The methods of synthesis of nanoparticles are well known for a long time as compared to the other nanomaterials. For the synthesis of nanoparticles, the processing conditions need to be controlled in such a manner that the resulting nanoparticles have the following characteristics:
(i) identical size of all particles,
(ii) identical shape,
(iii) identical chemical composition and crystal structure, and
(iv) individually dispersed with no agglomeration.
Nanoparticles can be synthesized by both top-down or bottom-up approaches. Two well-known top-down approaches are milling (or attrition) and thermal cycling. Attrition produces nanoparticles of a wide range of diameter ranging from 20 nm to several hundred nanometers.
The bottom-up methods are more popular than the top-down methods. There are several bottom-up methods such as homogeneous and heterogeneous nucleation processes, microemulsion based synthesis, aerosol synthesis, spray pyrolysis and template-based synthesis.
