Coagulation of Nanoparticles in Reverse Micellar Systems:  A Monte Carlo Model

Abstract

The process of formation of nanoparticles obtained by mixing two micellized, aqueous solutions has been simulated using the Monte Carlo technique. The model includes the phenomena of finite nucleation, growth via intermicellar exchange, and coagulation of nanoparticles after their formation. Using the model, an exploratory study has been conducted to analyze whether the coagulation of nanoparticles is the reason for the formation of nanoparticles whose sizes are comparable to the size of the reverse micelles. The model explains the possible mechanism of coagulation of semiconductor nanoparticles formed within reverse micelles and its effect on the evolution of their size with time. The model is predictive in nature, and the simulation results compare well with those observed experimentally.

Formation of Gold Nanoparticles in Water-in-Oil Microemulsions: Experiment, Mechanism, and Simulation

“…The above model was further extended by Jain et al and Ethayaraja et al to incorporate the particle–particle coagulation event during coalescence and redispersion of drops and predict the mean diameter of CdS nanoparticles. They considered that if two drops containing nanoparticles coalesce, then coagulation of particles occurs in such a way that it results in one empty drop and another drop containing a bigger coagulated particle.…”

“…Though this model was developed to predict the diameter of CdS and Fe(OH) 3 nanoparticles, experimental data of various metallic and bimetallics such as Au, CdS, BaSO 4 , CdS@Ag 2 S, CdS− ZnS, and PtBi nanoparticle diameter were well predicted using this generalized model. 27−33 The above model was further extended by Jain et al 34 and Ethayaraja et al 29 to incorporate the particle−particle coagulation event during coalescence and redispersion of drops and predict the mean diameter of CdS nanoparticles. They considered that if two drops containing nanoparticles coalesce, then coagulation of particles occurs in such a way that it results in one empty drop and another drop containing a bigger coagulated particle.…”

Metal Support Interactions in Co3O4/Al2O3 Catalysts Prepared from w/o Microemulsions

“…In the oil rich area of the ternary phase diagram of this mixture, small water droplets, stabilized by a surfactant layer, form in the oil continuum referred to as reverse micelles. Although these confined water droplets have been shown to undergo exchange of matter through fusion and separation [6,7] the reverse micelles have been successfully used as nano-reactors/templates for the formation of precipitates, as the size, geometry and nature of the precipitate is dependent on the size and nature of the reverse micelle [8][9][10][11][12][13][14]. While long known for its suitability to produce nano-sized metal/metal salt crystallites, the use of reverse micelles for the preparation of heterogeneous model catalysts has first been postulated only in the early 1970s [15] and it has since then been used by several researchers for a large number of microemulsion and metal precursor systems [3,4].…”

Predicting Complete Size Distribution of Nanoparticles Based on Interparticle Potential: Experiments and Simulation

“…It is defined as the fraction of collisions resulting in complete fusion, a factor that attempts to include the effects of different coating agents, solvents etc. into a single, lumped parameter. − This efficiency term is generally fitted to match the experimental, primary particle diameter. Other attempts have used more than one fitting parameter in an ad hoc fashion. , However, most of these works did not consider all the constituent steps from the beginning of the particle formation process, namely, nucleation and diffusion- and coagulation-growth rates of particles, which is essential to predict the final PSD.…”