The impact of the confinement of reactants on the metal distribution in bimetallic nanoparticles synthesized in reverse micelles

Abstract

SummaryA kinetic study on the formation of bimetallic nanoparticles in microemulsions was carried out by computer simulation. A comprehensive analysis of the resulting nanostructures was performed regarding the influence of intermicellar exchange on reactivity. The objects of this study were metals having a difference in standard reduction potential of about 0.2–0.3 V. Relatively flexible microemulsions were employed and the concentration of the reactants was kept constant, while the reaction rate of each metal was monitored as a function of time using different reactant proportions. It was demonstrated that the reaction rates depend not only on the chemical reduction rate, but also on the intermicellar exchange rate. Furthermore, intermicellar exchange causes the accumulation of slower precursors inside the micelles, which favors chemical reduction. As a consequence, slower reduction rates strongly correlate with the number of reactants in this confined media. On the contrary, faster reduction rates are limited by the intermicellar exchange rate and not the number of reactants inside the micelles. As a result, different precursor proportions lead to different sequences of metal reduction, and thus the arrangement of the two metals in the nanostructure can be manipulated.

AOT direct and reverse micelles as a reaction media for anisotropic silver nanoparticles functionalized with folic acid as a photothermal agent on HeLa cells

“…In the case of RMs, we used only one reducing agent, because in this systems the reaction is carried out in a confined environment (nanoreactor) where the properties of the aqueous medium are different from those of bulk water [41]. This confined environment allows controlling the shape and size [62]. In the case of this work, we used AOT, which is solubilized in isooctane and carry out the formation of spherical micelles [16] within which generates the reaction.…”

Core‐Shell Nanocatalysts Obtained in Reverse Micelles: Structural and Kinetic Aspects

“…The whole speed at which nanoparticle is built up depends not only on the chemical reduction rates but also on the intermicellar exchange rate and concentration. The final nanoparticle was proven to be due to the particular combination of these three factors, which in turn determine the particular sequence of deposition of the two metals on the growing particle [38]. The simulation model allows us to monitor the number of metal atoms produced in all micelles as the synthesis advances.…”

“…As an example, it was proved that the usual definition of pH cannot be employed inside micelles [37]. So chemical kinetics in micelles must take into account the compartmentalization of the reaction media [38]. Although the fact that reactants are trapped into micelles plays a key role in metal arrangement in bimetallic nanoparticles, studies in this direction are limited.…”