Nanosystems and nanostructured matter are terms that presently are very much en vogue, although at best semi-qualitative definitions of these expressions seem to exist. The prefix nano only makes sense when used in connection with physical units such as meters or seconds, usually then abbreviated by nm (nanometer) or ns (nanosecond):

1 Å= 10−8cm= 0.1 nm 1 nm = 10−9m

Quite clearly the macroscopic pre-Columbian statue in Fig. 1.1 made from pure gold nobody would call a nanostructured system because in "bulk" gold the atoms are separated only by few tenths of a nanometer. Therefore, in

FIGURE 1.1: Left: macroscopic golden artifact, right: microscopic structure of fcc Au.