Generating Materials with Complex, Life-like Morphologies

该项目将结合实验和数学建模，探索具有复杂生命形态的无机微结构的自组装。生命系统为新材料的设计和建造提供了独特的灵感。具有复杂三维形态和层次结构的生物矿物，如骨骼、牙齿和贝壳，表现出合成矿物无可比拟的特性。这些生物结构的一个关键特征是，它们通常在远离平衡的条件下通过基于组装的机制形成。在令人兴奋的新结果中，我们最近表明，市售的聚电解质可以在水溶液中直接形成具有显着形态的无机微结构，包括螺旋，圆锥和扭曲带。这是使用简单的一锅法实现的。值得注意的是，我们已经为包括碳酸钙和硫酸锶在内的一系列化合物制备了类似的结构。具有使人联想到活的生物材料的形态的无机结构被称为“生物形态”。然而，迄今为止，生物形态仅在硅酸盐离子存在下产生-并且仅限于金属碳酸盐。因此，我们的方法更加通用。现在将深入研究该系统，以探索反应条件（包括无机化合物、有机添加剂、溶液浓度和反应时间）对产物形态的影响。实验工作将产生“形态图”，将实验条件与形成的结构联系起来，并探索通过这种自组装路线可以形成的形态范围。将筛选各种不溶性无机化合物和有机聚合物以及溶液条件。将使用光学显微镜、扫描电子显微镜（SEM）、拉曼光谱和X射线衍射表征产物晶体的形态和结构。通过这种方式，我们将能够建立晶体化学和溶液条件如何决定形成的结构的理解。这些结构形成的机制具有重要意义，并将通过使用电子显微镜和分析技术表征演变的结构来确定。我们将使用冷冻TEM来研究这些结构形成的早期阶段，这种技术使我们能够保存并因此保留这些结构，因为它们在溶液中。冷冻电子断层扫描将被用来在3D中成像这些分层结构的内部结构。我们还将探索液体细胞（LC-TEM），以纳米分辨率在溶液中真实的时间内实际观察这些结构的形成过程。这将是第一次有人能够在原位研究这种结构的形成。在实验研究的同时，我们还将开发数学模型，通过模拟浓度分布、扩散速率、反应速率和结构曲率的相互依赖性，使这些微结构的形成合理化。已经提出二氧化硅/金属碳酸盐生物形态的形成源自自催化共沉淀循环，其由于当金属碳酸盐和然后二氧化硅形成时发生的pH的交替局部变化而发生。我们的系统中没有硅酸盐，并且可以从不涉及pH变化的化合物形成这些结构。这表明了一个更普遍的潜在机制。该项目最终将提供一个框架，使我们能够通过设计预测和控制形态复杂的微结构的合成，其中具有复杂形式的无机材料在包括下一代光学超材料在内的应用中非常重要。

This project will couple experiments and mathematical modelling to explore the self-assembly of inorganic microstructures with complex, life-like morphologies. Living systems provide a unique inspiration for the design and construction of new materials. With complex, three-dimensional morphologies and hierarchical structures, biominerals such as bones, teeth and seashells exhibit properties unparalleled by their synthetic counterparts. A key feature of these biological structures is that they often form by assembly-based mechanisms under far-from equilibrium conditions. In exciting new results we have recently shown that the commercially-available polyelectrolytes can direct the formation of inorganic microstructures with remarkable morphologies including spirals, cones and twisted tapes in aqueous solution. This is achieved using a simple one-pot method. Notably, we have produced comparable structures for a range of compounds including calcium carbonate and strontium sulfate. Inorganic structures that have morphologies reminiscent of living, biological materials have been termed "biomorphs". However, to date, biomorphs have only been generated in the presence of silicate ions - and have been restricted to metal carbonates. Our methodology is therefore far more general.This system will now be investigated in depth to explore the influence of the reaction conditions, including the inorganic compound, organic additives, solution concentrations and reaction times on the product morphologies. Experimental work will generate "morphology maps" that relate the experimental conditions to the structures formed, and explore the range of morphologies that can be formed by this self-assembly route. A wide range of insoluble inorganic compounds and organic polymers will be screened, as well as solution conditions. The morphologies and structures of the product crystals will be characterised using optical microscopy, scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction. In this way we will be able to build an understanding of how the crystal chemistry and solution conditions dictate the structures formed.The mechanisms by which these structures form is of significant interest and will be determined by characterising the evolving structures using electron microscopy and analytical techniques. We will use cryo-TEM to investigate the early stages of formation of these structures, where this technique allows us to preserve and thus characterise the structures as they are in the solution. Cryo-electron tomography will be used to image the internal structures of these hierarchical structures in 3D. We will also explore liquid cell (LC-TEM) to actually watch the process of formation of these structures in real time in solution with nanometre resolution. This would represent the first time anyone has been able to study in situ the formation of such structures.In parallel with the experimental studies we will also develop mathematical models that can rationalise the formation of these microstructures by modelling the interdependence of concentration profiles, diffusion rates, reaction rates and curvature of the structures. The formation of silica/ metal carbonate biomorphs has been proposed to derive from an autocatalytic co-precipitation cycle, that occurs due to alternating local changes in pH that occur when metal carbonate, and then silica forms. We have no silicate in our system, and can form these structures from compounds whose formation does not involve a pH change. This suggests a much more general underlying mechanism. This project will ultimately deliver a framework that will allow us to predict and control the synthesis of morphologically-complex microstructures by design, where inorganic materials with complex forms are important in applications including next-generation optical metamaterials.