(179d) Combining Oxidases and Metal Nanoparticles for Sequentially Catalyzed Reactions

There is great potential in combining heterogeneous metallic nanoparticle catalytic active sites and enzymatic active sites for selective chemical transformations. This work combines enzymes, namely oxidases, and metallic nanoparticles into one hybrid material for sequential catalytic reactions, analogous to substrate channeling. We investigate the cooperativity between the metallic and oxidase catalytic active sites in two selective oxidation reaction systems.

This presentation will include the synthesis and catalytic application of monometallic Au and Au alloy nanoparticles capped with glucose oxidase enzymes. Au and Au alloy nanoparticles are known to be selective oxidation catalysts when using hydrogen peroxide as an oxidant. Hydrogen peroxide will be generated by the oxidase enzyme using glucose as a substrate in both systems. In the first system, glucose itself will be oxidized twice, once by the glucose oxidase and the oxidized product, gluconic acid will be oxidized again by Au or Au alloy nanoparticles to form glucaric acid. In a second system, benzyl alcohol is oxidized to benzaldehyde by the Au or Au alloy nanoparticles using the hydrogen peroxide generated by the glucose oxidase. Cooperativity is demonstrated between the glucose oxidase and the metallic nanoparticles through increased production of the oxidized products in the hybrid system versus the metallic nanoparticles on their own. The effect of the alkalinity of the solution on the catalytic performance is also observed for both systems. The relationship between the composition of the alloy and the oxidation rates and selectivity will also be presented.