ICIQ Seminar Programme - Prof. Peer Fischer (Institute for Molecular Systems Engineering, Heidelberg University, Heidelberg, Germany)
Chemically active particles that self-propel due to catalytic reactions have been demonstrated at micron length scales. These so called “chemical motors” can interact with their environment, which may lead to interesting swimming behaviors, including in principle chemotaxis. This is an exciting concept as it may potentially enable the active targeted delivery of pharmaceuticals. If the catalytic activity arises in semiconducting particles, then their interaction with light yields tunable emergent phenomena. While these carefully fabricated half-sided Janus colloids are model systems whose swimming behavior can clearly be seen in a microscope, the extension of these concepts to the nano- and molecular scale is far from obvious. I will critically discuss recent claims that enzymes and molecules can actively swim when they are catalytically active. Interestingly, however, chemically active nanoparticles and enzymes can give rise to sizeable hydrodynamic effects when they are confined, even if their individual propulsion is limited. Finally, it is shown that the fabrication methods that can yield some of the smallest chemically active Janus nanostructures can also be adapted to address a longstanding issue in obtaining pure nanoporous gold and other metallic structures. These nanoporous metallic films are remarkably robust with many catalytically active sites.