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991.
对不同的样品消解方法及电感耦合等离子体质谱、电感耦合等离子体原子发射光谱、石墨炉原子吸收光谱法测定土壤中铅的测定结果进行比对。采用电热板、微波及水浴3种加热方式,选择硝酸、氢氟酸、双氧水、王水、高氯酸、盐酸的不同组合进行土壤样品消解,通过分析测定值的精密度和准确度,考察消解体系对电感耦合等离子体质谱、电感耦合等离子体发射光谱、石墨炉原子吸收光谱法测定结果的影响。结果表明采用电感耦合等离子体质谱法测定土壤中的铅,最适宜的消解体系是硝酸-氢氟酸-高氯酸(微波加热),采用电感耦合等离子体原子发射光谱法测定最适宜的消解体系是硝酸(电热板加热),采用石墨炉原子吸收光谱法测定最适宜的消解体系是硝酸-盐酸-高氯酸(微波加热)。电感耦合等离子体质谱法的精密度和准确度优于另外两种方法。 相似文献
992.
Danqi Yang Luming Dong Xudong Hou Weikang Zheng Jian Xiao Jianzhong Xu Haiyun Ma 《先进技术聚合物》2020,31(1):135-145
A highly cross‐linked poly (cyclotriphosphazene‐resveratrol) microsphere (PRV) was synthesized by using hexachlorocyclotriphosphazene (HCCP) and bio‐based resveratrol (REV) as raw materials, and the obtained PRV microspheres were applied to improve the flame retardancy and mechanical property of epoxy resin (EP). The TGA results showed that the PRV microsphere is an excellent charring agent and the char yield is as high as 62% at 800°C. The incorporation of PRV makes the initial degradation earlier yet significantly increases the char residue of EP composites. Moreover, the introduction of PRV microspheres into EP greatly promoted the flame retardancy performance. Under 3% of addition of PRV microspheres, the peak heat release rate (PHRR) and total heat release (THR) were decreased by 58.3% and 29.6%, respectively, the limited oxygen index (LOI) value was increased to 29.7% from 25.3% of pure EP. In addition, because of the uniform distribution in EP matrix and the enhancing effect of PRV microspheres, the mechanical properties including tensile modulus of EP composites were strengthened. PRV microspheres in this paper provide a possibility to synthesize a dual functional filler, which acts as both flame retardant and strengthening agent. 相似文献
993.
Marvin Vestal Lingjun Li Evgenia Dobrinskikh Yatao Shi Bowen Wang Xudong Shi Sicheng Li Christina Vestal Kenneth Parker 《Journal of mass spectrometry : JMS》2020,55(8)
A new high performance linear MALDI‐TOF mass spectrometer provides both high spatial resolution and high speed. This instrument employs a new ion optics system with a grounded ion source and efficient transfer and detection of ions over a broad mass range. This provides very high sensitivity, precision, and an extended dynamic range for both positive and negative ion detection. Here we demonstrate the capabilities of this system by imaging pancreatic tissue samples from rats and mice. 相似文献
994.
Shang‐Zheng Sun Yaya Duan Riccardo S. Mega Rosie J. Somerville Ruben Martin 《Angewandte Chemie (International ed. in English)》2020,59(11):4370-4374
A modular, site‐selective 1,2‐dicarbofunctionalization of vinyl boronates with organic halides through dual catalysis is described. This reaction proceeds under mild conditions and is characterized by excellent chemo‐ and regioselectivity. It thus represents a complementary new technique for preparing densely functionalized alkyl boron architectures from simple and accessible precursors. 相似文献
995.
Yuan Liu Xue Li Qinghua Zhang Weidong Li Yu Xie Hanyu Liu Lu Shang Zhongyi Liu Zhimin Chen Lin Gu Zhiyong Tang Tierui Zhang Siyu Lu 《Angewandte Chemie (International ed. in English)》2020,59(4):1718-1726
A challenging but pressing task to design and synthesize novel, efficient, and robust pH‐universal hydrogen evolution reaction (HER) electrocatalysts for scalable and sustainable hydrogen production through electrochemical water splitting. Herein, we report a facile method to prepare an efficient and robust Ru‐M (M=Ni, Mn, Cu) bimetal nanoparticle and carbon quantum dot hybrid (RuM/CQDs) for pH‐universal HER. The RuNi/CQDs catalysts exhibit outstanding HER performance at all pH levels. The unexpected low overpotentials of 13, 58, and 18 mV shown by RuNi/CQDs allow a current density of 10 mA cm?2 in 1 m KOH, 0.5 m H2SO4, and 1 m PBS, respectively, for Ru loading at 5.93 μgRu cm?2. This performance is among the best catalytic activities reported for any platinum‐free electrocatalyst. Theoretical studies reveal that Ni doping results in a moderate weakening of the hydrogen bonding energy of nearby surface Ru atoms, which plays a critical role in improving the HER activity. 相似文献
996.
Yulin Wang Run Shi Lu Shang Geoffrey I. N. Waterhouse Jiaqi Zhao Qinghua Zhang Lin Gu Tierui Zhang 《Angewandte Chemie (International ed. in English)》2020,59(31):13057-13062
Carbon‐supported NiII single‐atom catalysts with a tetradentate Ni‐N2O2 coordination formed by a Schiff base ligand‐mediated pyrolysis strategy are presented. A NiII complex of the Schiff base ligand (R,R)‐(?)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamine was adsorbed onto a carbon black support, followed by pyrolysis of the modified carbon material at 300 °C in Ar. The Ni‐N2O2/C catalyst showed excellent performance for the electrocatalytic reduction of O2 to H2O2 through a two‐electron transfer process in alkaline conditions, with a H2O2 selectivity of 96 %. At a current density of 70 mA cm?2, a H2O2 production rate of 5.9 mol gcat.?1 h?1 was achieved using a three‐phase flow cell, with good catalyst stability maintained over 8 h of testing. The Ni‐N2O2/C catalyst could electrocatalytically reduce O2 in air to H2O2 at a high current density, still affording a high H2O2 selectivity (>90 %). A precise Ni‐N2O2 coordination was key to the performance. 相似文献
997.
Dr. Lei Zhang Takumi Oishi Liuzhou Gao Shiyu Hu Linlin Yang Prof. Dr. Wei Li Shengjun Wu Prof. Dr. Rong Shang Prof. Dr. Yohsuke Yamamoto Prof. Dr. Shuhua Li Prof. Dr. Wei Wang Prof. Dr. Guxiang Zeng 《Chemphyschem》2020,21(23):2573-2578
A new efficient metal-based frustrated Lewis pair constructed by (PtBu3)2Pt and B(C6F5)3 was designed through density functional theory calculations for the catalytic dehydrogenation of ammonia borane (AB). The reaction was composed by the successive dehydrogenation of AB and H2 liberation, which occurs through the cooperative functions of the Pt(0) center and the B(C6F5)3 moiety. Two equivalents of H2 were predicted to be liberated from each AB molecule. The generation of the second H2 is the rate-determining step, with a Gibbs energy barrier and reaction energy of 27.4 and 12.8 kcal/mol, respectively. 相似文献
998.
Li Xu Zheng Tingting Zhang Lan Zhao Songtao Chen Yinuo Wei Miaojin Shang Chunyan Bao Jun Zeng Jie 《中国科学:化学(英文版)》2020,63(12):1705-1710
Science China Chemistry - Photocatalytic reduction of CO2 into value-added products is a promising strategy for mitigating environmental and energy problems simultaneously. Herein, we developed Au... 相似文献
999.
Chengcheng Hu Jie Mi Suli Shang Ju Shangguan 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1119-1125
This study is devoted to the thermal decomposition of ZnC2O4·2H2O, which was synthesized by solid-state reaction using C2H2O4·2H2O and Zn(CH3COO)2·2H2O as raw materials. The initial samples and the final solid thermal decomposition products were characterized by Fourier transform infrared and X-ray diffraction. The particle size of the products was observed by transmission electron microscopy. The thermal decomposition behavior was investigated by thermogravimetry, derivative thermogravimetric and differential thermal analysis. Experimental results show that the thermal decomposition reaction includes two stages: dehydration and decomposition, with nanostructured ZnO as the final solid product. The Ozawa integral method along with Coats–Redfern integral method was used to determine the kinetic model and kinetic parameters of the second thermal decomposition stage of ZnC2O4·2H2O. After calculation and comparison, the decomposition conforms to the nucleation and growth model and the physical interpretation is summarized. The activation energy and the kinetic mechanism function are determined to be 119.7 kJ mol?1 and G(α) = ?ln(1 – α)1/2, respectively. 相似文献
1000.
One‐Pot Synthesis of N‐Acetyl‐ and N‐Glycolylneuraminic Acid Capped Trisaccharides and Evaluation of Their Influenza A(H1 N1) Inhibition 下载免费PDF全文
Dr. Yun Hsu Hsiu‐Hwa Ma Larry S. Lico Dr. Jia‐Tsrong Jan Prof. Dr. Koichi Fukase Dr. Yosuke Uchinashi Dr. Medel Manuel L. Zulueta Prof. Dr. Shang‐Cheng Hung 《Angewandte Chemie (International ed. in English)》2014,53(9):2413-2416
Human lung epithelial cells natively offer terminal N‐acetylneuraminic acid (Neu5Ac) α(2→6)‐linked to galactose (Gal) as binding sites for influenza virus hemagglutinin. N‐Glycolylneuraminic acid (Neu5Gc) in place of Neu5Ac is known to affect hemagglutinin binding in other species. Not normally generated by humans, Neu5Gc may find its way to human cells from dietary sources. To compare their influence in influenza virus infection, six trisaccharides with Neu5Ac or Neu5Gc α(2→6) linked to Gal and with different reducing end sugar units were prepared using one‐pot assembly and divergent transformation. The sugar assembly made use of an N‐phthaloyl‐protected sialyl imidate for chemoselective activation and α‐stereoselective coupling with a thiogalactoside. Assessment of cytopathic effect showed that the Neu5Gc‐capped trisaccharides inhibited the viral infection better than their Neu5Ac counterparts. 相似文献