电子的发现与化学键电子理论的发展

1892年,荷兰物理学家洛伦兹通过创建电子论,为原子内部电子的发现提供了理论基础。1897年,英国物理学家汤姆逊从阴极射线中发现了自由电子,打破了原子不可分的传统观念,由此引发了卢瑟福、玻尔等人对原子内部结构的探索。同时,化学家们将物理学中的电子引入化学,开始用原子结构中的电子来解释化学行为,提出了化学键的电子理论,推动了化学键理论的发展。     

A Novel Method for the Detection of Chlorpyrifos by Combining Quantum Dot-labeled Molecularly Imprinted Polymer with Flow Cytometry

Uniform-sized fluorescent molecularly imprinted polymers were prepared by one-step swelling and suspension polymerization, while chlorpyrifos, methacrylic acid, ethylene glycol dimethacrylate, and oil-soluble CdSe/ZnS quantum dots were used as the carrier, template molecule, functional monomer, cross-linker, and fluorophor, respectively. The morphology, adsorption dynamics, binding ability, and selectivity of quantum dot-labeled molecularly imprinted polymers were evaluated. The dosage of quantum dots for labeling the molecularly imprinted polymers was optimized. The results showed that the optimized dose of quantum dots was 200?µL using a concentration of 8.0?µM. The microsphere size was approximately 10?µm with a honeycombed surface. The quantum dot-labeled molecularly imprinted polymers had an even brightness and a high selectivity. In the presence of different concentrations of chlorpyrifos, a decrease in the fluorescence intensity of the quantum dot-labeled molecularly imprinted polymer was clearly identified by flow cytometry. The whole detection process was accomplished within 2?h including pretreatment. This method was used for the determination of chlorpyrifos in tap water samples.     

孤对电子与赤道取向——sp3d杂化轨道中电子对排列的一种有趣现象

揭示了一种有趣的分子结构现象：在ABn型多原子分子或离子结构中,若中心原子A的轨道杂化方式为sp3d,且价层有孤电子对时,孤电子对总是呈三角双锥的赤道取向;若分子中A、B原子间有重键时,B原子也总是呈赤道取向。探讨了这一现象的内在原因,并通过归纳法论证了这一规律。     

基于零价铁的地下水化学还原修复体系中的电子转移有效性和电子竞争机制

近年来,基于零价铁的化学还原技术因其高效性逐渐被应用于受污染地下水的原位修复。但是,该技术在实际应用中仍面临一些亟待解决的问题。零价铁作为一种高活性的电子供体,除了和目标污染物反应外,还可以与地下水中其他的氧化性物质（如O₂、H⁺或NO₃^-等）反应。这些反应所造成的零价铁腐蚀,不仅会降低修复效率还会增加地下水修复成本。此外,同类或多类污染物间也存在对零价铁所释放电子的相互竞争,从而影响各自的去除效率。本文综述了基于零价铁的地下水修复体系中的电子传递过程和氧化物间的电子竞争机制,从零价铁的腐蚀和电子传递、零价铁电子选择性量化指标的提出和量化方法、地下水体中多种共存氧化物间电子竞争作用、电子效率的影响因素以及强化措施等方面进行详细介绍。最后,对该技术今后发展方向作出了展望,以期为其今后实际的地下水修复应用提供参考。     

Molecularly engineered graphene surfaces for sensing applications: A review

Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis.     

Optimization of Hydrogen‐Evolving Photochemical Molecular Devices

A molecular photocatalyst consisting of a Ru^II photocenter, a tetrapyridophenazine bridging ligand, and a PtX₂ (X=Cl or I) moiety as the catalytic center functions as a stable system for light‐driven hydrogen production. The catalytic activity of this photochemical molecular device (PMD) is significantly enhanced by exchanging the terminal chlorides at the Pt center for iodide ligands. Ultrafast transient absorption spectroscopy shows that the intramolecular photophysics are not affected by this change. Additionally, the general catalytic behavior, that is, instant hydrogen formation, a constant turnover frequency, and stability are maintained. Unlike as observed for the Pd analogue, the presence of excess halide does not affect the hydrogen generation capacity of the PMD. The highly improved catalytic efficiency is explained by an increased electron density at the Pt catalytic center, this is confirmed by DFT studies.     

Strong,Thermally Superinsulating Biopolymer–Silica Aerogel Hybrids by Cogelation of Silicic Acid with Pectin

Silica aerogels are excellent thermal insulators, but their brittle nature has prevented widespread application. To overcome these mechanical limitations, silica–biopolymer hybrids are a promising alternative. A one‐pot process to monolithic, superinsulating pectin–silica hybrid aerogels is presented. Their structural and physical properties can be tuned by adjusting the gelation pH and pectin concentration. Hybrid aerogels made at pH 1.5 exhibit minimal dust release and vastly improved mechanical properties while remaining excellent thermal insulators. The change in the mechanical properties is directly linked to the observed “neck‐free” nanoscale network structure with thicker struts. Such a design is superior to “neck‐limited”, classical inorganic aerogels. This new class of materials opens up new perspectives for novel silica–biopolymer nanocomposite aerogels.     

The electron microanalyzer (EPMA): a powerful device for the microanalysis of filled polymeric materials

The electron probe microanalyzer is a device often used in the field of geology or in the glass and steel industries. However, it is barely known or used in the polymer field. Thus, in this paper, we investigate the use of electron probe microanalyzer for polymer microanalyses and compared it with a scanning electron microscope equipped with an energy dispersive spectrometer. To show the unique potential of this technique only develop in our lab for polymer application, three different samples were studied: (i) a fire protective epoxy‐based coating submitted to aging in salt water, (ii) the distribution of organometallic catalysts into a thermal isolative silicone polymer, and (iii) the fouling growth of milk protein (biopolymer) on a stainless steel surface. Compared to an energy dispersive spectrometer, with an electron probe microanalyzer it is possible to quickly create X‐ray mappings of low concentration elements at a good resolution, as well as allowing the interpretation of the mechanism of action for the three samples which was impossible using only an energy dispersive spectrometer because of its too low detection resolution. Copyright © 2015 John Wiley & Sons, Ltd.     

红树林湿地土壤矿物的分析

以湛江湾南海堤典型红树林湿地土壤为研究对象,采用X射线衍射(XRD)和傅立叶变换红外光谱(FTIR)快速批量鉴定土壤中矿物成分,利用扫描电子显微镜(SEM)观察土壤颗粒形貌特征并获得化学成分组成信息;同时采集附近光滩土壤样品进行对比研究,以揭示红树林湿地土壤特殊的生态环境特征。结果表明,红树林湿地土壤矿物主要由高岭石、石英、白云母、埃洛石、地开石和蛇纹石等组成;与光滩土壤相比,红树林湿地土壤矿物类型多样,而光滩土壤矿物相对单一,主要为石英和高岭石;红树林湿地土壤颗粒以片状聚合体为主,主要元素组成为C、O、S、Al、Si、Mg、Fe等,常见含有Cu、Zn、Mo等重金属元素。同时发现红树林湿地土壤颗粒含有较丰富的硫化物;而光滩土壤未发现上述特征,表明红树林湿地处于一个特殊的生态环境,土壤沉积物中富含有机质、Fe、S等,比一般潮滩更易于富集硫化物或重金属。     

原位透射电镜研究正交相五氧化二铌纳米片的电化学储钠机制

由于正交相五氧化二铌(T-Nb₂O₅)为ReO₃型层状结构,锂、钠离子可以在其(001)平面快速脱嵌,而在[001]方向的传输一般较难。本研究通过原位透射电子显微镜(Transmission Electron Microscope,TEM)方法研究钠在T-Nb₂O₅纳米片(001)面内及[001]方向的钠离子电化学嵌入行为,发现由于纳米片晶体存在大量的位错和畴界,钠离子可通过这些缺陷穿越(001)面扩散,并进而在深层的(001)面内快速扩散。同时,本研究还发现刚合成的T-Nb₂O₅纳米片在[001]方向上存在调制结构,存在交替分布的压应变和张应变区域,而钠离子的嵌入可以调节这些应变分布。