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101.
以Se溶胶为模板,合成了多层核壳结构的Se@Pt@Au@Pt实心纳米粒子;采用化学与电化学相结合的除硒方法制得了(PtAuPt)HN/GC,并表征了(PtAuPt-Se)HN的表面形貌、结构与组成;以甲酸为探针分子,比较了(PtAuPt)HN/GC和Pt/C/GC对甲酸氧化的电催化行为,发现(PtAuPt)HN/GC催化甲酸氧化只有1个氧化峰,峰电位和峰电流分别约为0.35V和1.22mA/cm2,而Pt/C/GC则有2个氧化峰,在0.35V时所对应的电流密度仅约为0.30mA/cm2,前者在该电位时的电流密度是后者的4倍;在0.30mA/cm2的电流密度下,(PtAuPt)HN/GC对应的电极电位为0.01V,比Pt/C/GC负移了340mV;在600s时的计时电流分别为0.06和0.02mA/cm2.(PtAuPt)HN对甲酸氧化的电催化活性不但比Pt/C高,而且具有一定的抗CO中毒性能. 相似文献
102.
增压O2/CO2燃烧是一种可高效分离回收CO2的新兴燃烧技术,其燃烧机理与常压空气、常压O2/CO2燃烧存在较大差异。在加压热重分析仪上研究了增压条件下总压、氧浓度、气氛及粒径等反应参数对美国烟煤和淮北无烟煤燃烧特性的影响,确定了煤的着火温度,并对其进行燃烧动力学分析。结果表明,增压O2/CO2气氛下,随着压力或氧浓度的增加,DTG曲线向低温区移动,煤样整体燃烧速率加快。压力提升、氧浓度增加及煤粉细化均可改善O2/CO2气氛下煤样的着火特性。常压O2/CO2气氛下煤粉燃烧基本属于一级反应;增压O2/CO2气氛下,低温区属于0.5级反应,而高温区属于1.5级反应。 相似文献
103.
104.
Graphene‐sensitized microporous membrane/solvent microextraction for the preconcentration of cinnamic acid derivatives in Rhizoma Typhonii
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A novel graphene‐sensitized microporous membrane/solvent microextraction method named microporous membrane/graphene/solvent synergistic microextraction, coupled with high‐performance liquid chromatography and UV detection, was developed and introduced for the extraction and determination of three cinnamic acid derivatives in Rhizoma Typhonii. Several factors affecting performance were investigated and optimized, including the types of graphene and extraction solvent, concentration of graphene dispersed in octanol, sample phase pH, ionic strength, stirring rate, extraction time, extraction temperature, and sample volume. Under optimized conditions, the enrichment factors of cinnamic acid derivatives ranged from 75 to 269. Good linearities were obtained from 0.01 to 10 μg/mL for all analytes with regression coefficients between 0.9927 and 0.9994. The limits of quantification were <1 ng/mL, and satisfactory recoveries (99–104%) and precision (1.1–10.8%) were also achieved. The synergistic microextraction mechanism based on graphene sensitization was analyzed and described. The experimental results showed that the method was simple, sensitive, practical, and effective for the preconcentration and determination of cinnamic acid derivatives in Rhizoma Typhonii. 相似文献
105.
Li Yang Fu Xuan Li Xu-Xin Zhang Fang Wu Qiang Wang Yun Yan Ze-Yi 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(2):877-888
Journal of Radioanalytical and Nuclear Chemistry - In this study, the imidazole-based poly(ionic liquid)s (PILs) synthesized by one step method has been applied for the enrichment and recovery of... 相似文献
106.
A metallaphotoredox catalyzed hydroxyl aromatization of serine is developed to achieve rapid synthesis of aryl ethers of various serine derivatives. Under the catalytic system of ethylene glycol dimethyl ether nickel bromide (NiBr2 (dme))/4,4'-dimethoxy-2,2'-bipyridine/zinc powder and synergistic iridium photoredox catalysis, nickel is catalyzed and inserted into the C—Br bond, and then followed by transmetalation with the hydroxyl group of serine. The resulting Ni(Ⅱ)species are oxidized by the excited Ir(Ⅲ)species to a Ni(Ⅲ)intermediate. This intermediate is unstable and reductive elimination takes place rapidly to give the target product O-arylated serine in the yields from 65% to 39%. Through a metallaphotoredox catalysis strategy,the reaction features mild,efficient,clean and broad scope of substrate, providing a new way for the synthesis of various serine derivatives with medicinal value. © 2022, Science Press (China). All rights reserved. 相似文献
107.
将癸酸和香叶醇在10 mL玻璃管中以2∶1的物质的量之比混合,然后将混合物在80℃水浴锅中加热,直至形成稳定的低共熔溶剂(DES)。该溶剂易合成、低成本、低毒性且具有高生物降解性,是一种新型的疏水性DES,可用于水产品中内分泌干扰物的微萃取。取已粉碎的水产品样品1 g和乙腈2 mL置于5 mL离心管中,以转速2 000 r·min^(-1)涡旋振荡3 min。取上清液400μL,经0.45μm滤膜过滤,滤液与100μL DES混合,并迅速注入装有5 mL 80 g·L^(-1)氯化钠溶液的10 mL离心管中,以完成DES的分散。将上述离心管以转速3 500 r·min^(-1)离心5 min,然后置于冰浴中进行固化。将固化后所得样品溶解于150μL甲醇中,以Eclipse Plus C;色谱柱为分离柱,以体积比90∶10的甲醇-水的混合液为流动相,在激发波长228 nm,发射波长305 nm处测定双酚A、4-叔辛基苯酚和壬基酚等3种内分泌干扰物的含量。结果表明,DES在冰浴中固化,可促进其从水溶液中分离,简单且快速,利于萃取剂的收集。3种内分泌干扰物的质量分数均在0.25~10μg·g^(-1)内与其对应的峰面积呈线性关系,检出限(3S/N)均为0.075μg·g^(-1)。用此法对空白加标样品进行测定,测定值的日内和日间相对标准偏差(n=5)均小于4.0%。以空白样品为基体进行加标回收试验,所得回收率为78.7%~91.6%。 相似文献
108.
Li Yang Li-yuan Xie Xuan Chen Xiao-hong Bai Shuang Hu 《Journal of separation science》2022,45(13):2252-2261
A novel solvent terminated microextraction method based on a natural deep eutectic solvent (L-menthol and lactic acid at a molar ratio of 1:2) coupled with high-performance liquid chromatography was proposed, which was utilized for the separation and enrichment of bisdemethoxycurcumin, demethoxycurcumin and curcumin in Curcumae Longae Rhizoma and turmeric tea. The effects of independent parameters on extraction efficiency were optimized by single-factor analysis. Subsequently, four predominated parameters affecting the extraction procedure, including extractant volume, salt concentration, demulsifier consumption, and demulsification time, were further evaluated by a central composite design. Under the optimized conditions, the linear ranges of calibration curves were 0.005–0.5 μg/mL for bisdemethoxycurcumin, 0.004–0.4 μg/mL for demethoxycurcumin, and 0.0045–0.45 μg/mL for curcumin, respectively. In addition, the developed method provided low detection limits (0.1–0.4 ng/mL) and high enrichment factors (279–350). Its intra-day and inter-day precision were carried out by relative standard deviation ranging from 2.2 to 9.2%. Finally, the applicability of this method was assessed by the analysis of Curcumae Longae Rhizoma and turmeric tea samples. The results showed that these samples were detected successfully and the spiked recoveries over the range of 85.3-108.9% with relative standard deviations of 1.6-8.9% were attained, indicating its high relative recoveries with good precision in real sample analysis. 相似文献
109.
An efficient tandem route to obtain tetrasubstituted NH pyrroles in a one-pot manner has been developed, staring from simple nitriles, ethyl bromoacetates, and zinc. This reaction involves oxidative dimerization of the zinc bromide complex of β-enaminoesters using cerium ammonium nitrate (CAN) as an oxidant, affording 2,3,4,5-tetrasubstituted pyrroles in yields up to 91%. 相似文献
110.
Brian N. DiMarco Dmitry E. Polyansky David C. Grills Ping Wang Yutaka Kuwahara Xuan Zhao Etsuko Fujita 《Chemphyschem》2021,22(14):1478-1487
In this work, the differences in catalytic performance for a series of Co hydrogen evolution catalysts with different pentadentate polypyridyl ligands (L), have been rationalized by examining elementary steps of the catalytic cycle using a combination of electrochemical and transient pulse radiolysis (PR) studies in aqueous solution. Solvolysis of the [CoII−Cl]+ species results in the formation of [CoII(κ4-L)(OH2)]2+. Further reduction produces [CoI(κ4-L)(OH2)]+, which undergoes a rate-limiting structural rearrangement to [CoI(κ5-L)]+ before being protonated to form [CoIII−H]2+. The rate of [CoIII−H]2+ formation is similar for all complexes in the series. Using E1/2 values of various Co species and pKa values of [CoIII−H]2+ estimated from PR experiments, we found that while the protonation of [CoIII−H]2+ is unfavorable, [CoII−H]+ reacts with protons to produce H2. The catalytic activity for H2 evolution tracks the hydricity of the [CoII−H]+ intermediate. 相似文献