A Monte Carlo Model for the Formation of Core−Shell Nanocrystals in Reverse Micellar Systems

Abstract

The process of formation of core−shell nanocrystals, using a reverse micellar system, has been modeled using the Monte Carlo technique, and the post-core route for the formation of core−shell nanocrystals has been studied. The model is divided into two parts: (a) the formation of core nanoparticles and their subsequent growth due to coagulation, and (b) the formation of the shell via the ion-displacement mechanism. The model for core nanoparticle formation and subsequent growth includes the phenomena of finite nucleation, growth via intermicellar exchange, and coagulation of nanoparticles after their formation. The growth of the core is taken to be limited by the size of the micellar core. The model explains the possible mechanism of core−shell nanocrystal formation. The simulation results compare well with those observed experimentally.

Modeling Shell Formation in Core−Shell Nanocrystals in Reverse Micelle Systems

“…Ion-Displacement Mechanism. The model for the ion-displacement mechanism proposed by Jain et al assumes that when the outer surface of the core particle is fully covered by Ag 2 S ions no further displacement can take place. A new Ag + ion would be able to displace a Cd 2 + ion via the displacement reaction, subject to the availability of Cd 2 + ions on the surface of the core−shell crystal.…”

“…Although there are many models for the precipitation of nanoparticles in reverse micelles, there are very few investigations that have attempted to understand the mechanism of the formation of complex nanostructures such as core−shell nanoparticles, nanodisks, and so forth. Jain et al have modeled the process of the formation of core−shell nanoparticles in reverse micelles. Their model deals with shell formation via an ion-displacement mechanism and predicts the experimental results of Han et al In the current model, we investigate an alternative mechanism for shell formation in core−shell nanoparticles and analyze the conditions under which different mechanisms may operate and compete with each other.…”

Designing Bimetallic Nanoparticle Structures Prepared from Microemulsions

“…One of the most extensively studied ways to obtain nanoparticles is the microemulsion method. From the pioneering research of Boutonnet and her co-workers, water-in-oil microemulsions have successfully been employed to produce a variety of nanoparticle shapes and sizes, − including metals, − silica and other oxides, , polymers, , semiconductors, superconductors, and particles with a core–shell structure. − In this technique, small quantities of water are added to a solution of surfactant/oil. The resulting mixture, called water-in-oil microemulsion, consists of nanometer-size water droplets which are dispersed in a continuous oil medium and stabilized by surfactant molecules.…”

Mechanism of YF3 Nanoparticle Formation in Reverse Micelles

“…This article focuses on nanoparticle synthesis via the reverse microemulsion method. This method has been employed for the preparation of nanoparticles from a diverse variety of materials, including metals, − silica , and other oxides, − semiconductors, − polymers, − and even superconductors. − It has also been used to obtain particles with core–shell architectures. − The reverse microemulsion method can be applied to a wide range of materials because it is based on simple aqueous-phase reactions. In principle, any reaction between water-soluble reagents that does not destabilize the microemulsion can be carried out in the reverse micellar environment.…”