Our research is concerned with the synthesis, measurement and understanding nanometer-sized particles, collections of particles and composite materials. Solid materials with physical dimensions on the nanometer (10-9 m) scale exhibit properties which can be very different from bulk material properties. These unique properties derive, for the most part, from two effects related to the small size of the crystalline particle. First are "quantum confinement" effects. This refers to the physical confinement of the crystal excitations (electrons, excitons, phonons) inside the particle. The result is often a dramatic change in the optical, magnetic and electronic properties of the material. Second are surface effects. The surface of every material contributes to its electronic properties. In a nanometer-sized particle (nanoparticle), a very large fraction of the total number of atoms are on the surface. In this case, the properties of a nanoparticle can be extremely sensitive to the surface chemistry. In a composite material, the particle surfaces are interfaces between two different materials and therefore represent an energy barrier for both charge carriers and phonons. Quantum confinement and selective energy scattering at nanoparticle boundaries are used to tailor the properties of nanocomposite materials.