Engineering SI-RAFT-Modified Nanoparticle Surfaces for Reusable Photocatalysis of Oxidation Reactions

• Hannah Yang, Material Science, Pennsylvania State University

• Christian Pester, Materials Science and Engineering, University of Delaware

Photocatalysis harnesses visible light to drive chemical reactions under mild conditions, enabling cleaner and more effective processes in plastic recycling, wastewater cleaning, and photodynamic medical treatment. However, challenges in homogeneous photocatalysis include poor catalyst recovery, product contamination, and limited light penetration, reducing overall reaction efficiency and sustainability. This work investigated dye-functionalized silica nanoparticles as reusable heterogeneous photocatalysts with high interfacial area and simple recovery. Polymer brushes grown by SI-RAFT intermediated the tethering of Rhodamine B (RhB) dye to the nanoparticle surfaces. These RhB-coupled silica nanoparticles catalyzed the oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone (DMSO₂) as a model reaction, indicating that the photocatalyst’s light activation generated singlet oxygen (1O2), a highly reactive species useful in many applications. Nanoparticles maintained photocatalytic functionality across five subsequent tests and demonstrated consistent retrievability of up to 99.8 wt.%. To optimize reaction variables, solvent comparisons showed improved photocatalysis with polymer brush swelling. Having established consistent retrievability and sustained reusability with the SiO2~RhB configuration, we tested silica-coated iron oxide nanoparticles as magnetically recoverable heterogeneous photocatalysts, replacing centrifugation with faster magnetic separation. Coupling Eosin Y with the Fe3O4-SiO2 nanoparticles confirmed that the surface polymer configuration is compatible with multiple photocatalytic dyes. The resulting magnetic Fe3O4-SiO2~EY nanoparticles successfully accelerated a depolymerization reaction, demonstrating the platform’s versatility across different photocatalysts and chemical reactions. Collectively, these findings advance efficient catalyst-product separation and confirm recycled photocatalyst functionality, supporting more sustainable implementation as photocatalytic applications continue to expand.