In bottom up synthesis, the nanoparticles are built from smaller
entities, for example by joining atoms, molecules and smaller particles
(Mukherjee et al., 2001). In bottom up synthesis, the nanostructured
building blocks of the nanoparticles are formed first and then
assembled to produce the final particle (Thakkar et al., 2010). The
bottom up synthesis mostly relies on chemical and biological
methods of production. The probable mechanism of nanoparticle
synthesis by bottom up approach is shown in Fig. 2.