Semiconductor nanocrystal quantum dots: From science to applications Uri Banin Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, Israel; [email protected] Semiconductor nanocrystals manifest unique size, shape and composition dependent properties with both basic and applied significance and are emerging building blocks of devices in Nanotechnology. An example concerns the use of highly emitting core/shell nanoparticles as targeted markers for cancer cells. An additional example concerns highly fluorescent III-V semiconductor nanocrystals with near-IR emission tunable by size through the quantum confinement effect. With such systems we discovered a process of long range electronic to vibrational energy transfer between the nanocrystal and solvent overtone vibrational modes. Experimental and theoretical analysis of this process will be presented. It should be considered in matrix choice for optical applications of QDs. An important frontier in nanocrystal synthesis concerns the growth of composites of different materials in the same nanostructure as means of increasing functionality. One interesting combination of materials is that of a metal and semiconductor in the same nanoparticle where metal tips can provide anchor points for electrical connections and for self assembly. We developed the growth of metal tips on the apexes of semiconductor (CdSe) rods, forming 'nano-dumbbells' (NDB's), via a simple chemical reaction. We also found that by increasing the concentration of gold in the reaction, rods with a metal tip on one side are formed via a unique ripening process. Expansion to additional semiconductors and other metals is also in progress, and the various growth modes of hybrid nanocrystals will be discussed. Such systems manifest a unique model for a metal-semiconductor nanoscale junction, and exhibit charge separation upon light absorption. Photocatalytic activity and self assembly of the systems will be described A second combination is that of two semiconductors where a seeded growth approach can be used to create rod shaped particles with either type I or type II band-alignment. Using different seed dot particles, we describe growth of either types of rod architectures. The use of optical spectroscopy along with STM and STS (scanning tunneling spectroscopy), was used to reveal the electronic properties and measure the band-offsets in these systems. .