氟烷基化和氟烷氧基化的研究 21: 锌存在下全氟烷基碘与亚硝酸阴离子的反应及其机理探讨

在过量锌粉的存在下, 全氟烷基碘(RFCF2I, RF:CF3CF2, Cl(CF2)n, n=3,5,7)(1)能与亚硝酸阴离子反应, 一步生成全氟烷基羧酸钠, 酸化后得到相应的羧酸. p-DNB不能阻止反应. NO3^-, SCN^-或F^-等阴离子在同样条件下和1反应只能生成1-氢-全氟烷烃.反应可能经锌单电子转移诱发的非链式自由基亲核取代机理.     

A facile approach to synthesize poly(4-vinylpyridine)/multi-walled carbon nanotubes nanocomposites: highly water-dispersible carbon nanotubes decorated with gold nanoparticles

A facile approach to attach high-density and uniform gold nanoparticles on individual multi-walled carbon nanotubes (MWNTs) is achieved. By simple grinding, water-soluble linear polymers poly(4-vinylpyridine) (PVP)-wrapped around nanotubes and thus rendered them reversibly soluble in water, ethanol, and DMF. Individual tubes are clearly observed after PVP-wrapped nanotubes were spin-coated onto a silicon wafer. Subsequently, Au nanoparticles were densely decorated on the individual MWNTs by in situ reduction of HAuCl₄ in the homogeneous aqueous solution of MWNTs–PVP to form stable water-dispersible Au/PVP/MWNTs hybrid. Morphology of Au nanoparticles was determined by scanning electron microscope and atomic force microscope. The diameter of the Au nanoparticles is controlled in the range of 3.5 to 13.5 nm. The presence of gold nanoparticles with decreased particle size was also detected by UV–Vis spectroscopy.     

Novel phosphorescent neutral iridium(III) complex with the steric hindrance for highly efficient red organic light-emitting diodes

A novel and highly efficient thiophenquinolone-based red iridium(III) complex bearing a bulky fluorophenyl moiety is designed and synthesized. The complex shows intensive red phosphorescence (596 nm with shoulder at 642 nm), high photoluminescence efficiency (0.62) and broad full width at half maximum (81 nm). The bulky fluorophenyl moiety introduced into the complex could improve the efficiency of electroluminescence with the maximum current efficiency, power efficiency and the external quantum efficiency up to 29.0 cd/A, 30.4 lm/W and 17.6% due to the effective steric hindrance in solid states.     

微波消解-FAAS法测定三种蒙成药中铜、铁、锰、钙和镁

微波消解 -火焰原子吸收分光光度法测定蒙成药中 5种金属元素。实验结果表明 ,微波消解方法简便 ,消化时间短 ;测试方法具有较好的精密度和准确度     

过硫酸胺与N－［（3－二甲氨基）丙基］丙烯酰胺氧化还原引发体系的研究

过硫酸胺与Ｎ－［（３－二甲氨基）丙基］丙烯酰胺氧化还原引发体系的研究司堃，郭新秋，丘坤元（北京大学化学与分子工程学院北京１００８７１）关键词Ｎ－取代丙烯酰胺，氧化还原体系，反应动力学，端基分析，反应机理Ｎ－［（３一二甲氨基）两基］丙烯酸胺（ＤＭＡＰＡ...     

过硫酸胺与N－［（3－二甲氨基）丙基］丙烯酰胺氧化还原引发体系的研究

N-[(3-DimetLylamino)-propyll acrylamide(DMAPAA) and N-[(3dimetliylamino)-propyl] methacrylamide(DMAPMA) were synthesized by the reaction of 3-dimethylamino-propylamine with acryloyl and methacryloyl chloride respectively at 0-5℃ temperature. The kinetics of the aqueous solution polylmerization of acrylamide(AAm) by using ammonium persulfate(APS) combined with DMAPAA or DMAPMA was investigated. The rate equations were given as:respectively. The overall activation energies of the polymerization were determined as low as 35.0kJ/mol and 41.0kJ/mol respectively. Based on the end-group analysis results, the reaction mechanism of DMAPAA or DMAPMA with APS was proposed to be similar to the initiation reation of persulfate/tertiary aliphatic amine redox system,and the resulting aminomethyl radicals were responsible for initiation of vinyl polymerization as well as sulfate radical.     

Synthesis and characterization of ABA-type block copolymer of poly(trimethylene carbonate) with poly(ethylene glycol): Bioerodible copolymer

ABA-type block copolymers of poly(trimethylene carbonate) with poly(ethylene glycol) (M_n 6820), PTMC-b-PEG-b-PTMC, were synthesized by the ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) in the presence of poly-(ethylene glycol) with stannous octoate catalyst, and the copolymers with various compositions were obtained. The PTMC-b-PEG-b-PTMC copolymers were characterized with Fourier transform infrared and nuclear magnetic resonance spectroscopies. The intrinsic viscosities of resulting copolymers increased with the increase of 1,3-dioxan-2-one content in feed while the molar ratio of monomer over catalyst kept constant. It has been observed that the glass transition temperature (T_g) of the PTMC segments in copolymers, recorded from differential scanning calorimetry, was dependent on the composition of copolymers. The melting temperature (T_m) of PEG blocks in copolymer was lower than that of PEG polymer, and then disappeared as the length of PTMC blocks increased. The results of dynamic contact angle measurement clearly revealed that the hydrophilicity of resulting copolymers increased greatly with the increase of PEG content in copolymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 695–702, 1998     

场发射平板显示高低压电平转换电路

提出适用于场发射高压驱动的高低压电平转换电路设计及性能分析。通过模拟,此电路可以在100V的驱动工作电压以及10mA的驱动电流条件下安全工作,最高工作频率可达20MH_z。在50pF输出负载下上升时间和下降时间分别为14,25ns。同时分析了高压CMOS器件与0.8μm标准CMOS工艺兼容过程中的厚栅氧化对于低压器件及高压N管的阈值特性影响。     

垂直低温两相流管底液氮汽泡上升速度的实验研究

本文对垂直低温两相流管底部液氮汽泡的上升速度运用高速摄像机进行了可视化实验研究,对所采集的实时图像进行处理.在Cole和Mendelson汽泡上升速度经验公式的基础上,通过对液氮汽泡的上升速度的分析,提出了圆管管路底部液氮汽泡的上升速度的拟合公式,分析研究其变化规律,为进一步探求圆管内液氮弹状汽泡的生成机理提供依据.     

近红外光谱结合共识模型快速检测果酒的总酚含量

果酒发酵中的多酚是引起果酒口感、颜色变化的重要因素。为保证果酒品质,有必要开发一种快速监测发酵过程中多酚含量变化的技术。收集不同批次成熟期的蓝莓、桑葚为原料,分别碾压成汁,同时按比例混合二者,于小型发酵罐进行发酵。通过离线收集不同发酵时段的发酵液于离心管,高速离心后取上清液置于棕色瓶保存,共计得到48个果酒发酵样本。将上清液置于三个平行样比色皿,以傅里叶快速变换近红外光谱仪(FT-NIR)采集其透射光谱,取平均值作为该样本的光谱信号。然后将棕色瓶内的发酵液以国标法(即以标准液的吸光度值制定标准曲线)测定各样品的总酚含量,以duplex法计算样本光谱之间的距离且按2∶1的比例划分为训练集和预测集。采用间隔偏最小二乘法(iPLS)将训练集样本的透射光谱与总酚含量之间构建定量模型,间隔数从2依次变化到60个。该研究创新之处是使用共识方法融合多个已构建好的iPLS成员模型,按一定的共识规则分配权系数。通过各成员模型交互验证的残差及其残差之间的相关性来优化各成员模型的线性组合,以拉格朗日乘数法求解各成员模型的权系数,使间隔偏最小二乘-共识模型(consensual iPLS,CiPLS)的交互验证均方根误差最小。相比于全局PLS模型、划分不同间隔数量时的iPLS模型,CiPLS均具有较小的预测误差。当划分39个间隔时由三个iPLS成员模型(即14th,16th,18th)组成的共识模型误差最小为124.2,交互验证相关系数为0.944,对预测集样本的预测均方根误差为163.4,预测相关系数为0.931,预测性能均优于PLS和iPLS模型。另外,作为对比选用连续投影算法与无信息变量剔除法来优化光谱模型,其预测性能均不及本文提出的共识模型。分析各iPLS模型预测残差之间的相关性,发现共识模型主要是融合那些具有较高预测性能且模型间较低相关性的成员模型。结果表明,光谱分析结合共识方法可提高回归模型的预测精度、减少建模所需变量数,能够用于果酒总酚含量的离线快速检测。