The field of plasmonics is emerging as one of the key optical technologies of the 21st century; it holds promise for high-speed, all optical computing and plasmonic nanoparticles are the basis for many intriguing applications ranging from chemical sensing to cancer treatment and diagnostics. The high level of spatial and temporal control over light and photochemistry offered by plasmonics motivates the development of new materials, to be used, for example, for photocatalysis or in solar cells, and thus may have transformative impact on our way to a clean and sustainable society.
At the dawn of the age of plasmonics, scientists are seeking for novel materials, designed and tailored for new emerging applications. In the course of this project we will employ a new approach for the synthesis of plasmonic materials by producing plasmonic nanoparticles inside helium nanodroplets. A beam of liquid helium droplets with sizes up to only one micrometer provides an inert, cold and solvent free synthesis environment. As atoms or molecules can be added to the helium droplets sequentially, it is possible to assemble tailored nanoparticles by adding materials with different desired properties step by step to the droplet. In particular, we will explore material combinations for the passivation of nanoparticles which are highly reactive but with very exciting properties for plasmonics. Further experiments will be dedicated to the fabrication of active plasmonic core-shell particles with temperature dependent optical properties. These nanoparticles can then be deposited on any surface that is placed into the helium droplet beam.
Furthermore, at the Institute of Experimental Physics of TU Graz we will fabricate core-shell structures in which molecules are encapsulated in between layers of plasmonic materials, known as “nanomatryoshkas”. These materials are anticipated to enable Raman spectroscopy inside helium nanodroplets by exploiting the ability of plasmonic nanoparticles to concentrate light into very tiny regions around the Raman molecules.
From these experiments, we will learn about the properties of new materials, in particular, in a size regime where quantum effects are dominant, and about the interaction between molecules and plasmonic nanoparticles. Understanding the physics of these nanoscale objects is crucial for the design of large scale plasmonic devices and technologies. With the helium droplet synthesis approach, we think that a new, versatile method for the field of plasmonics will be established - a method capable of producing nanoparticles and nanostructures from an unprecedented variety of plasmonic materials with tailored properties.