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<p>A novel anhydrous sol–gel synthesis of carbon-modified silicon dioxide nanoparticles (SiO-NPs) is reported, utilizing oxalic acid as both a catalyst and a structuring agent. This unique approach facilitates the formation of a silicon oxalate intermediate network via transesterification, which upon thermal decomposition yields a defect-rich SiO<sub>2</sub> matrix with integrated carbon species (Si–O–C and residual Si–C bonds). Comprehensive characterization by FTIR, XPS, UPS, UV–Vis, and PL confirmed the amorphous nature, sub-stoichiometric Si/O ratio, and the presence of hybridized SiOC states and various intrinsic defect centers, which collectively modify the material's electronic and optical properties, including a reduced band gap and broad photoluminescence. The functional performance was demonstrated in a highly efficient two-stage process for methylene blue removal, achieving 73.95% overall efficiency through initial dark adsorption followed by rapid photo-induced degradation. The photoactivity is attributed to light absorption by carbon-induced defect states, leading to reactive oxygen species generation. This work presents a cost-effective route to synthesize dual-functional nanomaterials, highlighting their potential for advanced water treatment and contributing to the understanding of defect engineering in wide-bandgap oxides.</p>

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Anhydrous sol–gel synthesis of carbon-modified SiO2 nanoparticles: defect engineering for enhanced adsorption and photocatalytic dye degradation

  • 期刊论文

  • 发表日期：

    2025年12月15日

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  • Omar Mahmoud,
  • Djamila Bouazza,
  • M’Hamed Guezzoul,
  • Moumene Taqiyeddine,
  • Hafida Miloudi,
  • El Habib Belarbi,
  • Abdelkader Nebatti Ech Chergui

摘要

A novel anhydrous sol–gel synthesis of carbon-modified silicon dioxide nanoparticles (SiO-NPs) is reported, utilizing oxalic acid as both a catalyst and a structuring agent. This unique approach facilitates the formation of a silicon oxalate intermediate network via transesterification, which upon thermal decomposition yields a defect-rich SiO2 matrix with integrated carbon species (Si–O–C and residual Si–C bonds). Comprehensive characterization by FTIR, XPS, UPS, UV–Vis, and PL confirmed the amorphous nature, sub-stoichiometric Si/O ratio, and the presence of hybridized SiOC states and various intrinsic defect centers, which collectively modify the material's electronic and optical properties, including a reduced band gap and broad photoluminescence. The functional performance was demonstrated in a highly efficient two-stage process for methylene blue removal, achieving 73.95% overall efficiency through initial dark adsorption followed by rapid photo-induced degradation. The photoactivity is attributed to light absorption by carbon-induced defect states, leading to reactive oxygen species generation. This work presents a cost-effective route to synthesize dual-functional nanomaterials, highlighting their potential for advanced water treatment and contributing to the understanding of defect engineering in wide-bandgap oxides.