Final Report Summary - DCENSY (Doping, Charge Transfer and Energy Flow in Hybrid Nanoparticle Systems) The project “Doping, Charge and Energy transfer in hybrid Nanoparticle SYstems” (DCENSY) addressed a frontier area in nanoscience of combining disparate materials into a single “hybrid” nanoparticle system. This offers an intriguing route to engineer nanomaterials with multiple functionalities in ways that are not accessible in bulk materials or in molecules. Focusing on combinations of semiconductors and metals, new highly controlled hybrid nanoparticle systems were discovered, and their emergent synergistic properties were revealed, in the contexts of doping, and charge and energy transfer processes in nanoparticles.New hybrid nanoscale inorganic cages were discovered, synthesized via a novel edge growth mechanism, where a metal cage was grown selectively on the edges of a faceted semiconductor nanocrystal. Synergetic electrical properties that originate from the unique combination of the semiconducting-metallic interface in the hybrid cages were revealed. The nano-inorganic cage structures are of potential use in sensing, electrocatalysis, catalysis and photocatalysis.Doping of semiconductor nanoparticles with metal impurities was achieved, leading to heavily doped semiconductor nanocrystals. The emergence of a confined impurity band and band-tailing was discovered. An additional approach to doping was developed for Cu2S nanocrystal arrays using thermal treatment at moderate temperatures, and yielding significant conductance enhancement attributed to Cu vacancy formation. Successful control of doping and its understanding provide n- and p-doped semiconductor nanocrystals which greatly enhance the potential application of such materials in solar cells, thin-film transistors, and optoelectronic devices.We synthesized new hybrid nanoparticles and investigated the outcome of light induced charge separation yielding photocatalytic activity, with particular focus on the photocatalytic reduction of water producing hydrogen fuel by light irradiation. Strong effects of the surface coating on the photocatalytic function of hybrid nanoparticles were revealed, and assigned to effects of surface passivation by the different surface coatings affecting the surface trapping of charge carriers that competes with effective charge separation required for the photocatalysis. This is of importance for the potential application of hybrid nanoparticles as photocatalysts, opening a route for direct solar energy conversion to chemical energy in a clean fuel.Aspects of energy transfer in semiconductor nanoparticles were studied by combination of ensemble and single particle spectroscopy methods. Analysis of the interaction of semiconductor nanoparticles with an atomic force microscope tip, revealed an interplay between fluorescence quenching related to energy transfer, and fluorescence enhancement. In addition, studies of the dynamic process of energy transfer from semiconductor nanocrystals acting as donors to multiple dye acceptors attached to their surface allowed for understanding of the principles that govern dynamics of the energy transfer processes, and the role of the shape and dimensions of the nanocrystal in these. Understanding such energy transfer is of relevance for a range of applications including sensing, bio-labelling and energy funnelling.Further expansion of hybrid nanoparticles to additional materials systems was also initiated, focusing on the environmentally compatible system of Zn-chalcogenides. A general strategy for synthesis of nanorods was developed, and a new structure of nanorod-couples, which is formed via a self-limited self-assembly mechanism, was discovered.Overall, the field of hybrid nanoparticles was significantly advanced through the project in terms of discovery of new materials systems and obtaining deep understanding of their synergistic properties. This also sets the stage for the development of the potential applications of hybrid nanoparticle systems in diverse fields.
