Speaker
Description
Through aggregation inside superfluid helium droplets, metal nanoparticles and core-shell clusters of different morphology are generated and deposited on solid carbon, h-BN, ITO, or SiN substrates. The created nanoparticles are characterized by temperature dependent electron microscopy, up to 1000 degrees C, energy-dispersive x-ray spectroscopy, electron energy loss spectroscopy and photoemission electron microscopy. The structure, composition, and three-dimensional morphology of these particles are revealed at near-atomic resolution. In situ heating and cooling experiments uncover unique thermodynamic behaviours, such as nanowire breakup, alloying, and structural inversion, while studies on beam-induced effects expose atomic displacements and radiolysis-driven chemistry. Our investigations include the stability of a passivation of Ni, Fe, and Co cores of 2 to 3 nm diameter by a few layers of gold and the alloy formation at high temperature.
Ag@ZnO core@shell particles exhibit enhanced electron emission upon excitation of the localized surface plasmon resonance in Ag at around 3 eV. Vanadium oxides represent a prominent materials class for catalytic applications. When deposited after clustering in helium, we have shown that V2O5 nanoparticles keep the original stoichiometry. In combination with gold doping, Janus particles of Au and V2O5 with radii of about 20 nm are identified.