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991.
Physicochemical characterization of α‐chitin, β‐chitin,and γ‐chitin separated from natural resources
Mi‐Kyeong Jang Byeong‐Gi Kong Young‐Il Jeong Chang Hyung Lee Jae‐Woon Nah 《Journal of polymer science. Part A, Polymer chemistry》2004,42(14):3423-3432
We isolated α‐chitin, β‐chitin, and γ‐chitin from natural resources by a chemical method to investigate the crystalline structure of chitin. Its characteristics were identified with Fourier transform infrared (FTIR) and solid‐state cross‐polarization/magic‐angle‐spinning (CP–MAS) 13C NMR spectrophotometers. The average molecular weights of α‐chitin, β‐chitin, and γ‐chitin, calculated with the relative viscosity, were about 701, 612, and 524 kDa, respectively. In the FTIR spectra, α‐chitin, β‐chitin, and γ‐chitin showed a doublet, a singlet, and a semidoublet at the amide I band, respectively. The solid‐state CP–MAS 13C NMR spectra revealed that α‐chitin was sharply resolved around 73 and 75 ppm and that β‐chitin had a singlet around 74 ppm. For γ‐chitin, two signals appeared around 73 and 75 ppm. From the X‐ray diffraction results, α‐chitin was observed to have four crystalline reflections at 9.6, 19.6, 21.1, and 23.7 by the crystalline structure. Also, β‐chitin was observed to have two crystalline reflections at 9.1 and 20.3 by the crystalline structure. γ‐Chitin, having an antiparallel and parallel structure, was similar in its X‐ray diffraction patterns to α‐chitin. The exothermic peaks of α‐chitin, β‐chitin, and γ‐chitin appeared at 330, 230, and 310, respectively. The thermal decomposition activation energies of α‐chitin, β‐chitin, and γ‐chitin, calculated by thermogravimetric analysis, were 60.56, 58.16, and 59.26 kJ mol?1, respectively. With the Arrhenius law, ln β was plotted against the reciprocal of the maximum decomposition temperature as a straight line; there was a large slope for large activation energies and a small slope for small activation energies. α‐Chitin with high activation energies was very temperature‐sensitive; β‐Chitin with low activation energies was relatively temperature‐insensitive. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3423–3432, 2004 相似文献
992.
Young-Lae Kim Heon-Young Lee Serk-Won Jang Seung-Joo Lee Hong-Koo Baik Young-Soo Yoon Young-Shin Park Sung-Man Lee 《Solid State Ionics》2003,160(3-4):235-240
Thin film Ni3Sn2 anodes were deposited on a Cu substrate by e-beam evaporator at room temperature. The deposited films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). They were tested as anodes for thin film rechargeable lithium batteries. These film electrodes exhibited an excellent cycle performance over 500 cycles. Ni3Sn2 films remained without undergoing any crystallographic phase change during cycling. 相似文献
993.
Yang Chiang Ling‐Sheng Jang Sung‐Lin Tsai Ming‐Kun Chen Min‐Haw Wang 《Electroanalysis》2014,26(10):2129-2137
The electrical impedance analysis of single cells can provide information on cells’ pathological condition in various environments. Cell electrical properties are affected by factors such as the location, adhesion, and size of the cell. The proposed microfluidic device captures a single cell, maintains growth conditions, and allows single‐melanoma‐cell impedance to be measured using an impedance analyzer and a function generator. The rate of impedance variation (ROIV) can be used to determine cell growth conditions. Cellular apoptosis affects cell size and membrane surface area, and thus the electrical properties of cells. At 24 h without Antrodia cinnamomea (AC) addition, ROIV was 15.23 %, 17.04 %, and 12.60 % at temperatures of 34 °C, 37 °C, and 40 °C, respectively. At 24 h and 37 °C, ROIV was 17.04 %, 40.37 %, and 45.02 % for AC concentrations of 0, 20, and 40 µL/mL, respectively. The results show that the cell impedance variation of cells cultured without AC is much lower than that of cells cultured with AC. Regarding cellular morphology, with AC addition, the cells shrank obviously after 24 h, whereas they barely shrank without AC addition. 相似文献
994.
Daniel Klinger Cynthia X. Wang Luke A. Connal Debra J. Audus Se Gyu Jang Stephan Kraemer Kato L. Killops Glenn H. Fredrickson Edward J. Kramer Craig J. Hawker 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(27):7138-7142
We herein report a new facile strategy to ellipsoidal block copolymer nanoparticles that exhibit a pH‐triggered anistropic swelling profile. In a first step, elongated particles with an axially stacked lamellae structure are selectively prepared by utilizing functional surfactants to control the phase separation of symmetric polystyrene‐b‐poly(2‐vinylpyridine) (PS‐b‐P2VP) in dispersed droplets. In a second step, the dynamic shape change is realized by cross‐linking the P2VP domains, thereby connecting glassy PS discs with pH‐sensitive hydrogel actuators. 相似文献
995.
Yu-Chien Lin Yan Cao Jer-Huan Jang Chi-Min Shu Cathleen Webb Wei-Ping Pan 《Journal of Thermal Analysis and Calorimetry》2014,116(3):1249-1255
Graphene (G), and its derivatives, is an ideal two-dimensional material. It is comprised of a single sheet of hexagonally packed carbon atoms. Graphene has attracted significant research interest because of its excellent elastic, optical, electrical, thermal, and mechanical properties. Currently there are some synthesis methods regarding graphene production on the macroscopic-scale level; however, these methods, such as chemical vapor deposition, are expensive. A method for large-scale growth of graphene using widely accessible equipment is currently not an option. In this report, we select an approach based on the Modified Hummer’s method. A comparison is given between the Hummer’s method and the modified Hummer’s method based on extended characterizations using TG for their thermal stability, FTIR for their functional groups, TEM for their surface diagram, UV–Vis for their photo-activity, Raman spectroscopy for the identification of GO quality, and electrochemical methods for their reduction potentials. 相似文献
996.
Multifunctional Ag‐Decorated Porous TiO2 Nanofibers in Dye‐Sensitized Solar Cells: Efficient Light Harvesting,Light Scattering,and Electrolyte Contact
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Sun Hye Hwang Hee Song Jungsup Lee Prof. Jyongsik Jang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12974-12981
Designing the photoanode structure in dye‐sensitized solar cells (DSSCs) is vital to realizing enhanced power conversion efficiency (PCE). Herein, novel multifunctional silver‐decorated porous titanium dioxide nanofibers (Ag/pTiO2 NFs) made by simple electrospinning, etching, and chemical reduction processes are introduced. The Ag/pTiO2 NFs with a high surface area of 163 m2 g?1 provided sufficient dye adsorption for light harvesting. Moreover, the approximately 200 nm diameter and rough surface of the Ag/pTiO2 NFs offered enough light scattering, and the enlarged interpores among the NFs in the photoanode also permitted electrolyte circulation. Ag nanoparticles (NPs) were well dispersed on the surface of the TiO2 NFs, which prevented aggregation of the Ag NPs after calcination. Furthermore, a localized surface plasmon resonance effect by the Ag NPs served to increase the light absorption at visible wavelengths. The surface area and amount of Ag NPs was optimized. The PCE of pTiO2 NF‐based DSSCs was 27 % higher (from 6.2 to 7.9 %) than for pure TiO2 NFs, whereas the PCE of Ag/pTiO2 NF‐based DSSCs increased by about 12 % (from 7.9 to 8.8 %). Thus, the PCE of the multifunctional pTiO2 NFs was improved by 42 %, that is, from 6.2 to 8.8 %. 相似文献
997.
Young‐Hwan Jeong Minjung Son Hongsik Yoon Pyosang Kim Do‐Hyung Lee Prof. Dongho Kim Prof. Woo‐Dong Jang 《Angewandte Chemie (International ed. in English)》2014,53(27):6925-6928
An artificial light‐harvesting multiporphyrin dendrimer ( 8PZnPFB ) composed of a focal freebase porphyrin ( PFB ) with eight zinc(II) porphyrin ( PZn ) wings exhibited unique photophysical property switching in response to specific guest molecule binding. UV/Vis titration studies indicated stable 1:2 host–guest complex formation between 8PZnPFB and meso‐tetrakis(4‐pyridyl)‐porphyrin ( TPyP ) for which the first and second association constants were estimated to be >108 M ?1 and 3.0×107 M ?1, respectively. 8PZnPFB originally shows 94 % energy transfer efficiency from PZn to the focal PFB . By the formation of the host–guest complex ( 8PZnPFB? 2 TPyP ) the emission intensity of 8PZnPFB is significantly decreased, and an ultrafast charge separation state is generated. The energy transfer process from PZn wings to the PFB core in 8PZnPFB is almost entirely switched to an electron transfer process by the formation of 8PZnPFB? 2 TPyP . 相似文献
998.
Reaction of cyclic sulfates of vic-diols with sodium hydroxide in THF-MeOH produced the corresponding epoxides in excellent isolated yields at room temperature. Cyclic sulfates of trans-diols gave cis-epoxides, and cyclic sulfates of cis-diols afforded trans-epoxides exclusively. Various cyclic sulfates of vic-diols can be converted into the epoxides under the conditions. 相似文献
999.
α-Sulfonyl phosphonates were synthesized by direct sulfonylation of lithiated alkyl phosphonates with benzenesulfonyl fluoride which have shown different reactivity from benzenesulfonyl chloride, generally known as a sulfonylating reagent. 相似文献
1000.
Benzimidazole-based chromogenic chemosensor for the recognition of oxalic acid via counter ion displacement assay in semi-aqueous medium 总被引:1,自引:0,他引:1
An azo dye-coupled benzimidazole-based receptor 1 was synthesized and investigated as a receptor for metal ions in semi-aqueous medium. The receptor recognizes Cu2+ with high selectivity over other metal ions. The resultant complex 1·Cu2+ was found to selectively bind oxalic acid via counter ion displacement. 相似文献