The nanoscale is a range of dimensions conventionally around – nanometres, where a nanometre is metres. It describes a length scale, not a distinct substance. A film can have nanoscale thickness while extending over a macroscopic area.[ref]
Properties change when a relevant dimension approaches a physical length controlling the behaviour, such as an electronic confinement length or a characteristic surface region. For a sphere, surface area divided by volume is , so reducing its radius increases the relative importance of its surface. Nanoscale geometry can consequently influence chemical reactions and interaction with light even without changing the constituent chemical element.[ref]
What Is So Special about Nano? by the National Nanotechnology Coordination Office. Size-dependent properties and surface effects
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