= Nanoscale
The <nanoscale> is a range of dimensions conventionally around $1$–$100$ <nanometres>, where a <nanometre> is $10^{-9}$ <metres>. It describes a length scale, not a distinct substance. A film can have nanoscale thickness while extending over a macroscopic area.<About Nanotechnology by the National Nanotechnology Coordination Office>[Definition and scale]{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 $3/r$, 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>.<What Is So Special about Nano? by the National Nanotechnology Coordination Office>[Size-dependent properties and surface effects]{ref}
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