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<p>Graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) was synthesised by thermal polycondensation of melamine and subsequently exfoliated by calcination at 600&#xa0;°C for 30, 45, and 60&#xa0;min. The resulting nanoparticles—differing in morphology, size, and specific surface area—were dispersed in a poly(alkyl siloxane) hydrophobising agent at concentrations of 2&#xa0;g·L⁻¹ and 4&#xa0;g·L⁻¹ and applied to the surface of porous quartz sandstone. The effect of the degree of g-C<sub>3</sub>N<sub>4</sub> exfoliation on the self-cleaning performance of the resulting coatings and their interaction with water was evaluated. Photodegradation tests performed on sandstone samples artificially stained with Rhodamine B confirmed a self-cleaning effect for coatings containing particles exfoliated for 45 and 60&#xa0;min, at a concentration of 4&#xa0;g of g-C<sub>3</sub>N<sub>4</sub> per litre of poly(alkyl siloxane). The addition of nano-g-C<sub>3</sub>N<sub>4</sub> enhanced the hydrophobicity of the sandstone surface. The coatings substantially reduced water uptake into the stone’s pore system while still allowing water vapour to evaporate freely into the surrounding environment. g-C<sub>3</sub>N<sub>4</sub> thus appears to be a promising photocatalytically active nanomaterial for self-cleaning and water-repellent surface protection of building and sculptural stone—a field in which it has not yet been applied.</p>

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Photoactive and water-repellent g-C3N4/poly(alkyl siloxane) coatings on porous sandstone

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月12日

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  • Blanka Kolinkeová,
  • Kryštof Foniok,
  • Jiří Ščučka,
  • Petr Martinec,
  • Vlastimil Matějka

摘要

Graphitic carbon nitride (g-C3N4) was synthesised by thermal polycondensation of melamine and subsequently exfoliated by calcination at 600 °C for 30, 45, and 60 min. The resulting nanoparticles—differing in morphology, size, and specific surface area—were dispersed in a poly(alkyl siloxane) hydrophobising agent at concentrations of 2 g·L⁻¹ and 4 g·L⁻¹ and applied to the surface of porous quartz sandstone. The effect of the degree of g-C3N4 exfoliation on the self-cleaning performance of the resulting coatings and their interaction with water was evaluated. Photodegradation tests performed on sandstone samples artificially stained with Rhodamine B confirmed a self-cleaning effect for coatings containing particles exfoliated for 45 and 60 min, at a concentration of 4 g of g-C3N4 per litre of poly(alkyl siloxane). The addition of nano-g-C3N4 enhanced the hydrophobicity of the sandstone surface. The coatings substantially reduced water uptake into the stone’s pore system while still allowing water vapour to evaporate freely into the surrounding environment. g-C3N4 thus appears to be a promising photocatalytically active nanomaterial for self-cleaning and water-repellent surface protection of building and sculptural stone—a field in which it has not yet been applied.