Geometry control and optical tunability of metal-cuprous oxide core-shell nanoparticles.

Metal-semiconductor hybrid heteronanostructures may exhibit synergistically reinforced optical responses and significantly enhanced optical tunability that essentially arise from the unique nanoscale interactions between the metal and semiconductor components. Elaboration of multi-component hybrid nanoparticles allows us to achieve optimized or diversified material functionalities through precise control over the dimension and morphology of the constituent building units, on one hand, and through engineering their relative geometrical arrangement and interfacial structures, on the other hand. Here we study the geometry-dependent optical characteristics of metal-cuprous oxide (Cu(2)O) core-shell hybrid nanoparticles in great detail through combined experimental and theoretical efforts. We demonstrate that several important geometrical parameters, such as shell thickness, shell crystallinity, shell porosity, and core composition, of the hybrid nanoparticles can be tailored in a highly precise and controllable manner through robust wet chemistry approaches. The tight control over the particle geometries provides unique opportunities for us to develop quantitative understanding of how the dimensions, morphologies, and electronic properties of the semiconducting shells and the geometry and compositions of the metallic cores affect the plasmon resonance frequencies, the light scattering and absorption cross sections, and the overall extinction spectral line shapes of the hybrid nanoparticles. Mie scattering theory calculations provide further insights into the origin of the geometrically tunable optical responses and the interesting extinction spectral line shapes of the hybrid nanoparticles that we have experimentally observed.