Magnetic and Plasmonically Active Supports for Singlet Oxygen Photocatalysis

Our group has worked on the design of novel nanoplasmonic systems for their use as photocatalysts applied to organic transformations,¹ including the use of Ag nanocubes for hydrogen activation and hydrogenation of ketones and aldehydes,² and Ru decorated Au nanoparticles able to tackle the difficult arene hydrogenation under mild conditions.³ Plasmonic nanomaterials are also powerful antennae for other types of photocatalysts. In this talk I will focus on the work we did towards enhancing the properties of photocatalysts in the context of organic transformation. We designed a silica-covered Ag nanosupport to enhance the performance of tris(bipyridine)ruthenium in singlet oxygen triggered C=C oxidation.⁴ The excitation of the surface plasmon resonance of the Ag core enables an enhancement of both the catalytic activity as well as fluorescence of the dye, which is dependant on the distance between them. Transmission Electron Microscopy - Electron Energy Loss Spectroscopy allowed to gain insight into the intensity of the surface plasmon resonance around the plasmonic metal in this system. In an effort to understand the generality of such systems, we have also explored the effect of this support onto two other dyes: Rose Bengal and methylene Blue.⁵ This study has allowed us to better understand the effect of plasmonic enhancement as a function of the dye excitation wavelength (and its overlap with the surface plasmon resonance of the support) and of the quantum yield of the free dyes. This work will help expand the use of these strategies in the context of organic transformations. Finally, we have also work on magnetic supports for such dyes, as this approach could help their recovery. In this example, we studied how magnetic materials, such as iron nanoparticles, who strongly absorb light and compete with the dye for photons, have been modified to improve their efficacy.⁶