Pt（111）电极上O2与OHad的吸脱附及氧还原反应动力学

研究了Pt（111）电极在0．1mol／LHClO4溶液中O2吸附与OHad脱附及氧还原反应的动力学．研究发现OHad的可逆吸脱附速率很快;在氧还原的动力学或动力学与传质混合控制区,恒电位下氧还原的电流随反应时间缓慢衰减,在转速较大,扫速较慢的情形下正向扫描过程中氧还原的电流总是明显低于逆向扫描的电流;Pt／0．1mol／LHClO4从无O2切换到O2饱和时,其开路电位迅速从0．9V增加到1．0V．结果表明,Pt（111）电极上O2解离生成OHad速率很快,ORR过程中OHad会在表面缓慢积累,氧还原反应的动力学主要由反应 OHad＋H^＋＋e→←H2O的平衡热力学决定．     

室温下碘催化直接构建硫化吡唑啉酮

含硫化合物在有机合成、药物化学以及材料化学等领域具有重要的作用.到目前为止,科学家已经在C-S键的构建领域进行了很多工作.在构建C-S键的众多方法中,金属催化的C-S键合成反应是一类很重要的反应,但是此方法存在着催化剂对空气敏感、环境不友好等问题.因此,发展无金属催化的C-S键构建反应受到了人们越来越多的重视.基于我们在碘催化相关反应方面的研究,本文报道了一种碘催化的硫化吡唑啉酮类化合物的合成方法.我们选用3-甲基-1-苯基-2-吡唑啉-5-酮与二苯二硫醚为底物进行条件筛选实验,发现I2(10%)为催化剂,二氧六环为溶剂,H2O2为氧化剂为最优化的实验条件,目标产物硫化吡唑啉酮最高产率为88%.在最优化的反应条件下,我们尝试了带有不同官能团(NO2,Cl,OH等)的吡唑啉酮与二硫醚的反应,均能以较高产率得到目标产物.当含有杂环的二硫醚(2,2'-二硫二吡啶)作为反应底物时,也能以中等以上的产率得到相应的目标产物.另外还进行了对比试验,例如在反应体系中加入自由基捕获剂TEMPO,反应产率会大大降低,说明反应中应该有自由基中间体生成;如果反应体系中不加碘,则反应产率为零;如果反应体系中不加H2O2,则反应产率由88%降低至48%,说明碘和H2O2在反应中都起到了重要作用.通过以上对比试验,提出了可能的反应机理:首先,二硫醚发生均裂反应生成苯硫基自由基,然后苯硫基自由基与碘反应生成亲电的PhSI活性中间体,PhSI与异构化的吡唑啉酮发生亲电取代反应,生成目标产物硫化吡唑啉酮和HI,HI可以被H2O2氧化生成I2继续参与下一轮催化反应.以3-甲基-1-苯基-2-吡唑啉-5-酮与二苯二硫醚为底物,我们对此反应进行了放大试验,结果显示反应产率几乎没有降低,这为此反应的大规模应用奠定了基础.在此,我们发展了一种简单高效的合成硫化吡唑啉酮的反应,此方法无需金属催化剂,利用常见的碘为催化剂就可以以较高的产率得到目标产物.为合成含硫化合物提供了一种新的方法.     

冰晶石型氟化物(NH_4)_3FeF_6的水热合成及其磁学性质

首次采用水热法合成了冰晶石型氟化合物(NH_4)_3FeF_6,其结构和性质经X-射线粉末衍射、扫描电子显微镜和差热-热重分析表征。(NH_4)_3FeF_6属立方晶系,空间群Fm-3m,晶胞参数a=b=c=0.913 0 nm。对磁化率进行了表征。结果表明:随着温度降低,磁有序与晶体特征和孤立的磁单元有关。     

Simplified fabrication of high areal capacitance all-solid-state micro-supercapacitors based on graphene and MnO2 nanosheets

A universal simplified strategy was developed to fabricate all-solid-state planar micro-supercapacitors with high areal capacitance (~355 mF/cm²), based on interdigital patterned films of 2D pseudocapacitive MnO₂ nanosheets and electrochemically exfoliated graphene.     

Cu催化的单电子转移活性自由基聚合制备石墨烯/聚N,N-二甲基丙烯酰胺复合体系

以天然石墨为起始原料,采用改进的Hummer方法,通过强酸氧化水解和超声分散制备了氧化石墨烯,然后通过肼还原和重氮化反应得到含有羟基的石墨烯(G-OH),再通过酯化反应在石墨烯表面上引入了α-氯代羰基,从而得到了含有单电子转移活性自由基聚合(SET-LRP)引发基团的石墨烯(G-Cl).最后,在石墨烯表面原位引发N,N-二甲基丙烯酰胺(DMAA)单体的SET-LRP聚合,得到了G-PDMAA复合材料,G-PDMAA在常规的有机溶剂和水中具有良好的分散性.     

流动注射-分光光度法测定药物中克林霉素磷酸酯的含量

试验表明:在pH 3.8的乙酸盐缓冲介质中,克林霉素磷酸酯(CLP)能将铁(Ⅲ)还原为铁(Ⅱ),而所生成的铁(Ⅱ)与邻菲啰啉反应生成有色络合物(λmax=508nm),且生成的铁(Ⅱ)量与CLP之间存在定量关系,经换算所测得吸光度与CLP的质量浓度在0.70~140mg·L-1之间呈线性关系。据此并结合流动注射技术(FI)提出了FI-分光光度法间接测定药物中CLP的新方法优化的分析条件如下:①乙酸盐缓冲溶液的加入量:2.5mL;②铁(Ⅲ)溶液质量浓度:10.0mg·L-1;③邻菲啰啉溶液浓度:1.5×10-3 mol·L-1;④反应温度:85℃。该方法的检出限为0.060mg·L-1。应用此方法测定了药物中CLP的含量,测定值与国家药品标准方法的测定值相符。     

Enzymetically Regulating the Self‐Healing of Protein Hydrogels with High Healing Efficiency

Enzyme‐mediated self‐healing of dynamic covalent bond‐driven protein hydrogels was realized by the synergy of two enzymes, glucose oxidase (GOX) and catalase (CAT). The reversible covalent attachment of glutaraldehyde to lysine residues of GOX, CAT, and bovine serum albumin (BSA) led to the formation and functionalization of the self‐healing protein hydrogel system. The enzyme‐mediated protein hydrogels exhibit excellent self‐healing properties with 100 % recovery. The self‐healing process was reversible and effective with an external glucose stimulus at room temperature.     

Structural elucidation of new urinary tamoxifen metabolites by liquid chromatography quadrupole time‐of‐flight mass spectrometry

In this study, tamoxifen metabolic profiles were investigated carefully. Tamoxifen was administered to two healthy male volunteers and one female patient suffering from breast cancer. Urinary extracts were analyzed by liquid chromatography quadruple time‐of‐flight mass spectrometry using full scan and targeted MS/MS techniques with accurate mass measurement. Chromatographic peaks for potential metabolites were selected by using the theoretical [M + H]⁺ as precursor ion in full‐scan experiment and m/z 72, 58 or 44 as characteristic product ions for N,N‐dimethyl, N‐desmethyl and N,N‐didesmethyl metabolites in targeted MS/MS experiment, respectively. Tamoxifen and 37 metabolites were detected in extraction study samples. Chemical structures of seven unreported metabolites were elucidated particularly on the basis of fragmentation patterns observed for these metabolites. Several metabolic pathways containing mono‐ and di‐hydroxylation, methoxylation, N‐desmethylation, N,N‐didesmethylation, oxidation and combinations were suggested. All the metabolites were detected in the urine samples up to 1 week. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of trifloxystrobin and trifloxystrobin acid residue in rice and soil by a modified quick,easy, cheap,effective, rugged,and safe method using ultra high performance liquid chromatography with tandem mass spectrometry

A sensitive analytical method for the simultaneous determination of trifloxystrobin and its metabolite trifloxystrobin acid in rice including straw, bran, brown rice and soil was developed by using ultra high performance liquid chromatography coupled with tandem mass spectrometry. The fungicide trifloxystrobin and its metabolite trifloxystrobin acid were extracted using acetonitrile with 1% formic acid v/v and subsequently cleaned up by primary secondary amine, octadecylsilane or graphitized carbon black prior to ultra high performance liquid chromatography coupled with tandem mass spectrometry. The determination of two target compounds was achieved in less than 3 min using an electrospray ionization source in positive mode. The limits of detection were below 0.22 μg/kg and the limits of quantification did not exceed 0.74 μg/kg in all matrices, which were much lower than the maximum residue levels established by the Codex Alimentarius Commission. The overall average recoveries in four matrix at three levels (0.1, 1.0 and 5.0 mg/kg) ranged from 74.2 to 107.4% with a relative standard deviations of less than 7.8% (n = 5) for both analytes. The method was demonstrated to be convenient and reliable for the routine monitoring of trifloxystrobin and its metabolite. The developed method was validated and applied for the analysis of degradation study samples.     

Label-free colorimetric aptasensor for sensitive detection of ochratoxin A utilizing hybridization chain reaction

The combination of high selectivity of aptamer with the peroxidase-mimicking property of DNAzyme has presented considerable opportunities for designing colorimetric aptasensor for detection of ochratoxin A (OTA). The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. Hybridization chain reaction (HCR) between two hairpin DNAs was employed to further improve the sensitivity of this method. The presence of OTA triggers the opening of the hairpin structure and the beginning of HCR, which results in the release of many DNAzyme, and generates enhanced colorimetric signals, which is correlated to the amounts of OTA with linear range between 0.01 to 0.32 nM, and the limit of detection is 0.01 nM under optimal conditions. OTA in yellow rice wine and wheat flour samples was also detected using this method. We demonstrate that a new colorimetric method for the detection of OTA has been established, which is simple, easy to conduct, label-free, sensitive, high throughput, and cost-saving.