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Bimetallic nanoparticles exhibit enhanced properties relative to their single composition cousins in catalytic activity, changes in the plasmon energy band, and expected electronic gains.
These properties are dependent upon nanoparticle size, structural organization, and composition of the bimetallic material. Approaches to their synthesis have involved the use of dendrimer hosts, reverse micelles, polyol processes, and microemulsions.
Unfortunately, these approaches offer little control of the structural arrangement of each metallic component, and as a result, translate into poorly defined structures. Fundamentally, this is due to a lack of template specificity in arranging multiple metals in a fixed spatial orientation, such as templates containing single functionalities (OH or NH2) which bind many different metals (Pd, Ag, Au, Pt).
Consequently, there is no discretion as to how metals are organized to form the bimetallic material which ultimately affects the final physical properties mentioned above.
It is known that peptides designed with multi-functionality expand nanoparticle synthesis beyond single composition metal nanoparticles making it possible to controllably synthesize mixed compositions of inorganic nanoparticles in defined structures as outlined below.
Air Force researchers have leveraged this knowledge to use a single peptide template for the synthesis and assembly of two or more different inorganic nanoparticles as an integrated hybrid nanoparticle structure with a defined spatial organization, composition, structure, and geometry.
Briefly, a peptide coated metal nanoparticle is synthesized from a selected peptide sequence and the appropriate metal salt precursor. The particle is purified to remove excess peptide and then used as a template for the synthesis of a second inorganic nanoparticle. This is prepared by adding a second metal ion precursor that selectively binds to the exposed groups of the peptide surface of the first nanoparticle.
The bound metal ions are subsequently reduced to form zero-valent metal nanoparticles at the peptide interface resulting in the dual composition nanoparticle material. In sum, this is a peptide-mediated approach for the synthesis of bimetallic nanoparticle structures from two or more inorganic materials.
- Resulting hybrid particles exhibit enhanced properties relative to their single nanoparticle counterpart as a result of their controlled structural assembly, which includes gains in electrical properties, catalytic activity, and optical properties
- Components of the hybrid nanostructure include any combination of metals, metal ions, semiconductor quantum dots, nanoparticles, magnetic materials, and negative index materials
- Geometry of the inorganic materials includes any combination of spheroidal particles, rods, cubes, tetrahedrons, multiple faceted particles, and planar surfaces
- US patent 7,905,943 available for license