【作者】 李祥村；

【导师】 贺高红；

【作者基本信息】 大连理工大学 ， 化学工程， 2009， 博士

【摘要】 形貌和性能的控制是纳米材料制备的主要目标。微乳软界面模板法制备纳米材料具有结构、尺寸可控,实验条件温和,操作简单等特点,已成为纳米材料合成中最具应用前景的方法。研究微乳模板界面性质、微结构对晶体生长的诱导和控制效应是制备不同形貌、光电和催化性能纳米材料的关键。为研究合成纳米颗粒的分散性,论文首先以电导率实验证明了曲拉通（TritonX-100）微乳体系中微乳液滴以簇体或分散状态存在,并计算了液滴的水核半径等结构参数。以微乳水热法合成ZnO为例,提出了微乳界面和不同分子量聚乙二醇（PEG）对ZnO生长过程的协同控制机理。Zn（NO₃）₂溶液中PEG400浓度为12.5%或25.0%时,微乳界面强度增加,ZnO（0001）方向的生长得到控制,合成了直径50-80nm、长度80-100nm的单分散ZnO纳米柱。PEG400浓度为50%时,合成了粒径约45nm的球形颗粒,并存在一定程度的团聚现象。水核尺寸（2-20nm）小于颗粒粒径（40-200nm）,说明颗粒生长过程中液滴发生了重组合并或界面强度降低。PEG400浓度由0.0%,12.5%,25.0%,50.0%逐渐增加时,氧化锌的带宽由3.06eV,3.02eV,2.95eV,2.85eV逐渐降低,低于主体氧化锌能带3.37eV,表明合成的ZnO材料吸收波长向可见光红移,吸光范围增加。论文将控制ZnO晶体生长的W/O微乳模板扩大到不同界面强度的双连续相、O/W微乳区域,在不同区域合成了粒径6-10nm的TiO₂颗粒。并通过控制水热温度调节同一微乳体系界面膜强度,制备了不同形貌和催化活性的TiO₂颗粒。水热温度由120℃逐渐升高到350℃,微乳界面波动增加、强度减弱,合成的颗粒结晶度提高,大小和晶体尺寸均增大,比表面积逐渐降低,TiO₂颗粒由球形转化为棒状和方形。其中在200-350℃温度范围内合成的TiO₂颗粒催化活性为0.086-0.097min^-1,高于或接近商品化P-25 TiO₂颗粒活性(0.091min^-1),这缘于材料结晶度提高,光电子和正空穴重新结合几率降低。为进一步控制TiO₂的结构和形貌,将TritonX-100微乳模板延伸到高界面强度双表面活性剂分子2-二乙基己基酯磺酸钠/大豆卵磷脂软模板。钛酸异丙酯在模板水通道和油相界面迅速水解,水通道结构保持完整,制备了多孔TiO₂材料。剪切处理该模板使其水通道排列方向一致,并以此制备了孔道同向排列的TiO₂多孔材料,其通孔可使更多的光能进入到材料内部,增大材料对光的吸收效率,其催化活性较非剪切模板制备的材料有所提高,如W=70,提高36.0%。模板含水量由W=70增加到W=200,模板中的水通道直径增大,使合成材料平均孔径由100nm增大到200nm,且剪切材料的催化活性常数由0.0378min^-1增大到0.0417min^-1,非剪切材料由0.0278min^-1增大到0.0335min^-1。更多还原

【Abstract】 Precise control on the morphology and the function are the main objectives for preparation of nanomaterials.Surfactant molecule self-assembly soft template has attracted considerable interests due to its promising applications in preparation of nanomaterials.The study on the inducing and controlling effect of the template interface and the microstructure on crystal growth is crucial to the synthesis of nanomaterials with different structures, photoelectric and catalytic properties.It was proved by the conductivity property that there were clusters/aggregates or dispersed droplets in the microemulsion system.The state of the microemulsion droplets can be used to study the dispersity of the as-synthesized particles.Furthermore,the parametrs such as water core and hydrodynamic diameter of the droplets were calculated.The synergistic controlling mechnism of microemulsion interface and PEG400 on the growth of ZnO crystal have been proposed and discussed in detail.The monodispersed ZnO nanocolumns with 50-80nm in diameter and 80-100nm in length were prepared with 12.5%or 25.0%of PEG400 in Zn（NO₃）₂ solution,and this was due to the controlling effect on（0001） direction of ZnO crystal.ZnO nanostructures with band gap energy of 3.06eV,3.02eV, 2.95eV and 2.85eV were obtained with 0.0%,12.5%,25.0%and 50.0%of PEG400 in Zn（NO₃）₂ solution respectively,which are lower than that of bulk ZnO（3.37eV）.The result demonstrates ZnO nanostructures with low band gap energy and different morphologies can be prepared by controlling the microemulsion interface strength.TiO₂ nanoparticles with 6-10nm in diameter were prepared in W/O,bicontinuous and O/W microemulsion zones respectively.TiO₂ nanostructures with different shapes and photocatalytic activities were obtained in a microemulsion system with different interface strength resulting from increasing the hydrothermal temperature.The increase of fluctuation and the decrease of strength of microemulsion interface with the increase of hydrothermal temperature result in the reduction of restrictions on the crystal growth.Accordingly,TiO₂ nanoparticles were synthesized at temperature of 120-200℃and TiO₂ nanorods and cubes were obtained at 200-350℃.The photocatalytic constants increase to 0.86-0.966cm^-1 at 200-350℃,which is comparable or higher than that of P-25.The higher photoactivity of TiO₂ samples can be assigned to their higher crystallinity and lower surface defects. In order to further control the structure and the morphology of TiO₂ material,the bisurfactant AOT/Lecithin template with high interface strength instead of TritonX-100 microemulsion system were used to prepare porous TiO₂ nanostructure.The rapid hydrolysis of titanium isopropoxide（TIP） at the interface of water channels and oil phase resulted in the formation of porous titania material,leaving the integrity of the water channels in the template.The water channels in AOT/Lecithin template exhibit highly order upon shearing alignment.The patterned porous TiO₂ materials were prepared using the sheared soft template. The photocatalytic activity of the sheared samples increase by 36.0%compared with the unsheared TiO₂ samples at W=70.The enhancement of the activities of the sheared samples can be attributed to their open-end channels and higher photoenergy absorption efficiency. The average diameters of the pores in the sheared and unsheared materials increased from 100nm to 200nm with adjusting the water content from W=70 to W=200 respectively. Furthermore,the photocatalytic activities for degradation of Rhodamine B increased with the increase of pore diameters(0.0378-0.0417min^-1 for sheared samples;0.0278-0.0335min^-1 for unsheared materials).更多还原