Nisha Shukla and her team at Carnegie Mellon University, US, have developed a number of simple synthesis procedures that lead yield metal and alloy nanoparticles with control of both particle size and shape. In a recent study published in Nanotechnology the authors describe the synthesis of FexPt1–x nanoparticles with a variety of shapes including spheres, nanocubes, high aspect ratio nanowires and hexagons. They are able to control the nanoparticle shape by using various solvents and surfactants in the reaction mixture.

In related work, the group has also synthesized FePt nanocubes that can be self-assembled in such a way that their crystallographic axes are aligned and oriented with respect to the substrate. Other achievements include nanoparticles that have platinum cores embedded in an iron shell, chiral gold nanoparticles, nickel nanorods coated in silica and highly crystalline silver nanowires (see image for examples).

Shukla's group is currently focusing on the development of sintered resistant multiphase, multicomponent-shaped nanoparticles for applications in catalysis. Other uses for the shape-controlled material includes magnetic data recording.

Nanoparticles with anisotropic shapes such as rods or hexagons and with aspect ratios greater than one, can maximize their packing density when self-assembled on surfaces and can allow easy alignment of the magnetic axes of the nanoparticles. Shapes such as cubes will self assemble with their crystallographic axes aligned in space.