Conclusion
Properties of nano-objects : critical lengths, size and shape effects

As the size of an object decreases, specific effects appear due to the increase in the number of surface atoms compared to the number of volume atoms, quantum confinement effects, the absence (or presence) of specific defects... However, it is impossible to define a universal critical dimension below which the properties of a nano-object differ from those of a bulk material. Indeed, each property is characterized by one or more characteristic lengths below which physical phenomena are greatly modified. When a nano-object has a dimension below such a critical length, its properties will differ from those of the bulk material. So, for example, for a nanoparticle smaller than the mean free path of electrons, it is the collisions of electrons with the surface of the particle that become important. Similarly, a metal nanoparticle smaller than the penetration depth of a wave will have specific...