Nanoparticule

A nanoparticule is a assembly of a few hundreds to a few thousands of Atomes, leading to a Objet of which at least one of its dimensions is of nanometric size (1 to 100 Nm).

The nanoparticules are located at the border between the matter on a macroscopic scale and an atomic or molecular scale. They have an interest at the same time fundamental and applied and are very studied currently. Many physicists and chemists synthesize them, other physicists study them in order to include/understand the physics of these objects nanometric and of the biologists use them as cellular markers.

The characteristics of materials change when their sizes approach those of the nanoparticules. That is due partly to the fact that the surface of a material plays an increasingly large part in its physical properties when its size decrease; whereas surface is negligible in the case of a macroscopic material, the percentage of the atoms of a nanoparticule pertaining to its surface is far from being negligible. Inter alia, one can note that:

the temperature of fusion of a pure Substance of macroscopic size is identical to its temperature of Solidification (0°C for water for example). For a nanoparticule, that is not true any more and the material present a Hystérésis centered around the temperature of Transition from phase of the macroscopic pure substance, this hysteresis depends on the size of the nanoparticule;
the Dureté of a macroscopic material is not same as that of material nanometric.
the dynamics of the interaction between the electrons of a nanoparticule and the modes of vibration of its crystal lattice (phonons) depends drastiquement on the size of the nanoparticule.

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