Abstract—This study reports the structural, optical, and photocatalytic characteristics of Si, Ti, and Silica-Titania-Manganese (STiM) nanocomposites synthesized under controlled conditions. X-Ray Diffraction (XRD) revealed distinct differences in crystallinity, with Si exhibiting the highest crystallinity (67.31%) and the smallest crystallite size (0.159 nm), Ti showing moderate crystallinity (56.3%, 0.223 nm), and STiM displaying the lowest crystallinity (42.2%) with the largest crystallite size (0.302 nm), indicating composite-induced disorder. Fourier-Transform Infrared (FTIR) spectra confirmed the presence of Si–O–Si vibrations in Si, Ti–O and Mn–O bonds in Ti, and combined features in STiM, suggesting strong interfacial interactions. Scanning Electron Microscopy (SEM) revealed particle sizes of 168 nm (Si), 932 nm (Ti), and 300 nm (STiM), while Energy-Dispersive X-ray (EDX) analysis confirmed the presence of TiO₂, SiO₂, and Mn dopants (0.37%) in the composite. Brunauer–Emmett–Teller (BET) analysis demonstrated significant differences in surface area, with Si exhibiting the highest SBET (763.2 m²/g) and STiM showing hierarchical microporous–mesoporous structures. UV-Vis Diffuse Reflectance Spectroscopy (UV-DRS) revealed bandgap narrowing in STiM (indirect Eg = 1.08 eV), enhancing visible-light absorption. Photocatalytic tests against methylene blue showed superior performance of STiM (77.4%) compared to Ti (27.4%) and Si (7.4%), with adsorption kinetics best described by the pseudo-second-order model. These results highlight the synergistic role of Si–Ti interactions and Mn doping in optimizing photocatalytic activity.
Keywords—Si-Ti-Mn, nanocomposites, visible-light photocatalysis, methylene blue degradation, pseudo-second-order kinetics, bandgap narrowing
Cite: Maria Ulfa and Amellia Ardhany, "Methylene Blue Photodegradation over STiM Composite," International Journal of Environmental Science and Development vol. 17, no. 4, pp. 328-338, 2026.
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