As reported by Dasgupta et al and is expressed using the Arrhenius relation, τN = τ0 exp (EA/kBT), where kB is the Boltzmann's constant, T is the temperature and τ0 is the attempt time characteristic of the material (10 -13 -10 -9 s) . However, the Brownian relaxation mechanism is much controlled by the viscosity of the medium (η) in which the nanoparticles are suspended and is given by τB