Platinum and its alloys/intermetallics such as PtM (M=Fe, Co, Ni, Pb, Ru, etc) are known for their unique properties.  They are excellent catalysts in hydrogenation and dehydrogenation reactions.  Recently the alloys and intermetallics between Pt and various transition metals have also been studied for their magnetic properties.  All these properties depend highly on the size, shape and composition of the nanoparticles.  In this talk, I will present our recent research results on the synthesis, structure and property of several Pt-based nanostructures.  I will focus on the formation of multipods and dendritic nanostructures, various planar shapes in particular, on the composition control of alloy and intermetallic nanostructures and on the use of ionic liquid as solvents in these syntheses.  The magnetic and catalytic properties and the biological responses of these nanomaterials will also be discussed.