2 x Catalysis on mixed-metallic subnanometer-sized particles
The helium-droplet technique is used to create our `Nano-Mozartkugeln', which are mixed-metallic clusters of Au and Cu with diameters in the nanometer range. The particles are then deposited on supports of amorphous carbon or SiO2. The results are checked by electron microscopy imaging with the help of our colleagues at the FELMI-ZFE. A newly designed reaction chamber has to tested for leaks and for the accessible temperature range given by the built-in sample heater. After that, first BET adsorption measurements of nitrogen gas are planned. Finally, a selection of materials is then placed into the reaction chamber and exposed to a He-diluted mixture of butadiene, propene and hydrogen for a series of temperature-controlled reaction measurements. Gas composition during reaction will be monitored by the quadrupole mass spectrometer attached to the chamber.
Our recent work is geared towards the formation of nanoparticles with core-shell structure: Onion-like particles with shells consisting of different materials. Our group has a long tradition in the preparation of nanoparticles in cold superfluid helium nanodroplets at temperatures of only 0.37 K. We are now looking for a motivated master student in order to push our approach to the next step: Adding an additional layer of molecules between a metal shell and a metal core to form particles known in literature as “quantum matryoshkas”. The special plasmonic properties of these particles, based on localized surface plasmon resonances, can locally cause a strong enhancement of electromagnetic radiation. We are planning to exploit this effect in order to perform Raman spectroscopy on the molecular matryoshka layer in-situ, while still inside the helium droplets, as well as with deposited particles.
You will be involved in the setup of a gas pickup-oven in order to introduce gaseous molecular dopants into helium droplets. You will further be involved in the development of an optical LIF spectroscopy setup (LIF – laser induced fluorescence). The experiments will be carried out at our ultra-high vacuum helium droplet machine in ClusterLab III, various different laser systems will be employed.