蛋白石、反蛋白石结构光子晶体的制备进展

近30年来,蛋白石结构光子晶体(简称蛋白石)和反蛋白石结构光子晶体(简称反蛋白石)成为光波导、光催化、化学及生物传感器、光伏电池等研究领域的热点。对蛋白石制备方法进行了归纳,从毛细管力、电磁场力及其他外加力的作用方面对自组装方法进行了分类和讨论;将反蛋白石制备方法归纳为三步法和两步法,详细地介绍、分析了三步法中反蛋白石前驱体充填方法,总结了两步法制备大面积、无缺陷反蛋白石研究进展,并进行了讨论;最后对蛋白石、反蛋白石制备进行了总结和展望。     

反蛋白石结构光子晶体材料中光传输的仿真研究

单分散胶体球可自组装出面心立方结构(周期常数为a)的三维光子晶体材料,进一步用高折射率光学材料填充其间隙再除去胶体球则可制得高折射率差、反蛋白石结构的三维光子晶体材料,从而应用于集成光子器件。了解其光子带隙以及光在缺陷中的传输性质是设计与制造该光子晶体材料与器件的基础,因此采用时域有限差分法仿真,研究不同波长λ的光在完整与含直线、L形线缺陷的反蛋白石结构光子晶体材料中的传输性质。研究结果表明该材料光子禁带的归一化频率a/λ在0.45~0.55之间,光在直线缺陷和L形线缺陷中传输的透过系数分别为~65%和~72%。     

近红外光学带隙硅三维光子晶体的制备

用溶剂蒸发法将单分散SiO2微球组装成三维有序结构的胶体晶体模板,用低压化学气相沉积法填充高折射率材料硅,酸洗去除SiO2模板,获得了硅反蛋白石三维光子晶体.通过扫描电镜、X射线衍射仪和紫外-可见-近红外光谱仪对硅反蛋白石三维光子晶体的形貌、成分、结构和光学性能进行了表征.研究结果表明:Si在SiO2微球空隙内具有较高的结晶质量,填充致密均匀;通过控制沉积条件,可控制硅的填充率;制备的硅反蛋白三维光子晶体在近红外区(1.4μm左右)具有明显的光学反射峰,表现出光学带隙效应,测试的光学性能与理论计算基本吻合.     

基于胶体微球自组装光子晶体的结构生色

综述了近年来基于胶体微球自组装光子晶体结构生色的研究进展.先简要介绍了光子晶体和结构生色理论,然后阐述了以胶体微球为基本结构基元构筑光子晶体的自组装方法,探讨了光子晶体的结构色效果的表征方式和稳固性增强方法,最后总结了用胶体微球自组装法制备光子晶体的困难并展望了发展方向.     

ZnO光子晶体的自组装工艺及带隙特征研究

以Zn（Ac）2和DEG为原料,采用胶体自组装工艺制备了不同胶粒尺寸的ZnO光子晶体,探索了胶体自组装ZnO光子晶体的制备工艺,研究了自组装温度、溶剂、悬浮液浓度、热处理温度等因素对光子晶体排布平整度、周期性和空间紧密度的影响规律,对各种工艺条件下光子晶体的带隙特征进行了研究,试验结果表明,通过自组装工艺条件选择可实现对光子晶体带隙结构的可控性制备。     

SiO2胶体晶体的自组装结构及其带隙特征

光子晶体是一种具有光子带隙的新型功能材料.利用垂直沉积自组装法制成SiO2胶体晶体,并利用扫描电子显微镜和紫外分光度计对胶体晶体的显微形貌和光学特征进行了研究.结果表明,利用垂直沉积法自组装得到的SiO2胶体晶体具有面心立方结构;在可见光波段,胶体晶体在＜111＞面方向存在光子带隙.     

TiO2/SrTiO3光子晶体薄膜的制备及光电催化性能

以单分散聚苯乙烯(PS)微球在FTO导电玻璃表面自组装形成的蛋白石(Opal)结构为模板,使用溶胶-凝胶法进行TiO2前驱体的填充,退火后制备出反蛋白石结构的TiO2光子晶体薄膜。进一步通过水热反应将部分TiO2反应生成SrTiO3从而形成TiO2/SrTiO3异质结。通过多种手段技术表征了所制备材料和结构的晶型,形貌及其光电化学性能。研究结果表明,SrTiO3的负载量和晶粒大小可以通过水热反应时间调控。在经过0.5h的水热反应后,SrTiO3的负载量为9.6%,TiO2/SrTiO3薄膜保持了原有的光子晶体结构,且光电流增大了82%。TiO2/SrTiO3异质结构的形成能有效地促进光生载流子的分离,提高光电催化性能。     

NaGd(WO4)2:Yb3+/Tm3+反蛋白石光子晶体的制备与上转换发光调制研究

三维光子晶体具有长程有序的结构特点, 在可见和近红外光谱范围内有着广泛的应用。光子晶体的一个重要性质是其对嵌入其中的发光中心自发辐射具有调制作用。本研究利用自组装和模板辅助法制备高质量的三维NaGd(WO₄)₂:Yb³⁺/Tm³⁺反蛋白石光子晶体, 探究了光子带隙对Tm³⁺离子上转换荧光发射与发光动力学的调制作用。通过对比分析发现, 由于反蛋白石光子晶体独特的周期性大孔结构和光子带隙效应, 处于光子带隙内的Tm³⁺离子¹G₄-³H₆的发光强度被抑制约45%, 自发辐射速率(SDR)被抑制约30%, 同时上转换局域热效应得到有效的调制。本实验结果对探索新型高效稀土掺杂上转换发光材料和提高上转换发光效率有指导意义。     

有序多孔结构二氧化钛薄膜的制备和应用

本文探讨了一种制备二氧化钛高度有序多孔结构的方法及其在染料敏化太阳电池中的应用。采用聚苯乙烯悬浮液,采取垂直沉积法得到了聚苯乙烯胶体晶体;以该模板制备了高度有序的纳米二氧化钛反蛋白石多孔薄膜。对胶体晶体模板和二氧化钛反蛋白石有序膜的微观结构进行表征和讨论。用所制得的二氧化钛反蛋白石有序膜组装成染料敏化太阳电池。通过电流...     

垂直沉积自组装法与复杂结构光子晶体的研究进展

作为一种折光指数呈周期性分布的材料,光子晶体在功能器件、光学纤维和光学伪装材料等方面有潜在重要的应用。总结了以垂直沉积自组装法为基础,通过不同方法来制备光子晶体的研究进展,以及利用这些方法进一步制备各种具有不同复杂结构光子晶体的进展,总结了这些方法制备光子晶体的优缺点,并展望了垂直沉积自组装法制备光子晶体的发展趋势。     

Preparation and characterization of bowl-like porous ZnO film by electrodeposition using two-dimensional photonic crystal template

A rapid and low-cost method combining electrodeposition with two-dimensional (2D) photonic crystal template technique to prepare large scale bowl-like porous ZnO films is described. The 2D photonic crystal templates were fabricated by self-assembly of monodispersed polystyrene (PS) microspheres on indium-tin-oxide coated glass substrates using spinning coating method. The interstitial spaces among the spheres of the templates were filled with ZnO via electrodeposition from an aqueous solution containing 0.02 M zinc nitrate as electrolyte under a constant potential of ?1.0 V at 65 °C for 10 min. After removal of the PS photonic crystal template, bowl-like porous ZnO film was obtained. The entire process can be accomplished within 30 min. Scanning electron microscopic images showed good homogeneity in morphology, X-ray diffraction spectra demonstrated the wurtzite structure of the obtained ZnO film, and transmission electron microscopy indicated the single-crystallinity of the ZnO. Ultraviolet–visible (UV–vis) spectrophotometer was used to detect the absorption in UV–vis region of the PS template, opal ZnO-PS composite and inverse opal ZnO respectively. Two strong emission bands at 400 and 550 nm were displayed in photoluminescence spectrum.     

Fabrication and characterization of novel composite membranes composed of photonic crystals and TiO2 nanotube array films

Novel composite membranes composed of photonic crystals (PCs) and TiO₂ nanotube array (TNA) films have been fabricated by combining the room temperature floating self-assembly (RTFSA) method, recently developed by our research group, and the liquid-phase deposition technique. By applying this combined procedure, polystyrene (PS) opal PC/TNA and TiO₂ inverse opal PC/TNA composite membranes were prepared. Scanning electron microscopy and ultraviolet/visible spectroscopy analyses showed that the membrane samples possessed very high crystalline quality. Notably, the ordered packing of the PS microspheres from the top to the bottom of the opal PC film was not affected by the surface roughness of the porous TNA substrate. This is attributed to the self-assembly mechanism of the colloidal particles, which produces a three-dimensional ordered structure in the RTFSA method. Herein, the crystallization of the colloidal particles occurred at the surface of the colloidal suspension, and the crystal growth proceeded downward from the surface of the suspension to the substrate.     

Layer‐by‐Layer Approach to (2+1)D Photonic Crystal Superlattice with Enhanced Crystalline Integrity

Large‐area polystyrene (PS) colloidal monolayers with high mechanical strength are created by a combination of the air/water interface self‐assembly and the solvent vapor annealing technique. Layer‐by‐layer (LBL) stacking of these colloidal monolayers leads to the formation of (2+1)D photonic crystal superlattice with enhanced crystalline integrity. By manipulating the diameter of PS spheres and the repetition period of the colloidal monolayers, flexible control in structure and stop band position of the (2+1)D photonic crystal superlattice has been realized, which may afford new opportunities for engineering photonic bandgap materials. Furthermore, an enhancement of 97.3% on light output power of a GaN‐based light emitting diode is demonstrated when such a (2+1)D photonic crystal superlattice employed as a back reflector. The performance enhancement is attributed to the photonic bandgap enhancement and good angle‐independence of the (2+1)D photonic crystal superlattice.     

Synthesis and characterizations of three-dimensional ordered gold- nanoparticle-doped titanium dioxide photonic crystals

We developed a simple method to prepare gold-nanoparticle-doped titanium dioxide (GTD) sol-gel solution. The optimized GTD sol-gel solutions were a mixture of TEA, titanium (IV) butoxide, HAuCl₄, and deionized water in 0.3:1:0.5:3 volume ratios at room temperature. Using this sol-gel solution, we fabricated the GTD photonic crystal structure by infiltrating this solution by dip-coating into a polystyrene (PS) template. It was found that high quality of thin films was obtained by infiltrating twice the PS templates with the synthesized GTD sol-gel solutions. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectra revealed the doping of TiO₂ and Au in the GTD photonic crystals. X-ray diffraction showed that TiO₂ and Au existed as anatase phase and metallic Au phase, respectively, in the GTD photonic crystals. The results indicated that the gold nanoparticles were doped into the framework of the photonic crystals.     

Self-assembly of colloidal crystals from polystyrene emulsion at elevated temperature by dip-drawing method

The self-assembly of colloidal crystal arrays from polystyrene (PS) sphere emulsion at elevated temperature by dip-drawing method was investigated. The dependence of effective sphere transfer in the meniscus of emulsion on temperature was discussed. The results show that the assembled arrays formed at 50 °C have fewer defects than those at room temperature. The elevated emulsion temperature during the ordered arrangement of colloidal crystals causes quicker solvent evaporation, hence quicker sphere transfer. However, exceeding solvent flux and crystal growth induced by over high temperatures result in more fracture lines displayed in arrays. At 50 °C, the effective sphere transfer by the solvent flux to the array edge can also be enhanced by increasing the PS volume fraction of emulsion, which obviously reduces fracture lines on the surface of multilayer.     

Color tunability of upconversion emission in YBO3: Yb, Er inverse opal

Upconversion (C) light-emitting photonic band gap materials (YBO₃: Yb, Er) with inverse opal structure were prepared by a self-assembly technique in combination with a sol-gel method. The effect of the photonic stop-band on the upconversion luminescence of Er³⁺ ions has been investigated in the YBO₃: Yb, Er inverse opals. Significant suppression of the green or red UC emission was detected if the photonic band-gap overlaps with the Er³⁺ ions emission band. We successfully achieved the color tuning of the UC optical properties of the inverse opal by controlling the structure of the photonic crystal.     

Preparation of three-dimensional ordered macroporous Cu2O film through photonic crystal template-assisted electrodeposition method

Three-dimensional ordered macroporous (3DOM) Cu₂O film was prepared on indium-tin-oxide (ITO) glass using photonic crystal template-assisted electrodeposition approach. The technological process involved the following steps: preparation of three-dimensional (3D) photonic crystal template, potentiostatic electrodeposition of Cu₂O into the template, and template removal. 210 nm polystyrene (PS) spheres were used to prepare the 3D photonic crystal template by means of a vertical deposition technique on ITO glass. A two-electrode cell was used for electrodeposition, in which the anode was graphite and the cathode was PS-coated ITO glass. The electrodeposition solution consisted of 0.1 M sodium acetate and 0.02 M copper acetate and was acidified at pH 5.7. Via electrodeposition, the interstitial space of the packed PS photonic crystal template was filled with Cu₂O. After removal of the PS photonic crystal template by immersing in tetrahydrofuran solution, 3DOM Cu₂O film with a homogeneous area of 20 × 10 mm² was obtained. The film was characterized by field emission scanning electron microscopic (FE-SEM) and X-ray diffraction. The results indicated that the as-prepared Cu₂O film was of high purity, good homogeneity, and a well-ordered macroporous structure.     

Fabrication of multi-walled carbon nanotube reinforced polyelectrolyte hollow nanofibers by electrospinning

Hybrid hollow multi-walled carbon nanotubes (MWCNTs)/polyelectrolytes (PE) nanofibers were prepared by a combination of the electrospinning method and layer-by-layer (LbL) technique. The mixed polystyrene (PS)/MWCNTs nanofibers were obtained by electrospinning method, which were employed as templates to self-assembly multilayered polyelectrolytes by LbL technique. Hollow MWCNTs/PE nanofibers were obtained by selectively removed part of the template: PS, which is confirmed by Raman spectra, transmission electron microscopy (TEM) and scanning electron microscopy (SEM).