助剂形态对Pt/γ-A12O3催化剂抗积炭性能的影响

采用CO和H2脉冲吸附、程序升温还原、NH3程序升温脱附及X射线衍射等手段对各金属氧化物改性的Pt/Al2O3催化剂进行了表征,研究了助剂形态对Pt/Al2O3催化剂在非临氢条件下催化环己烷脱氢反应性能的影响.结果表明,催化剂稳定性从高到低依次为Zr-Pt/Al2O3＞ Ca-Pt/Al2O3＞ Ce-Pt/Al2O3...     

Dynamics of ice nucleation on water repellent surfaces

Prevention of ice accretion and adhesion on surfaces is relevant to many applications, leading to improved operation safety, increased energy efficiency, and cost reduction. Development of passive nonicing coatings is highly desirable, since current antiicing strategies are energy and cost intensive. Superhydrophobicity has been proposed as a lead passive nonicing strategy, yet the exact mechanism of delayed icing on these surfaces is not clearly understood. In this work, we present an in-depth analysis of ice formation dynamics upon water droplet impact on surfaces with different wettabilities. We experimentally demonstrate that ice nucleation under low-humidity conditions can be delayed through control of surface chemistry and texture. Combining infrared (IR) thermometry and high-speed photography, we observe that the reduction of water-surface contact area on superhydrophobic surfaces plays a dual role in delaying nucleation: first by reducing heat transfer and second by reducing the probability of heterogeneous nucleation at the water-substrate interface. This work also includes an analysis (based on classical nucleation theory) to estimate various homogeneous and heterogeneous nucleation rates in icing situations. The key finding is that ice nucleation delay on superhydrophobic surfaces is more prominent at moderate degrees of supercooling, while closer to the homogeneous nucleation temperature, bulk and air-water interface nucleation effects become equally important. The study presented here offers a comprehensive perspective on the efficacy of textured surfaces for nonicing applications.     

Hollow fiber supported liquid membrane extraction for ultrasensitive determination of trace lead by portable tungsten coil electrothermal atomic absorption spectrometry

Hollow fiber supported liquid membrane extraction (HF-SLME) was used to separate and enrich trace lead from a large volume of 250 mL water sample to a final tiny volume of 30 μL of 1-octanol, 5 μL of which was inject into a tungsten coil electrothermal atomic absorption spectrometer (W-coil ET-AAS) for determination of lead. Some important parameters that influenced the extraction and determination were investigated in detail, such as the concentration of ammonium pyrrolidine dithiocarbamate (APDC), pH of sample solution, stirring rate, extraction time, pyrolysis current, atomization current, carrier gas flow rate, as well as interferences. Under the optimized conditions, a practical enrichment factor of 499 and a limit of detection (3σ) of 0.2 ng mL^{− 1} were obtained. The calibration curve was linear in the range of 0.5–10 ng mL^{− 1}. The relative standard deviation (RSD) was 5.6% for five measurements of a 4 ng mL^{− 1} lead standard solution. The accuracy of this method was examined by the analysis of certified reference water samples (GBW(E)080398 and GSBZ(E) 50009-88) for lead. Finally, the proposed method was applied to the determination of lead in local tap water, pond water and river water, with recoveries in the range of 96–109% for spiked samples.     

固载离子液体刷/过氧磷钨酸盐催化剂催化H2O2选择性氧化硫醚

以二氧化硅为载体,合成了一种新型的双层离子液体刷固载过氧磷钨酸盐催化剂.采用元素分析、IR和SEM-EDAX等手段对催化剂进行了表征.室温下,考察了该催化剂催化30％(质量分数)H2O2溶液选择性氧化硫醚为亚砜或砜的催化性能.结果表明,该催化剂具有很高的催化活性和选择性.采用1.1倍H2O2时,反应选择性地生成亚砜,仅...     

Tracing the evolution of the mitochondrial protein import machinery

Mitochondria are eukaryotic organelles originated from a single bacterial endosymbiosis about 2 billion years ago. One of the earliest events in the evolution of mitochondria was the acquisition of a mechanism that facilitated the import of proteins from cytosol. The mitochondrial protein import machinery consists of dozens of subunits, and they are of modular design. However, to date, it is not clear when certain component was added to the machinery. Using extensive homology searches, the evolutionary history of the mitochondrial protein import machinery was reconstructed. The results indicated that 6 of the 35 subunits have homologs in prokaryote, suggesting that they were prokaryotic origin; the major subunit gains were occurred in the earliest stage of eukaryotic evolution; subsequent to the gain of these conserved set of subunits, the mitochondrial protein import machinery components diversified along the eukaryotic lineages and a number of lineage-specific subunits can be observed. Furthermore, protein import systems of mitochondria-like organelles (hydrogenosomes and mitosomes) have dramatically reduced their subunit contents, however, they share most of the prokaryotic origin components with mitochondrion.     

微波辅助快速制备核-壳型尿苷印迹聚合物及其在线富集应用研究

采用微波辅助加热,以尿苷为模板分子,丙烯酰胺(AA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,快速制备尿苷印迹聚合物,聚合时间大大缩短,仅为传统加热的1/8.采用红外光谱和扫描电镜对印迹聚合物进行表征,结果表明二氧化硅表面成功包覆尿苷印迹壳层;该印迹聚合物颗粒分散均匀,印迹壳层厚度约为100 nm.将该印...     

组合催化剂上丙烷选择氧化制丙烯酸

考察了在C3H8氧化脱氢的NiZrO催化剂和C3H6选择氧化的Mo基催化剂组成的组合催化剂上C3H8选择氧化制取丙烯酸的反应性能.结果表明,两个催化剂比例适当时,反应的丙烯酸收率可达最大.优化温度、烷氧比、空速以及N2含量等反应条件的结果发现,反应体系中O2的匮乏会严重影响反应性能.在有氧分布器的反应装置中对所选组合催化剂在优化的反应条件下进行了30h稳定性测试,结果表明,在340oC,反应性能基本稳定,C3H8转化率和丙烯酸选择性可分别维持在～20%和～74%.     

纳米材料在电化学生物传感器及生物电分析领域中的应用

纳米尺度上的生物分析化学是当今国际生物分析领域研究的前沿和热点.该文阐述了纳米粒子在电化学免疫传感器及电化学DNA传感器领域的应用,着重介绍了以纳米材料为载体设计新型的具有生物分子识别和电信号增强作用的纳米标记粒子在构建高灵敏电化学生物传感器以及多组分同时检测中的应用.     

液相色谱-三重串联四极杆质谱测定粮油中的黄曲霉毒素

建立了超声提取-液相色谱-电喷雾三重串联四极杆质谱测定玉米、大米、大豆等粮油固体样品中黄曲霉毒素B1、B2、G1和G2(AFB1、AFB2、AFG1和AFG2)的方法。分析前对样品进行超声提取,优化得到最佳超声提取条件: 溶剂为甲醇-水(含40 g/L NaCl) (80:20, v/v)溶液、料液比为1:3(g:mL)、温度为50 ℃、时间为3 min。然后对提取的样品进行免疫亲和特异性净化。最后与液相色谱-电喷雾三重串联四极杆质谱联用,使用C18反相色谱柱,流动相为甲醇-10 mmol/L乙酸铵水溶液梯度洗脱,以黄曲霉毒素M1(AFM1)作为内标进行定量测定。结果表明,AFB1、AFB2、AFG1和AFG2的检出限分别为0.002、0.004、0.004和0.012 μg/kg。方法的加标回收率为87%～111%,日内相对标准偏差(RSD)和日间RSD分别不大于6.7%和5.6%。实验结果表明该方法可以有效地降低基质效应的影响,相比于外标法能极大地提高方法的准确度。     

高效液相色谱-电喷雾电离三级四极杆质谱检测动物源食品中氯霉素、甲砜霉素、氟苯尼考残留量

建立了动物源产品中氯霉素、甲砜霉素、氟苯尼考残留量的高效液相色谱-电喷雾电离三级四极杆质谱(LC-ESI-MS/MS)的方法。前处理方法包括添加同位素内标氯霉素-d5,碱化乙酸乙酯提取,C18小柱净化。该方法采用负离子,多反应监测氯霉素四对离子(321.0/151.9,321.0/256.6,321.0/194.2,321.0/175.4),甲砜霉素两对离子(354.1/185.0,354.1/290.0),氟苯尼考两对离子(356.0/335.9,356.0/185.1)和同位素内标氯霉素-d5(326.0/157.1)。该方法线性范围为0.1~1.6μg/kg;对不同基质样品的加标回收率为80%~112.5%;相对标准偏差小于11%;方法的测定低限为0.1μg/kg。