Nanomaterials are of strong interest for both fundamental and technological purposes. At the fundamental level, nanomaterials possess novel physical and chemical properties that differ from those of bulk matter due to quantum confinement effects and exceedingly larger surface-to-volume ratio. These novel properties are highly promising for applications in emerging technologies such as solar cells and biomedicine. Our lab has been actively engaged in the study of optical and dynamic properties of nanomaterials for solar energy conversion and biomedical applications. One example is hydrogen generation from water splitting based on novel semiconductor nanostructures with improved properties. We also design and characterize metal nanostructures for chemical sensing based on surface enhanced Raman scattering (SERS) and biomedical imaging and therapy. An example is hollow gold nanospheres that have demonstrated outstanding photophysical properties for photothermal ablation therapy of cancer both in vitro and in vivo, due to their unique structural and optical characteristics.