Congratulations to Dr. Joris Keok on a successful PhD defense, during which he defended his PhD thesis, supervised by Prof. Bert Weckhuysen and Dr. Freddy Rabouw.

In his PhD thesis, Joris advanced the understanding and application of Surface-Enhanced Raman Spectroscopy (SERS) and Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) in heterogeneous catalysis research. While SERS can enhance Raman signals by up to 10¹¹ times through electromagnetic “hot spots” on nanostructured metal surfaces, Joris critically examined both the advantages and limitations of this technique. He demonstrated that signal enhancement in isolated locations can be disadvantageous in complex systems, requiring extremely careful data evaluation.

Joris investigated new SERS substrates with controlled interparticle spacing using polymer spacers, though these proved limited for detecting catalytic phenomena. A pivotal finding came from his systematic investigation of the SHINERS technique, where he showed that silica shells were not as perfectly isolating as commonly presumed in the literature. He demonstrated that small gaseous molecules easily permeate such shells and that SERS spectra themselves contain valuable information about metal surface-bonding through modulated peak positions and widths.

Finally, Joris explored the potential of picocavities for enhancing signals from weakly scattering molecules, potentially enabling single-molecule detection of catalytic events. He observed picocavity-like behavior with catalytically active metals, including Ru, Pt, and Pd nanoparticles.