Nanostructures

Nanostructures have at least one dimension or internal feature roughly 1–100 nanometers across. Their small size can produce optical, electrical, chemical, or mechanical properties unlike those of larger materials.

Nanometer: A unit of length equal to one billionth of a meter. Nanostructures are defined by features measured on this scale.
Localized surface plasmon resonance: A resonant collective oscillation of conduction electrons in a small metallic structure driven by light. It gives some metal nanoparticles strong, size-sensitive colors and light scattering.
Carbon nanotube: A cylindrical carbon structure with a nanoscale diameter and a graphene-like atomic arrangement. Its electrical and mechanical properties motivate use in composites and electronics.
Bulk material: A material whose properties are measured in a region large enough to be largely independent of its surface. Bulk behavior is the baseline that nanoscale size effects can depart from.
Surface-to-volume ratio: The amount of surface area an object has relative to its volume. It rises as structures shrink, making surface atoms more influential.
Quantum dot: A semiconductor nanocrystal whose electronic states are confined in three dimensions. Its emission color can change with particle size through quantum confinement.
Nanoporous material: A solid containing pores with nanoscale dimensions. Its large internal surface area supports separation, storage, and catalytic uses.
Molecule: A group of atoms held together by chemical bonds as a discrete unit. Nanostructures contain many atoms and often retain material-like collective properties.
Quantum confinement: The restriction of charge carriers to small regions, which changes their allowed energy states. It can make a nanostructure's electronic and optical behavior size-dependent.
Superparamagnetism: A magnetic state in which a small particle's moment fluctuates thermally while responding strongly to an applied field. It can emerge in sufficiently small magnetic nanostructures.

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