In Situ Crystallization and Growth Dynamics of Acentric Iron Iodate Nanocrystals in w/o Microemulsions Probed by Hyper-Rayleigh Scattering Measurements

A detailed experimental investigation of the formation mechanisms of acentric iron iodate [Fe(IO3)3] nanocrystals in AOT-based reverse micelles according to the water-in-oil (w/o) microemulsion (ME) composition and temperature was performed. A low chemical reaction rate was first demonstrated by means of UV−vis absorption spectroscopy. Attainment of iron iodate crystalline nanorods was then attributed to an oriented aggregation mechanism of 10−20-nm amorphous primary nanoparticles. As for the intermicellar exchange of reactants, the aggregation mechanism was also found to be determined by the ME composition because clear effects of the surfactant and reactant concentrations, the nature of the oil phase, and the water droplet size were observed. Moreover, a combination of dynamic light scattering, X-ray diffraction, and transmission electron microscopy experiments revealed that hyper-Rayleigh scattering is a fast, valuable, and nondestructive alternative to probe, in real time, the crystallization and formation dynamics of acentric nanoparticles in microemulsions. This experimental approach can be extended to studies dealing with the formation of metal nanoparticles for which scattering of second-harmonic light is readily observed.