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

调节材料物理特性的能力非常有吸引力。通常情况下，材料的性能是两个重要特性之间的折衷，例如高透明度和高导电性或低导热性和高导电性。解决这个问题的显而易见的方法是将材料组合起来生成复合结构。然而，通过简单地混合具有互补性能的材料来创造一种新的混合材料很少会产生净优势。关键是在多个长度尺度上对组件材料的装配施加控制。该项目的目标是开发一种强大而通用的方法来合成一类独特的功能性纳米复合材料——含有均匀分布的无机纳米颗粒的单晶。我们的方法从生物矿物中获得灵感，例如骨骼，牙齿和贝壳，这些都是具有分层结构的无机/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中的复合材料。因此，《自然》表明，尽管结晶是一种常见的纯化方法，但在晶体和添加剂的适当配对下，完全有可能在晶格内遮挡添加剂。使用具有重要生物学意义的矿物方解石（碳酸钙）作为测试系统，我们已经取得了令人激动的发现，这种生物生成策略可以转化为合成系统，以实现单晶中有效的纳米颗粒遮挡。我们现在希望在这些初步结果的基础上，开发我们的仿生结晶策略——将共聚物稳定的纳米颗粒用作简单的晶体生长添加剂——用于合成功能性纳米颗粒/单晶纳米复合材料。该策略提供了许多关键特性。我们正在制造纳米复合材料，其中纳米颗粒嵌入在单晶中，而不是典型的无定形或多晶基质中，纳米颗粒不会聚集。这提供了一种独特的结构，其中没有晶界有望提高许多物理性能。它在实验上是直截了当的，可以按比例放大，我们可以很容易地生产出足够的材料来确定结构/属性关系。我们还受益于传统离子化合物结晶的大量知识，以控制纳米复合材料的大小、形状和孔隙度。共聚物的合理设计将提供对纳米复合材料在纳米和中观长度尺度上的结构控制，我们将建立一个控制纳米颗粒负载、颗粒间分离以及纳米颗粒与晶体宿主之间界面的工具包。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颗粒/量子点的功能金属氧化物，并研究它们的传输和光催化性能。特别强调的是评估结构/性能关系，其中没有晶界和我们调整材料结构的能力有望为我们提供有关其材料性能的独特信息。然而，我们的合成方法是相当通用的，并且可以设想它可以作为一个平台，用于制造广泛的材料，包括电容器、电池、热电和电致变色材料。最后，虽然已经做出了重大努力来确定生物体控制结晶的策略，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.