气-液界面有序介孔SiO2无机膜的仿生合成

早在几百万年以前,自然界就通过生物矿化过程形成了结构高度有序的有机/无机复合材料,如哺乳动物的牙床、骨骼以及贝壳珍珠层等[1]。随着对天然生物材料生物矿化过程研究的逐渐深入,材料研究者从中得到极为重要的启示:先形成有机物自组装体,无机先驱物在自组装聚集体与溶液相的界面处发生化学反应,在有机自组装体的模板作用下,形成有机/无机复合体,再将有机模板去除即可得到具有一定形状与组织结构的无机材料。这种模仿生物矿化中无机物在有机物调制下形成过程的材料合成,称为仿生合成(biomimetic synthesis)[2]。仿生合成过程中,通过选择有…     

有机凝胶自组装模板法制备纳米材料

利用溶胶一凝胶聚合过程人工模拟生物矿化进程的技术,已经融人无机材料和超分子有机化学的研究领域.小分子有机凝胶因子在溶剂中发牛自组装,形成多种形态的有机凝胶超分子结构,以其为模板,经过溶胶一凝胶过程,可以诱导转录形成各种形态的纳米材料.本文介绍了利用有机凝胶因子自组装结构为模板制备形态可控无机材料的研究进展及模板结构诱导转录的两种可能机制.     

仿生矿化增强材料

近年来,随着材料科学领域的发展,机械性能优异且具有特定功能的有机-无机复合材料成为了研究热点。而天然的生物矿化过程产生了在自然界中分布广泛、结构特征多样性、机械性能优异的天然生物矿物,比如牙齿、骨骼、珍珠、贝壳、海胆刺、海洋红虫颚等。这些天然复合增强材料中的矿化组织结构特点和矿化机理为仿生设计与合成具有特定结构、特定功能和优异机械性能的材料提供了理论依据。通过模拟天然过程的仿生矿化方法,利用有机基质调控无机矿物成核生长为固态矿物,最终能够定向组装具有特定有序结构和先进功能的有机-无机复合材料。本文主要综述了自然界中通过生物矿化过程得到的高强度、高韧性的天然复合增强材料,以及受生物矿化增强现象的启发,在化学与材料仿生矿化合成中出现的一些有机-无机复合的增强材料。     

二氧化硅的仿生矿化

自然界的进化赋予某些生物体在生理条件下制备复杂结构生物矿物的能力。它们复杂而多尺度有序的结构、特殊的功能以及物种特异的遗传控制特征远非当前的人工合成技术所能实现,因此,师法自然,仿生矿化成为先进材料制备的重要手段之一。研究发现,生物体中的有机基质在生物矿物的形成过程中起着至关重要的作用,例如从含有生物二氧化硅的硅藻、海绵骨针中分离得到的silaffins、长链聚胺,从海绵中提取的silicateins等,这些生物分子通过操纵有机-无机界面作用,从分子水平上控制无机矿物的成核与生长,从而使生物矿物具有特殊的分级结构和组装方式。人们设计或选用具有相似结构或功能的有机分子,模拟生物矿化过程,仿生制备了不同形态、结构和功能的二氧化硅纳米材料。本文以有机-无机界面作用为核心,以认识自然、学习自然、矿物合成及构型调控为主线,从生物二氧化硅的形成机制、仿生矿化的研究进展、应用概况进行了评述,指出了当前研究存在的问题及相应的解决思路,并对仿生矿化的前景进行了展望。     

凝胶介质中仿生矿化过程的研究*

本文综述了凝胶介质中仿生矿化过程的研究进展。仿生矿化是当前化学、生物学和材料科学的研究前沿和热点。近年来,越来越多的生物学证据表明：生物体中的蛋白质和多糖等生物大分子,往往通过超分子组装形成凝胶状基质网络,进而对生物矿化过程施加影响。因此,凝胶介质中的仿生矿化研究对深入了解生物矿化机理,以及从理论上指导先进功能材料的设计和合成具有重要意义。迄今为止,研究人员已经对天然和合成高分子凝胶、超分子水凝胶和无机凝胶等多种凝胶介质中的仿生矿化过程进行了研究。结果表明：凝胶介质主要通过其三维网络结构限制反应离子在其内部的扩散速率,并掺杂到无机矿物的晶体结构中,从而影响生成晶体的形貌和构造。而且在有机基质(如水溶性有机高分子和自组装单层等)的协同作用下,凝胶介质中的仿生矿化过程也呈现出与水溶液中不同的特点。此外,本文还介绍了当前对凝胶介质中矿物形貌的调控和矿化机理的几种不同观点,并对该领域未来的研究和应用进行了展望。     

生物矿物及其矿化过程

生物体内有机基质指导矿物晶体的成核、生长和聚集,使得生物矿物具有特定的形貌、取向和组装方式,从而产生特殊的功能.本文从有机基质与矿物的晶格匹配、立体化学互补和空间定位、静电作用和电荷匹配,以及分子间弱相互作用力等方面综述了生物矿化过程中所涉及的机理,并讨论了生物矿物的分布和特性、生物矿化过程中的有机基质、生物矿化的过程和类型.     

超临界水中煤基多孔炭孔隙形成过程的研究

在半连续超临界水反应器(SCWR)中考察了不同温度、反应时间下昭通褐煤的转化特性,结合半焦有机官能团及碳微晶结构分析,推测在超临界水中半焦孔隙的形成过程以及煤中矿物质的作用。结果表明,超临界水首先快速萃取出褐煤热解产物,促进了半焦石墨化,形成良好的炭素前驱体,此过程对半焦孔结构基本无作用;当温度高于550 ℃,炭素前驱体发生气化反应,产生了较多的C-O-C交联结构,比表面积明显提高,逐渐形成多孔炭材料;脱灰后的煤在升温过程中具有更高的萃取率,形成有利于微孔产生的炭素前驱体,煤中的矿物质更有利于中孔的形成。     

生理盐水中牛血清白蛋白与碳酸钙的相互作用研究

珍珠、贝壳和甲壳是生物矿化的产物,具有高强度、高韧性。人们已对它们的组成、结构等进行了大量的研究犤１～４犦。结果表明,它们的主要成分是碳酸钙,但由于含有少量的蛋白质等有机基质,使其结构具有特殊的组装方式,从而显示出与纯碳酸钙迥然不同的优良物理性质和重要的生物功能。另一些研究表明胆结石、尿结石等异常生物矿化产物中也含有一定量的碳酸钙犤５犦。然而生物矿化过程非常复杂,其机理至今尚无统一说法。因此模拟生物矿化过程,了解有机基质在矿化过程中的作用,已成为化学、生物、医学和材料等多学科相互渗透和相互交叉的…     

有序介孔碳材料的软模板合成、结构改性与功能化

有序介孔碳材料在吸附、分离、催化以及能量存储/转化等方面具有广阔的应用前景。相较于复杂的硬模板路线,基于两亲性嵌段共聚物和聚合物前驱体间（如酚醛树脂）自组装的软模板路线是合成有序介孔碳材料更为有效的方法。本文讨论比较了溶剂挥发诱导自组装法、水相协同自组装法和无溶剂法等三种典型软模板路线的基本过程和特点,并介绍了近年来在新型碳前驱体应用、介孔碳的结构改性和功能化等方面的一些重要进展,最后总结了介孔碳的合成研究中所需解决的关键问题。     

蜜胺-巴比妥酸衍生物有机复合物纳米结构组装的化学微环境调控

综述了从互补的蜜胺和巴比妥酸衍生物分子组分出发, 通过调节组装过程中的化学微环境, 可控制分子组分所包含的信息表达从而制备不同有机纳米结构的研究进展. 研究结果表明, 在经严格无水处理的氯仿中进行组装得到的是一种周期为4.1 nm的非中心对称的层状结构. 如果在含有微量的极性溶剂如乙醇的氯仿进行组装得到的是一种直径为6 nm、长度为数百纳米的有机纳米管结构, 这种有机纳米管在合适的极性溶剂诱导下可以进一步组装形成直径为300 nm, 长度为几十微米的超螺旋结构. 这是由于诱导组装的分子间非共价键相互作用其焓变较小, 外部环境的微小变化就会打破原有的平衡条件, 从而导致组装体结构的重排和转化.     

Mineralization mechanism of calcium phosphates under three kinds of Langmuir monolayers

Three kinds of Langmuir monolayers formed by dipalmitoylphosphatidylcholine (DPPC), arachidic acid (AA), and octadecylamine (ODA) were used as templates to study the initial stage of nucleation and crystallization of calcium phosphates. It was demonstrated that the combination of calcium ions (or phosphates) to the monolayer/subphase interface is a prerequisite for subsequent nucleation. It was found that calcium phosphate dihydrate (DPCD) formed at 25.0 degrees C for 12 h has a biphasic structure containing both amorphous and crystalline phases. These results showed that calcium phosphates were formed through a multistage assembly process, during which an initial amorphous phase DPCD was followed by a phase transformation into a crystalline phase and then the most stable hydroxyapatite (HAp). This provided new insights into the template-biomineral interaction and a mechanism for biomineralization.     

Oriented attachment and mesocrystals: non-classical crystallization mechanisms based on nanoparticle assembly

In this review, we highlight particle based crystallization pathways leading to single crystals via mesoscopic transformation. In contrast to the classical mechanism of atom/molecule mediated growth of a single crystal, the particle mediated growth and assembly mechanisms are summarized as "non-classical crystallization", including exiting processes like oriented attachment and mesocrystal formation. Detailed investigations of non-classical crystallization mechanisms are a recent development, but evidence for these pathways is rapidly increasing in the literature. A major driving force for these investigations originates from biomineralization, because it seems that these crystallization routes are frequently applied by natural organisms. We give a non-exhaustive literature survey on these two mechanisms with a focus on recent examples and studies, which are dedicated to a mechanistic understanding. Furthermore, conditions are introduced for which these non-classical crystallization mechanisms can be expected, as they are always an alternative reaction pathway to classical crystallization.     

Peptide‐Based Methods for the Preparation of Nanostructured Inorganic Materials

With their unique sequence‐specific self‐assembly and their substrate recognition properties, peptides play critical roles in controlling the biomineralization of inorganic nanostructures in natural systems and in directing the assembly of important soft matter. These attributes render them particularly useful molecules for the fabrication of new materials. Researchers from many scientific disciplines now use peptides to direct the synthesis of new inorganic nanostructures and the assembly of soft biomaterials. In this Review we describe the developments in this field and focus on the versatility of peptides and their ability to direct the composition and structure of new inorganic materials.     

生物矿化中的无定形碳酸钙

本文综述了无定形碳酸钙的结构、合成和表征方法,阐明了无定形碳酸钙是一种热力学上的不稳定相.具有功能基团的有机高分子、功能蛋白质以及无机镁离子等添加剂对它有一定的稳定作用,抑制它的转化;但是在一定条件下它将转化成结晶态的碳酸钙.无定形碳酸钙具有高可溶性、各向同性和可塑性,正是这些特性使得生物采用它作为生物矿物的前体来矿化,形成具有精美结构的各种生物矿物.通过对无定形碳酸钙的研究,能够更加深入地了解生物矿化的机理,更好地仿生合成和制备各种功能材料.     

无机材料的仿生合成

生物矿化重要的特征之一是细胞分泌的有机基质调制无机矿物的成核和生长, 形成具有特殊组装方式和多级结构特点的生物矿化材料(如骨、牙和贝壳)。仿生合成就是将生物矿化的机理引入无机材料合成, 以有机物的组装体为模板, 去控制无机物的形成,制备具有独特显微结构特点的无机材料, 使材料具有优异的物理和化学性能。仿生合成已成为无机材料化学的研究前沿。本文综述了无机材料仿生合成的发展现状。     

Fabrication of Chiral Materials via Self‐Assembly and Biomineralization of Peptides

With different scales of chirality, chiral materials have various particular properties and potential applications in many fields. Peptides are the fundamental building units of biological systems, and a variety of ordered functional nanostructures are produced through self‐assembly and biomineralization of peptides in nature. This Personal Account describes chiral silica materials fabricated by using amphiphilic peptides as building blocks. Three particular biomineralization approaches are described based on different kinds of geometry of amphiphilic peptides: the influence of the specific amino acid proline in the peptide sequence, the hydrophilicity of amphiphilic peptides, and different kinds of hydrophobic tails in amphiphilic peptides. These strategies are useful for designing peptides toward the bottom‐up synthesis of nanomaterials as well as improving the understanding of the mechanism of peptide self‐assembly.     

Two modes of transformation of amorphous calcium carbonate films in air

Large-area amorphous calcium carbonate (ACC) films in air are shown to be transformed into crystalline calcium carbonate (CaCO(3)) films via two modes-dissolution-recrystallization and solid-solid phase transition-depending on the relative humidity of the air and the temperature. Moisture in the air promotes the transformation of ACC into crystalline forms via a dissolution-recrystallization process. Increasing the humidity increases the rate of ACC crystallization and gives rise to films with numerous large pores. As the temperature is increased, the effect of moisture in the air is reduced and solid-solid transition by thermal activation becomes the dominant transformation mechanism. At 100 and 120 degrees C, ACC films are transformed into predominantly (110) oriented crystalline films. Collectively, the results show that calcium carbonate films with different morphologies, crystal phases, and structures can be obtained by controlling the humidity and temperature. This ability to control the transformation of ACC should assist in clarifying the role of ACC in the biomineralization of CaCO(3) and should open new avenues for preparing CaCO(3) films with oriented and fine structure.     

Intermolecular interaction-induced hierarchical transformation in 1D nanohybrids: analysis of conformational changes by 2D correlation spectroscopy

We have examined both self-assembly and confinement effect in room-temperature ionic liquid (RTIL)-aluminum hydroxide hybrids (RAHs) to attain a fundamental understanding of special phenomena in nanoscale spaces as well as to design functional nanomaterials for practical applications. Phase-controlled one-dimensional (1D) RAHs were synthesized through a simple ionothermal process. The RAHs were hierarchically transformed in terms of the molecular structures, morphologies, and phases of the materials during the ionothermal process with respect to the concentration of RTIL. In addition to the hierarchical transformation, the RTIL/aluminum hydroxide nanohybrids revealed unexpected physical behaviors, including thermal transition variation of the RTIL in confined environments and a phase transition from nanosolid to nanoliquid affected by changes of the melting points. More importantly, intermolecular interaction induced-self-assembly and confinement effect of RTILs inside an integrated hybrid system, which have not been clearly explained to date, were analyzed by 2D infrared correlation spectroscopy (2D IR COS); dynamic behaviors of RTILs, i.e., sequentially spatial reorientation and kinetically conformational changes, were attributed to the interactions between RTILs and aluminum hydroxides. 2D IR COS offers a new way to interpret highly complex, veiled systems such as the formation mechanism of nanoparticles, biomineralization, self/supramolecular assembly, and nanoconfinement.     

Re-entrant Photoinduced Morphological Transformation and Temperature-Dependent Kinetic Products of a Rectangular Amphiphilic Diarylethene Assembly

An amphiphilic rectangular-shaped photochromic diarylethene bearing two hydrophobic alkyl chains and two hydrophilic tri(ethylene glycol) chains was synthesized, and its photoinduced morphological transformation in water was investigated. Two unexpected phenomena were revealed in the course of the experiments: a re-entrant photoinduced macroscopic morphological transformation and temperature-dependent kinetic products of supramolecular assembly. When the pure closed-ring isomer was dispersed in water, a re-entrant photoinduced morphological transformation, that is, a photoinduced transition from the hydrated phase to the dehydrated phase and then back to the hydrated phase, was observed by optical microscopy upon irradiation with green light at 20 °C; this was interpreted by the V-shaped phase diagram of the LCST transition. The aqueous assembly of the pure closed-ring isomer was controlled by changing the temperature; specifically, rapid cooling to 15 and 5 °C gave J and H aggregates, respectively, as the kinetic products. The thermodynamic product at both temperatures was a mixture of mostly H aggregate with a small amount of J aggregate. This behavior was rationalized by the temperature-dependent potential energy surface of the supramolecular assembly.     

Hierarchical CaCO3 Chromatography: A Stationary Phase Based on Biominerals

In biomineralization, acidic macromolecules play important roles for the growth control of crystals through a specific interaction. Inspired by this interaction, we report on an application of the hierarchical structures in CaCO₃ biominerals to a stationary phase of chromatography. The separation and purification of acidic small organic molecules are achieved by thin‐layer chromatography and flash chromatography using the powder of biominerals as the stationary phase. The unit nanocrystals and their oriented assembly, the hierarchical structure, are suitable for the adsorption site of the target organic molecules and the flow path of the elution solvents, respectively. The separation mode is ascribed to the specific adsorption of the acidic molecules on the crystal face and the coordination of the functional groups to the calcium ions. The results imply that a new family of stationary phase of chromatography can be developed by the fine tuning of hierarchical structures in CaCO₃ materials.