An INS-MAPS Study on Adsorption-induced Vibrational Features of Methylene Blue and Methyl Orange on TiO2-modified Mesoporous Silica

The extensive use of synthetic dyes in the textile industry estimated at 700,000 tons annually poses serious environmental challenges, as a significant fraction of these compounds, including methylene blue (MB) and methyl orange (MO), are released into water bodies without adequate treatment. Titanium dioxide (TiO2) is a widely studied photocatalyst for pollutant removal due to its stability, low cost, and non-toxicity. However, its performance is limited by low surface area and rapid charge-carrier recombination. Integrating TiO2 with mesoporous silica offers a promising strategy to overcome these limitations by increasing surface area, improving adsorption, and enhancing mass transport to active sites. Our preliminary studies indicate that TiO2-modified mesoporous silica exhibits superior dye-removal efficiency and faster kinetics compared to its individual components, suggesting a strong synergistic effect between adsorption and photocatalysis. To probe this synergy at the molecular level, this work proposes the use of inelastic neutron scattering (INS) on the MAPS. The experiment will target the high-energy stretching region (2400-4000 cm-1) to identify adsorption-induced vibrational features, chemical interactions, and potential intermediate species of MB and MO on TiO2-modified mesoporous silica. Complementary measurements are proposed on TOSCA to capture the low-energy vibrational region.