双尺寸胶体晶体的制备及其结构表征

采用垂直沉积法制备了双尺寸胶体晶体结构,并实现多种双尺寸SiO2胶体晶体结构的自组装.通过场发射扫描电子显微镜(FE-SEM)对胶体晶体的结构及排列方式进行测试分析.对双尺寸胶体晶体的生长过程进行探讨,研究大小胶体球的粒径比及体积比对结构的影响规律.研究结果表明大小球粒径比过小时,双尺寸胶体晶体排列结构有序性差.增大大胶体球的粒径时,合成相同双尺寸胶体晶体结构所对应的大小胶体球体积比增大.     

SiO2-BaTiO3异质双尺寸超材料结构的制备

采用垂直沉积法自组装制备了SiO2胶体晶体模板,并结合Pechini溶胶-凝胶法实现多种SiO2-BaTiO3异质双尺寸超材料结构的制备.通过X射线衍射分析仪(XRD)和场发射扫描电子显微镜(FE-SEM)对所得粉体和光子晶体的晶型、形貌及排列方式进行测试分析.对比钛酸钡粉体,对SiO2-BaTiO3异质超材料的结构进行探讨,研究不同pH值对钛酸钡粉体的形貌和粒径的影响,进而研究不同凝胶对异质超材料结构的影响.研究结果表明异质结构中胶体晶体模板的排列更加紧密有序,缺陷减少,纳米颗粒的粒径与原钛酸钡粉体的粒径基本一致,利用不同凝胶可获得LS2、LS4、LS6型结构及层-层复合结构.     

不同膜厚对SiO2光子晶体形貌及光学性能的影响

利用改良的St6ber法制成了粒径均一的SiO2胶体颗粒,胶体微球颗粒平均粒径为200 nm.保持SiO2悬浮液体积分数相同,对双基片自组装垂直沉积进行改造,改变夹层厚度,沉积得到厚度不同的SiO2光子晶体薄膜.利用扫描电子显微镜观察了膜厚不同的SiO2光子晶体薄膜样品的表面以及断面微观形貌,测试了样品的光反射性能,此外还讨论了光子晶体薄膜厚度对样品表面的形貌以及样品光反射性能带来的影响.     

空心和实心SiO2胶体晶体微球的快速制备方法

胶体晶体微球因其独特的内部结构被广泛地应用到诸多领域.本文提供了一种简单、快速合成SiO2胶体晶体微球的方法,即:将单分散SiO2微球悬浮液加入到有机溶剂(正辛醇或二甲基硅油)中超声乳化,使SiO2微球在溶剂中自组装,形成SiO2胶体晶体微球,用扫描电镜(SEM)观察其形貌结构,用Nano Measurer 1.2软件统计其粒径分布.实验表明,SiO2胶体晶体微球在正辛醇中形成空心结构,在二甲基硅油中形成实心结构;悬浮液浓度,悬浮液与溶剂的质量比,单分散SiO2微球粒径不会明显影响SiO2胶体晶体微球的形貌和结构,但会对其粒径分布产生一定的影响.     

单分散SiO2微球的制备及疏水改性研究

采用改进的凝胶-溶胶法制备了200~800 nm的单分散SiO2微球,并通过真空冷冻干燥法得到不易团聚的单分散SiO2粉体,采用乙醇超临界方法对制备的SiO2微球进行疏水改性.通过扫描电镜和氮吸附-脱附分析仪对SiO2微球的表面形貌、粒径以及孔径分布进行表征;用傅里叶红外变换测试和测量接触角对疏水改性的SiO2微球进行分析.结果表明SiO2微球粒径随二次加入TEOS体积增加呈先增大后减小.经过乙醇超临界处理,SiO2微球表面成功接枝上了疏水烷基,微球尺寸越小,疏水性越好,其接触角高达149°,单次SiO2微球处理量对结果无明显影响.采用本方法可以单次处理12 g以上的SiO2微球,接触角均在140°左右,可充分满足实验室使用需求.经过真空冷冻技术和乙醇超临界技术得到疏水单分散SiO2微球粉体,具有不易团聚及单分散性良好的优点,能够作为胶体晶体原料和三维有序材料(3-DOM)模板剂进行广泛应用.     

化学还原法向二氧化硅人工欧泊中填充Se

本文提出了一种新的调节人工欧泊晶体的光学带隙的方法.采用改进的溶剂蒸发法将单分散SiO2微球组装成在红外光区具有光子带隙的人工欧泊,采用化学还原法向欧泊中填充高折射率材料Se,改变其光学带隙特性.采用扫描电子显微镜(SEM)、X射线衍射和可见-近红外光谱仪(VIS-NIR)等对Se-SiO2三维光子晶体的形貌、结构和光学性能进行了观察测试.研究结果表明Se以纳米晶粒的形式均匀地包覆在SiO2微球表面,与相同晶格周期的SiO2光子晶体相比,Se-SiO2光子晶体的带隙发生明显的红移.     

具有梯度结构的蛋白石光子晶体的制备

具有梯度结构的蛋白石光子晶体具有独特的光学性能。本文通过垂直沉积法和电场诱导沉积等方法共同作用将具有不同直径的聚苯乙烯(Polystyrene)胶体微球逐层组装在一起,制备出具有梯度周期尺寸变化的蛋白石结构。     

扫描电镜用于人工蛋白石模板中填充InP的形貌研究

扫描电子显微镜是对人工欧泊光子晶体进行形貌观察、研究的重要手段.本文利用扫描电子显微镜对人工欧泊晶体及其填充InP后的形貌进行了分析.结果发现,二氧化硅微球短程有序而在较大的区域则出现台阶、空位和失配等缺陷;在选定生长条件下,InP在SiO2球空隙间具有较高的填充率和较好的结晶质量.此项研究为制备三维InP光子晶体提供了科学依据.     

异质结构光子晶体的制备与带隙特性研究

本文采用多次垂直沉积法制备出了可见光范围的多重异质结构光子晶体,并对其形貌特征和带隙特性进行了分析.扫描电镜图像表明:所制备的异质结构光子晶体排列规整、不同结构间界面明显.光学吸收光谱分析结果表明:异质结构光子晶体与各单一结构光子晶体带隙相比,带隙明显增大,为各单一结构光子晶体带隙的叠加,且与不同结构的叠加顺序无关.     

蓝色聚苯乙烯胶体晶体膜的制备及其呈色机理研究

以粒径为340±10 nm的单分散聚苯乙烯微球为原料,采用垂直沉积法制备了蓝色聚苯乙烯胶体晶体膜.通过研究不同组装容积对聚苯乙烯胶体晶体膜的微观形貌和宏观呈色性能的影响规律,探索制备大面积蓝色聚苯乙烯胶体晶体膜的方法.结果表明,当聚苯乙烯乳液浓度为0.1wt;,干燥温度为40℃,自组装容积为50 mL时,所得聚苯乙烯胶体晶体膜呈现高质量的密排六方结构,宏观上呈现均匀明亮的蓝色,该蓝色具有一定的角度依赖性.研究发现,采用该方法制备聚苯乙烯胶体晶体膜时,在基片上和玻璃器皿壁上同时进行着垂直自组装.同时,在玻璃器皿底部也进行着蒸发自组装,形成了较大面积的蓝色聚苯乙烯胶体晶体膜,有望为制备大面积聚苯乙烯胶体晶体膜提供新的方法.     

利用水平沉积法制作PS微球二元胶体薄膜及其它复杂结构

本文采用水平沉积方法,制作出各种胶体晶体薄膜.以聚苯乙烯微球为构建单元,制作了多种二元胶体晶体和非单一平面的胶体晶体.为实现太赫兹光子晶体波导,还采用这一方法将线缺陷植入胶体晶体.结果显示通过该方法可以获得很好的有序结构,说明水平沉积方法可以广泛于各种胶体晶体制作.     

An alternative method to obtain direct opal photonic crystal structures

We describe the protocol that we have elaborated in order to obtain monosize polystyrene spheres. Starting from these spheres a simple and effective method, based on spin-coating technique, was developed to realize colloidal photonic crystal structures. The process produces compact 3D arrays of polystyrene microspheres (opals) that are organized into crystalline lattices. This process offers the ability to rapidly form 3D photonic crystals using inexpensive instrumentation, which makes it attractive for an array of applications. Process parameters, fabricated structures, and their experimental characterization are presented.     

Template effects on the morphology of ZnO via colloidal crystals with different functional groups

ZnO is an important wide bandgap compound semiconducting material and exhibits a wide range of novel structures that can be grown by tuning the growth rates along its fast growth directions. Highly ordered macroporous materials by using colloidal crystal template method are of great interest in many fields including photonic crystals and catalysts. In this study, ZnO with highly ordered porous structure was deposited by different electrochemical method. Nanomeshes, inverse opal structures, and spherical/ellipsoidal particles with pore arrays are fabricated by the colloidal crystals with different functional groups. The template effects on the morphology of the macroporous structures for different surface groups are studied. All the nanomeshes grows along the {111} plane family by colloidal crystals without functional groups. Disordered arrangements of the nanomeshes are induced by colloidal crystals with hydroxyl groups. The inverse opal structures fabricated by template with carboxyl groups are smoother in surface.     

Nematic Defects and Colloids as Photonic Elements

Birefringent structures in liquid crystalline fluids, such as colloidal assemblies or topological defects, show high potential for use as photonic elements. Here, we present a brief overview of two photonic phenomena originating from coupling light fields with complex birefringent nematic profiles: (i) the generation of vector laser beams from simple Gaussian beams by propagating light along nematic discliantions, and (ii) tunable photonic crystals from blue phase colloidal crystals conditioned by the different underlying symmetries of the particle lattice and the blue phase birefringence. The polarization profile of initially simple linearly polarized Gaussian beams is shown to change into a defect structure at distinct distances travelled along the disclination with the topological invariant (winding number) of the light field and nematic director distinctly coupled. Upon pulsed laser illumination, the nematic discliantions are also shown to split the light pulse into multiple intensity regions. Blue phase I face centred cubic colloidal crystals are shown as examples of tunable photonic crystals, where local band-baps can open by differently combining the symmetries of the two components, e.g. by changing the particle size. The spatial profiles of selected photonic bands in the blue phase colloidal crystals are shown, finding the particles and blue phase double twist cylinders as possible carriers of high-light-intensity regions.     

Processing optimization and optical properties of 3-D photonic crystals

The synthesis optimization of three-dimensional photonic crystals (direct and inverse opals) is discussed in terms of the influence of processing parameters on the final optical quality. A colloidal/sol–gel route, starting with the self-organization of polystyrene microspheres into opal structures by convective self-assembly, followed by infiltration with a dielectric matrix precursor sol and heat treatment, has been followed. Several substrate hydrophilization methods have been tested and different substrates. Sol–gel infiltration of the opal template interstices with silica was achieved by dip-coating or micro-syringe application and it was followed by removal of the polymeric template. The concentration of the colloidal sol, containing polystyrene spheres of 235 or 460 nm in diameter, was optimized. The structural and optical properties of the opals and inverse opals have been studied by field emission scanning electron microscopy and optical reflectivity spectroscopy, in order to assess the relationship between their structure and the photonic properties obtained. By using borosilicate glass substrates hydrophilized with hydrochloric acid, colloidal photonic crystals of good quality have been obtained, with well ordered regions up to ～100 μm². By monitoring the effective refractive index change with relative humidity of the surrounding atmosphere, using spectroscopic ellipsometry with an environmental chamber, it was concluded that the present photonic crystals are suitable for humidity sensing applications.     

Topological Soft Matter for Optics and Photonics

Liquid crystal colloids are interesting for a variety of mechanisms—including self-assembly, optical-tweezers assisted assembly, topology, and material flow—that can be used to create various complex optical and photonic structures. Here, we present a brief overview of liquid crystal colloidal structures, as recently achieved by numerical modeling and experiments. Central to the structures are complex conformations of topological defects, as they can bind, stabilize, or distort the structure. Using topological and geometrical arguments, we show that the defects can be controllably rewired and imprinted, for example by using optical tweezers. We show that 3D colloidal crystals can be assembled from elastic dipoles of spherical beads in nematic liquid crystals or via inherently inhomogeneous order profiles in bulk and confined cholesteric blue phases. Colloidal crystals are generalized to close-packed colloidal lattices, which we show can serve as natural templates for defect networks. Finally, photonic bands are calculated for selected structures and possible defects in the structure are discussed.     

空气放电中自组织等离子体光子晶体研究

采用平板双水电极介质阻挡放电装置,通过放电丝的非线性自组织,在空气放电中获得不同对称性二维等离子体光子晶体.随外加电压升高,等离子体光子晶体经历了从等边三角晶格到四方晶格结构的转化.在实验测量数据的基础上,采用平面波展开方法计算了等离子体光子晶体转化过程中的带隙结构变化.提出了一种在空气放电中实现的新型可调等离子体光子晶体.     

Three-dimensional circular spiral photonic crystal structures recorded by femtosecond pulses

Photonic crystal structures having three-dimensional (3D) circular spiral architecture have large theoretical photonic band-gap but cannot be implemented by most of the existing microfabrication techniques. We have successfully used a highly versatile 3D microstructuring technique called femtosecond laser microfabrication to prepare templates of the circular spiral photonic crystals in a commercially available photoresist SU-8. The structures fabricated have good structural quality, are highly periodic and exhibit spectral signatures of photonic bands dispersion in the short infrared wavelength region.