铜催化的共轭硅化反应的研究进展

有机硅化合物在有机合成中具有广泛的应用.它可以经过简单的反应转化为一系列的功能性的化合物.铜催化的不饱和化合物的共轭硅化反应是一种重要的合成有机硅化合物的方法.综述了铜催化的不饱和化合物的共轭硅化反应的发展过程及用于硅化反应的硅试剂的发展历程,重点总结了近些年的相关报道,尤其是不对称共轭硅化反应的进展.     

如何教给同学系统的，巩固的化学基础知识

在中学化学教学大纲上指示,中学化学教学的基本任务:“第一就是使学生获得一定的系统的和巩固的化学基本知识……。”我觉得这样的要求是非常恰当的。系统的鞏固的化学基本知识,就不是零碎的、片面的、散乱的一堆化学材料,而是系统的、科学的、自然界物质变化的规律;不是无用的、累赘的、死板的知识,而是学了化学之後,能获得合乎高等学校要求的化学基础,或是直接为国家的生产建设服务。因而在正确的进行系统的、鞏固的基本化学知识的讲授     

编者的话

在过去几年中,化学通报,无论在质的方面或量的方面,都有不少的进步,在这里边,作者的支持和读者的关怀,都起了很大的作用。值此新年佳节,我们谨向作者和读者祝贺并致谢意。“中国共产党第八次全国代表大会关于政治报告的决议”里指出了文化教育以及科学事业的发展,对于国家工业化的重要性。在周恩来同志的“关于发展国民经济的第二个五年计划的建议的报告”里,也把提高高等教育的和中等教育的质量作为一项任务。化学通报的主要服务对象,仍然和过去一样,是中等学校教师和大中学生。它的质量的高低,对于国家当前的任务完成的好坏,有直接的影响。我们愿和全国的化学工作者,共同努力,把通报的质量,进一步提高。     

DNA上电荷转移的理论研究

DNA上电荷的转移过程对许多生物化学和生物物理过程起着相当重要的作用，而本论文的主要研究方向即是利用动力学的方法发展双链模型研究DNA上电荷转移过程。根据已有的donor-bridge-acceptor模型的基本想法，论文给出了双链模型的哈密尔顿算符，解释了环境振子哈密尔顿算符与总的哈密尔顿算符中耦合项的关系。在双链模型的计算中，获得了良好的电荷密度衰减曲线。在对桥链长度变化的计算中，得出具有3或4个碱基对的桥链作为电荷转移机理的转折点，在这个折点两边的不同桥链长度的DNA链具有不同的衰减常数。而在对序列变化的计算中，可以看出，由于碱基之间的转移积分的差异导致了不同序列的链上电荷转移速度具有明显的差异，但是这种差异要远小于由于桥链长度不同而带来的速率的快慢。     

物质的量的测量向摩尔溯源的标准

1 物质的量的基本单位——摩尔 物质的量的基本概念起源于完全确定的化学物质的本质属性—一存在的数目,换句话说起源于物质的特殊性质。按照这种理解表示“量”的最简单的方法就是指示所研究物质的粒子个数。单元是表述物质微粒数的一个合适的单位。然而,由于处理很大的数不方便,就选用了一个大的微粒数,组成一个     

从高考化学实验题的特点谈实验复习要"形神"兼备

随着高考改革的深入,能力考查的比重将越来越大。而实验题又正是综合能力考查的首选题型之一。对实验题的特点及导向进行分析会有效地提高化学实验复习的质量。1高考化学实验题的特点及导向分析近几年高考化学实验的都具备以下共同的特点:(1)形式上不再出现大型装置的连接,均是小型的又带有研究性的试题。(2)命题的立意上往往用常规搭建平台考查创新。如2002年化学实验的考查,既有氨气的制备方法的常规考查,又有喷泉实验装置的改进创新;2003年的既有制氢氧化亚铁的常规考查,又有氢氧化亚铁的制取的改进和创新。(3)重操作细节的考查。如2002…     

1997年全国高中学生化学竞赛(初赛)试题与试题分析

今年的全国高中学生化学竞赛的初赛刚刚结束。我们认为这次竞赛的试题较好地体现了今年5月全国高中学生化学竞赛工作会议上再次肯定的试题的水平要求:原理水平大致与人民教育出版社的《化学读本》相当,基本上不涉及更高一级的,即大学化学的原理,但考虑到冬令营的优胜选手以及参加国际竞赛的选拔,需要补充一定量的静态立体化学的知识(包括立体异构),当然试题涉及的具体化学内容本身对中学生是陌生的,但用竞赛学生的已有知识以及适当增加的知识为基础是可以理解的。为进一步考察试题的难易,我们对试题作如下的分析。     

结构化学展望

结构化学是探讨化学物质的微观结构以及它和宏观性能之间相互关系的基础科学,是化学学科的一个重要分支。这里所谓微观结构,指的是原子-分子层次的结构,包括分子中原子的空间排列以及原子基团之间的相对空间排布;分子的各种内部运动,包括分子的转动,原子间的振动和其中电子的运动;这些不连续的(即量子化的)运动状态给出的能级的分布。经典的化学结构理论曾经正确地指出:物质的内部结构完全决定了它的典型化学反应性能(实际上也同时决定了大部分其它方面的性能);反过来,通过这些典型化学反应性能的研究,原则上也应该能定出化     

泽林斯基学派底发展道路(一)

一、烃类的合成二、烃的相互转变三、关于石油成因的研究四、■■类的催化反应五、硫化物的催化反应六、关于蛋白质化学的研究社会主义劳动英雄,泽林斯基院士是苏联著名的化学家。他曾经领导过卓越的化学学派,在碳氢化合物化学的研究中表现了出色的成就,他也是有机化合物催化反应创始人之一,对於苏联的有机化学工业作出了杰出的贡献。他发明了防毒面具,在第一次世界大战中拯救了十万人的生命。此外,在一、烃类的合成二、烃的互相转变三、关于石油成因的研究四、杂环类的催化反应五、硫化物的催化反应六、关於蛋白质化学的研究     

11R(-)-双氢青蒿酸的分离鉴定和青蒿酸的同位素标记

青蒿素是中药青蒿抗疟的有效成份。青蒿素不仅具有新颖的倍半萜结构,而且又有突出的抗疟药效。我们小组进行了它的生物合成的研究,以了解自然界合成这类物质的途径,生物合成中间体的分离鉴定,中间体的同位素标记和标记了的中间体的生物转化是生物合成研究的     

Optical Sol-Gel-Based Dissolved Oxygen Sensor: Progress Towards a Commercial Instrument

A dissolved oxygen sensor based on fluorescence quenching of the oxygen-sensitive ruthenium complex, [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline]2+, which has been immobilized in a porous silica sol-gel-derived film, is reported. Ormosil sensing films were fabricated using modified silica precursors such as methyltriethoxysilane (MTEOS) and ethyltriethoxysilane (ETEOS) and were dip-coated onto planar glass substrates. Tailoring of the films for dissolved oxygen (DO) sensing is described whereby sensor response is optimized by maximizing film hydrophobicity by the use of the modified precursors. Sensor performance parameters such as limit of detection and sensor resolution are reported. Issues such as dye leaching and photobleaching are discussed. Progress towards a commercial instrument is reported.     

Sol-Gel-derived Film for Oxygen Sensor

Oxygen concentration is an important parameter in environmental, chemical and other fields. Oxygen sensor based on luminescence quenching by oxygen have been developed and wide applied. The oxygen quenching process is described by the Stern-Volmer equation. Ruthenium complex are chosen as fluorescence indicator because they are particularly attractive for oxygen sensing, exhibit high luminescent quantum yield, long excited-state lifetime, large Stokes shift, and strong absorption in the blue-green spectral region^[1]. The sensor involves immobilizing the ruthenium complex within a porous sol-gel-processed film. Sol-gel process has many advantages as a method of immobilization. At ambient temperature, it allows the fabrication of a tough, inert, porous glass material with a high surface area. Sol-gel-derived silica film has a low optical absorption in the visible and UV region of the spectrum and is relatively inexpensive to produce^[2].     

Dual optical sensor for oxygen and temperature based on the combination of time domain and frequency domain techniques

In measuring specific conditions in the real world, there are many situations where both the oxygen concentration and the temperature have to be determined simultaneously. Here we describe a dual optical sensor for oxygen and temperature that can be adapted for different applications. The measurement principle of this sensor is based on the luminescence decay times of the oxygen-sensitive ruthenium complex tris-4,7-diphenyl-1,10-phenanthroline ruthenium(III) [Rudpp] and the temperature-sensitive europium complex tris(dibenzoylmethane) mono(5-amino-1,10-phenanthroline)europium(III) [Eudatp]. The excitation and emission spectra of the two luminophores overlap significantly and cannot be discriminated in the conventional way using band pass filters or other optical components. However, by applying both the frequency and time domain techniques, we can separate the signals from the individual decay time of the complexes. The europium complex is entrapped in a poly(methyl methacrylate) (PMMA) layer and the ruthenium complex is physically adsorbed on silica gel and incorporated in a silicone layer. The two layers are attached to each other by a double sided silicone based tape. The europium sensing film was found to be temperature-sensitive between 10 and 70 °C and the ruthenium oxygen-sensitive layer can reliably measure between 0 and 21% oxygen.     

Luminescence Quenching Behavior of Oxygen Sensing ORMOSIL Films Based on Ruthenium Complex

An organically modified silicate(ORMOSIL) based optical sensor response to gaseous O2 or O2 dissolved in water is presented. The oxygen sensing film mechanism is based on the principle of fluorescence quenching of tris(4,7-diphenyl-l , 10-phenanthroline) ruthenium ( ) ([Ru(dpp)3]2+), which has been entrapped in a porous ORMOSIL film. In order to establish optimum film-processing parameters, comprehensive investigations, including the effects of the polarity and the hydrophobicity of the sensing film on oxygen quenching response and response time, were carried out. The film hydrophobicity increased as a function of dimethyl-dimethoxysilane (DiMe-DMOS) content, which is correlated with enhanced oxygen sensor performance. The sensor developed in the present work exhibits the advantages of fast response time and good reversibility. The detection limits are 0. 5 % and 0. 3 g/mL for O2 in the gaseous and the aqueous phases, respectively.     

Optimization of Ormosil Films for Optical Sensor Applications

Recent work has indicated that Ormosil films, fabricated from organically modified precursors, produce better sensor performance for some specific applications, compared to films fabricated from conventional sol-gel precursors such as TEOS or TMOS. This paper aims to compare film properties and sensor behavior for films fabricated from tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS) silica precursors and both methyltrimethoxysilane (MTMS) and methyltriethoxysilane (MTES) organically modified precursors. Microstructural differences, for example, porosity changes due to the different precursor backbone structures, are interrogated by monitoring oxygen gas and aqueous-phase sensor response. Oxygen sensing using these films is enabled by incorporating in the films an oxygen-sensitive ruthenium dye whose fluorescence is quenched in the presence of oxygen. Film properties such as thickness, thickness stabilization time, as well as sensor response, are discussed in terms of relative hydrolysis and condensation behavior for the different precursors. Film hydrophobicity, an issue which has been identified as being of crucial importance for optimum dissolved oxygen sensor response, is discussed and contact angle measurements are used to investigate the degree of hydrophobicity for different film types. The main motivation for this work is film optimization for optical gas-phase and dissolved oxygen sensors.     

Polarization-based oxygen sensor

A new approach to oxygen sensing based on the luminescence polarization observed from a novel type of sensor is described. The oxygen sensor consists of an oxygen-sensitive silicone film containing tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) chloride [Ru(dpp)3Cl2] and an oxygen-insensitive film of Styryl 7 in poly(vinyl alcohol). Polarizers are used to select orthogonally polarized emission components from Ru(dpp)3Cl2 and Styryl 7. The polarization of the combined emission was found to be highly sensitive to the partial pressure of oxygen. This method of polarization sensing is generic and can be used with any fluorophore which displays an analyte-dependent change in intensity.     

Lifetime-based optical sensor for high-level pCO2 detection employing fluorescence resonance energy transfer

An optical sensor for the measurement of high levels of carbon dioxide in gas phase has been developed. It is based on fluorescence resonance energy transfer (FRET) between a long-lifetime ruthenium polypyridyl complex and the pH-active disazo dye Sudan III. The donor luminophore and the acceptor dye are both immobilised in a hydrophobic silica sol–gel/ethyl cellulose hybrid matrix material. Tetraoctylammonium hydroxide (TOA-OH) is used as an internal buffering system. Fluorescence lifetime is measured in the frequency domain, using low-cost phase modulation measurement technology. The use of Sudan III as an acceptor dye has enabled the sensor to have a dynamic range up to 100% carbon dioxide. The sensor displays 11.2° phase shift between the limit of detection (LOD) of 0.06 and 100% CO₂ with a resolution of better than 2%. The encapsulation in the silica/polymer hybrid material has provided the sensor with good mechanical and chemical stability. The effect of molecular oxygen, humidity and temperature on the sensor performance was studied in detail.     

Fiber-optic fluorescence sensor for dissolved oxygen detection based on fluorinated xerogel immobilized with ruthenium (II) complex

A fiber-optic sensor based on fluorescence quenching was designed for dissolved oxygen (DO) detection. The fluorinated xerogel-based sensing film of the present sensor was prepared from 3, 3, 3-trifluoropropyltrimethoxysilane (TFP–TriMOS). Oxygen-sensitive fluorophores of tris (2, 2′- bipyridine) ruthenium (II) (Ru(bpy)₃²⁺) were immobilized in the sensing film and the emission fluorescence was quenched by dissolved oxygen. In the sensor fabrication, a two-fiber probe was employed to obtain the best fluorescence collection efficiency and the sensing film was attached to the probe end. Scanning electron microscope (SEM), UV–Vis absorption spectroscopy (UV–Vis) and fourier transform infrared spectroscopy (FTIR) measurements have been used to characterize the sensing film. The sensor sensitivity is quantified by I _deoxy/I _oxy, where I _deoxy and I _oxy represented the detected fluorescence intensities in fully deoxygenated and fully oxygenated environments, respectively. Compared with tetramethoxysilane (TMOS) and methyltriethoxysilane (MTMS)-derived sensing films, TFP–TriMOS-based sensor exhibited excellent performances in dissolved oxygen detection with short response time of 4 s, low limit of detection (LOD) of 0.04 ppm (R.S.D. = 2.5%), linear Stern–Volmer calibration plot from 0 to 40 ppm and long-term stability during the past 10 months. The reasons for the preferable performances of TFP–TriMOS-based sensing film were discussed.     

Optimisation of Sol-Gel-Derived Silica Films for Optical Oxygen Sensing

Sol-gel-derived silica films were fabricated by dip-coating onto planar and optical fibre substrates. The films were pre-doped with the oxygen-sensitive ruthenium complex [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline)], whose fluorescence is quenched in the presence of oxygen. The structure and behaviour of sol-gel films is related to the fabrication parameters. In order to optimise the films for oxygen sensing in gaseous and in aqueous media, the quenching behaviour was monitored as a function of dip-speed and water: precursor ratio. By adjusting the above parameters, film properties can be tailored to optimise oxygen quenching in particular concentration ranges and environments.     

基于钌配合物荧光猝灭原理的新型氟化有机改性溶胶-凝胶氧传感膜的研究

选用3,3,3-三氟丙基三甲氧基硅烷为前驱体,制备氧光化学传感膜材料.利用4,7-二苯基-1,10-邻菲咯啉钌(Ⅱ)([Ru(dpp)3(ClO4)2])为氧荧光猝灭指示剂,通过优化制备条件获得对氧浓度变化具有敏感响应的传感膜.研究结果表明:所制备的氧传感膜对水体中的溶解氧的线性响应范围为0.5～16.0 mg/L,最...