基于微量热技术原位研究无机纳米仿生材料的组装机理

Production of higher ordered inorganic crystals by a self-assembly process has received much attention not only for its importance on crystallization theories but also for the potential to design new materials used in many fields. Self-assembly is used in biological systems to regulate the synthesis of biominerals, in which the structure, size, shape, orientation and texture of the constituents are precisely controlled. Inspired by these results, research began by looking first at individual organisms and attempting to unravel the mechanisms by which their component minerals are produced, more recent times have seen efforts to replicate key fabrication strategies and structural features into materials design. However, by mimicking the design and synthesis of biomaterials, to date no synthetic materials have evolved that show properties which are superior to those found in their natural counterparts. In order to improve the properties of biomimetric materials,the mechanism in the mimicking should be further studoed, where in situ study becomes one of the main problems. The special property of microcalorimetry is to study changing processes in situ. As one of the most common biological minerals, calcium carbonate has been found to show different polymorphs in calcareous structures of organisms, such as calcite, aragonite, and to a lesser extent in the amorphous state, vaterite and monohydrate. These crystals have a wide range of naturally occurring crystal habits and are often found assembled into hierarchical structures which result in a difference of intriguing properties in organisms. In the present work, nanosized calcium carbonate crystals with the hierarchical structure and special assembly will be fabricated, where different templates will be employed to control growth of calcium carbonate crystals on basis of interfacial molecular recognition, including lattice geometrical matching, stereochemistry structure complementary and electrostatic compatibility. Microcalorimetry is used to determine the power during these processes, and the power-time curves for these processes will be obtained in situ. Based on these curves, different processes will be obtained, thermodynamic and kinetic functions corresponding to these processes will be calculated. At the same time, structures and morphologies of the samples fabricated in different processes can be characterized by XRD, SEM, FT-IR, TEM and HRTEM, etc. These results will be used to investigate the mechanism for production of these calcium carbonate crystals. The mechanism may be useful to study further biomineralization, provide new method for the controlling process in materials production, and give theoretic base and experimental data for the calorimetry used in situ investigation on biomimetric synthesis.

仿生合成是近年来受生物矿化原理启示而发展起来的，所研制的仿生材料是具有特殊性能的新型材料。但是，自然界广泛存在的天然生物矿物常常具有仿生材料无可比拟的优越功能。为了提高仿生材料的性能，应对其形成机理进行深入研究，而解决此问题的关键之一是其形成过程的原位检测。本课题拟采用微量热技术，原位检测在水溶性和非水溶性模板协同调控下，具有复杂形态和结构的纳米碳酸钙仿生材料的成核、生长、组装形态和结构变化，不但能够科学获知反应所经历的每一过程，而且获得每一过程相应的热动力学参数，结合在每一反应过程中所获得样品的其它表征测试结果，深入探索其组装机理。为研制高性能仿生材料和材料制备中类似的控制问题提供新思路，为揭示生物体精细控制矿化的奥秘奠定基础，为探索将微量热技术应用于仿生材料形成过程中的原位研究，提供一定的科学理论基础和实验数据。

生物矿化过程广泛存在于自然界中，它是生命参与并通过细胞、有机分子等调控无机矿物沉积的高度控制过程。天然生物矿物具有独特的高级结构和组装方式，这种结构赋予其特有的性能。因此，科研工作者模拟生物矿化条件，通过控制目标产物的成核、生长、组装堆积方式，构筑和制备具有复杂形态和结构的无机纳米材料，探索其组装机理，更深入的了解生物矿化过程，同时为材料科学相似的控制问题提供思路，为材料合成提供新的理论指导和设计依据。为了更深入探索其生成机理，本课题选择微量热原位测试技术，并结合其他表征测试手段，研究了在不同反应体系中，有机分子对无机纳米材料形成过程的调控作用，获得了一下结果：.1..在表面活性剂作用下，合成了新颖形貌的碳酸钙晶体。同时可将碳酸钙的物相从纯球霰石转化为纯方解石，并推断出了相应的反应机理。.2..在表面活性剂和有机小分子(三甲基苯TMB)共同作用，系统调控了碳酸钙的成核和结晶行为。.3..研究了邻、间、对苯二甲酸对碳酸钙晶型的影响。研究发现这三种苯二甲酸具有的不同立体化学结构是影响碳酸钙晶型和形貌的主要原因。.4..探索了溶剂热条件下，纳米无机材料铁酸盐的生长机理。在此基础上，通过添加表面活性剂，有效调控了所制备材料的成核和生长，达到了改变其磁性的目的。并通过进一步添加稀土离子，调节了样品的磁性质。.5..应用有机碱做沉淀剂，采用共沉淀方法制备了纳米无机材料铁酸盐，通过添加表面活性剂，有效调控了所制备材料的成核和生长，达到了改变其磁性的目的。.6..采用高温液相还原法，制备了高饱和磁化强度、均匀的球形钴纳米粒子；通过在反应体系中添加乙二胺、表面活性剂，调节钴纳米粒子的形貌。该材料显示了较高的催化制取氢气的催化活性。.7..在所获得机理的基础上，制备了不同类型的复合材料，如核-壳结构、复合碳纳米管（石墨烯）、无机-高分子等，并研究了相应的吸附和催化性能。