Doped-Up: Bio-Inspired Assembly of Single Crystal Nanocomposites

调整材料物理属性的能力非常有吸引力。通常情况下，材料的性能是高透明度和高导电性或低导热性和高导电性两种重要特性之间的折衷。这个问题的明显解决方案是将材料组合起来形成复合材料结构。然而，通过简单地混合具有互补特性的材料来创造一种新的杂化材料很少产生净优势。这个项目的目标是开发一种稳健和通用的方法来合成一类独特的功能纳米复合材料-含有均匀分布的无机纳米颗粒的单晶。我们的方法的灵感来自于生物矿物，如骨骼、牙齿和贝壳，这些都是具有层次结构的无机/有机复合材料。事实上，即使是单晶生物矿物也是有机分子嵌入晶格的复合材料。因此，自然证明，虽然结晶是一种常见的提纯手段，但如果晶体和添加剂的适当配对，完全有可能将添加剂封闭在晶格中。使用具有生物重要性的矿物方解石(碳酸钙)作为测试系统，我们已经取得了现有的发现，这种生源策略可以转化为合成系统，以实现有效的纳米颗粒在单晶中的封闭。我们现在希望在这些初步结果的基础上，开发我们的生物启发结晶策略-其中共聚物稳定的纳米颗粒被用作简单的晶体生长添加剂-用于合成功能纳米颗粒/单晶纳米复合材料。这一战略提供了许多关键功能。我们正在创造纳米复合材料，其中纳米颗粒嵌入到单晶体中，而不是典型的非晶或多晶基质中，并且纳米颗粒不会聚集。这提供了一种独特的结构，其中没有晶界有望增强许多物理性能。它在实验上是简单的，并且易于放大，我们可以很容易地生产足够的材料来确定结构/性质关系。我们还受益于有关传统离子化合物结晶的广泛知识，以控制纳米复合材料的尺寸、形状和孔隙率。合理的共聚物设计将在纳米和介观尺度上控制纳米复合材料的结构，我们将建立一个工具包来控制纳米颗粒的负载、颗粒间的分离以及纳米颗粒和晶体主体之间的界面。作为一个合适的测试系统，我们将重点研究含有贵金属纳米粒子/量子点的功能性金属氧化物，并研究它们的传输和光催化性能。重点将放在评估结构/性能关系上，在这种关系中，没有晶界和我们调整材料结构的能力有望为我们提供关于材料性能的独特信息。然而，我们的合成方法是相当通用的，预计它可以用作制造包括电容器、电池、热电和电致变色在内的广泛材料的平台。最后，尽管已经做出了重大努力来确定生物控制结晶的策略，但这些策略很少应用于功能材料。该项目将展示这种方法的可行性和潜力，并有望激励其他研究人员使用生物启发的结晶策略来控制先进材料的结构和性能。

The ability to tune the physical properties of materials is extremely attractive. All too often, the performance of a material is a compromise between two important properties such as high transparency and high conductivity or low thermal conductivity and high electrical conductivity. The obvious solution to this problem is to combine materials to generate composite structures. However, the creation of a new hybrid material by simply mixing materials with complementary properties rarely results in a net advantage. The key is to exert control over the assembly of the component materials over multiple length scales.The goal of this project is to develop a robust and general methodology for the synthesis of a unique class of functional nanocomposites - single crystals containing a uniform distribution of inorganic nanoparticles. Our approach takes its inspiration from biominerals, such as bones, teeth and seashells, where these are invariably inorganic/ organic composites with hierarchical structures. Indeed, even single crystal biominerals are composites in which organic molecules are embedded within the crystal lattice. Nature therefore demonstrates that although crystallisation is a common means of purification, it is entirely possible to occlude additives within a crystal lattice given the appropriate pairing of the crystal and additive. Using the biologically-important mineral calcite (calcium carbonate) as a test system, we have made the exiting discovery that this biogenic strategy can be translated to synthetic systems to achieve efficient nanoparticle occlusion in single crystals. We now wish to build on these preliminary results to develop our bio-inspired crystallisation strategy - in which copolymer-stabilised nanoparticles are used as simple crystal growth additives - for the synthesis of functional nanoparticle/ single crystal nanocomposites. This strategy delivers a number of key features. We are creating nanocomposites in which the nanoparticles are embedded within a single crystal, rather than the typical amorphous or polycrystalline matrix, and the nanoparticles are not aggregated. This provides a unique structure where the absence of grain boundaries is expected to enhance many physical properties. It is experimentally straightforward and amenable to scale-up, and we can easily produce sufficient material to determine structure/property relationships. We also benefit from the vast knowledge that is available concerning the crystallisation of traditional ionic compounds to control the size, shape and porosity of the nanocomposites. Judicious design of the copolymer will provide control over the structures of the nanocomposites at the nano- and meso- length scales, and we will establish a tool-kit for controlling the nanoparticle loading, the inter-particle separations and the interfaces between the nanoparticles and the crystal host. As a suitable test-system we will focus on functional metal oxides containing noble metal nanoparticles/ quantum dots and study their transport and photocatalytic properties. Particular emphasis will be placed on evaluating the structure/property relationships, where the absence of grain boundaries and our ability to tune the structures of our materials is expected to provide us with unique information about their material properties. Our synthetic method is quite general however, and it is envisaged that it can be used as a platform for creating a broad spectrum of materials including capacitors, batteries, thermoelectrics and electrochromics. Finally, while significant efforts have been made to identify the strategies by which organisms control crystallisation, these have seldom been applied to functional materials. This project will demonstrate the feasibility and potential of this approach, and will hopefully inspire other researchers to use bio-inspired crystallisation strategies to control the structure and properties of advanced materials.