Studies of Helium Droplet Mass Spectrometry and Magnetic Nanoparticles
thesisposted on 04.09.2019, 10:32 by Charlotte Pughe
As the title suggests, this MPhil thesis is separated into two research topics. The first topic is based in the field of superfluid helium droplet science, and explores mass spectrometry of conjugated molecules in superfluid helium droplets. Recent observations have suggested conjugated molecules behave very differently to other molecules upon electron ionization in the helium droplet environment. The helium droplet mass spectrum of p-benzoquinone was recorded and compared to the gas phase mass spectrum. To try to explain the fragmentation process, density functional theory calculations were performed on the initial fragmentation pathways. By combining the experimental data and the theoretical calculations, a model to explain the reduced parent ion signal in the helium droplet mass spectrum of p-benzoquinone was developed. The model suggests the high energy of the proton loss pathway and the potential of a large energy barrier to parent ion ejection, forces p-benzoquinone to almost completely fragment upon ionisation inside the helium droplet. Further studies with other conjugated molecules could reveal more information about the influence of the helium matrix on dopant species. The second research topic investigates new methods to produce high moment iron oxide/iron nanoparticles. Iron oxide nanoparticles have been the focus of great research interest due to their various applications. Here, a modified approach to make iron oxide based on the co-precipitation technique was explored as a simple route to increase the nanoparticle magnetic moment. By applying a weak magnetic field to the reaction vessel it was found the magnetic saturation of the nanoparticles could be increased by a few emu/g. A novel method of producing pure iron nanoparticles based on liquid plasma nanosynthesis has also been proposed. The design for the liquid plasma reactor could allow iron nanoparticles, which have even higher moments than iron oxide, to be produced on a large scale.