Helium Droplets – A Very Clean and Controlled Way to Produce Nanoparticles Clusters and nanoparticles are an interesting class of materials because their properties can differ from the bulk material as well as from the pure atomic species. Their optical, magnetic and catalytic characteristics can strongly depend on their size and shape as well as on their surroundings (oxide layers, ligands, solvents, substrates). The utilization of helium droplets as reactors to grow nanoparticles allows a good control over the size of the produced particles and provides an ultra-pure environment, excluding any unwanted reactions. Recently, the existence of quantized vortices inside helium droplets has been demonstrated, opening the possibility to create one-dimensional shapes on the nanoscale. Furthermore, sequential addition of two or more species to the helium droplet allows material combinations which would not be possible using other techniques. |