The decay of surface plasmons into electron/hole pairs via Landau damping can be exploited in a context of surface chemistry and catalysis if these "hot" carriers can be harvested before thermalization with the lattice occurs. We utilize the ultrafast dynamics of this process to control the surface chemistry of silver and gold plasmonic nanoantennas with nanoscale resolution. Specifically, we demonstrate mapping of reactivity hot spots, decoupled from the well-known electromagnetic hot spots of plasmonic nanosystems. We then show how the hot electron dynamics can be utilized for control over nanoscale self-assembly of molecular overlayers, allowing functionalization of specific parts of plasmonic nanoantennas with desired molecules. Coupled with interrogation via super-resolution microscopy, this allows for the local probing of plasmon decay and hence absorption with nanoscale resolution. Applications in controlled self-assembly of molecules and colloids as well as for the purification of collodial mixtures will be discussed.