A variety of polyhedral nanocages are provided having a hollow interior, ultrathin walls, and well-defined facets of metal atoms. The nanocages can include a variety of precious metals such as Pt, Au, Ru, Rh, or Ir. The metal atoms can take a face-centered cubic structure with {111} facets on the surface. The walls can be thin, sometimes less than 1 nm in thickness or only a few atomic layers in thickness. The nanocages can provide for efficient uses of valuable precious metals, among other things, in catalysis. For example, catalysts are provided exhibiting high mass activities in oxygen reduction reactions. Methods of making and methods of using the nanocages and catalysts are also provided.

Disclosed herein are method and design rules for making polyelemental systems with specific heterostructures, including tetra-phase nanopartides with as many as six junctions. In accordance with an embodiment, a method of making a tetra-phase polyelemental nanoparticle using tri-phase nanoparticle architectures can include selecting two or more triphase nanoparticle architectures, wherein the two or more tri-phase nanoparticle architectures are one or more striped tri-phase architectures, one or more pie-shaped tri-phase architectures, or combinations thereof; identifying from the selected two or more tri-phase nanoparticle architectures groups of metals for generating each of the two or more tri-phase nanoparticle architectures; contacting a tip coated with an ink to a substrate to form a nanoreactor, the ink comprising block copolymer and the metals from the groups of metals identified for generating each of the two or more tri-phase nanoparticle architectures; and annealing the nanoreactors under conditions sufficient to synthesize a tetra-phase polyelemental nanoparticle.

Methods of synthesizing gold nanodendrites (AuNDs) using amines, such as long chain amines, as a structural directing agent are disclosed. Degree of branching (DB) of the AuNDs can be tuned by adjusting certain synthetic parameters, such as solvent type, and the type and concentration of the long chain amines. DB control results in dramatic tunability of the optical properties of the AuNDs in the near infrared (NIR) range enabling improved performance, for example as a photothermal cancer therapeutic.

Proposed is a three-dimensional chiral metal nanoparticle, comprising a heterometal nanoparticle including: a seed region formed of a first metal; and a heterogeneous region disposed on an external side of the seed region to enclose the seed region and formed of a second metal. The first metal is gold (Au), and the second metal is palladium (Pd). In a rectangular parallelepiped structure, a rectangular band shape rotates in a clockwise direction or a counterclockwise direction on each surface and protrudes towards a center of the surface.

Proposed is a three-dimensional chiral metal nanoparticle, comprising a heterometal nanoparticle including: a seed region formed of a first metal; and a heterogeneous region disposed on an external side of the seed region to enclose the seed region and formed of a second metal. The first metal is gold (Au), and the second metal is palladium (Pd). In a rectangular parallelepiped structure, a rectangular band shape rotates in a clockwise direction or a counterclockwise direction on each surface and protrudes towards a center of the surface.

Methods of forming metal multipod nanostructures. The methods may include providing a mixture that includes a metal acetylacetonate, a reducing agent, and a carboxylic acid. The mixture may be contacted with microwaves to form the metal multipod nanostructures. The methods may offer control over the structure and/or morphology of the metal multipod nanostructures.

Methods of forming metal multipod nanostructures. The methods may include providing a mixture that includes a metal acetylacetonate, a reducing agent, and a carboxylic acid. The mixture may be contacted with microwaves to form the metal multipod nanostructures. The methods may offer control over the structure and/or morphology of the metal multipod nanostructures.

A method of preparing biocompatible and stable gold nanoparticles comprises preparing at least one flavonoid-rich plant extract, and mixing at least one of the plant extracts with an aqueous solution of at least one gold salt. The flavonoid-rich plant extract is an extract of Hubertia ambavilla or Hypericum lanceolatum. The gold nanoparticles may be used for medical and/or cosmetic purposes.

Methods of forming metal multipod nanostructures. The methods may include providing a mixture that includes a metal acetylacetonate, a reducing agent, and a carboxylic acid. The mixture may be contacted with microwaves to form the metal multipod nanostructures. The methods may offer control over the structure and/or morphology of the metal multipod nano structures.

Methods of forming metal multipod nanostructures. The methods may include providing a mixture that includes a metal acetylacetonate, a reducing agent, and a carboxylic acid. The mixture may be contacted with microwaves to form the metal multipod nanostructures. The methods may offer control over the structure and/or morphology of the metal multipod nano structures.