表面活性剂对制备MoS2纳米微粉的影响

Mo0_2纳米微粉在催化l‘l、敏感元件［‘·’］及磁记录材料［‘］等方面具有特殊用途,其传统制备方法是通过在高温下用氢还原l’,‘l,利用这种方法制备M。0。纳米微粉、所得产品粒子尺寸较大,比表面积小,且反应在条件苛刻,从而限制了M00。纳米微粉的使用范围．文献曾报导用y一辐照法制备了一系列金属、合金和氧化物的纳米粒子”－‘Q’,这种方法利用水辐解产生的水合电子（efo）作为还原剂,具有在常温常压下进行操作的显著优点,因而受到普遍关注．本实验室l‘’1曾报导通过v一辐照法可制备Moo。纳米非晶,其颗粒尺寸为8－30urn…     

Preparation of Nanocrystalline MoS2 Hollow Spheres

NanocrystaUine MoS2 with hollow spherical morphology has been prepared by the hydrothermal method. The products are characterized by means of X-ray powder diffraction,transmission electron microscopy and high-resolution transmission electron microscopy. The experimental results give the evidence that the sample is consists of hollow spheres 400～600nm in diameter, and there is much whisker on the surface of MoS2 hollow sphere.     

单电子转移反应

本文对重要有机反应之一的单电子转移过程作了综述。单电子转移反应与极性反应的根本区别在于,前者每次只发生一个电子的转移,而后者通常每次发生一对电子的转移。影响这二种历程的主要因素是反应物的立体因素,电子结构及氧化还原能力。单电子转移按其反应方式又被细分(?)inner-sphere ET (?) outer-sphere ET 二种历程。一些典型的单电子转移反应已被分类介绍。     

N^α—磷酰化二肽甲酯的氧化和氧化中电子转移的研究

用纳秒级脉冲辐解动态吸收光谱法研究了Ｂｒ＾－２自由基引发Ｎ－（Ｎ－二异丙氧基磷酰化甲硫氨酰）色氨酸甲酯的氧化和电子转移过程，结果表明：Ｂｒ２＾－ｔｈｍｈａｄ ａｄ ｍ ｈｉ ｒｎｕｄｗｘ Ｎ＾α－磷酰化二肽中的甲硫氨酸和色氨酸部位。     

光诱导电子转移反应在有机合成中的应用

对近十年来报道的在有机合成中有重要意义的光诱导电子转移反应做了简要的总结. 包括六个部分: (1)光诱导电子转移(PET)反应的基本原理, (2) PET诱导的自由基离子裂解和去保护基反应, (3) PET诱导的加成和环加成反应, (4) PET诱导的环化反应和串联环化反应, (5)不对称PET反应, (6)微反应器中的PET反应.     

基于过硫酸盐活化的微界面电子转移氧化技术

基于过硫酸盐活化的高级氧化技术是当前环境领域的研究热点.然而,环境中广泛存在的基质严重地制约了这一技术的实际应用.最新研究表明,在某些催化剂的作用下,过硫酸盐能够以电子转移的非自由基机制氧化降解污染物,而催化剂主要起电子转移媒介的作用.这一技术不易受水环境中氯离子、碳酸氢根离子等常见阴离子和天然有机物的影响,对目标污染...     

电子转移的外电场效应──苯分子与苯正离子自由基间电子转移的从头算研究

基于半经典电子转移理论,结合量子化学计算,在HF/DZP水平上,研究外电场作用下平行的苯分子-苯正离子自由基体系(C₆H₄)₂⁺的分子内电子转移问题.在给体和受体几何构型优化的基础上,用线性反应坐标确定电子转移过渡态,分别用两态变分方法和基于Koopmans定理的分子轨道跃迁能方法计算电子转移矩阵元V_AB,讨论了V_AB对给体和受体中心距d的指数衰减关系.取中心距为0.6nm,研究了外电场对反应热的影响,计算得到在不同外电场强度下分子内气相电子转移的速率常数k.     

铁基粉末冶金材料中稀土元素与MoS2的交互作用研究

通过实验研究了添加到铁基粉末冶金摩擦材料中的稀土在材料中存在的位置和状态以及稀土对MoS2分解所产生的影响.电子探针检测的结果表明, 稀土在铁基粉末冶金磨擦材料中主要集中分布于孔隙处, 且其分布呈聚集的粒状, 常与Pb等重金属共存; 稀土有强烈的促进MoS2分解的作用, 当加入量超过3倍单位量时即可使加入的4%(质量分数)的MoS2完全分解.     

表面活性剂与血红蛋白的作用对转移电子数的影响

将不同浓度(0.15-10.0 mmol·L-1)的双十二烷基二甲基溴化铵(DDAB)和血红蛋白(Hb)依次修饰到热解石墨电极(PG)上, 制备了稳定的Hb-DDAB/PG电极. 利用循环伏安和紫外光谱研究了Hb-DDAB/PG电极的性质. 由Laviron模型得到的转移电子数表明该电化学反应由双电子过程逐步过渡到单电子过程, 进而证明DDAB膜厚的增加导致血红蛋白亚基间作用的减弱和亚铁血红素的释放.     

磷酰化肽链中电子转移的ESR研究

当前生命科学正以前所未有的速度向前发展，从对核酸的深入研究开始过渡到对蛋白质结构与功能的注意，尤其是近年来基因调控研究的重大进展是发现非组蛋白具有高度的磷酸化的特性［1］，研究证明，核内蛋白磷酸化和去磷酸化则是基因表达调控的重要方式之一［2，3］，它是酶活性调节、基因表达调控、细胞转化恶变的关键环节；同时在解决肿瘤的发生和治疗、病毒的感染和诊治、辐射损伤、抗衰老等实际问题上有突出意义，如1992年Krebus和Fisher因为在蛋白的可逆磷酸化方面的突出贡献而获得诺贝尔生理和医学奖．而电子转移是一切化学变化的基础…     

Surface Modulation of Iron-doped MoS2 Nanosheets by Phytic Acid for Enhanced Water Oxidation

Surface modulation and heteroatom doping are important approaches for boosting the electrocatalytic performances of MoS₂ nanosheets. As a molecular electrocatalyst, the natural organic phytic acid (PA) offer attractive intermediate for oxygen evolution reaction (OER). Here, a surface modulation strategy is demonstrated through the decoration of PA onto the basal plane of iron (Fe)-doped MoS₂ nanosheets supported on nickel foam (NF) for boosted OER activity. Experimental results indicate that the PA modification and Fe doping could effectively boost the charge transfer and mass transport during the OER process. Specially, PA2-Fe−MoS₂ grown on NF (PA2-Fe−MoS₂/NF) exhibits excellent OER activity (218 mV@20 mA cm⁻²) and durability, even superior to RuO₂ and many other previously reported OER catalysts. This natural organic molecule modification provides a facile strategy to designing low-cost and efficient electrocatalytic materials.     

双吡啶盐/酞菁体系的光诱导电子转移的ESR研究

研究了五种金属酞菁化合物与一系列双吡啶高氨酸盐（PQ2+）之间在苯中的光诱导电子转移．对于酞菁／PQ2+／苯体系，在可见光辐照下，酞菁化合物的价带电子可被激发至导带，然后于界面发生电子转移使PQ2+盐变成离子基PQ+，给出较弱的ESR信号；当有表面活性剂氯代十四烷基吡啶和电子给体三乙醇胺存在时，可使PQ基的ESR信号显著增强5～6信以上．当有氧存在时，PQ+基信号迅速消失，给出较明显的超氧负离子基O2-的信号．氧能严重抑制电子转移的过程．     

Electron Transfer Reactions in Pyrazole-2-in-5-ones and Their Thioanalogues

Electron transfer processes in a series of pyrazole-2-in-5-ones (pyrazolones-5) and some of their thioanalogues are studied experimentally and theoretically for the first time. The electrochemical behavior of thiopyrazolones and oxygen analogues is found to differ. The effect the nature of the electrode, heteroatom, and substituents exerts on the redox potentials is established. Schemes of redox processes for the compounds studied in nonaqueous media are suggested. The schemes take account the ability of pyrazolones-5 to autoprotonation. Electrooxidation of 1-phenyl-3-methyl-4-benzoylpyrazole-2-in-5-one and its thioanalogues is shown to occur similarly to electroless oxidation with the formation of various dimers. It is established that, in the absence of active substituents during the electroreduction of compounds under study, the reaction center is the pyrazolone cycle, whose reduction does not involve decomposition of heterocyclic system.     

氟化镁锶中铕和铽的电荷迁移及其平衡解析

在氩气氛中，合成了SrMgF4：xEu，yTb复合组化物磷光体．该体系中Eu3 和Eu2 共存．随共掺入Tb浓度的增加，Eu3 的荧光发射强度降低，Eu2 的发光增强；并且Eu2 的ESR信号增强．认为Eu3 和Tb3 之间存在电荷迁移．即Eu3 ＋Tb3 →Eu2 ＋Tb4 .通过半定量手段研究了这一电荷迁移反应的平衡常数     

甲醇在纳米TiO2作用下进行光催化氧化反应的机理研究

以纳米TiO2为催化剂,以主波长为364 nm的汞灯为光源,用气相色谱法分别考察了0.1 mol/L的甲醇、甲醛和甲酸水溶液进行光催化氧化反应的动力学规律.Langmuir-Hinshelwood方程进行核算结果证明,该组反应均为零级反应.用TEM、 XRD、 SSA和XPS对催化剂进行表征.根据XPS的检测结果提出了甲醇光催化氧化的反应机理.TiO2光激发活化时间约为30～60 min,生成物及剩余反应物浓度随时间变化的曲线表明,该反应速率为HCH2OH相似文献   

Nα-磷酰化二肽甲酯的氧化和氧化中电子转移的研究

用纳秒级脉冲辐解动态吸收光谱法研究了Ｂｒ２－自由基引发Ｎ－（Ｎ－二异丙氧基磷酰化甲硫氨酰）色氨酸甲酯的氧化和电子转移过程，结果表明：Ｂｒ２－自由基同步氧化Ｎα－磷酰化二肽中的甲硫氨酸和色氨酸部位，并发生由色氨酸向含硫三电子键自由基的分子内电子转移过程，求算了有关动力学参数，推导了氧化和电子转移机理     

GaAs(100)表面氧化的XPS研究

X-ray photoelectron spectroscopy（XPS）was used to study two different oxidation treatments on the GaAs（100）surface———the thermal oxidation in the air,and the ultraviolet-light oxidation in the UV-ozone. A series of properties including the oxide composition,chemical states,the surface Ga/As atomic ratio and the thickness of the oxide layer grown on GaAs surface were compared. The results indicate that the oxide composition,the surface Ga / As atomic ratio and the thickness of the oxide layer oxide on GaAs surface are different for different oxidation methods. The oxides on GaAs surface grown by thermal oxidation in the air are composed of Ga2O3,As2O5,As2O3 and elemental As;and the Ga/As atomic ratio is drifted off the stoichiometry far away. The Ga/As atomic ratio of oxide layer on GaAs surface is increases with the thickness of oxide. However,the oxides on GaAs surface grown by UV-ozone are made up of only Ga2O3 and As2O3,As2O5 and elemental As are not detected,the Ga/As atomic ratio is close to unity. The thickness of oxide layer on GaAs can be controlled by the UV exposing time. The mechanism of oxidation of GaAs is also discussed. The UV-light radiation not only causes the oxygen molecular excited forming atomic oxygen,but also induces the valence electrons of the GaAs excited from the valence band,and then the reactivity of Ga and As atom increase,and they can easily react with the excited atomic oxygen at the same reactive velocity.     

Surface characterization and radical decay studies of oxygen plasma‐treated PMMA films

Polymethylmethacrylate (PMMA) films were modified by RF oxygen plasma with various powers applied for different periods, and the effects of these parameters on the surface properties such as hydrophilicity, surface free energy (SFE), chemistry, and topography were investigated by water contact angle, goniometer, X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy, and the types of the created free radicals and their decay were detected by electron spin resonance spectroscopy (ESR). SFE and contact angle results varied depending on the plasma parameters. Oxygen plasma treatment (100 W–30 min) enhanced the hydrophilicity of PMMA surface as shown by decreasing the water contact angle from 70° to 26°. XPS analysis showed the change in the amounts of the present functionalities as well as formation of new groups as free carbonyl and carbonate groups. The roughness of the surface increased considerably from ~2 nm to ~75 nm after 100 W–30 min oxygen plasma treatment. ESR analysis indicated the introduction of peroxy radicals by oxygen plasma treatment, and the intensity of the radicals increased with increasing the applied power. Significant decrease in radical concentration was observed especially for the samples treated with higher powers when the samples were kept under the atmospheric conditions. As a conclusion, RF plasma, causes changes in the chemical and physical properties of the materials depending on the applied parameters, and can be used for the creation of specific groups or radicals to link or immobilize active molecules onto the surface of a material. Copyright © 2012 John Wiley & Sons, Ltd.