Atomic Ligand Passivation of Colloidal Nanocrystal Films via their Reaction with Propyltrichlorosilane

Colloidal nanocrystal films of different materials (semiconductors, metals) and shapes (spheres and rods) were dipped in solutions of propyltrichlorosilane (PTCS) in acetonitrile. This process removed most of the surfactants covering the surface of the tested nanocrystals, leaving their surface either unpassivated or passivated with chlorine atoms, depending on their composition. PTCS was reactive toward most of the surfactants used in nanocrystal synthesis and therefore such a procedure could be applied to a large variety of materials. All samples were characterized with FTIR, XRD, and XPS measurements. In nanocrystal films, the reduction of the separation between the nanocrystals resulting from the removal of surfactants led to an enhancement in both dark and photocurrent. The surface of Au nanocrystals is left unpassivated by the reaction with PTCS, which makes the process potentially useful for applications in catalysis and plasmonics.