tolterodine), used as a model drug substance, and the influence of different parameter settings was evaluated using factorial design. A comparison between SSI and electrospray ionization (ESI) was made for tolterodine, tolterodine metabolites, and a set of steroids.SSI was found to give slightly poorer repeatability and broader peaks for tolterodine compared to ESI. However, there was no significant difference in chromatographic peak shape, and the repeatability using SSI was similar to that obtained using ESI if a ratio (area of tolterodine/area of metabolite) was used. In this study, the sensitivity was higher using SSI. For the analysis of pregnanolone, less water loss was obtained using SSI, probably due to less energy being transferred to the analyte upon ionization. 相似文献
54.
V. Maleev M. SemenovV. Kashpur T. BolbukhA. Shestopalova D. Anishchenko 《Journal of Molecular Structure》2002,605(1):51-61
The aim of this paper is to summarize the original results concerned with the elucidation of the role of water environment in the formation of different structures of polyribocytidylic acid (poly(rC)), depending on the pH, temperature and ion content. To solve this problem, we studied the hydration of poly(rC)-K+ in films differing in water content, by methods of infrared spectroscopy and piezogravimetry, and in solution, using the dielectric measurements at a wavelength of 7.6 mm (extremely high frequencies — EHF). The experimental results were confirmed by a Monte Carlo simulation of the interaction between water molecules and single-strand and double-strand poly(rC) fragments in clusters of 800 water molecules. A model of hydration of double-strand complex of poly(rC)+-poly(rC) has been proposed based on our results and the known X-ray parameters of the complex. The obtained results and proposed structure of poly(rC)+-poly(rC) suggest that, the stabilization of this complex occurs due to intra- and inter-chain water bridges, together with the hydrogen bonds between neutral and protonated cytosines in pairs. 相似文献
55.
Mariusz Klobukowski 《Theoretical chemistry accounts》1992,83(3-4):239-248
Summary The effective core potential and model potential methods were used in post-SCF calculations on HC1, HBr, Cl2, and Br2 in order to gain insight into the effect of insufficient representation of inner nodes in the valence orbitals of the approximate methods. The results show that while the correlation energy may be slightly overestimated (by 1–7%), both the electric moment functions and the quantities depending on energy differences are consistently similar for the methods studied and close to the results from all-electron calculations.Dedicated to Prof. Klaus Ruedenberg 相似文献
56.
Summary INDO molecular orbital calculations are reported for 35 selected angiotensin-converting enzyme inhibitors. QSARs are developed between pI50 data and molecular electronic indices. The QSARs obtained reflect the importance of both charge-charge interactions between inhibitor and receptor and of specific interactions between groups on the inhibitor with points around the molecule which are postulated to correspond to binding sites at the receptor. 相似文献
57.
Xinliang Cai Yexuan Pu Prof. Chenglong Li Dr. Zhiheng Wang Prof. Yue Wang 《Angewandte Chemie (International ed. in English)》2023,62(27):e202304104
Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials are considered a class of organic materials with exceptional electronic and optical properties, which make them promising for the applications in organic light-emitting diodes (OLEDs). In this study, we improved, synthesized, and characterized a multiple-resonance type emitter based on the assembly of MR-building blocks (MR-BBs). By optimizing the geometric arrangement of MR-BBs, we were able to generate narrowband emission in the longer wavelength region and shorten the delayed excited-state lifetime, resulting in improved emission efficiency compared to the parent molecule. Our proof-of-concept molecule, m-DBCz, exhibited narrowband yellowish-green TADF emission with a full width at half-maximum of 32 nm and a small singlet-triplet energy gap of 0.04 eV. The OLED developed using m-DBCz as the emitter demonstrated electroluminescence at 548 nm and achieved a high external quantum efficiency (EQE) of 34.9 %. Further optimization of the device resulted in a high external quantum efficiency of 36.3 % and extremely low efficiency roll-off, with EQE values of 30.1 % and 27.7 % obtained even at high luminance levels of 50 000 and 100 000 cd m−2. These results demonstrate the full potential of MR-TADF materials for applications on ultrahigh-luminance OLEDs. 相似文献
58.
59.
Sai Luo Junjie Wang Dr. Nengquan Li Dr. Xiu-Fang Song Xintong Wan Prof. Dr. Kai Li Prof. Dr. Chuluo Yang 《Angewandte Chemie (International ed. in English)》2023,62(49):e202310943
B- and N-embedded multiple resonance (MR) type thermally activated delayed fluorescence (TADF) emitters usually suffer from slow reverse intersystem crossing (RISC) process and aggregation-caused emission quenching. Here, we report the design of a sandwich structure by placing the B−N MR core between two electron-donating moieties, inducing through-space charge transfer (TSCT) states. The proper adjusting of the energy levels brings about a 10-fold higher RISC rate in comparison with the parent B−N molecule. In the meantime, a high photoluminescence quantum yield of 91 % and a good color purity were maintained. Organic light-emitting diodes based on the new MR emitter achieved a maximum external quantum efficiency of 31.7 % and small roll-offs at high brightness. High device efficiencies were also obtained for a wide range of doping concentrations of up to 20 wt % thanks to the steric shielding of the B−N core. A good operational stability with LT95 of 85.2 h has also been revealed. The dual steric and electronic effects resulting from the introduction of a TSCT state offer an effective molecular design to address the critical challenges of MR-TADF emitters. 相似文献
60.
Konrad Seppelt 《Angewandte Chemie (International ed. in English)》1991,30(4):361-374
Alkylidene and alkylidyne sulfur fluorides contain sulfur–carbon multiple bonds. In contrast to the sulfur ylides, alkylidene sulfur fluorides fulfill all the criteria for double bonds, i.e. they have short bond lengths, strong anisotropic distribution of electron density, and rotation about the C? S bond is restricted. Alkylidyne sulfur fluorides have especially short bond distances and, due to a high amplitude bending motion, appear to be more or less linear, depending on the physical state. The advantage of the C? S multiple bond systems in contrast with numerous others, e.g. those of phosphorus and silicon, is that they exist without steric stabilization. Moreover, the limits of the triple-bond principle are outlined: the prognosis for triple bonds between two elements of higher periods is poor, because carbene-like or fully bridged structures win in terms of stability. 相似文献