Nanoparticles have unique technical characteristics due to their extremely small size (in the order of a few nanometers). Their properties differ from those of large-scale materials due to their large surface area and smaller volume. Nanoparticles are present everywhere and many innovations in various fields are based on these very special compounds. The great difficulty in the process of controlling these elements lies in the wide variety of existing nanoparticles that can differ in shape, size, as well as in chemical composition and physicochemical properties.
The INRS defines nanomaterials as "a material with at least one external dimension on the nanometric scale, i.e. between 1 and 100 nm, or with an internal or surface structure on the nanometric scale" (definition found in the ISO TS 80004-1 standard). The European Commission considers a threshold concentration of 50% of nanoparticles to define a nanomaterial.
Nano-objects can be synthesized in different forms, including spheres, tubes, rods, thin films... They can be classified according to their size for each of their dimensions in three distinct categories :
Moreover, nanomaterials can be composed of chemical elements: carbon, polymers, metals, biological molecules... This further diversifies these particular elements.
Among the specific properties of nanoparticles can be cited: