【作者】 胡佳琪；

【导师】 旷亚非；

【作者基本信息】 湖南大学 ， 应用化学， 2010， 硕士

【摘要】 纳米材料由于具有不同于常规材料和单个分子的特殊性质,已成为当今科学研究的热点。制备纳米材料的方法有很多,其中以微乳液和胶束等表面活性剂聚集体为代表的软模板法正逐渐引起研究者的重视。微乳液是由油、水、表面活性剂以及助表面活性剂在适当的比例下自发形成的透明的热力学稳定体系。利用微乳液特别是反相微乳液中的“纳米域”作为化学反应的“微反应器”,采用化学法或电化学法可以制备出尺寸和结构可控的纳米材料。但是,反相微乳液一般被认为是不导电或导电性较差的体系,无法完全满足电化学研究的需要。本论文基于表面活性剂复配理论,采用聚乙二醇辛基苯基醚(Triton X-100)分别与阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)及阴离子表面活性剂二(2-乙基己基)琥珀酸磺酸钠(AOT)构成复配体系,将这两种复配体系与正己烷、正己醇和水构成反相微乳液,研究了表面活性剂复配比、助表面活性剂浓度、水油体积比及温度等因素对体系导电性能的影响,同时采用循环伏安法(CV)考察了Fe(CN)63-/Fe(CN)64-电化学对在该体系中的电化学行为。结果表明：所研究的两种混合表面活性剂反相微乳体系的导电性明显好于单一表面活性剂体系,在Triton X-100/CTAB反相微乳液中,体系的电导率随非离子型表面活性剂与离子型表面活性剂质量比w(w=mTritonX-100"mCTAB)的增大而提高,当w达到2.3时,体系电导率达到稳定值。在Triton X-100/AOT反相微乳液中,体系的电导率随离子型表面活性剂与非离子表面活性剂质量比w(w=mAOT：mTritonX-100)的增大而提高,当w达到0.6时电导率达到稳定值。同时,在两种混合表面活性剂反相微乳液中,电导率均随水油体积比的增大及温度的上升而提高；而增加助表面活性剂可显著降低体系的电导率。Fe(CN)63-/Fe(CN)64-电化学反应对在所研究体系中的氧化还原峰电位几乎不随扫描速度变化,峰电位差约为70 mV-75 mV,峰电流的比值约为1,氧化峰电流与扫速的平方根成正比,说明Fe(CN)63-/Fe(CN)64-电化学对在上述两种混合表面活性剂反相微乳体系中显示出良好的氧化还原可逆性,反应由扩散步骤控制。利用混合表面活性剂反相微乳液具有的良好导电性能,可以将其作为软模板直接应用于电化学研究。选取Triton X-100/CTAB复配体系,与正己烷、正己醇和硝酸银水溶液构成反相微乳液,采用电沉积法制备了纳米银镀层,研究了镀层的形貌以及纳米银对于苄基氯的电催化还原。结果表明,在Triton X-100/CTAB混合表面活性剂反相微乳液中可以得到纳米尺度的银镀层,该镀层对苄基氯的还原具有良好的电催化活性,而沉积电流密度、体系中Ag+的浓度以及沉积方法的改变都会影响所形成镀层的催化能力。更多还原

【Abstract】 Nowadays, the nanomaterial has become a major research area due to its characteristic which is different from the conventional material and single molecule. In the preparation methods of nanomaterial, the soft templet such as microemulsion and reverse micelles have attracted more attentions recently. Microemulsion is a transparent, isotropic, thermodynamically stable dispersion which is stabilized by surfactant and cosurfactant molecules and its nanopools can be used in the preparation of controllable nanomaterials. However, due to the defect of electrical conductivity, conventional reverse microemulsion can not be used as electrolyte in electrochemistry research.P-octyl polyethylene glycol phenyl ether (Triton X-100) was used with cetyltrimethylammonium bromide (CTAB) and bis(2-ethylhexyl) sulfosuccinate sodiumsalt (AOT) respectively to form mixed surfactants. Then microemulsions were prepared with the mixed surfactants, n-hexane, n-hexanol and water. We studied the effects of surfactant weight ratio, temperature, concentrations of water and cosurfactant on the conductivity of mixed surfactants reverse microemulsion. And the electrochemical behavior of potassium ferricyanide [K3Fe(CN)6]/potassium ferrocyanide [K4Fe(CN)6] in the two systems was investigated by cyclic voltammetry(CV). The results indicate that the conductivity of the mixed surfactants reverse microemulsion is greatly higher than that of the single surfactant system. In the Triton X-100/CTAB system, the conductivity increases with the increase of surfactant weight ratio w(w=mTriton X-100:mCTAB) and stabilized when w reaches 2.3. Also in the Triton X-100/AOT system, the conductivity increases with the increase of surfactant weight ratio w(w=mAOT:mTrito X-100) and stabilizes when w reaches 0.6. Simultaneously, the increase of water concentration and temperature enhances the conductivity while the increase of cosurfactant concentration decreases the conductivity obviously. The CV result shows the redox peak potentials of Fe(CN)63-/Fe(CN)64- are almost constant with the change of scan rate, and the redox potential gaps are about 70 mV-75 mV in the mixed surfactants reverse microemulsion. Furthermore, the ratios of redox peak currents at all scan rates are close to 1.The oxidation peak current increases linearly with the square root of scan rate. The electrochemical reaction of Fe(CN)63-/Fe(CN)64-is reversible and is controlled by diffusion in the system. Based on the ideal conductivity of the mixed surfactants reverse microemulsion, it can be used as soft templet directly in the electrochemistry research. The Triton X-100 and CTAB were mixed with n-hexane, n-hexanol and AgNO3 solution to prepare reverse microemulsion. The obtained system was used in the electrodeposition of Ag nanoparticles. The morphology and electrocatalytic capability of the Ag nanoparticles were investigated. The results indicate that the Ag nanoparticles prepared in the mixed surfactants reverse microemulsion exhibit remarkable catalytic properties for the reduction of benzyl chloride. And the current density, the concentration of Ag+ and the electrodeposition method have effects on electrocatalytic properties of Ag nanoparticles.更多还原