A new frontier in nanochemistry: formation of novel core-shell nanoparticles using liquid helium droplets

纳米粒子是分子或原子的集合体，其直径是人类头发的10,000-100,000倍。核壳纳米颗粒是一类具有核层和壳层的纳米颗粒(S)。核壳纳米粒子是一类具有与纯核壳材料完全不同的光学、电学、表面化学性质和催化性能的复合材料。它们的性质可以通过改变壳的厚度或核壳比来改变。传统的纳米颗粒合成方法分为湿法和气相法。这两种方法都有其局限性。核壳纳米粒子可以用这两种传统的方法生长，但核壳材料存在严重的限制，在许多情况下很难获得定义良好的核壳层。为了绕过这些困难，我们提出了一种新的方法，可以几乎完全控制核壳纳米颗粒的逐层生长。这项提议寻求开发一种新的、高度通用的技术，其中生长溶剂由微米尺寸的超流液氦液滴组成。这项技术在纳米化学中提供了巨大的和革命性的可能性，这项提议的目的是开发一个独特的研究计划来研究这些可能性。这项工作的范围很广，但这里的目标是通过专注于某些特定类别的纳米颗粒来展示可能性，许多纳米颗粒具有一个或多个潜在的应用。除了应用之外，还可以生长出任何其他技术都无法生产的全新的核壳纳米颗粒。虽然这项工作是概念验证研究，但它代表了基础科学与潜在的非常广泛的一系列应用的令人兴奋的结合。

A nanoparticle is an ensemble of molecules or atoms with a diameter 10,000 - 100,000 times than a human hair. A core-shell nanoparticle is a particular class of nanoparticle with a core and shell layer(s). Core-shell nanoparticles constitute a class of composite materials that can show optical, electrical, surface chemical and catalytic properties that are totally different from either the pure core or shell materials. Their properties can be altered by changing the thickness of the shell or core-to-shell ratio. Conventional nanoparticle synthesis methods divide into 'wet' methods and gas-phase methods. Both methods have their limitations. Core-shell nanoparticles can be grown with both of the conventional methods, but there are severe limitations on the core and shell materials and in many cases there are difficulties in obtained well-defined core and shell layers. To circumvent these difficulties, we propose a new method that would allow almost complete control of the layer-by-layer growth of core-shell nanoparticles. This proposal seeks to develop a new and highly versatile technique in which the growth solvent consists of micron-sized superfluid liquid helium droplets. This technique offers enormous and revolutionary possibilities in nanochemistry and the purpose of this proposal is to develop a unique research programme to investigate these possibilities. The scope of this work is vast, but the aim here will be to demonstrate the possibilities by focusing on certain selected classes of nanoparticles, many with one or more potential applications. In addition to the applications, entirely novel core-shell nanoparticles can be grown which could not be produced by any other technique. Although this work is proof-of-concept research, it represents an exciting combination of fundamental science with a potentially very wide array of applications.