(784f) Reversible Ionic Surfactants for the Preparation of Monodisperse, Supported Nanoparticles

The preparation of monodisperse supported nanoparticles remains a non-trivial task. Organic surfactants are usually required to passivate the surface of nanoparticles to limit their growth to control the size of the particles. Calcination or annealing is typically required following the deposition of the particles onto a catalyst support to remove the surfactant. This calcination/annealing typically causes growth of the nanoparticle, destroying the monodispersity created during the synthesis. This undesired growth can additionally lead to a decline in the catalytic activity of the nanoparticles.

We present the use of Reversible Ionic Surfactants (RevIS) for the preparation of supported, monodisperse nanoparticles. RevIS are switchable molecules which display drastically different properties when an external physical stimulus is applied. The RevIS can be â??turned-onâ? to template nanoparticles to aid in the synthesis and then â??turned-offâ? to release a base nanoparticle for deposition onto a catalyst support. The RevIS contains an amine functionality which is capable of reacting with CO₂ to form the Ionic Surfact. The templating synthesis via a hypothesized reverse-micelle process allows for the creation of monodisperse nanoparticles controllable by varying the size of the RevIS or the continuous phase. The template is broken by "reversing" the RevIS by simply heating the solution to drive off the CO₂ in the presence of a catalyst support. The deposition of a bare nanoparticle allows for the formation of highly active supported nanoparticles that do not require calcination thus maintaining the monodispersity of the nanoparticles. Supported gold nanoparticles prepared using RevIS are more active than their traditionally prepared counter-parts while requiring less processing thus maintaining the size of the nanoparticle catalysts throughout the preparation.