Simulation of precipitation reactions in reverse micelles

Precipitation involving mixing of two sets of reverse micellar solutions-co ntaining a reactant and precipitant respectively-has been analyzed. Particl e formation in such systems has been simulated by a Monte Carlo (MC) scheme (Li, Y.; Park, C. W. Langmuir 1999, 15, 952), which however is very restri ctive in its approach. We have simulated particle formation by developing a general Monte Carlo scheme, using the interval of quiescence technique (IQ ). It uses Poisson distribution with realistic, low micellar occupancies of reactants, Brownian collision of micelles with coalescence efficiency, fis sion of dimers with binomial redispersion of solutes, finite nucleation rat e of particles with critical number of molecules, and instantaneous particl e growth. With the incorporation of these features, the previous work becom es a special case of our simulation. The present scheme was then used to pr edict experimental data on two systems. The first is the experimental resul ts of Lianos and Thomas (Chem. Phys. Lett. 1986, 125, 299, J. Colloid Inter face Sci. 1987, 117, 505) on formation of CdS nanoparticles. They reported the number of molecules in a particle as a function of micellar size and re actant concentrations, which have been predicted very well. The second is o n the formation of Fe(OH)(3) nanoparticles, reported by Li and Park. Our si mulation in this case provides a better prediction of the experimental part icle size range than the prediction of the authors. The present simulation scheme is general and can be applied to explain nanoparticle formation in o ther systems.