Highly Efficient Plasmonic Membrane Flow Reactor

A plasmonic flow reactor, consisting of thin Au film at exits of monolithic anodized aluminum oxide (AAO) membranes under LED illumination is demonstrated. The system shows over 200% quantum efficiency (QE) for peroxide activation and the ability to limit to single oxidation reaction by controlling residence time with flow rate and pore geometry. Periodic pore arrays (20-200 nm diameter) with 25 nm thick Au on AAO are modeled by finite-difference time-domain (FDTD) simulations and predicted largest E-field enhancements for the larger 200 nm pore diameters. Peroxide activation, as measured by O-2 generation is most efficient with a 200 nm pore diameter system under 523 nm LED illumination. The optimal wavelength falls near the absorption peak of Au@AAO with 200 nm pore diameter suggesting that hot electron generated from gold plasmonic response is the primary mechanism for activation of H2O2. QE for gold plasmonic flow system calculated from O-2 generation experiments is as high as 250%, which indicates a mechanism of hot-electron activation of peroxide that leaves a still energetic hot-electron to catalytically activate multiple reactions. The formation of Au surface oxides that are catalytically active in dark is also observed and must be accounted for in Au plasmonic photochemical studies.

Automated summary

The study demonstrates a plasmonic flow reactor utilizing thin gold film at exits of monolithic anodized aluminum oxide membranes under LED illumination. By controlling residence time with flow rate and pore geometry, the system achieves high efficiency for peroxide activation and restricts reactions to single oxidation. The mechanism primarily involves hot electron generation from gold plasmonic response.