Nanocrystal

A crystalline particle with nanoscale dimensions. Its shape and growth kinetics depend on exposed interfaces, defects and material supply, not just its bulk crystal structure.

A bimetallic nanocrystal is a crystalline particle containing two metallic chemical elements, with important dimensions on the nanoscale. Its atoms may form an alloy, chemically ordered regions, a core surrounded by a shell or spatially separated domains. Composition alone does not determine which arrangement is present.

For example, a gold–silver particle can expose a surface composition different from its bulk average. That affects surface chemistry and interaction with light. Establishing its structure requires complementary evidence: electron microscopy can reveal morphology, elemental mapping can locate the elements, and diffraction can constrain the crystal structure. These measurements answer different questions rather than providing interchangeable particle descriptions.

Addition or rearrangement of material in a nanocrystal. Solute addition, Ostwald ripening and oriented attachment are distinct mechanisms that can coexist.

Preferential adsorption of charged species onto particular crystal faces, reducing their normal incorporation rates. Both solution speciation and actual surface charge matter; crystallographic polarity alone does not fix adsorption selectivity.

Selection of unequal growth along otherwise equivalent directions, through defects, selective adsorption, kinetics or external asymmetry. A lower-symmetry shape need not imply a different bulk lattice.

Joining of crystallites after compatible crystallographic alignment. Elimination of exposed interface drives the process; incomplete rotation and healing can leave defects.

Growth by incorporation of dissolved individual atoms, ions or molecular units into a crystal, driven by supersaturation and limited by transport or attachment kinetics.