Cold Injection Synthesis of Nanoheterostructures based on Cluster Decomposition

基于团簇分解的纳米异质结构冷注射合成

• 批准号: 390144869
• 负责人: Professor Dr. Klaus Boldt
• 金额: --
• 依托单位: Abteilung Physikalische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/390144869?language=en
• 关键词: Cold; Injection; Synthesis; Nanoheterostructures; based

Nanocrystals have attracted considerable interest, because they promise large potential for miniaturisation of functional materials and have physical properties that depend on their size. They have been synthesised by wet-chemical means with more and more complex architectures. Complexity is either achieved by making particles with anisotropic shape (e.g. nanorods) or in complex heterostructures of different materials (e.g. particles with multiple shells), or both. The deposition of a new material onto a nanostructure requires the reaction of usually two precursor molecules that react at the surface of a seed particle in a heterogeneous nucleation reaction. Therefore precursor reactivities need to be matched. In addition, lattice mismatch and effects of surface ligands need to be taken into account. Therefore, the fabrication of nanoparticles usually occurs at high temperatures. If complex morphologies are exposed to heat they quickly degrade. Anisotropic shapes melt into spherical particles, while interfaces in heterostructures form a material gradient. High temperature thus poses a limit to the complexity of nanostructures that are accessible by wet-chemical methods. Mild reaction conditions, low temperature, and the absence of precursor decomposition reactions would evade these restrictions and allow the synthesis of a much wider range of nanomaterials. In this project, we aim to establish a new synthetic route to form nanocrystalline heterostructures based on a "cold injection" approach. Here, chemical triggers rather than physical parameters initiate the growth reaction of a nanocrystal.We intend to employ ultrasmall semiconductor clusters as source of material for seeded growth. These clusters can be produced ex-situ and act as a reservoir of the target material. Due to their molecular structure they can be decomposed under well-defined conditions. By separating the formation of the semiconductor compound from the growth reaction the general approach will be applicable to a broad spectrum of seed materials. The use of a chemical trigger to initiate the reaction allows working under very mild conditions and thermodynamic control, which is crucial for thermally unstable morphologies. Fabrication of defined heterostructures will thus be possible at much reduced energy costs. We will apply the principle to two semiconductor model systems, the formation of "hard" potential steps in core/shell particles and regio-selective growth of anisotropic particles in only one direction. Both systems are of high interest for both a fundamental understanding of nanoheterostructures and future application of colloidal nanocrystals in complex materials and electronic devices. However, the proposed reaction will be highly beneficial beyond the scope of this project, e.g. for modification of nanocrystals with impurity doping, in which dopant diffusion must be suppressed, or for nanocrystals that have been assembled into a larger superstructure.

纳米晶体引起了人们极大的兴趣，因为它们在功能材料的小型化方面具有巨大的潜力，并且具有取决于其尺寸的物理特性。它们通过湿化学方法合成，具有越来越复杂的结构。复杂性可以通过制造具有各向异性形状的颗粒（例如纳米棒）或不同材料的复杂异质结构（例如具有多个壳的颗粒）或两者兼而有之来实现。将新材料沉积到纳米结构上通常需要两个前体分子发生反应，这两个前体分子在异质成核反应中在种子颗粒的表面发生反应。因此前体反应性需要匹配。此外，还需要考虑晶格失配和表面配体的影响。因此，纳米粒子的制造通常在高温下进行。如果复杂的形态受热，它们会迅速降解。各向异性形状熔化成球形颗粒，而异质结构中的界面形成材料梯度。因此，高温限制了可通过湿化学方法获得的纳米结构的复杂性。温和的反应条件、低温和不存在前体分解反应将规避这些限制，并允许合成更广泛的纳米材料。在这个项目中，我们的目标是建立一种基于“冷注入”方法形成纳米晶异质结构的新合成路线。在这里，化学触发因素而不是物理参数引发纳米晶体的生长反应。我们打算采用超小型半导体簇作为晶种生长的材料来源。这些簇可以异位产生并充当目标材料的储存库。由于其分子结构，它们可以在明确的条件下分解。通过将半导体化合物的形成与生长反应分开，通用方法将适用于广泛的种子材料。使用化学触发器来引发反应可以在非常温和的条件和热力学控制下进行，这对于热不稳定的形态至关重要。因此，可以以大大降低的能源成本制造特定的异质结构。我们将把这一原理应用于两个半导体模型系统，即核/壳粒子中“硬”势阶的形成以及各向异性粒子仅在一个方向上的区域选择性生长。这两个系统对于纳米异质结构的基本理解以及胶体纳米晶体在复杂材料和电子设备中的未来应用都具有很高的意义。然而，所提议的反应将在本项目范围之外非常有益，例如用于通过杂质掺杂对纳米晶体进行改性，其中必须抑制掺杂剂扩散，或者用于组装成更大的超结构的纳米晶体。