【作者】 王霞；

【导师】 陈启明；

【作者基本信息】 华东师范大学 ， 物理化学， 2015， 硕士

【摘要】 单分散纳米微球自组装胶体晶体因其在光子晶体、电子器件等方面的广泛应用而引起了广大研究者的极大关注。纳米SiO2微球因其表面能高、稳定性好而常被用作制备胶体晶体的材料,单分散性好且稳定性高的纳米SiO2微球是制备高质量胶体晶体的主要原料。传统的自组装方法,如：水平沉积法、重力沉降法等均有一些不可避免的缺陷,因此,选取简单易行且效率高的自组装方法是制备高质量胶体晶体的关键因素。本论文在大量文献调研的基础上,围绕单分散SiO2微球的制备以及胶体晶体的自组装,主要开展了以下几个方面的研究：(1)制备不同粒径的单分散SiO2微球,探讨了各反应物浓度及反应条件对SiO2微球粒径和单分散性的影响；在室温条件下陈化反应混合物,探讨了微球粒径、单分散性和ζ位随着陈化时间的变化关系,并得出了单分散微球的最佳陈化时间；测定不同粒径的胶体悬浮液的pH与ζ电位的关系,并得出其等电点(IEP)(2)采用恒电压电泳沉积和脉冲电压电泳沉积自组装SiO2胶体晶体,选择水作为电泳沉积的分散剂,分别探讨了不同实验条件对组装效果的影响。对于平均粒径为378nm的SiO2颗粒,恒电压电泳沉积的优化实验条件为：pH=11.22,ζ=-72.26mV,沉积电压为4V或5V,沉积时间为5min。脉冲电压电泳沉积可以大大提高SiO2胶体晶体的质量,对于平均粒径为207nm的SiO2颗粒,脉冲电压电泳沉积的优化实验条件为：脉冲宽度为0.2s,脉冲电压为4V,沉积时间为4min。(3)利用物理吸附CTAB改性亲水性SiO2微球,调节最佳ζ电位,使用自制的气液界面自组装法的装置,在空气-水界面形成紧密有序堆积结构的胶体晶体。CTAB的最佳浓度为0.01mM,对应的ζ=-36.67mV,甲醇为气液界面法中的优选分散剂；利用气液界面法的装置得到单层SiO2胶体晶体膜,其紫外-可见透射峰的波长位置与理论计算值基本符合,AFM图表明胶体晶体为有序密堆积结构,且有序结构覆盖整个膜表面；多层胶体晶体膜的透射光谱图中存在明显的一级衍射峰和二级衍射峰,这符合光子晶体的性质；随着颗粒粒径的增大,紫外-可见透射峰的位置发生红移,通过Bragg方程的计算,利用透射峰波长的位置可以得到颗粒的粒径,计算得到的理论粒径与NTA测试所得到的结果能够很好吻合。(4)选取两种粒径的SiO2微球,采用气液界面法的两种形式尝试得到有序性较好的二元胶体晶体。在两种粒径交替取膜制备二元胶体晶体中,实验结果分析表明小粒径的SiO2颗粒可以提高胶体晶体的有序性,而大粒径颗粒对胶体晶体有序性有一定的干扰。在两种粒径混合自组装二元胶体晶体中,结果表明：当大小颗粒同时存在时,大粒径颗粒表现为有序组装,而小粒径颗粒填充在其中,随着小粒子与大粒子数目比值(Ns/L)增大,小颗粒干扰了胶体晶体的有序结构而使胶体晶体的有序性降低。本论文首先合成不同粒径的单分散SiO2微球,然后采用电泳沉积法和气液界面法快速形成有序结构的胶体晶体,并尝试通过气液界面法得到不同空间结构的二元胶体晶体,这对胶体晶体的自组装具有创新意义。更多还原

【Abstract】 Colloidal crystals have attracted a great deal of attention due to their important applications in photonic crystals and electronic devices, etc. Nano-SiO2 microspheres with good monodispersity and high stability are the main material to obtain the colloidal crystals with high quality. Traditional self-assembly methods, such as horizontal deposition and gravity sedimentation, etc, have some inevitable defects. Therefore, it is important to find a simple and high efficiency method to prepare high quality colloidal crystals. Based on a plenty of literature investigation, we focused on the preparation of monodisperse silica microspheres and the self-assembly of colloidal crystals, and then carried out the following works:(1) Monodisperse SiO2 particles with different sizes were prepared, the effect factors such as the concentration of reactants and the reaction temperature on particle size and monodispersity were discussed. Then, the particle size and zeta potential with the different aging time were studied, and concluded the best aging time of colloidal suspension. Moreover, the relationship of pH and zeta potential of different particle sizes were discussed, and the isoelectric point (IEP) of all particles was obtained.(2) The SiO2 colloidal crystals were prepared by electrophoretic deposition in two modes, constant voltage and pulse voltage, and water as dispersing agent in each experiment. For the average particle size was 378nm, the optimum experimental conditions of constant voltage electrophoretic deposition were:pH= 11.22, ζ=-72.26 mV, deposition voltage was 4V or 5V, and deposition time for 5min. Pulse voltage electrophoretic deposition can greatly improve the quality of SiO2 colloidal crystal. For the average particle size was 207nm, the optimum experimental conditions of pulse voltage electrophoretic deposition were:pulse width was 0.2s, pulse voltage was 4V, and deposition time for 4min.(3) Hydrophilic SiO2 microspheres were modified with CTAB by physical adsorption, the monolayers with closed and ordered structure were obtained by gas-liquid interface device which was made by ourselves. The optimum CTAB concentration was 0.01 mM (corresponding Zeta potential was -36.67mV), and methanol as the best dispersant; When we used the device to get the monolayer silica colloidal crystal film, the UV-vis transmission peaks were great consistent with the theoretical values which were calculated by Bragg equation, and the AFM figures showed that the colloidal crystals with close packing structure, and the orderly structure covered the whole membrane surface. For the multilayers, there were two transmission peaks in each spectra, which were the first and the second diffraction, respectively, and this was the characteristics of the photonic crystals; With the increase of particle size, the position of the transmission peak appeared red shift, the particle size can be calculated from the wavelength location of transmission peak by Bragg equation, and the results showed that the particle size can be matched well with measured values by Nanosight.(4) We tried to build binary colloidal crystals with ordered structures by the gas-liquid interface method in two forms. Alternate structure of lager and small microspheres showed that the small particles can improve the integrity of colloidal crystal, and the lager particles destroyed the ordered structure to some extent. When we mixed two kinds of particle sizes to get binary colloidal crystal by the same method, the results showed that the large particles were arranged in good order and the small particles filled in their spaces. The ordering of colloid crystals was declining with the NS/L increase.In this paper, monodisperse silica microspheres of different particle sizes were synthesized at first. Then, a couple of quick and easy ways were released to obtain orderly structures of colloidal crystals. The way to build binary colloidal crystals with different structures was studied in the last part of this paper. These works were significant-innovative for the self-assembly of colloidal crystals.更多还原