Understanding Nanoparticle Synthesis and Processing

Nanoparticles lie at the heart of catalysis: small metal clusters which enable chemistries to occur at moderate conditions and at industrially-necessary reaction rates. There are fundamental challenges for industrial catalysis when using nanoparticles: 1) control of the size of nanoparticles during synthesis, 2) recycling and reuse of colloidal nanoparticle catalysts, and 3) depositing and activating supported nanoparticle catalysts.

We have made significant advancements in understanding commonly utilized nanoparticle synthesis techniques, in using tunable solvents to purify, recover, and reuse dispersed, polymer-stabilized nanoparticle catalysts, and in the preparation of supported nanoparticle catalysts which are highly active and sinter-resistant using Switchable Surfactants. We have used Pulsed-Field Gradient (PFG) NMR to measure the self-diffusion coefficients of nanoparticle-ligand complexes to conclusively determine the mechanism of nanoparticle formation using quaternary-ammonium surfactants and demonstrated how to leverage that mechanism to control the size of nanoparticles . We have developed a technique to control the dispersibility of polymer-stabilized nanoparticle catalysts in order to separate them from a product mixture, recover the nanoparticles, and reuse the nanoparticle catalysts in additional reactions. This was possible via a high-pressure, tunable, CO2-induced phase separation in a solvent mixture allowing for the control of the polymer-solvent interactions. This technique can recover more than 99% of the dispersed nanoparticles and reuse the catalysts as the catalytic activity was maintained throughout the recovery process.

Publications

Reynolds, S. R., Markland, K., Rood, J., Leonard, E., Saunders, S. R. “Manipulating Ligand-Nanoparticle Interactions and Catalytic Activity through Organic-Aqueous Tunable Solvents.” RSC Advances, 2016, 6, 78496-78504

Collaborators

Ryan Renslow – PNNL
Niri Govind – PNNL