Au Bipyramids@mSiO2 Core-Shell Nanoparticles for Singlet Oxygen Photooxygenations in Continous-Flow Microreactors

Gold nanomaterials display interesting plasmonic features with potential application in various fields depending on the size and shape of the metal nanostructures. Synergy between Au nanoparticles and chromophores can enhance the photophysical properties of nearby
molecules1. Au bipyramids (AuBPs) exhibit intense and well-defined plasmon resonance, easily
tunable with the aspect ratio. In Rose Bengal-NPs systems for the production of singlet oxygen (1O2), it is now well established that the control of the dye-to-nanoparticle distance ranging from 10 to 20 nm is crucial to achieve the proper coupling between the plasmon resonance and the dye1,2. We have developed AuBPs@mSiO2 core-shell nanostructures to control the distance between metallic surface and photosensitizers in order to increase the production of 1O2 (metal-enhanced 1O2 production – ME1O2). An enhancement of 1O2 generation has been shown for the obtained anisotropic AuBPs and AuBPs@mSiO2 in presence of RB using three indirect methods of 1O2 detection, namely Electron Paramagnetic Resonance (EPR) with TEMP as chemical trap in situ under visible photoexcitation3, photooxidation of the fluorescence probe anthracene dipropionic acid (ADPA), and photooxygenation of methionine to methionine sulfoxide in a continuous-flow
microreactor4.