单分散SiO2微球的合成及胶体晶体的生长

对传统的"Stober-Fink"合成SiO2微球的工艺进行了改进,运用"籽晶生长法"合成了单分散SiO2微球,该法可以准确地控制微球尺寸,提高微球的球形度.采用垂直沉积法制备了胶体晶体,并对样品的结构和光学性能进行了表征.研究了微球尺寸对垂直沉积SiO2胶体晶体光子带隙的影响,结果表明,通过控制微球粒径,可调节光子晶体的带隙位置.     

单分散SiO2胶体球制备及其胶体晶体组装

运用胶体化学法在乙醇介质中合成SiO2胶体球,将制得的样品在30℃下用双氧水浸泡处理48h.用扫描电子显微镜(SEM)、傅立叶红外光谱(FT-TR)、Zeta电位仪和标准氢氧化钠滴定法对其形貌、结构和表面电学性质进行分析.结果表明样品平均粒径为292nm,平均标准偏差小于5%;经双氧水浸泡处理后,SiO2胶体球表面羟基数目增多,在水溶液中的Zeta电位从-55.72mV提高到-63.26mV,表面电荷密度从0.19μC/cm2提高到0.28μC/cm2.通过垂直沉积法,在40℃和60%相对湿度条件下制备出有序性较好、密排结构的SiO2胶体晶体.在SEM下,观察到这种胶体晶体是面心立方(fcc)密排结构,其(111)晶面平行于基底.透射光谱表明,所制备的胶体晶体在(111)方向具有光子晶体的不完全带隙性质.     

CdSe-SiO2光子晶体的垂直沉积及近红外变频特性

在氧化铟锡玻璃上电化学合成了CdSe薄膜,采用垂直沉积法首次在CdSe薄膜上制备了SiO2胶体晶体, 实现了CdSe表面介电常数的调节.扫描电镜观察表明,500nm微球在CdSe薄膜上呈面心立方密堆结构排列,在微米尺度上胶体晶体显示出一定的多晶序.与SiO2胶体晶体相比,CdSe-SiO2光子晶体的UV-vis-NIR透射谱只有一个较宽的光子带隙,带隙在近红外波段随入射角减小向短波方向移动.所得CdSe-SiO2光子晶体样品可作为地面目标针对红外卫星成像的伪装材料.     

氘代聚苯乙烯胶体晶体的制备及光学性质研究

以水作为介质合成了高度单分散的氘代聚苯乙烯微球,并利用垂直沉积法制备了高质量的氘代聚苯乙烯胶体晶体.傅立叶变换红外光谱清楚地表明氘代苯乙烯单体发生了聚合反应;扫描电镜表面分析展示出胶体微球的高度有序排列,断面分析表明氘代聚苯乙烯胶体晶体为面心立方结构;光学透射谱显示出氘代聚苯乙烯胶体晶体的高次布拉格衍射特征,通过和理论计算的能带结构对比,进一步证实了氘代聚苯乙烯胶体晶体为面心立方结构;变角度光学透射谱测量显示,随着入射角的增大,(111)面的衍射峰蓝移,而(200)和(220)面的衍射峰发生红移.     

光子晶体用二氧化硅胶体球的改性制备及其自组装

采用一步法制备了表面接枝甲基丙烯酰氧基三甲氧基硅烷(MPS)的单分散SiO2胶体球,并通过垂直沉积法在40℃、60%相对湿度下组装出有序性较好的密排结构的SiO2光子晶体.傅立叶红外光谱(FT-IR)和X射线光电子能谱(XPS)结果证明SiO2胶体球表面接枝上了MPS;扫描电子显微镜(SEM)结果表明改性后SiO2胶体球平均粒径为284nm,单分散性较高,平均标准偏差＜5%;制备出的光子晶体是面心立方(fcc)紧密堆积结构;吸收光谱表明,所制备的光子晶体在(111)方向具有光子晶体的带隙特性,带隙中心波长为646nm.     

Se-SiO2三维光子晶体的制备

报道了一种新的调节二氧化硅光子晶体带隙的方法;通过化学镀向SiO2胶体晶体中填充半导体材料Se,获得了Se-SiO2两种介质复合的三维光子晶体;采用扫描电子显微镜(SEM)、X射线衍射和紫外-可见光谱仪(UV-VIS)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,形成了Se壳层,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了明显的红移.     

SiO_2/魔芋葡甘聚糖微球制备纤维多层结构的结构色

为了研究出一种光学和力学性质良好的结构色纤维,文中将魔芋葡甘聚糖应用于结构色纤维的加工,利用表面涂覆技术制备结构色纤维。通过显微镜观察结构色纤维的反射光谱,结果表明,提拉速度与纤维表面的胶体晶体层数成负相关关系,胶体浓度以及纤维尺寸与纤维表面的胶体晶体层数成正相关关系,纤维颜色随微球尺寸增大而红移,随微球尺寸变小而发生蓝移,而且当纤维表面的胶体晶体层数达到10层时,结构色纤维的颜色是稳定的。     

聚苯乙烯蓝色胶体晶体膜的制备工艺

本文以单分散的粒径为340±10nm的聚苯乙烯微球为原料,采用垂直自组装法制备了蓝色聚苯乙烯胶体晶体膜。研究了乳液浓度、干燥温度、组装容积等因素对聚苯乙烯胶体晶体膜的微观形貌和呈色性能的影响。结果表明:当乳液浓度较小时,微球呈现单层均匀分布,局部发生自组装,当乳液浓度达到0.1wt%时,微球呈现多层密排六方排列,宏观上呈现明亮的蓝色。当干燥温度为40℃时,该胶体晶体膜微观形貌为高质量的密排六方结构,呈现均匀明亮的蓝色。对比试验得出,在50mL的容器中,PS微球容易发生自组装且呈现明亮均匀的蓝色。同时发现,该胶体晶体膜在较低强度的光线下呈色比较微弱,蓝色饱和度较低,在强烈的光照下,呈现出绚丽的蓝色。     

含Eu(DBM)_3的SiO_2纳米微球的制备与性质研究

采用溶胶-凝胶方法,将已经合成Eu(DBM)3·H2O纳米微晶分散到SiO2纳米微球中,通过红外光谱、元素分析、透射电子显微镜(TEM)、荧光光谱等测试方法对其组成结构、荧光性质以及微观形貌等进行了表征。结果表明,Eu(DBM)3·H2O成功地被引入到SiO2纳米微球中,从而使SiO2纳米微球发出了铕离子的特征荧光,使SiO2纳米微球可在光电学、磁学以及激光等领域被应用。     

AlN/SiO2纳米多层膜的超硬效应与高温抗氧化性

采用反应磁控溅射法制备了一系列不同SiO2层厚的AlN/SiO2纳米多层膜,利用X射线衍射仪,高分辨透射电子显微镜、扫描电子显微镜和微力学探针表征了多层膜的微结构和力学性能,研究了多层膜微结构与力学性能随SiO2层厚的变化,考察了AIN/SiO2纳米多层膜的高温抗氧化性.结果表明,受AlN层晶体结构的模板作用,溅射条件下以非晶态存在的SiO2层在厚度<0.6nm时被强制晶化为与AIN相同的六方结构赝晶体,并与AlN形成共格外延生长结构,多层膜相应产生硬度升高的超硬效应. SiO2随自身层厚的进一步增加又转变为以非晶态生长,致使多层膜的外延生长结构受到破坏,其硬度也随之降低.高温退火研究表明,高硬度的AIN/SiO2纳米多层膜的抗氧化温度为800℃,与AlN单层膜相当. SiO2层的加入尽管能使多层膜获得较高硬度,但是并不能提高其抗氧化温度.     

Fabrication of hollow silica spheres and their application in polyacrylate film forming agent

Polystyrene (PS)/silica core/shell spheres were fabricated using mono-dispersed PS as templates by hydrolysis and condensation of two different silica precursors. The PS cores of PS/silica core/shell spheres were dissolved subsequently in the tetrahydrofuran medium to form mono-dispersed hollow silica spheres. The structures and morphologies of hollow silica spheres were characterized by scanning electron microscopy and transmission electron microscopy. Then, polyacrylate/hollow silica composite film forming agents were prepared via physical blending of polyacrylate and two different hollow silica spheres, and the water vapor permeability of their films were compared. The results showed that the structure of hollow silica spheres were very typical and obvious. The silica shell was continuous and uniform using tetraethylorthosilicate as precursor, which was accumulated by many silica seeds with size of 10–20 nm, and the thickness of silica shell was about 16.7 nm. However, the hollow silica spheres using tetraethylorthosilicate and vinyl triethoxysilane as precursors had mesoporous structure in the shell. The introduction of hollow silica spheres could significantly improve the water vapor permeability of polyacrylate film. At last, a possible mechanism for the formation of hollow silica spheres was proposed and the process of water vapor through polyacrylate/hollow silica composite films was modeled.     

Characterisation of hollow Russian doll microspheres

Poly(1-methylpyrrol-2-yl)squaraine (PMPS) particles have been characterised using SEM. The PMPS particles were used as templates to prepare bare silica and iron–silica hollow spheres, which were characterised using TEM and SEM. The PMPS particles and the hollow spheres are not uniformly sized and are agglomerated. The hollow spheres with larger diameters (>900 nm) contain an internal ‘Russian doll’ structure. The iron–silica hollow spheres are fused to one another, and the hollow spheres have a heterogeneous wall thickness. The silica and iron–silica hollow spheres both aggregate by size. There are two different size populations (for the diameter) of the bare silica and iron–silica hollow spheres. The smaller silica spheres have thinner walls compared to the larger silica hollow spheres. The larger silica hollow spheres and the iron–silica hollow spheres have similar wall thicknesses. The iron compound in the iron–silica hollow spheres has an oxidation state of 3+ and is crystalline.     

A facile method to synthesize hierarchical SiO2@CdSe and CdSe hollow spheres

In this paper, a facile method was developed to synthesize SiO₂@CdSe particles by using silica colloidal spheres which efficiently avoided complex prior surface modification. In the experiment, ammonia was introduced to activate silica colloidal spheres with negative charge, which acted as active sites for the nucleation of CdSe nanocrystals around silica colloidal spheres. Then the corresponding CdSe hollow spheres were obtained by dissolving the silica cores. The TEM results exhibited CdSe hollow spheres were consisted of nanorods. On the basis of experimental results, the formation process of the hollow spheres was studied and possible growth mechanism for one-step coating process was proposed.     

Fabrication of hollow silica spheres in an ionic liquid microemulsion

Hollow silica spheres have been successfully synthesized by using the ionic liquid microemulsion droplets as the template. The morphology and microstructures of the silica spheres were investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), and Nitrogen adsorption-desorption measurements. The obtained images showed that the average size of the silica spheres was almost between 150 and 300 nm. The Nitrogen adsorption-desorption investigation on the silica spheres indicated the amorphous structure on the interface. Both of these two results provide us new insights into this novel template and hollow silica spheres were for the first time prepared free of additional acid and alkali conditions. The possible mechanism for the formation of silica spheres has been put forward and discussed in details.     

A dual template method for synthesizing hollow silica spheres with mesoporous shells

PS/silica core/shell composites were synthesized by the modified Stöber method using polystyrene spheres and cetyltrimethylammonium bromide as dual templates under room temperature. The silicate species and the templates were self-assembled to form mesoporous silica shell on the surface of the PS spheres. Hollow silica spheres with mesoporous shell were obtained by removing the polymer core and the templates through calcination. The hollow silica spheres showed high specific surface area of 1099.5 m²/g and narrow pore size distribution centered at 2.31 nm.     

A novel synthesis of micrometer silica hollow sphere

Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented.     

Self-assembly of modified silica nanospheres at the liquid/liquid interface

A stabilized 2 or 3D silica sphere structure was successfully prepared by a 3-step method. First, the surfaces of silica spheres were modified with a functional silane coupling agent 3-methacryloxypropyltrimethoxysilane (γ-MPS); then, the surface-modified silica spheres were self-assembled at the liquid/liquid interface to fabricate a two- or three-dimensional ordered structure; and finally, the formed ordered structure was stabilized by a stable polymerization reaction among the modified silica spheres. The polymerized silica sphere film can be transferred from solution to quartz substrates without destroying its ordered structure. This ordered structure could be potentially used as a photonic band gap material or the template for fabrication of other highly ordered structures.     

Fabrication of nanoscaled silica layer on the surfaces of submicron SiO2-Ag core-shell spheres

A two-step silica deposition process, including prefunctionalization with poly(vinylpyrrolidone) and the following silica deposition, has been used to fabricate silica layer on the surface of nanoscaled silver shell. The influencing parameters of silica coating process were optimized to prevent the precoated silver nanoparticles from desquamating from silica spheres, finally to obtain mono-dispersed silica spheres with silver and silica multilayer films. The resulted silica layer was dense and uniform, its thickness was controllable in the range of 20–50 nm. Such coated silica layer can provide improved thermal stability of the SiO₂-Ag core-shell structural spheres.     

Surface synthesis of PbS nanoparticles on silica spheres by a sonochemical approach

A simple sonochemical approach for the preparation of PbS nanoparticles homogeneously coated on sub-micrometer silica spheres has been described. The transmission electron microscopy and scanning electron microscopy images show that the PbS nanoparticles with size of 30 nm were coated on the silica spheres, without any free nanoparticles. X-ray diffraction reveals that the PbS nanoparticles are of cubic rock-salt structure. Moreover, by dissolving the silica cores with a diluted hydrofluoric acid solution, stable PbS hollow structures were obtained. It is considered that the sonochemical process in which triethanolamine acted as complex agent played an important role for the homogenouse coating of PbS nanoparticles on silica spheres.     

Fabrication of photonic crystal heterostructures by a simple vertical deposition technique

This paper describes a facile method for the fabrication of photonic crystal heterostructures (PCHSs) composed of photonic crystals (PCs) of core–shell spheres with different diameters and effective refractive indexes. The PCs are fabricated by a simple vertical deposition technique. The PCs of monodisperse polystyrene/silica core–shell (PS@SiO₂) spheres or hollow silica spheres are used as substrates to fabricate PCHSs, respectively. The results indicate that the resultant PCHSs formed from PS@SiO₂ spheres or hollow silica spheres have a very high quality and a good adsorbing interface between the PCs. Transmission spectra show that there are two optical stop bands of the PCHSs, and the positions of optical stop bands are controlled by tuning the size and the effective refractive index of spheres. The PCHSs formed from hollow silica spheres may facilitate the development of the potential applications due to the novel properties of hollow silica spheres, such as, low density, low refractive index, and high specific surface area.