Tiny filaments and cylinders are studied for possible uses
in energy, electronics, optics and other fields.
Nanowires and nanotubes, slender structures that are only a
few billionths of a meter in diameter but many thousands or millions of times
longer, have become hot materials in recent years. They exist in many forms —
made of metals, semiconductors, insulators and organic compounds — and are
being studied for use in electronics, energy conversion, optics and chemical
sensing, among other fields.
The initial discovery of carbon nanotubes — tiny tubes of
pure carbon, essentially sheets of graphene rolled up unto a cylinder — is
generally credited to a paper published in 1991 by the Japanese physicist Sumio
Ijima (although some forms of carbon nanotubes had been observed earlier).
Almost immediately, there was an explosion of interest in this exotic form of a
commonplace material. Nanowires — solid crystalline fibers, rather than hollow
tubes — gained similar prominence a few years later.