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111.
Photophysics of Calix[4]biscrown-Based Ditopic Receptors of Caesium Containing One or Two Dioxocoumarin Fluorophores 总被引:1,自引:0,他引:1
The ditopic receptors Calix-COU1 and Calix-COU2 consist of a calix[4]biscrown containing one or two dioxycoumarin fluorophores, respectively, inserted into the crown. They can form 1:1 and 2:1 (metal:ligand) complexes with caesium ions. The photophysical properties of the 1:1 complexes can be explained by (i) cation tunneling through the tube-shaped cavity (composed of the four phenyl rings) of the calix[4]biscrown, (ii) photodisruption of the interaction between the bound cation and the oxygen atoms belonging to both the coumarin moiety and the crown, (iii) photoinduced motions of the cation. 相似文献
112.
Yuan Wang 《Journal of luminescence》2008,128(3):373-376
The Schiff base, H2L, was derived from 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and diethenetriamine. The crystal structure of [NiL(C2H5OH)]·H2O obtained from ethanol solution was determined by X-ray diffraction analysis. The coordination geometry of Ni(II) ion is a distorted octahedron with three oxygen atoms and three nitrogen atoms. Under the excitation of ultraviolet light, strong fluorescence of solid Zn(II) complex was observed. In addition, the fluorescence enhancement was obtained in the presence of Zn2+ in THF solution of the ligand, indicating that H2L may be a potential fluorescent sensor for Zn2+. 相似文献
113.
Alberto García‐Peas Yu Wang Alexandra Muoz‐Bonilla Marta Fernndez‐García Florian J. Stadler 《Journal of Polymer Science.Polymer Physics》2019,57(20):1386-1393
The effect of the molecular weight on the lower critical solution temperature (LCST) has been discussed extensively, where LCST increased with molar mass, decreased or kept constant, which leads to confusion. This work is focused on the preparation of poly(N‐isopropyl acrylamide) homopolymers, obtained in a wide molecular weights range. The LCST behavior is analyzed by calorimetry and rheology, and a deep study of molecular features is carried out for a better knowledge of the influence of various parameters involved on LCST. Finally, the molecular weight trend is observed, and its influence on LCST is compared with the effect of other parameters as polymer concentration in water, end‐group effect, and tacticity. It is observed that other parameters such tacticity and end‐group effect will affect the LCST behavior over molecular weight, if this one is not high enough. Furthermore, the study of the LCST ranges will be a useful tool for analyzing the molecular weight trends. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1386–1393 相似文献
114.
In this paper, we established an analytical formula for the second virial coefficient (SVC) with Morse potential without using any numerical methods, and the obtained formula is applied to the calculation of the speed of sound of some matter at high temperature. This approach is based on the series expansion formula and special functions, which allows the exact evaluations of any thermodynamic properties of matter using the SVC. As an application, the obtained analytical formula is used for evaluation of the SVC with Morse potential for high‐temperature gas and the plasma region of the intermolecular interactions of neutral atom gases of B, Si, Zn, H2, N2, O2, NO, CO, He, Ne, Ar, Kr , and Xe . Based on the obtained formula of SVC, the speed of sound for gases of N2, Ar , and Zn are also determined analytically. A specific maximum temperature is chosen for every gas to ensure that there are still neutral atoms in the gas, and low temperatures are avoided due to quantum effects. The results are compared with numerical data and another analytical data from the literature. The new analytical solution is shown to be in good agreement with the compared data and is verified to supply proper thermodynamic data. 相似文献
115.
High brightness amine‐terminated silicon nanocrystals (Si NCs) have been utilized in a simple and rapid assay for the highly selective and sensitive detection of Fe3+ via quenching of their strong blue luminescence, without the need for analyte‐specific labeling groups. Sensitive detection of Fe3+ is successfully demonstrated, with a linear relationship observed between luminescence quenching and Fe3+ concentration from 5 × 10?6 to 900 × 10?6m and a limit of detection of 1.3 × 10?6m . The Si NCs show excellent selectivity toward Fe3+ ions, with no quenching of the luminescence signal induced by the presence of Fe2+ ions, allowing for solution phase discrimination between the ionic species in different charge states. 相似文献
116.
Berran Sanay Bernd Strehmel Veronika Strehmel 《Journal of polymer science. Part A, Polymer chemistry》2020,58(22):3196-3208
Investigation of photopolymerization kinetics of 4-(4-methacryloyloxyphenyl)-butan-2-one (1) in comparison with 2-phenoxyethyl methacrylate (2) and phenyl methacrylate (3) using a UV-LED emitting at 395 nm shows significantly faster polymerization of 1 compared to both 2 and 3 at 40°C. Vitrification affects photopolymerization kinetics of all methacrylates under investigation. Interestingly, quantitative final conversion is observed during photoinitiated polymerization of 1 and 2 whereas 3 shows limited conversion at about 80%. Furthermore, higher degree of polymerization is obtained by photoinitiated polymerization of 1 compared to 2 and 3. This shows that the 3-oxobutyl substituent at the phenyl ring of 1 significantly affects both polymerization kinetics and final conversion of the photoinitiated polymerization. Moreover, an additional higher molecular weight fraction is observed in case of polymerization of 1 at 85°C that is above the glass transition temperature of the polymer formed during photoinitiated polymerization. As a thermal polymerization at 85°C in the absence of light results in a high molecular weight polymer as well, an additional thermal process may be discussed as reason for the higher molecular weight polymer fraction in case of the photopolymer made at 85°C. 相似文献
117.
Gakhyun Kim Dr. Ranjan Dutta Dr. Won-Young Cha Dr. Seong-Jin Hong Dr. Juwon Oh Dr. Dikhi Firmansyah Hongil Jo Prof. Dr. Kang Min Ok Prof. Dr. Chang-Hee Lee Prof. Dr. Dongho Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16434-16440
π–π Stacking is omnipresent not only in nature but in a wide variety of practical fields applied to our lives. Because of its importance in a performance of natural and artificial systems, such as light harvesting system and working layer in device, many researchers have put intensive effort into identifying its underlying nature. However, for the case of π–π stacked systems composed of antiaromatic units, the understanding of the fundamental mechanisms is still unclear. Herein, we synthesized a new type of planar β,β’-phenylene-bridged hexaphyrin (1.0.1.0.1.0), referred as naphthorosarin which possesses the 24π-electron conjugated pathway. Especially, the corresponding antiaromatic porphyrinoid shows the unique property to form dimeric species adopting the face-to-face geometry which is unprecedented in cases of known annulated naphthorosarins. In order to elucidate the intriguing properties derived from the stacked dimer, the current study focuses on the experimental support to rationalize the observed π–π interactions between the two subunits. 相似文献
118.
《中国化学快报》2020,31(7):1919-1922
A novel BODIPY (boradiazaindacene) dye denoted as BODIPY-DT containing terpyridine unit has been designed and characterized. The dye is found to be selective and visual solvatochromic sensor toward DMF among test organic solvents. The sensing process displays time-controllable, dynamic signal outputs in the emission colors including red, purple, yellow and even white emission colors. It is presented that selective free radical oxidation reaction happens during the recognition process. 相似文献
119.
In order to investigate the influence of steam ingestion on the aerodynamic stability of a two-stage low-speed axial-flow compressor, multiphase flow numerical simulation and experiment were carried out. The total pressure ratio and stall margin of the compressor was decreased under steam ingestion. When the compressor worked at 40% and 53% of the nominal speed, the stall margin decreased, respectively, by 1.5% and 6.3%. The ingested steam reduced the inlet Mach number and increased the thickness of the boundary layer on the suction surface of the blade. The low-speed region around the trailing edge of the blade was increased, and the flow separation region of the boundary layer on the suction surface of the blade was expanded; thus, the compressor was more likely to enter the stall state. The higher the rotational speed, the more significant the negative influence of steam ingestion on the compressor stall margin. The entropy and temperature of air were increased by steam. The heat transfer between steam and air was continuous in compressor passages. The entropy of the air in the later stage was higher than that in the first stage; consequently, the flow loss in the second stage was more serious. Under the combined action of steam ingestion and counter-rotating bulk swirl distortion, the compressor stability margin loss was more obvious. When the rotor speed was 40% and 53% of the nominal speed, the stall margin decreased by 6.3% and 12.64%, respectively. 相似文献
120.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(10):1046-1057
We have explored two novel comonomers, namely, 4,16‐dicarboxyl[2.2]paracyclophane and 5,5′,6,6′‐tetraamino‐3,3,3′,3′‐tetramethyl‐1,1′‐spirobi[indane], for the synthesis of co‐polybenzimidazoles (co‐PBIs) with intrinsic porosity. Both these monomers possess twisted structures that can lead to “awkward” macromolecular shapes that cannot pack efficiently. The consequences of introducing these two monomers on the structure and properties of PBIs are reported. The random copolymers synthesized are amorphous and possess glass transition temperatures (Tgs) greater than 400 °C. Tg decreases with increasing comonomer content indicating an increase in fractional free volume. The copolymers have low surface area. TEM and BET measurements show evidence of mesopore formation. The copolymers show significant carbon dioxide adsorption. Single chain molecular dynamics simulation of 24‐mer repeat units shows intramolecular void spaces arising as a result of distorted polymer chain with reduced conformational mobility. These studies define a new synthetic strategy for “bottoms‐up” synthesis of PBIs with intrinsic porosity. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1046–1057 相似文献