用于治疗白内障的人工晶体材料及表面修饰研究进展

从材料角度对人工晶体材料及其表面修饰以及材料的发展做了详细介绍.通过表面改性提高了材料的生物相容性,降低术后并发症.人工晶体材料的发展,使得人工晶体植入手术切口更小,倾向于生理调节.     

基于温敏水凝胶的可调胶体晶体制备

基于单分散胶体粒子悬浊液在温敏水凝胶表面可以形成湿润型胶体晶体的现象, 利用温敏水凝胶对水的控释作用制备了温度敏感的可调制胶体晶体. 在室温下利用提拉法在温敏水凝胶聚N-异丙基丙烯酰胺(PNIPAAm)表面制备湿润型胶体晶体膜. 由于胶体粒子的有序排列, 胶体晶体显示出一个尖锐的反射峰. 当温度上升到34 ℃以上时, 由于PNIPAAm水凝胶中的水被释放, 导致胶体晶体中粒子浓度降低, 粒子间距增加; 反射峰发生红移. 这些特性可以通过温度变化进行调制.     

准晶体的发现、性质及其价值——2011年诺贝尔化学奖解读

2011年诺贝尔化学奖授予以色列科学家达尼埃尔.谢赫特曼）Daniel Shechtman）,以表彰他发现准晶体）Quasicrystals）的贡献。准晶体与传统晶体不同,它具有5次旋转轴的长程有序结构,它的发现和研究具有重要学术和应用价值。     

反蛋白石光子晶体的研究进展

反蛋白石晶体是一类重要的光子晶体,由于其制备材料的广泛性以及容易实现对光子禁带的多重调制而受到广泛关注.本文介绍了目前反蛋白石晶体结构的主要制备技术和方法,详细阐述了反蛋白石晶体结构的最新研究进展.     

基于胆甾相液晶的可调制光子晶体

将胆甾相液晶填充进胶体晶体内部空隙, 通过胆甾相液晶与胶体晶体的耦合, 构建了一种新型可调制液晶光子晶体. 填充于胶体晶体内部的胆甾相液晶织构呈现典型的手性近晶相(S)特征. 由于胆甾相液晶具有特定的选择性反射, 当胶体晶体的带隙处于胆甾相液晶的反射波长范围之内, 则随着温度的改变, 胶体晶体的带隙与胆甾相液晶的带隙同时发生蓝移. 在一定温度条件下, 胆甾相液晶的带隙将与胶体晶体的带隙发生耦合, 实现了光子晶体带隙在单峰与双峰之间的可逆切换.     

三维胶体光子晶体对光的调控与应用研究

21世纪在光子技术领域中操控光子已成为核心的研究内容.胶体光子晶体因其特殊的周期结构而具有光子禁带的特性,从而可以对特定频率的光进行调控,其应用涵盖了光、电、催化、传感、显示、检测等众多领域,为光功能材料的结构设计和性能优化提供了参考依据.本文主要从两个方面阐述近年来胶体光子晶体对光的调控作用与应用,一方面,光子晶体的...     

纳米和微米一水草酸钙对Vero细胞毒性的浓度效应

采用扫描电子显微镜(SEM)、激光共聚焦显微镜(LSM)和流式细胞仪等技术比较了纳米级和微米级一水草酸钙(COM)对非洲绿猴肾上皮细胞(Vero)的毒性差异。结果显示,尺寸为100 nm和6μm的COM晶体都能引起Vero细胞活力下降、乳酸脱氢酶(LDH)释放量升高、透明质酸(HA)表达量增多、溶酶体完整性降低、线粒体膜电位下降、细胞死亡率升高和细胞周期滞留,表明这些晶体对Vero细胞都有损伤作用且呈现浓度依赖性,但纳米COM的毒性及其在细胞表面的粘附量均大于微米COM晶体。     

防灰雾剂对T-颗粒乳剂晶体表面形貌的影响

应用原子力显微镜对硫加金化学增感后的T 颗粒掺杂乳剂晶体表面形貌进行观察,直接测得了晶体颗粒的大小和厚度.颗粒表面精细结构观察显示样品表面并不平整,存在很多突起.这些突起呈线形平行排列,接近网格状.经曝光后突起变得更高,更集中.表面吸附足量的防灰雾剂后,晶体表面突起不明显.曝光后表面高度变化不大.     

带电悬浮粒子胶体晶体的固定化

采用光固化技术, 以丙烯酰胺单体与亚甲基双丙烯酰胺交联剂在紫外光的照射下发生光聚合反应, 嵌入聚苯乙烯胶体晶体, 实现了胶体晶体的固定化. 结合反射光谱和Kossel衍射技术研究对照了固定化前后胶体晶体的变化, 实验结果表明, 通过这种水凝胶固定化的胶体晶体保存了未固定前悬浮液中胶体晶体的结构. 但固定化后的胶体晶体的晶面间距和晶体的尺寸都略微减小. 通过对固定化后的水凝胶长时间的反射光谱观测, 发现固定化后胶体晶体在Milli-Q水中起初会发生溶胀, 经过2-5天溶胀-消溶胀过程达到平衡, 平衡后的水凝胶胶体晶体十分稳定, 可以长时间保持胶体晶体的结构. 因此, 胶体晶体固定化不但极大地提高了悬浮液中胶体晶体的抗剪切能力, 还克服了悬浮液中胶体晶体对离子、外界干扰的敏感性, 扩大了胶体晶体的实际应用价值.     

自组装方法与三维光子晶体制作

光子晶体,特别是三维光子晶体,可能成为信息处理和通信等领域的新型功能材料.光子晶体的制作方法可分为"自上而下"的物理方法和"自下而上"的化学自组装方法.化学自组装方法是制作三维光子晶体最为经济有效的方法.本文在阐述自组装方法的种类、一般过程、优点和不足等内容的基础上,分别分析和总结了带有各种功能缺陷的三维光子晶体的制作,这些缺陷主要包括线缺陷、面缺陷和点缺陷.从研究中可以看出,化学自组装方法通常需要结合其他方法才能实现缺陷的嵌入.近些年,三维光子晶体制作在材料选取、结构设计和方法改进等方面都有一些最新进展,本文对此进行了较为详尽的评述,并对我们课题组的研究进行了总结.最后对光子晶体的研究和制作方向进行了展望.     

铌酸锂、钽酸锂晶体的结构特征

从铌酸锂和钽酸锂晶体的结晶学数据出发,分析其结构特征和组成化学键的结合情况.对于这两个晶体的结晶学格位占有情况和阳离子的位移进行了理论上的分析.作者首次明确地给出了铌酸锂和钽酸锂晶体中与晶体组成有关的阳离子位移趋势.     

Optical Properties of Ce-Doped Lithium Niobate Crystals with Various Li/Nb Ratio

Ce-doped lithium niobate （LiNbO3） single crystals were grown from the melts with various Li/Nb molar ratios （0.750, 0.850, 0.946, 1.100, 1.250 and 1.380） by Czochralski method, while doping concentration of Ce was 0.1 mol%. Infrared spectra （IR） and Ultraviolet-visible absorption spectra （UV） of the crystals were measured to investigate the location of Ce ions and defect structure in crystals. The writing time, erasing time, photorefractive sensitivity and dynamic range were measured by two-wave coupling equipment. The results showed that Ce takes the place of Li lattice site, and the LiNbO3 crystal grown from the melt with Li/Nb ratio of 1.250 is stoichiometric crystal, which has the best properties due to the synergistic effect of Ce ion and Li/Nb ratio. Also the influence of various Li/Nb ratios on the defect structure and optical properties of the crystal was reported.     

Composition investigation of lithium niobate crystals and its influence on the optical damage resistance

Optical methods of investigation of the defect structures and the composition of lithium niobate (LiNbO₃) single crystalsis discussed. The intrinsic defects concentrations in lithium niobate crystals (lithium vacancies (V_Li)⁻ and (Nb_Li)⁴⁺ defects, Nb on Li site in the valence state 4+), as a function of the Li/Nb ratio, are also reported. The optical damage resistance of various lithium niobate samples was investigated as a function of the composition. A remarkable increase in the optical damage resistance was found in MgO-doped almost stoichiometric lithium niobate crystals.     

The Growth of KLN Crystals

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Investigation of new fluxes for the single-crystal growth of stoichiometric lithium niobate

Thermoanalytical and crystal growth investigations of the ternary system Cs₂O-Li₂O-Nb₂O₅ are presented in order to grow stoichiometric LiNbO₃ (LN) crystals. Part of the phase diagram is determined and subsolidus phases are identified at room temperature by X-ray powder diffraction. Among the constituent phases, a new tetragonal cesium lithium niobate phase is assessed. From the Cs₂O-Li₂O-Nb₂O₅ system, good quality quasi-stoichiometric LN crystals can be grown.     

Investigation of lithium niobate composition by optical spectroscopy methods

Indirect methods of investigation of composition and defect structures of lithium niobate (LiNbO₃) single crystals with different compositions are discussed. The analysis of two methods for the determination of the Li/Nb ratio in the samples is carried out, viz., the fundamental UV absorption edge and IR vibrational spectra of the OH⁻ group defects. Intrinsic defect concentrations in lithium niobate crystals (lithium vacancies, $ V_{Li^ - } $ V_{Li^ - } and defects, $ Nb_{Li^{4 + } } $ Nb_{Li^{4 + } } ) as a function of the Li/Nb ratio in the samples are given. The results obtained can serve as an effective way of express non-destructive composition analysis in a mass production of parallel-plane plates.     

Effects of piezoelectricity on acoustic axes in crystals

The following three effects of piezoelectricity on acoustic axes in crystals are considered: (i) shift in the positions of acoustic axes, (ii) disappearance of acoustic axes, (iii) generation of new acoustic axes. The examples of these effects are given for (i) gallium orthophosphate (ii) lithium niobate, (iii) barium titanate and lithium tetraborate.     

New Approach to the Preparation of Doped Lithium Niobate Batches for Single Crystal Growth

Technological approaches have been developed to the preparation of single-phase lithium niobate batches doped with magnesium, zinc, iron, and rarer-earth elements (TR = La, Pr, Nd, Sm, Gd, Dy, or Er) from high-purity niobium-containing solutions to avoid niobium pentoxide separation, its mixing with lithium carbonate, and LiNbO₃ preparation from this mixture by a solid-phase reaction. Two process flowsheets have been proposed, being applicable over the entire ranges of the studied dopant concentrations. Optimal parameters for preparing single-phase LiNbO₃ batches of tailored compositions have been determined. The batches prepared by the developed technology are intended for growing doped optical-quality lithium niobate single crystals.     

Synthesis of homogeneously mg-doped lithium niobate batch and study of the effect of non-metal impurities on the properties of LiNbO<Subscript>3</Subscript>:Mg crystals

The preparation conditions for the homogeneously doped precursor Nb₂O₅:Mg for the synthesis of granulated lithium niobate batch was studied. The effect of non-metallic impurities in the Nb₂O₅:Mg precursors and the lithium niobate batch on the characteristics of the melt–crystal system and the physicochemical and optical characteristics of the LiNbO₃:Mg crystals was established.     

Bond energy prediction of Curie temperature of lithium niobate crystals

A general expression of the Curie temperature (Tc) and spontaneous polarization (Ps) of lithium niobate (LN) crystals is energetically proposed by employing the viewpoint of the bond energy of constituent chemical bonds within the LN crystallographic frame. The calculated Tc values of various pure and doped LN crystals are in a good agreement with those reported data. Ps values of these LN crystals can also be quantitatively estimated in this work. It is found that the Li site is a sensitive lattice position to dominate the ferroelectricity of LN crystals. This novel method provides us a good understanding of ferroelectric behaviors of LN crystals, which may be applicable to the estimation of ferroelectric behaviors of LN-type solids.