Control of shape and size of anisotropic and core/shell nanostructures using microemulsions and related methods have been at the core of our research. The nanostructures have been chosen for applications in water splitting, photocatalysis and photovoltaics. 1-D core-shell nanostructures have been designed for water splitting and photocatalytic activity. Coupling of wide band gap semiconductor such as ZnO, NaNbO3 with a narrow band gap semiconductor gives efficient semiconductor heterostructures (core/shell) for visible-light photocatalysis. Metallic/alloy, metal oxide nanoparticles and Mo-based nanocomposites have been designed to show very efficient electro-catalysis for hydrogen and oxygen generation