A design strategy for constructing hierarchically structured materials
using nanoparticles and synthetic biopolymers has been developed. Block
copolypeptides or homopolymer polyelectrolytes are used as
structure-directing agents to arrange nanoparticles (composed of metals,
metal non-oxides, metal oxides, or organics) into unusual
microstructures, such as spheres, "apples" and "cups." Hollow spheres can
be made wherein nanoparticles of one composition are spatially oriented
completely interior or exterior to nanoparticles of a second composition.
These aggregates contain nanoparticles only in the shell walls, and
maintain their hollowness upon calcination. These shapes can also be
fabricated into films. These robust materials are anticipated to have
great promise in applications that require surface catalysis,
magnetic/electronic/optic properties, transport capabilities, and
combinations thereof, such as drug delivery, packaging, catalysis, and
sensors.