凝胶体系中生物分子-金属离子沉淀的LIESEGANG现象研究:胆酸与金属离子形成的周期性沉淀及其影响因素

讨论了凝胶介质、胆酸浓度、金属离子种类及其浓度等因素对胆酸与金属廓了常常的影响规律,实验结果表明：沉淀的ＬＩＥＳＥＧＡＮＧ现象与胆酸分子和金属离子之间的作用有密切的关系。三价稀土离子倾向于和胆酸分子形成周期性环状结构篱子与胆酸分子形成的沉淀形成外貌则比较复杂。有的形成了规则的周期性沉淀环;有的则由较大球形颗粒形成。排列也不规则;还有的在形成环结构时,形成了分形图案。多离子体系中离子之间存在强烈的相     

胆结石组成和形成机理的研究进展

综述了利用多种方法(如: F T-IR, Raman, NMR, EPR, 凝胶色谱, 元素分析, ICP, 原子吸收谱, 差热-热重谱, X射线荧光分析, EXAFS及XRD等)对胆结石组成和形成机理进行研究的进展. 结果表明, 胆结石中含有多种生物小分子、生物大分子(如蛋白等)、金属离子, 以及具有非化学计量特征的胆红素络合物等. 金属离子与胆盐的相互作用与结石沉淀的形成密切相关. 从结石截面可以看到环状结构, 所以利用体外模拟实验对结石的形成机理进行了研究, 并将非线性的科学概念引入到结石的形成机理中, 提出结石生长不是逐层生成沉淀, 而是首先生成周期环形模板的观点.     

穿插程度对高分子链结晶初始阶段的影响

用分子动力学方法模拟了具有不同穿插程度的寡链凝聚体系结晶初始阶段的有序化过程. 链间穿插程度通过径向分布函数的统计进行表征. 模拟计算结果表明, 链间的穿插程度对体系的有序化过程具有明显的影响, 穿插程度越小的体系有序化越快, 形成的有序结构也更完整. 与实验结果的比较表明, 在聚合物粒子结晶的初始阶段, 体系由穿插引起的缠结就已经起到了作用.     

二维琼脂凝胶体系中过渡金属离子对草酸钙晶体生长和周期性沉淀的影响

在二维凝胶圆盘体系中,研究过渡金属离子对草酸钙晶体生长和周期性环状沉淀的影响,并对其形成机理进行探讨.结果表明:在一定浓度的Fe3 存在下,体系中出现了周期性环状沉淀现象.同时发现在此条件下抑制了一水合草酸钙(COM)晶型生成.此外,加入Zn2 、Co2 、Ni2 体系中的晶体都以二水合草酸钙(COD)为主;而加Cu2 离子的圆盘中,三水合草酸钙(COT)占据了主要的成分,这说明不同的过渡金属离子对三种草酸钙晶型的生成影响不同.另外,还对出现的与尿结石有关的特殊现象(白斑和放射状的条纹)进行了探讨.     

两嵌段共聚物反相溶剂中组装结构转变动力学的模拟研究

利用耗散粒子动力学方法,分别研究了不同结构的组装体在改变溶剂的选择性后,在溶液及界面上的结构演变动力学.模拟结果表明,在改变溶剂的选择性后,大球形胶束在溶液中转变形成反向球形胶束,而在界面上则转变形成反向环状胶束,当前模拟结果与已有的实验结果一致.此外,模拟结果还预测出,在改变溶剂的选择性后,环状胶束在溶液中转变形成反向环状胶束,而在界面处受限形成反向的支化蠕虫状胶束;蠕虫状胶束则在溶液中转变形成反向环状胶束,而在界面处受限形成多层纳米球结构;囊泡在溶液中转变形成分散的小胶束聚集体,而在界面处受限形成球形的补丁纳米粒子.     

石墨烯狭缝受限孔道中水分子的分子动力学模拟

石墨烯是一种具有广泛应用前景的纳米材料,特别是由石墨烯片层自组装形成的二维纳米通道能够应用于物质的过滤分离.本文采用分子动力学模拟方法研究了原态石墨烯/羟基改性石墨烯狭缝孔道中水分子的微观行为,模拟计算了水的界面结构性质和扩散动力学性质,所研究的石墨烯孔宽为0.6-1.5 nm.模拟结果表明,在石墨烯狭缝孔道中,水分子受限结构呈现层状分布,在超微石墨烯孔道(0.6-0.8 nm)中水分子可形成特殊的环状有序结构,石墨烯表面可诱导产生特殊的水分子界面取向.在石墨烯孔道中,水分子的扩散运动低于主体相水分子的扩散运动,羟基化石墨烯孔道可以促使水分子的扩散能力降低.对于改性石墨烯狭缝孔道,由于羟基的作用,水分子可以自发渗入0.6 nm的石墨烯孔道内.模拟所得到的受限水分子的动力学性质与水分子在石墨烯孔道内的有序结构有关.本文研究结果将有助于分析理解水分子通过石墨烯纳米通道的渗透机理,为设计基于石墨烯的纳米膜提供理论指导.     

琼脂凝胶中形成铬酸铅周期性沉淀的机理研究

选择硝酸铅和铬酸钾作为相互扩散的反应物以形成铬酸铅在琼脂凝胶中的周期性沉淀．分别在光照和黑暗中对六种不同浓度的硝酸铅溶液进行了实验．根据实验现象对周期性沉淀的形成提出了可能的机理．认为光辐射可使铬酸铅部分电离，从而减慢了胶核成长速率，有利于汇聚成带．     

ACB三嵌段粒子分级自组装的布朗动力学研究

利用布朗动力学方法研究了ACB三嵌段粒子的分级自组装过程.由第一级组装得到的结构作为第二级组装的初始构型,通过调控体系中补丁B部分的吸引强度和补丁粒子的浓度,研究了第二级组装过程中形成有序结构的影响因素.通过设计组装模型、组装规则和组装路线,得到了蜂巢状网络结构和金刚石状结构.结果表明,在较高的吸引强度和适当的浓度下,可以得到更多且更规整的蜂巢状结构;较高和较低的吸引强度和浓度都不利于金刚石状结构的形成.     

磷脂水解与胆固醇型胆结石时的可能生成机理

用胆酸盐-磷脂-胆固醇-水体系模拟胆汗的化学行为。在体系中发现,磷脂可 以发生降解形成脂肪酸。而在胆汗中,磷脂在增溶固醇的过程中起到了十分重要的 作用。依此,我们提出磷脂的水解可能与胆固醇型胆结石的生成有密切关系。     

金属Ni熔化前后结构变化的分子动力学模拟

使用Tight-binding势函数, 对FCC-Ni升温熔化过程的结构变化进行了分子动力学模拟. 在定压条件下模拟得到的Ni的熔点在1850 K与1900 K之间. 计算得到了体系在各温度下的径向分布函数和配位数分布等静态结构信息以及动力学性质. 计算得出的液体Ni的扩散系数在1900 K时约为5.02×10−9 m2•s−1, 与实验数据相符. 对液态体系中FCC短程有序结构可能发生的畸变以及由此导致的H-A键型变化进行了分析, 结合配位体构型搜索和键对分析方法计算了各温度下不同短程有序结构的分布. 计算表明, Ni在熔化之后仍保留有部分晶态短程结构, 但发生了较大的畸变, 同时液态中有少量的缺陷二十面体结构存在. 而液体Ni中大多数的配位体的几何构型介于FCC与缺陷二十面体之间.     

Sedimentation and drying dissipative patterns of binary suspensions of colloidal silica spheres having different sizes

The sedimentation and drying dissipative structural patterns were formed during the course of drying binary mixtures among colloidal silica spheres of 183 nm, 305 nm, and 1.205 μm in diameter in aqueous suspension on a watch glass, a glass dish, and a cover glass, respectively. The broad ring-like sedimentation patterns were formed within several hours in suspension state for all the substrates used. Colorful macroscopic broad ring-like drying patterns were formed for the three substrates. In a watch glass, macroscopic drying patterns were composed of the outer and inner layers of small and large spheres, respectively. The two colored layers were ascribed to the Bragg diffractions of light by the dried colloidal crystals of the corresponding spheres. The width ratio of the layers changed in proportion to the mixing ratio of each spheres. In a glass dish, wave-like macroscopic drying patterns were observed in the intermediate areas between the outside edges of the broad ring and the inner wall of the cell. On a cover glass, the sphere mixing ratios were analyzed from the widths of the drying broad rings of the small spheres at the outside edge. High and distinct broad rings of small spheres and the low and vague broad one formed at the outer edges and in the inner area, respectively. Drying dissipative pattern was clarified to be one of the novel analysis techniques of colloidal size in binary colloidal mixtures.     

Sedimentation and drying dissipative patterns of ternary mixtures of colloidal silica spheres having different sizes

The sedimentation and drying dissipative structural patterns were formed during the course of drying ternary mixtures of colloidal silica spheres of 183 nm, 305 nm, and 1.205 μm in diameter in aqueous suspension on a watch glass, a glass dish, and a cover glass. The patterns were observed by closed-up pictures, metallurgical optical microscopy, 3D profile microscopy, reflection spectroscopy and AFM images. The concentrations of the three spheres ranged from 0.0023 to 0.0128 keeping the same concentrations for each spheres. Broad ring-like sedimentation patterns were formed within a short time in suspension state especially in a glass dish. In a watch glass, colorful three layered ring-like drying patterns were observed and composed of the outer, middle and inner layers of small, medium, and large spheres, respectively. The three colored segregated layers were formed by the balancing between the outward convectional flow and the inward sedimentation of spheres. In a glass dish, wave-like macroscopic drying patterns were observed in the intermediate areas between the outside edge of the broad ring at the central area and the inner wall of the cell especially at low sphere concentrations. The size of the broad ring at the central area increased as sphere concentration increased. On a cover glass, size segregation also took place, i.e., small, medium, and large spheres located at the outer, medium, and central areas, though these segregations were not so complete compared with those on a watch glass.     

过渡金属卡宾正离子的从头算研究

过渡金属卡宾正离子被认为是如烯烃的聚合和烷基金属的分解过程等许多反应的中间体．较为稳定的环丁烷金属离子和环戊烷金属离子已从相应酮的脱羰反应获得［１］．Ｊａｃｏｂｓｏｎ等［２］研究了ＦｅＣＨ＋２和ＣｏＣＨ＋２与烯烃和环烷烃的气相反应．Ｍｃｋｅｅ［３］在...     

The designing strategies of graphene-based peroxidase mimetic materials

Natural enzymes have been praised highly as ideal catalysts, presumably owing to their remarkable advantages of high efficiency, high selectivity, and mild reaction conditions. The reports of chemical simulation and systematic synthesis of natural enzymes such as peroxidase (POD) are rare because of their complex biological structures. POD represents a large family of oxidoreductases and offers a wide range of applications in many fields of science. Recent advance in the fusion of nanomaterial, catalysis, and biochemistry has inspired the development of artificial enzymes implemented with desired catalytic features of natural enzymes. Herein, we review the redox chemistry of POD and compare its catalytic performance to graphene-based nanomaterials (G-NMs) as POD mimetic nanoenzymes bases on catalytic center, binding site, and carrier function. Based on the viewpoints of stereo chemistry and molecular kinetic and dynamics in heterogeneous system, we evaluate and compare the suitability of different NMs as artificial enzyme constituent. We propose that reevaluates design strategies of graphene-based peroxidase (G-POD) mimetic materials and emphasizes on their selectivity (role as catalytic center, binding site, or carrier) is of uttermost.     

Protein directed assembly of lipids

Highly ordered ring-like structures are formed via the directed assembly of lipid domains in supported bilayers, using the extracellular matrix protein fibronectin. The ability of biological molecules to guide nanoscale assembly suggests potential biomimetic approaches to nanoscale structures.     

人造玫瑰花花瓣的微结构分布与水滴黏附性质的关系

本文采用模板印刷法制备得到了“人造玫瑰花花瓣”,即具有玫瑰花花瓣结构的PDMS薄膜,通过对该薄膜逐级拉伸改变微观结构的分布;采用环境扫描电镜（ESEM）观察了不同拉伸程度下薄膜表面微观结构的变化,采用高敏感性微电力学天平测试了样品表面微观结构变化过程中水滴的粘附力,分析了微观结构分布与水滴粘附性质的关系;采用接触角测量仪表征不同拉伸条件下薄膜的浸润性.实验结果表明随着PDMS薄膜被逐次拉伸,单位面积内玫瑰花花瓣乳突的数目减少,纳米褶皱面积不断增加,而纳米级褶皱结构尺寸随着拉伸基本上不发生变化,直到样品破坏;与微观结构变化相对应的,该表面对水滴的粘附力先增大后减小,直到该表面彻底破坏.由此可见,微米结构及纳米结构的分布是影响玫瑰花花瓣对水滴粘附的主要因素.     

Multifold curdlan gel formation by dialysis into aqueous solutions of metal salts

We have found that the dialysis of curdlan dissolved in alkaline solution into aqueous solutions of metal salts yielded multifold gel structures. Aqueous sodium chloride and potassium chloride as well as pure water induced isotropic gels. Aqueous calcium salts induced liquid crystalline gel with refractive index gradient/amorphous gel alternative structure. Aqueous salts of trivalent aluminum and ferric cations induced a rigid liquid crystalline gel, which shrank above a threshold concentration of each salt. On the other hand, Liesegang ring-like pattern was observed with aqueous solutions of mixed salts of calcium chloride and magnesium chloride. The patterns have been classified to discuss the mechanism of forming the variety of structures.     

卤代类卡宾结构和反应活性的理论研究(Ⅱ)——类卡宾CHClFLi的结构和稳定性

用从头算分子轨道理论,研究了不同卤代类卡宾CHClFLi的结构和稳定性.优化得到4种平衡构型和相应过渡态结构.对各构型的特点进行了分析,并与相同卤代类卡宾做了比较.     

Dissipative structures formed in the course of drying the colloidal crystals of silica spheres on a cover glass

Macroscopic and microscopic dissipative structural patterns formed in the course of drying the deionized aqueous colloidal crystal suspensions of silica spheres (diameter: 103 nm) on a cover glass have been observed. Spoke-like and ring-like patterns are formed in the macroscopic scale; the former is the crack in the sphere film and the latter is the hill accumulated with spheres formed around the outside edge. The neighbored inter-spoke angle, thickness of the film, and other morphological parameters have been discussed as a function of sphere concentration, concentration of sodium chloride, and the inclined angle of the cover glass. Fractal patterns of the mud cracks are observed in the microscopic scale. Capillary forces between spheres at the air-liquid surface and the relative rates between the water flow at the drying front and the convection flow of spheres are important for the pattern formation. Electronic Publication     

Bubble guidance of tubular growth in reaction-precipitation systems

Numerous types of reaction-precipitation systems involve the growth of tubular structures similar to those formed in "silica gardens". As a model case for this phenomenon, we investigate the rapid growth of hollow tubes in the reaction between sodium silicate and cupric sulfate. The latter solution is injected hydrodynamically at constant flow rates of 1-20 mL h(-1) into a large reservoir of waterglass. In this study, the growth is templated and guided by single, buoyant gas bubbles. The resulting tubes can be several decimetres long and have constant radii in the range of 100-600 microm. Systematic measurements show that bubble size governs the tube radius. According to this radius, the system selects its growth velocity following volume conservation of the injected solution. Moreover, scanning electron microscopy reveals intricate ring patterns on the tube walls. We also show evidence for the existence of a minimal and a maximal tube radius. Finally, we report an intriguing collapse of tubes created at high silicate concentrations, which yields twisted ribbon-like structures. Critical radii and tube collapse are discussed in terms of simple competing forces.