Influence of silicon-modified TiO₂ nanocomposites on the photocatalytic degradation of methyl orange and imidacloprid

Titanium dioxide (TiO₂) and its composites are widely investigated for environmental remediation due to their favorable physicochemical properties. In this study, Si/TiO₂ nanocomposites were synthesized by incorporating a very low amount (0.1 wt%) of silicon nanoparticles prepared via a free-space reactor (FSR) into a TiO₂ matrix using a sol–gel method. Three types of silicon nanoparticles with distinct intrinsic properties, denoted as Si(1), Si(2), and Si(3), were employed to systematically evaluate the influence of silicon structure on photocatalytic performance under identical synthesis conditions. The photocatalytic activity of the nanocomposites and pristine TiO₂ was assessed using two reference pollutant molecules widely reported in the literature, methyl orange as a model dye and imidacloprid as a representative persistent organic contaminant, under UV, UV + visible, and visible-light irradiation using low-energy light sources. Among the investigated samples, Si(1)/TiO₂ exhibited the highest photocatalytic efficiency, achieving degradation rates of 94 % for methyl orange (UV irradiation, 240 min) and 60 % for imidacloprid (UV irradiation, 360 min), outperforming pristine TiO₂ (76 % and 53 %, respectively). The enhanced performance is attributed to improved interfacial charge transfer, optimized textural properties, and extended light absorption induced by silicon incorporation. The research demonstrates that Si/TiO₂ nanocomposites with ultra-low silicon content and reduced energy input represent promising, energy-efficient photocatalysts for sustainable water treatment and environmental remediation applications.