1. Introduction to size and shape effects

Nano-objects can have very different properties to the massive materials from which they are derived. Their properties derive from three size-related characteristics: (i) the high ratio between the number of surface atoms and the number of volume atoms, (ii) quantum confinement and (iii) the possible absence of defects. The size below which the properties of a nano-object differ quantitatively and/or qualitatively from those of a bulk object depends on the property under study, and more precisely on the critical lengths characteristic of the property.