【作者】 单锋；

【导师】 路庆华；

【作者基本信息】 上海交通大学 ， 高分子化学与物理， 2014， 博士

【摘要】 有序介孔薄膜由于具有比表面积大、结构规整、介孔结构可调节的特点并能够作为理想的寄主材料，因此在主客体化学、气体传感器、膜分离、分子设计和光电敏感器件等领域有着广泛的应用前景，引起了科研工作者极大的关注。根据国际纯应用化学联合会(IUPAC)的定义，介孔薄膜是指孔径在2～50nm之间的固体孔状薄膜。传统方法制备的介孔薄膜其内部的孔道呈混乱无序排列，限制了介孔薄膜在器件制造中的应用价值。如何控制介孔薄膜内部的孔道在宏观尺度上沿着同一方向取向排列是人们关心的课题。虽然科研人员已经开发出多种方法成功的制备出宏观平行取向或者垂直取向的介孔薄膜。然而这些方法都依赖于特殊结构的基底或者复杂的装置，制备较为复杂，并且不能够精确的控制介孔孔道取向排列的角度。另外，目前关于取向介孔薄膜的制备主要研究的是介孔二氧化硅薄膜，由于二氧化硅本身是绝缘材料，如果能够用其他半导体氧化物如二氧化钛等替代二氧化硅制备成宏观取向薄膜，将能够大大提高其应用价值。然而由于非硅前驱体的水解缩合反应剧烈，难以控制，因而关于非硅材料的取向介孔薄膜的报道寥寥无几。如果我们能够利用一种简单易行的方法来制备取向的介孔二氧化钛薄膜并且可以对其孔道的取向方向进一步调控，那么将会是取向介孔薄膜研究领域的一大进步，并且这种取向的二氧化钛介孔薄膜在光电领域将有着广阔的应用前景。本文的创新和主要内容包括：1.首先利用热空气流法制备得到了宏观平行取向的介孔二氧化钛薄膜，其中介孔孔道沿着气流方向定向排列。当气流速度过大时，平行取向的介孔孔道被破坏，导致蠕虫状无序介孔孔道的形成。进一步研究发现通过改变热气流的速度和入射角度，可以调节二氧化钛薄膜的介孔孔道的取向方向，制备得到孔道倾斜取向和垂直取向的介孔二氧化钛薄膜。利用热空气流法可以在不同的基底如载玻片、硅片、FTO导电玻璃、金属基底上制备取向可控的介孔二氧化钛薄膜。孔道取向不同的介孔二氧化钛薄膜的孔径大小有所不同，平行取向的介孔薄膜的孔径为4.0nm，倾斜取向的介孔薄膜的孔径为9.0nm。在气流法制备取向介孔二氧化钛薄膜的过程中，介孔孔道的取向受到了施加的热气流产生的外剪切力和溶胶液自身溶剂挥发产生的向上作用力共同影响。气流作用的剪切力使得溶胶液中的棒状胶束沿着气流方向取向排列，而溶胶液中溶剂的挥发又给胶束提供了一个向上排列的作用力，这就为我们制备垂直取向的介孔薄膜提供了可能。与无规取向和平行取向的介孔薄膜相比，垂直取向的介孔薄膜有着很好的离子导通特性，有望应用于离子传输分离膜。2.通过热空气流法和层层堆积法在FTO导电玻璃基底上制备出了单层和多层的垂直取向的介孔二氧化钛薄膜，薄膜内部的垂直孔道以锐钛矿纳米晶体的形式存在。当薄膜厚度不超过5层时，染料的吸附量、电流密度均随着薄膜厚度的增加而线性增加；当薄膜层数超过5层时，此时染料的吸附量以及电流密度随着薄膜层数的增加变化的不是很明显。出现这种情况的原因是因为在层层堆积制备多层薄膜时，靠近FTO导电玻璃基底处的薄膜由于经过多次煅烧，介孔逐渐收缩，当薄膜层数超过5层时，增加薄膜的厚度不能明显的提高薄膜的内表面积，因而限制了染料的吸附量，进而抑制了电流密度的增加。我们发现利用热空气流制备的垂直取向的二氧化钛介孔薄膜制备的染料敏化太阳能电池的性能要优于旋涂法制备的无规取向的太阳能电池。这是由于垂直取向的介孔孔道有利于电子从二氧化钛电极传输到FTO导电玻璃上，并且传输距离较无规取向的介孔孔道大大缩短，因而光生电子寿命得到了提高，从而提高了太阳能电池的光电转换效率。3.利用热空气流法制备得到了宏观平行取向的介孔二氧化硅薄膜，其中介孔孔道沿着气流方向取向排列。研究发现当外界湿度过高时（>50%R.H.），二氧化硅薄膜中的孔道呈蠕虫状无序排列。制备温度过低时，不易成膜；温度过高则容易形成蠕虫状的介孔孔道。气流速度过低时靠近基底处的溶胶液由于受到的剪切力的强度不够，形成的介孔孔道不能取向排列。改变气流的入射角度可以得到倾斜排列的二氧化硅介孔孔道。通过调节二氧化硅溶胶前驱液的浓度可以改变介孔薄膜的厚度，当薄膜厚度由650nm降至420nm后，利用倾斜的热气流可以制备得到完全倾斜取向排列的介孔二氧化硅薄膜。4.利用热气流法在FTO导电玻璃基底上制备了宏观取向的介孔二氧化硅薄膜，然后利用离子交换的方法在薄膜的介孔孔道中引入Cd2+，再通入H2S气体在介孔孔道内原位反应生成CdS量子点。由于介孔孔道的限制作用CdS量子点以纳米棒的形式均匀的分散在介孔孔道中，且沿着介孔孔道的方向取向排列，CdS量子点直径大小与介孔孔道的直径相当。由于CdS量子点能够吸收光子产生电子，因而CdS量子点填充的复合薄膜有着很好的光电响应特性，并且研究发现CdS量子点填充的薄膜有着良好的各向异性的光电特性。进一步利用层层堆积法制备的下层为CdS量子点填充上层为PbS量子点填充的双层取向复合薄膜可以拓宽单层薄膜薄膜吸收波长的范围，提高薄膜对太阳光的利用率。5.分别对四氢呋喃、二氧六环和甲苯三种不同的溶液体系利用气流法制备嵌段共聚物薄膜，由于溶剂性质的不同，在外加气流作用下溶剂的挥发速度也有所不同，导致了嵌段共聚物薄膜表面形貌的不同。其中由于四氢呋喃溶剂的挥发速度明显快于其他两种溶剂，因而更容易制备出表面垂直取向的规整的薄膜。采用UVO刻蚀的方法，利用AFM研究发现我们利用四氢呋喃溶液体系制备的薄膜呈现出表层和底层均为垂直取向结构，内部为无序结构的类似三明治结构的形貌。并且气气流温度过高或者速度过快会对薄膜表面规整的形貌有所破坏。对比无规的嵌段共聚物薄膜，染料分子在三明治结构的薄膜有着更好的通透性，并且薄膜的厚度与染料分子的通透性呈反比。同时三明治结构的嵌段共聚物薄膜对VO2+/H+离子有着很好的选择透过性。更多还原

【Abstract】 Ordered mesoporous films have attracted great interests due to their relatively large surface area,high ordered mesostructure, adjustable mesopores and potential applications in host-guest chemistry,gas sensor, filtration membrane, molecule design and photoelectric device, etc. According to thedefinition of international unit of pure and applied chemistry (IUPAC), mesoporous films are definedas solid porous film with pore size of2~50nm. The mesochannels were randomly oriented in themesoporous films prepared by traditional methods, which limited their applications. Nowadays, how tocontrol the mesochannels macroscopically uniaxially aligned has become a hot topic. Althoughdifferent approaches have been developed for the preparation of parallelly or perpendicularly orientedmesoporous films, most of approached are dependent on specific substrates or complex equipment andthe mesochannels cannot be controlled to align in desired direction. Besides, if the insulatedmesoporous silica film can be substituted by semiconductor films such as mesoporous titania film, theusing value of oriented mesoporous films will be enhanced greatly. However, the main hurdle in thesynthesis of uniaxially oriented mesoporous transition-metal-based films is the high reactivity of metalion precursors toward hydrolysis and condensation. How to prepare the aligned mesoporous titaniafilms and further control the mesochannels in any direction is the main purpose of our work. Thecontent of this dissertation could be summarized as follows:1. Controlling of the orientation of mesochannels in mesostructured thin films is important for thedevelopment of novel molecular devices and, in particular, generating vertically aligned mesochannelswith respect to the substrate plane is extremely challenging for nonsiliceous materials. We describe afacile and highly effective air flow method, which is able to control the unidirectional alignment oftitania mesochannels in a desired direction (e.g., parallel, perpendicular, or oblique) on a large scale,via manipulation of the air flow rate and incident angle. The titania mesochannels were characterized by TEM, SEM, SAXRD, and GISAXS. The unidirectional, vertically aligned mesostructured titaniafilms were found to exhibit excellent ion conductivity.2. Highly crystallized mesoporous titania films with obliquely aligned mesochannels have beensuccessfully synthesized by utilizing a simple air flow method and subsequent layer-by-layerdeposition. The morphology of oriented mesoporous titania films were characterized by cross-sectionalTEM. The obliquely aligned mesoporous titania films outperformed the disordered counterpart of thesame thickness in both short circuit current and efficiency. The4-layer-thick obliquely alignedmesoporous film shoed enhanced solar conversion efficiency by about12%compared to that ofdisordered mesoporous film of the same thickness. The improved cell performance of the alignedmesoporous films is ascribed to the enhanced electron transport and significantly inhibited chargerecombination in the unidirectionally oriented titania mesochannel.3. The air flow method was applied for the orientation control of mesoporous silica films.Macroscopically oriented mesoporous silica films were prepared by horizontal air flow withmesochannels parallelly oriented along the air flow direction. The environment condition and thetemperature and speed of air flow play an important role on the mesochannel orientation. By adjustingthe incident angle of air flow, the obliquely aligned mesoporous silica films can be obtained. Furtherdecreasing the film thickness from650nm to420nm, the alignment of oblique mesochannels was wellenhanced.4. Hybrid film of mesoporous silica film with oriented mesochannels and semiconductor quantumdot has been prepared. Encapsulation of CdS and PbS within the oriented mesochannels leads to aregular arrangement at the macro scale. The hybrid film thus obtained showed remarkable anisotropicphotoelectronic properties due to the confinement effect of the oriented mesochannels. Furthermore,due to the independence of the orientations of the mesochannels on the substrate, bilayer filmscontaining both CdS and PbS could be prepared. This design has allowed an extension of the range oflight absorption by the thin film as well as an amplification of the response to external photoelectroniceffects. Such a hybrid film may prove useful in the design of anisotropic electrodes and electronicnanodevices. 5. The effect of applied air flow on the surface morphology of polystyrene-block-poly(ethylene oxide)copolymers were investigated using atomic force microscopy and ultraviolet ozone etching technique.The adjusted solvent evaporation rate and the applied external shear force conduced to thesandwich-mode films with the orientated cylindrical microdomains perpendicular to both the top andbottom surface and the irregular oriented cylinders located in the middle part. The velocity andtemperature of air flow affected the film surface morphology. This film demonstrated high molecularpermeability and selectivity toward H/V ions.更多还原