【作者】 程冰；

【导师】 王秀峰；

【作者基本信息】 陕西科技大学 ， 材料学， 2008， 博士

【摘要】 光子晶体,是目前材料领域研究的热点。它是一种存在带隙的周期结构材料,这种材料具有独特的调节光子传播状态的功能,是目前信息功能材料的前沿领域。光子晶体的制备主要是通过两种或多种材料一定尺寸的周期性排布来实现的。采用一些精密加工的方法,如层层叠加（Layer-by-layer Method）蚀刻,已经可制备出在近红外波段的三维（3D）光子晶体。这些方法的缺点是设备昂贵,制备过程复杂。自组装法被认为是制备三维近红外、可见光及更短波段光子晶体最简单有效的方法。在已知的自组装单分散体系中,以SiO₂体系和聚苯乙烯（PS）体系最为成熟,通过严格控制反应条件可制备出符合光子晶体要求的单分散体系。由SiO₂胶体球自组装的光子晶体,虽然在近红外到可见光波段可以产生赝光子带隙,但是其存在两个缺点:一是介质的介电常数对比值小;二是介质微球排列不完整。后者导致光子晶体引入不可控的缺陷。高折射率材料（如ZnO、CdS和ZnS等）的引入,能增强光子晶体的介电参数反差,提高周期性介电函数的变化幅度。另外,提高用于自组装光子晶体的SiO₂微球的表面电荷,也可有效提高自组装的效果,减少不可控缺陷的产生。本论文主要研究了光子晶体用结构基元的制备方法,基元材料主要包括ZnO、CdS、ZnS半导体材料及SiO₂胶体材料。通过控制反应温度、反应物浓度及溶液pH值来控制ZnO颗粒的形貌。随后深入研究了不同形貌ZnO颗粒的微观结构特征,发现其微观结构具有共同特点。在此基础上,探索了ZnO纳米颗粒光致发光性能及其发光机理。本论文还通过用超声辅助湿化学法制备了球形形貌的CdS和ZnS纳米颗粒,研究了其晶体结构及其形貌特征,为以后作为光子晶体基元自组装光子晶体打下了基础并对超声辅助在合成中的作用机理作了一些探索研究。另外,本论文采用St（o|¨）ber法制备SiO₂颗粒,为了改善SiO₂颗粒自组装性能,提高其表面电荷,分别采用了电解质NaCl改进St（o|¨）ber法和表面包覆琥珀酸这两种方法来达到目的。最后,采用垂直沉积法制备了SiO₂蛋白石光子晶体,并对其光学性能做了研究。论文的主要工作成果如下:1)采用超声辅助法,通过改变反应温度、反应物浓度和溶液pH值,制备了圆锥形、哑铃形、球形、橄榄形、飞镖形和花形六种不同形貌的ZnO颗粒。以橄榄石ZnO颗粒为典型,系统研究了ZnO颗粒的微观结构。发现在ZnO颗粒中心区域为单晶结构,主要沿着{10（?）0}这组面生长,在其中心附近区域存在孪晶缺陷层,这层缺陷层决定了ZnO颗粒最终的形貌特征。随后ZnO颗粒将沿着[0001]方向生长变大,最后得到各种形貌的ZnO颗粒。通过对ZnO颗粒的微观结构分析,本论文提出了一种新的ZnO颗粒生长机制。随后,分析了反应温度、反应物浓度和溶液pH值对ZnO颗粒形貌的影响。最后,研究了不同形貌ZnO颗粒的光致发光性能,发现ZnO可见光波段的发光与ZnO中缺陷密切相关。2)采用超声辅助法,制备球形纳米CdS和ZnS颗粒。SEM测试表明所获得CdS和ZnS颗粒为球形,粒径范围在150-500nm,且CdS为六方纤锌矿结构,而ZnS为立方相结构。3)采用传统的St（o|¨）ber法制备了粒径范围在300-800nm内的,相对标准偏差小于5.0%的SiO₂胶体球。为改善SiO₂胶体球的自组装性能,对St（o|¨）ber法进行改进,在反应过程中加入电解质NaCl,以提高SiO₂胶体球的表面电荷。试验发现,电解质NaCl的加入能有效提高SiO₂胶体球的表面电荷,但其对颗粒大小有一定的影响。SiO₂胶体球表面Zeta电位由未改进前的48.7mV提高到56.6mV,而粒径由315nm增长到380nm。实验发现当电解质NaCl的加入量在一定范围内时,SiO₂胶体球的粒径随着NaCl量的增加而变大;当超出这个范围,SiO₂胶体球将出现双尺寸的现象。研究发现,NaCl的加入能改善SiO₂胶体球的自组装性能,减少缺陷在光子晶体内出现点几率。另外,SiO₂光子晶体的光学性能与其粒径有直接关系。4)采用有机物表面改性的方法对SiO₂胶体球进行改性,是另一种可有效提高SiO₂胶体球表面电荷的方法。实验中,采用琥珀酸作为改性剂,用乙腈作为溶剂,通过酯化反应,使琥珀酸一端的羧酸基团与SiO₂胶体球表面自带的不饱和羟基键相互反应,从而使琥珀酸键合到SiO₂胶体球表面。测试表明,经过表面改性后,SiO₂胶体球的表面电荷有明显提高,自组装的性能也显著改善。5)探索性地制备了CdS@SiO₂核壳微球,以用于光子晶体的自组装。本实验试图将CdS用化学沉积的方式沉积到SiO₂胶体球表面。实验结果显示,CdS虽然在SiO₂胶体球表面有一定的沉积,但是沉积的量非常有限,并未达到实验设计的致密均匀要求。更多还原

【Abstract】 Photonic crystal material is one of the hotspots in material research. It is a kind of materials with regular periodicity of dielectric structures, which has the ability to manipulate, confine, and control light. So photonic crystal becomes the frontier of functional materials.The method to prepare photonic crystal is to arrange in order using two or more different materials with uniform morphology. The 3D photonic crystal with near-infrared region forbidden band-gap has already been fabricated by Precision Process, such as layer-by-layer etch. The defects of this method is expensive and complex systems. Self-assemby method is an easy way to fabricate photonic crystal with near-infrared or shorter wave regioin photonic band-gap. As we know, SiO₂ particles and polystyrene particles which meet the requirements of photonic crystal are easy to be prepared under reaction condition control.The photonic crystal assembled by SiO₂ particles possesses the near-infrared and visible region photonic band-gap, but there are two defects. One is that the relative value of dielectric constant contrasted with medium is small, another is unperfect arrangement of SiO₂ particles which result in accident defect. The materials with high refractive index, such as ZnO, CdS and ZnS, possess high relative value of dielectric constant and widen the range of periodicity Dielectric function. Additionally, enhancement the surface charge of SiO₂ particles assembled for photonic crystal is a effective way to reduce the accident defects in the photonic crystal.The thesis worked on the preparation of structure unit which was used to self-assemble photonic crystal. The unit contained ZnO, CdS, ZnS and SiO₂ particles. The morphology of ZnO particles was controlled by the reaction temperature, the reactant concentration and the pH value. The deep research indicated the mico-structure feature of ZnO particles with various morphology possessed the same structure. On this basis, the photoluminescence property and the mechanism were researched.The thesis worked on the preparation of spherical CdS and ZnS particles by wet chemical synthesization assisted by ultrasonic, too. The crystal structures and morphologies were researched. And the effect of ultrasonic during synthesization was researched.Additionally, we prepared SiO₂ particles by Stober method and modified this method by electrolyte NaCl to enhance the surface charge, which improved the property of self-assembly SiO₂ particles. And another method, surface modification by succinic acid, was used again for the same purpose. Finally, the SiO₂ opal photonic crystal was fabricated by vertical deposition method and the optical properties were researched.The results were listed:1) The various morphologies ZnO particles, including taper-like, dumbbell-like, spherical, rugby-like, dart-like and flower-like, were prepared by control of reaction temperature, reactant concentration and pH value by wet chemical synthesization assisted by ultrasonic. As research model, the micro-structure of rugby-like ZnO particles were researched. We found out that the single crystal structure was created in the center of ZnO particles, a great number of micro-twins were formed around the center, and polycrystal was formed on the fringe. The defect layers was the key of morphology of ZnO particles and then ZnO particles grew along [0001] direction. Base on the structure research, we suggested a new mechanism on the preparation of ZnO particles. And then the effects of temperature, pH value and reatant concentration were researched. At last, the photoluminescence property of ZnO particles was researched and we found out that the defects was the key of photoluminescence property of ZnO particles.2) The spherical CdS and ZnS particles were prepared by chemical synthesization assisted by ultrasonic. SEM images showed that the morphologies of CdS and ZnS particles were spherical and the sizes ranged from 150-500 nm. XRD test indicated that CdS particles possessed wurtzite structure of the six-party. Otherwise, ZnS particles possessed cubic structure.3) SiO₂ particles were prepared by St（o|¨）ber method, which the sizes ranged from 300-800 nm and The relative standard deviation was less than 5%. In order to improve self-assembly ability, the traditional St（o|¨）ber method was modified. The tlectrolyte NaCl was added during process to enhance the surface charge of SiO₂ particles. We found out that the surface charge of SiO₂ particles were enhanced after NaCl had been added. Moreover, the size of SiO₂ particles is larger. Zeta potential of SiO₂ particles enchanced from 48.7 mV to 56.6 mV, and the size become large from 315 nm to 380 nm. When the quantity of NaCl added is in a certain range, the size of SiO₂ particles become large with NaCl added. However, beyond the scope of this, double-size SiO₂ particles happened. Research showed that there was no effect to optical properties of photonic crystal assembled by SiO₂ particles modified by NaCl. Additionally, the optical properties were only effected by the size of SiO₂ parcles.4) In order to enhance surface charge of SiO₂ particles, they were modified by Organic. Succinic acid was modifier and acetonitrile was solvent. One carboxyl of the succinic acid reacted with the -OH on the surface of the SiO₂ particles and the product is carboxylate. Zeta potential proved that the surface charge of SiO₂ particles was enhanced after they had been modified.5) We attempted to prepare CdS@SiO₂ nucleus-shell particles by chemical deposition. Results showed that a little CdS deposited on the surface of SiO₂ particles, but the quantity is very small.更多还原