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21.
Jianping X Jiyou Z Jiaqin L Jianniao T Xingguo C Zhide H 《Biomedical chromatography : BMC》2005,19(1):9-14
A rapid, sensitive and reproducible micellar electrokinetic chromatographic method using hexamethyldisilazane as on-line regenerating covalent coating was developed for the quantification of ephedrine (E) and pseudoephedrine (PE). E and PE were derivatized with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol for laser-induced fluorescence detection. The on-line regenerating covalent coating formed a combinative double coating with the subsequently produced dynamic SDS coating. The total coating can be easily removed and conveniently regenerated on-line. The simple coating procedure was described. By a series of optimization, a running buffer of 20 mm Na(2)B(4)O(7) + 16 mm SDS was applied for the separation of the derivatives. Linear relationships for E and PE were obtained in the range of 0.044-6.60 microg mL(-1) (correlation coefficients: 0.9975 for E, 0.9981 for PE), and the detection limits for E and PE were 1.71 and 0.67 ng mL(-1), respectively. The separation speed, the reproducibility and the sensitivity were much improved over those of other capillary electrophoresis methods more recently reported. The method was applied to the analysis of the two alkaloids in traditional herbal preparations with recoveries in the range 92.8-104.8%. 相似文献
22.
A MORPHOLOGICAL STUDY OF POLY(DIVINYLBENZENE-co-ACRYLIC ACID) IN CROSSLINKING PRECIPITATION POLYMERIZATION 总被引:1,自引:0,他引:1
Feng Bai Xin-lin Yang Wen-qiang Huang 《高分子科学》2006,(2):163-171
Divinylbenzene-80 (DVB-80) and polar monomer acrylic acid (AA) having hydrogen bonding at a total monomer loading of 5 vol% were precipitated-copolymerized in a variety of organic solvents with 2,2'-azobis(isobutyronitrile) (AIBN) as initiator. The experiments were investigated from a two-dimensional matrix, i.e., the actual crosslinking degree of DVB varying from 0 to 80% and the solvent composition varying from 0 to 100% of toluene mixture with acetonitrile, when the mixture of acetonitrile and toluene was used as the reaction solvent. Under various reaction conditions, six distinct morphologies including soluble polymers, swellable microgels, coagulum, irregular microparticles, and nano-/micrometer microspheres were formed and the structures of these polymer architectures were described. A morphological map was utilized to discuss the effects of both crosslinking degree of DVB and composition of solvent on the transitions between morphology domains. The results demonstrated that the microspheres are formed by an internal contraction due to the marginal solvency of the continuous phase and the crosslinking of the polymer network through the covalent bonding from DVB as well as the interchain hydrogen-bonding between the carboxylic acid units. 相似文献
23.
Natalia V. Avramenko M. V. Korobov Aksana M. Parfenova P. A. Dorozhko Natalia A. Kiseleva P. V. Dolgov 《Journal of Thermal Analysis and Calorimetry》2006,84(1):259-262
In an effort to improve
understanding of dissolution behaviour of fullerenes and their simple chemical
derivatives the binary systems of C60, C70
and the piperazine monoadduct of [60] fullerene C60
N2C4H8
with a series of aromatic solvents have been studied by means of DSC. In certain
systems solid solvates have been found to be the thermodynamically stable
phases relative to saturated solution at room temperature. Identified solid
solvates were characterized by their compositions, temperatures and enthalpies
of incongruent melting transitions. The regularities in thermodynamic stability
of the solvated crystals have been discussed along with dissolution properties
of fullerenes and the derivative. Certain correlations have been observed. 相似文献
24.
J. P. Bastide K. Ezzemouri J. M. Létoffé P. Claudy A. Bouamrane 《Journal of Thermal Analysis and Calorimetry》1996,47(3):833-846
The thermal behaviour of complexes [Li+-EC](AlH4)– withEC=12-C-4, 15-C-5, DC 18-C-6 (cis-anti-cis andcis-syn-cis isomers) was investigated by Differential Scanning Calorimetry (DSC). These complexes were prepared as solids from benzene solutions. Pure EC and several solvated species [Li+-EC](AlH4)–·nC6H6 (EC=15-C-5, DC 18-C-6syn) were also studied. DSC has revealed various phenomena. Solid-solid transitions were observed before melting for [Li+-EC](AlH4)– withEC=12-C-4 and 15-C-5. They are probably explained by small molecular modifications strongly dependent on the thermal history of the sample. A glass-transition was found for the pure crown-ether DC 18-C-6anti, the complex [Li+-EC](A1H4)– withEC=DC-18-C-6anti and the two solvates mentioned above. 相似文献
25.
Dr. Joice Thomas Dr. Liliana Dobrzańska Prof. Luc Van Meervelt Prof. Mario Alfredo Quevedo Prof. Krzysztof Woźniak Marcin Stachowicz Prof. Mario Smet Prof. Wouter Maes Prof. Wim Dehaen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):979-987
A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert‐butyl ester groups. Single‐crystal X‐ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level. In both crystal structures, solvent channels are present and differ in both shape and capacity. Furthermore, the methoxy‐substituted macrocycle undergoes a single‐crystal‐to‐single‐crystal transformation during which the molecular structure changes its conformation from 1,3‐alternate (loaded with THF/water) to 1,2‐alternate (apohost form). Molecular modelling techniques were applied to explore the conformational and energetic behaviour of the macrocycles. 相似文献
26.
Dr. Yuling Zhao Yue Zhao Dr. Cailing Wu Dr. Jikuan Qiu Dr. Huiyong Wang Dr. Zhiyong Li Prof. Yang Zhao Prof. Jianji Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9391-9397
As an important member of crystalline porous polymers, acylhydrazone-linked covalent organic frameworks (COFs) have gained much attention in recent years. However, the low structural stability imparts a limit on their practical applications. To tackle this problem, we report a simple strategy to increase the chemical stability of acylhydrazone-linked COFs by incorporating azobenzene groups in the conjugated framework. Through reinforcing the π-π stacking interactions between the adjacent layers with increased π-surface, it is surprising to find that the resulting materials exhibit extreme stability in harsh environments, such as in strong acid, strong base, aqueous educing agent and boiling water, even exposed to air for one year. As a proof-of-concept, such frameworks have been used to remove various organic micropollutants such as antibiotics, plastic components, endocrine disruptors, and carcinogens from water with high capacity, fast speed and excellent reusability over a wide pH range at environmentally relevant concentrations. The results provide a new avenue to significantly enhance the stability of COFs for practical applications. 相似文献
27.
Dr. Manuel Vázquez Sulleiro Ramiro Quirós-Ovies Mariano Vera-Hidalgo Dr. I. Jénnifer Gómez Dr. Víctor Sebastián Prof. Jesús Santamaría Prof. Emilio M. Pérez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(9):2993-2996
The combination of 2D materials opens a wide range of possibilities to create new-generation structures with multiple applications. Covalently cross-linked approaches are a ground-breaking strategy for the formation of homo or heterostructures made by design. However, the covalent assembly of transition metal dichalcogenides flakes is relatively underexplored. Here, a simple covalent cross-linking method to build 2H-MoS2–MoS2 homostructures is described, using commercially available bismaleimides. These assemblies are mainly connected vertically, basal plane to basal plane, creating specific molecular sized spaces between MoS2 sheets. Therefore, this straightforward approach gives access to the controlled connection of sulfide-based 2D materials. 相似文献
28.
Patrick W. Fritz Prof. Ali Coskun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(27):7489-7501
With the advent of silicon-based semiconductors, a plethora of previously unknown technologies became possible. The development of lightweight low-dimensional organic semiconductors followed soon after. However, the efficient charge/electron transfers enabled by the non-porous 3D structure of silicon is rather challenging to be realized by their (metal-)organic counterparts. Nevertheless, the demand for lighter, more efficient semiconductors is steadily increasing resulting in a growing interest in (metal-)organic semiconductors. These novel materials are faced with a variety of challenges originating from their chemical design, their packing and crystallinity. Although the effect of molecular design is quite well understood, the influence of dimensionality and the associated change in properties (porosity, packing, conjugation) is still an uncharted area in (metal-)organic semiconductors, yet highly important for their practical utilization. In this Minireview, an overview on the design and synthesis of porous semiconductors, with a particular emphasis on organic semiconductors, is presented and the influence of dimensionality is discussed. 相似文献
29.
Dr. Benoit Colasson Dr. Thomas Devic Dr. Joël Gaubicher Dr. Charlotte Martineau-Corcos Prof. Philippe Poizot Dr. Vincent Sarou-Kanian 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(37):9589-9596
The synthesis and characterization of a polyrotaxanated covalent organic network (CON) based on the association between the viologen and pillar[5]arene (P[5]OH) units are reported. The mechanical bond allows for the irreversible insertion of n-type redox centers (P[5]OH macrocycles) within a pristine structure based on p-type viologen redox centers. Both redox units are active on a narrow potential range and, in water, the presence of P[5]OH greatly increases the electroactivity of the material. 相似文献
30.
Sunny K. S. Freitas Felipe L. Oliveira Thiago C. dos Santos Danilo Hisse Claudia Merlini Célia M. Ronconi Prof. Dr. Pierre M. Esteves 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2342-2347
A thermally stable carbocationic covalent organic network (CON), named RIO-70 was prepared from pararosaniline hydrochloride, an inexpensive dye, and triformylphloroglucinol in solvothermal conditions. This nanoporous organic material has shown a specific surface area of 990 m2 g−1 and pore size of 10.3 Å. The material has CO2 uptake of 2.14 mmol g−1 (0.5 bar), 2.7 mmol g−1 (1 bar), and 6.8 mmol g−1 (20 bar), the latter corresponding to 3 CO2 molecules adsorbed per pore per sheet. It is shown to be a semiconductor, with electrical conductivity (σ) of 3.17×10−7 S cm−1, which increases to 5.26×10−4 S cm−1 upon exposure to I2 vapor. DFT calculations using periodic conditions support the findings. 相似文献