"离子晶体、分子晶体和原子晶体"研究性教学初探

1　前言新编高中教材第三册 (限选 )第一章“晶体的类型与性质” ,是高中教材中重要的知识环节。而第一节“离子晶体、分子晶体和原子晶体”又是本章中的关键一节 ,它对高中化学所涉及到的晶体及典型物质的晶体结构进行了阐述。若仍像以往一样 ,仅泛泛的讲授 ,学生收获不大 ,如果作为研究课来学习 ,它却是开发学生智力 ,发展学生能力的好内容。因为它对于培养学生的三维空间想象能力、慎密的逻辑思维和综合分析问题的能力 ,是再好不过的教材。正是基于这种想法 ,我们开展了以网络课方式教学的研究性学习的尝试。2　教学重点1.掌握 3种典型晶…     

人文精神与现代技术在"晶体的空间结构"一课中的融合

化学中如何渗透人文精神 ?这节课要完成的教学目的很难 ,充斥着立体化学中的数学思想 ,枯燥、乏味。为使这堂课上好 ,迫使我思考应如何引发学生学习的兴趣、激发学生的情感 ,我用了化学史 ,结果枯燥乏味的内容被化学人文韵味感化了 ,一节课的主要问题解决了。有的课讲究渐入佳境 ,但这节课的课题较难 ,内容较深 ,如果课的开始不能吸引住学生 ,整堂课可能会显得乏味枯燥 ,我想用一段精彩的引言在课的发端就掀起高潮 ,使学生立即进入兴奋状态 ,最后决定用C60 的发现史作为开端。“2 0世纪 80年代初 ,科学家正热衷于研究碳原子团簇 ,其中包括…     

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。     

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.     

2',4"-O-双(三甲基硅)红霉素A 9-O-(1-乙氧基-1-甲基乙基)肟的区域选择性甲基化

一锅煮合成并表征了2',4"-O-双(三甲基硅)红霉素A 9-O-(1-乙氧基-1-甲基乙基)肟, 首次在丙酮-水混合溶剂中培养出了单晶. X射线衍射表明, 其结构为四方晶系, I4空间群, 晶胞参数: a＝b＝2.9536(1) nm, c＝1.4488(1) nm, V＝12.63897(4) nm³, Z＝8, R＝0.068, wR＝0.067. 对区域选择性影响因素的研究表明: 甲基化时溶液浓度应控制0.052 mol/L和0.067 mol/L之间; 分别采用了四氢呋喃、二氯甲烷、甲基叔丁基醚、甲苯与二甲亚砜作为混合溶剂进行甲基化反应, 发现在甲苯-二甲亚砜中的效果最好, 6-OH的甲基化选择性可达到81.69%.     

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.     

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.     

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...     

胶体晶体自组装排列进展*

自组装排列胶体晶体是发展光子晶体等亚微米周期有序结构及新型光电子器件十分重要的环节.高电荷密度单分散胶体球在较弱的离子强度和稀浓度下会自发排列形成紧密堆积的周期性结构(ccp),常常是面心立方(fcc),科学家们以此为基础发展了多种结晶化胶体粒子的方法,包括重力场沉积、电泳沉积、胶体外延技术、垂直沉积、流通池、物理束缚排列及其他的许多方法.目前排列的胶体粒子基本为球形,材料也多为SiO2、PS、PMMA,此外一些复合粒子,主要为核壳粒子的排列这里也稍作介绍,这些方法及其变通的使用可以形成类蛋白石及反蛋白石结构,最终实现光子带隙及其它多种用途。     

一种新的有机非线性光学晶体——L-精氨酸磷酸盐

近年来,在探索新的有机非线性光学晶体的工作中,对含有给电子或受电子基团的芳香族化合物已有广泛深入的研究,并已研制出像2,4-二硝基苯丙氨酸甲酯(MAP)等具有较大倍频系数的新的非线性光学晶体。但是,由于强的共轭效应使它们大π键各能级间的距离接近而使此类晶体无法应用于紫外区。     

三草酸合铁(Ⅲ)酸钾的制备及结构组成测定

通过对三草酸合铁(Ⅲ)酸钾合成的实验条件进行优化,可在2 h内获得晶体产物。用KMnO4滴定法和磁化率测定方法,对产物结构组成进行测定,确定所合成的配合物化学式为K3[Fe(C2O4)3]·3H2O,有关测定数据与理论值相吻合。     

Researches on the Growth Habit and Optical Properties of Fe^3＋ Ion Doped KDP Crystal

During the process of KDP crystal growth,metal ions strongly affect the growth habit and optical properties of KDP single crystal. In this paper,KDP crystals were grown from an aqueous solution doped with different concentration of Fe3+ dopant by traditional temperature-reduction method and "point-seed" rapid growth method. Furthermore,we examined the light scatter and measured the transmission of these KDP crystals. It is found that the dopant of Fe3+ ion can improve the stability of the KDP growth solution when its concentration is less than 30 ppm. The effects of Fe3+ ion on the growth habit and optical properties of KDP crystal are also obvious.     

The growth and characterization of a metal organic crystal, potassium thiourea thiocyanide

The growth and characterization of a new non-linear organometallic crystal, potassium thiourea thiocyanide (PTT) is reported. The growth of single crystals was accomplished by the slow evaporation solution growth method. The grown crystals were characterized by XRD, TG–DTA, UV, and FTIR spectral analyses. PTT has good optical transmission in the entire visible region which is an essential requirement for a non-linear crystal. TG curve of PTT undergoes complete decomposition between 176 and 1,000 °C in three steps with corresponding three DTA peaks. The high thermal stability of organometallic crystals are due to strong bonding existing between the conjugation layers of thiourea molecule and the potassium ions.     

Effect of sunset yellow dye on morphological,optical, dielectric,thermal and mechanical properties of KDP crystal

Herein, we describe the growth and morphology of well-defined dyed crystals of KH₂PO₄ (potassium dihydrogen orthophosphate; KDP) containing organic azo (sunset yellow; SSY) dye in the {1 0 1} & {0 0 1} pyramidal growth sectors. An understanding on selective dye inclusion in various growth sector of host crystal is proposed, which will help in designing novel tailor-made dyed photonic crystals. The structural analysis and the identification of various functional groups present in as grown KDP crystals were carried out using powder XRD, FTIR and Raman studies. Solid state transmittance spectra for dyed KDP crystals displayed three absorption peaks at 230 nm, 311 nm and 477 nm, which were blue shifted for SSY dye in KDP crystal relative to neutral aqueous solution of SSY dye. These blue shifts in the absorption maxima confirm the successful incorporation of sunset yellow dye into the pyramidal growth sectors of dyed KDP crystals. The band around 409 nm in the photoluminescence emission spectrum indicates a violet emission. SSY dye doped KDP crystals showed enhanced dielectric properties and thermal stability as compared to pure KDP crystal. The mechanical strength of the KDP crystals estimated using Vickers microhardness test was found to decrease with the increase in SSY dye doping.     

Crystal growth and characterization of potassium(I)-doped tetrakis(thiourea)nickel(II) chloride

The influence of alkali metal potassium(I)-doping on the properties of tetrakis(thiourea)nickel(II) chloride crystals has been investigated. The variation in the intensity observed in powder X-ray diffraction (XRD) of doped specimen and slight shifts in vibrational frequencies confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the alkali metal are observed by scanning electron microscopy. The incorporation of K(I)- into the crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The crystal is further characterized by UV–Vis and Kurtz powder technique.     

Colloidal crystals of core–shell-type spheres in deionized aqueous suspension

The structure, crystal growth kinetics and rigidity of colloidal crystals of core–shell-type latex spheres (diameters 280–330 nm) with differences in shell rigidity have been studied in aqueous suspension, mainly by reflection spectroscopy. The suspensions were deionized exhaustively for more than 2 years using mixed-bed ion-exchange resins. The five kinds of core–shell spheres examined form colloidal crystals, where the critical sphere concentrations, _c, of crystallization (or melting) are high and range from 0.01 to 0.06 in volume fraction. Nearest-neighbor intersphere distances in the crystal lattice agree satisfactorily with values calculated from the sphere diameter and concentration. The crystal growth rates are between 0.1 and 0.3 s^–1 and decrease slightly as the sphere concentration increases, indicating that the crystal growth rates are from the secondary process in the colloidal crystallization mechanism, corresponding to reorientation from metastable crystals formed in the primary process and/or Ostwald-ripening process. The rigidities of the crystals range from 2 to 200 Pa, and increase sharply as the sphere concentration increases. The g factor, the parameter for crystal stability, is around 0.02 irrespective of the sphere concentration and/or the kind of core–shell sphere. There are no distinct differences in the structural, kinetic and elastic properties among the colloidal crystals of the different core–shell-type spheres, showing that the internal sphere structure does not affect the properties of the colloidal crystals. The results show that colloidal crystals form in a closed container owing to long-range repulsive forces and the Brownian movement of colloidal spheres surrounded by extended electrical double layers and that their formation is not influenced by the rigidity and internal structure of the spheres.     

Spectroscopic and thermal studies of γ-glycine crystal grown from potassium bromide for optoelectronic applications

Single crystals of an organic nonlinear optical material γ-glycine have been synthesized by slow evaporation technique from aqueous solutions of α-glycine and potassium bromide at room temperature. Single crystal X-ray diffraction analysis confirmed the growth of γ phase of glycine. The powder X-ray diffraction of the grown crystal was recorded and indexed. Functional groups present in the sample were identified by FTIR spectral analysis. The optical absorption studies show that the UV cut-off wavelength of γ-glycine is at 238 nm and has a wide transparency window. The thermal characteristics of the grown crystal were determined by thermogravimetric and differential thermal analysis (TG/DTA), which show the thermal stability of the grown crystals. The powder second harmonic generation (SHG) efficiency of γ-glycine crystals was measured by Kurtz and Perry powder technique using Nd:YAG laser and it was found to be 2.56 times that of potassium dihydrogen phosphate (KDP) crystals.     

New simulation model of multicomponent crystal growth and inhibition

We review a novel computational model for the study of crystal structures both on their own and in conjunction with inhibitor molecules. The model advances existing Monte Carlo (MC) simulation techniques by extending them from modeling 3D crystal surface patches to modeling entire 3D crystals, and by including the use of "complex" multicomponent molecules within the simulations. These advances makes it possible to incorporate the 3D shape and non-uniform surface properties of inhibitors into simulations, and to study what effect these inhibitor properties have on the growth of whole crystals containing up to tens of millions of molecules. The application of this extended MC model to the study of antifreeze proteins (AFPs) and their effects on ice formation is reported, including the success of the technique in achieving AFP-induced ice-growth inhibition with concurrent changes to ice morphology that mimic experimental results. Simulations of ice-growth inhibition suggest that the degree of inhibition afforded by an AFP is a function of its ice-binding position relative to the underlying anisotropic growth pattern of ice. This extended MC technique is applicable to other crystal and crystal-inhibitor systems, including more complex crystal systems such as clathrates.     

双盘状ZnO的可控制备

采用水热法制备了形貌可控、 尺寸均一的双盘状ZnO. X射线粉末衍射(XRD)、 扫描电子显微镜(SEM)及透射电子显微镜(TEM)等测试结果表明, 制备的ZnO具有六方纤锌矿结构, 由2个直径约为4 μm, 厚度约为600 nm的圆盘复合而成. 考察了反应温度和乙酸锌与柠檬酸钾的摩尔比对产物形貌与尺寸的影响, 实现了双盘状ZnO的可控合成, 并初步探讨了其形成机理. 荧光光谱显示, 双盘状ZnO的紫外发射峰半高宽约为10 nm, 比块体ZnO的紫外发射峰半高宽(18 nm)窄, 表明双盘状ZnO具有更好的光学特性.     

Osmotically driven crystal morphogenesis: a general approach to the fabrication of micrometer-scale tubular architectures based on polyoxometalates

The process of osmotically driven crystal morphogenesis of polyoxometalate (POM)-based crystals is investigated, whereby the transformation results in the growth of micrometer-scale tubes 10-100 μm in diameter and many thousands of micrometers long. This process initiates when the crystals are immersed in aqueous solutions containing large cations and is governed by the solubility of the parent POM crystal. Evidence is presented that indicates the process is general to all types of POMs, with solubility of the parent crystal being the deciding parameter. A modular approach is adopted since different POM precursor crystals can form tubular architectures with a range of large cationic species, producing an ion-exchanged material that combines the large added cations and the large POM-based anions. It is also shown that the process of morphogenesis is electrostatically driven by the aggregation of anionic metal oxides with the dissolved cations. This leads to the formation of a semi-permeable membrane around the crystal. The osmotically driven ingress of water leads to an increase in pressure, and ultimately rupture of the membrane occurs, allowing a saturated solution of the POM to escape and leading to the formation of a "self-growing" microtube in the presence of the cation. It is demonstrated that the growth process is sustained by the osmotic pressure within the membrane surrounding the parent crystal, as tube growth ceases whenever this pressure is relieved. Not only is the potential of the modular approach revealed by the fact that the microtubes retain the properties of their component parts, but it is also possible to control the direction of growth and tube diameter. In addition, the solubility limits of tube growth are explored and translated into a predictive methodology for the fabrication of tubular architectures with predefined physical properties, opening the way for real applications.