Self-Cleaning Ag-TiO2 Heterojunction Grafted on a 3D-Printed Metal Substrate: Photocatalytic Degradation of Rhodamine B and Surface-Enhanced Raman Spectroscopic Monitoring of Kinetics

Surface-enhanced Raman scattering (SERS) spectroscopic “live monitoring” of photocatalytic degradation of an organic compound is considered a promising approach to the environmental remediation and monitoring of organic pollutants. To achieve that, an efficient photocatalyst and SERS-active plasmonic nanostructure need to be incorporated into a single multifunctional substrate. However, mass production of such substrates, their reusability, and prevention of secondary pollution are the major challenges. This present work demonstrated the fabrication of TiO₂, and silver nanostructure-functionalized 3D-printed metal substrates, which are shown here as efficient photocatalysts and highly enhancing SERS substrates. These functional substrates can combine photocatalysis and SERS, therefore, they can be promising candidates for monitoring the reaction kinetics and removal of organic pollutants. Chemically inert and highly rough surfaces of the printed TiAlV substrates pose challenges in the functionalization of these substrates with SERS-active plasmonic silver nanostructures and photocatalytically active TiO₂. The migration of Ti ions from the printed metal structures to the TiO₂ functional layer was a new and unique phenomenon, which was supported by the detailed characterization. Silver nanoparticles were introduced into the TiO₂ functional layer using the electroless deposition method, which renders these substrates SERS and photocatalytically active. These functionalized TiAlV brushes showed excellent photocatalytic activity in removing RhB as well as significant SERS enhancement in Rhodamine B dye sensing. Another advantage of using this alloy composition (TiAlV) was the migration of Ti from the underlying printed TiAlV substrate into the TiO₂/Ag functional layer, which eventually helped to enhance the recyclability of these substrates.