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Multimodal in-situ spectroscopy of novel enzyme mimics with optofluidic microreactors https://doi.org/10.17863/CAM.124936 Ellis, Matthew Euser, Tijmen Fruk, Ljiljana Photocatalysis plays a key role in ensuring a more sustainable future through harnessing the power of the sun for solar fuel production, degrading harmful environmental pollutants and driving the green synthesis of valuable organic products. Despite their significant potential, the current performance of photocatalysts is insufficient for widespread deployment in sustained practical applications. This has created the demand to design and optimise novel photocatalysts with enhanced properties to overcome limitations such as poor photostability, recyclability and specificity. However, this requires a detailed understanding of photocatalytic kinetics, mechanisms and reaction intermediates. To tackle these issues, this thesis explores strategies to improve flavin-based photocatalysts, including the immobilisation of riboflavin tetraacetate (RTA) onto Laponite clay (Flaponite) and the synthesis of silver and gold alloy nanoparticles (Ag-AuNP) for plasmon-enhanced photocatalysis. Flaponite demonstrated superior recyclability compared to RTA alone, allowing for the repeated degradation of the harmful azo dye pollutant amaranth in water. Both surfactant and surfactant-free approaches for the synthesis of Ag-AuNP were developed, allowing for highly tuneable size, shape and elemental composition properties. In addition, an optofluidic microreactor utilising hollow-core photonic crystal fibres (HC-PCF) was developed to monitor photocatalysis using in situ absorbance, fluorescence, and Raman spectroscopy in sub-microlitre volumes. By combining all three spectroscopic techniques onto a single setup, the approach allowed for the rapid characterisation of deazaflavin, an emerging photo-reductive catalyst. Crucially, this work demonstrates, for the first time, the in-situ monitoring of a photocatalytic reaction within a microreactor using Raman spectroscopy, highlighting the potential for this setup to be a powerful tool for identifying reaction intermediates. Finally, this thesis concludes with an examination of HC-PCF surface functionalization strategies that have the potential to explore heterogeneous photocatalysis. University of Cambridge 2025-09-27 Thesis Doctoral Doctor of Philosophy (PhD) eng https://www.repository.cam.ac.uk/handle/1810/395419 embargo 2027-01-15 https://www.repository.cam.ac.uk/bitstreams/c068b93e-7106-402a-a616-400323433da5/download 5a69dc6be129367b6604348033f7b43c https://www.repository.cam.ac.uk/bitstreams/c9a7c19d-d950-4373-b371-6ad8c8113dab/download 87eda9de84448d1f82354d60eee3eb5f https://creativecommons.org/licenses/by/4.0/ Optofluidics Photocatalysis Plasmonics Raman spectroscopy