nanòmetres

A nanometre (nm) is a unit of length equal to one billionth of a metre (10^-9 m). The prefix nano- denotes a factor of 10^-9 in the metric system, and the nanometre is a key scale in the study of nanoscale phenomena. In practical terms, it is used to describe objects and features of nanometer size, as opposed to micrometres (10^-6 m) or metres.

The nanometre scale encompasses the sizes of many molecules and structures. For example, the width of DNA is about 2 nm; typical proteins range from a few to several nanometres in size; lipid and mineral nanoparticles vary widely from a few to a few hundred nanometres. Biological cells are generally micrometres in size, so nanoscale features exist well within larger organisms.

Measuring and fabricating at the nanometre scale relies on specialized techniques. Electron microscopes, including transmission and scanning electron microscopes, can resolve features below 1 nm. Scanning probe methods such as atomic force microscopy and scanning tunneling microscopy visualize and manipulate surfaces at the nanoscale. Fabrication methods include top-down lithography and bottom-up chemical synthesis.

Nanometres are central to nanotechnology and modern electronics. Transistor features in cutting-edge integrated circuits are described in nanometre process nodes (for example, 5 nm or 7 nm). In materials science and medicine, nanoscale materials such as graphene, carbon nanotubes, and nanoparticles enable new properties and functions, including catalysis, drug delivery, and imaging.

Because size alone does not determine behavior, assessments of nanoscale materials require consideration of composition, surface chemistry, and exposure. Standards and regulatory definitions of nanoscale materials vary by jurisdiction, but the nanoscale is routinely used as a descriptive term in science and engineering.