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

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.