The physical behaviour of thin films often remarkably deviates from that of the corresponding bulk material.
For example, a cluster of 20 or 30 atoms typically has a melting point far lower than that of the corresponding bulk.
In particular, the equilibrium phase diagram of nanoparticles differs from the corresponding bulk one.
Through sintering, the nanoparticle films acquired bandgaps similar to those of the corresponding bulk materials and became more conductive.
The coatings produced by reactive plasma spraying showed much higher microhardness and wear resistance than the corresponding bulk material.
Optical properties of metal clusters are more like those of the corresponding bulk metals than like those of the constituent atoms.
Smaller particles are generally more toxic than the corresponding bulk material at the same mass concentration20,21,22, and the mobility, biological fate and bioavailability depend on size, shape, charge and other nanoparticle properties23, 24.
Medium-size clusters have properties that vary smoothly with the number of constituent particles (denoted N), but their properties, such as the melting point, differ significantly from those of the corresponding bulk.
An important consequence is that the vapour pressure of a cluster is higher than the vapour pressure of the corresponding bulk, and accordingly the boiling point of a liquid cluster i.e., the temperature at which the vapour pressure of a liquid is equal to the pressure of the surrounding atmosphere is lower than that of the corresponding bulk liquid.
Although Curie temperatures increase with increasing x, they are significantly lower than those of the corresponding bulk materials.
For comparison, the corresponding bulk materials prepared by reflux or by hydrothermal synthesis have been also prepared.
