A nanostructure has structural features on the nanoscale. The relevant dimension may be the thickness of a thin film, the diameter of a nanowire, or the overall size of a nanoparticle. A material can therefore be macroscopically large while containing nanostructures internally.
The geometry matters because it changes the relative importance of surfaces, the distances over which charge carriers move, and sometimes the allowed quantum states. A thin film and a nanoparticle made from the same chemical material need not have the same properties: their quantum confinement dimensions and exposed surface areas differ. Characterizing a nanostructure requires specifying which dimensions are small, its shape and its chemical chemical composition, rather than reporting a single size alone.[ref]
About Nanotechnology by the National Nanotechnology Coordination Office. Nanoscale dimensions and differences from bulk materials
Nanostructures are materials or objects with dimensions in the nanometer range, typically between 1 and 100 nanometers (1 nanometer is one billionth of a meter). At this scale, the physical and chemical properties of materials can differ significantly from those of the same materials in bulk form due to a high surface-area-to-volume ratio and quantum effects.
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