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<p>Carbon quantum dots (CQDs) have attracted increasing attention in environmental remediation due to their tunable optical properties, high surface functionality, and sustainable synthesis potential. In this study, biomass-derived CQDs were synthesized using the green macroalgae <i>Ulva rigida</i> and incorporated into thermally exfoliated graphitic carbon nitride (TE-g-C₃N₄) to fabricate a sustainable UCQD/TE-g-C₃N₄ composite with enhanced photocatalytic and adsorptive performance. Structural, morphological, and optical characterization confirmed the successful integration of CQDs onto the TE-g-C₃N₄ framework and revealed improved charge separation behavior, enhanced visible-light absorption, lower photoluminescence intensity, and higher photocurrent response compared to pristine g-C₃N₄. The environmental applicability of the composite was evaluated through the photocatalytic degradation of carbamazepine (CBZ), a persistent pharmaceutical contaminant, and the adsorption of the methylene blue (MB) dye in aqueous media. The UCQD/TE-g-C₃N₄ composite increased CBZ removal efficiency from 16.2% to 32.7% under visible-light irradiation within 6&#xa0;h. Photocatalytic performance was influenced by operational parameters such as solution pH, catalyst dosage, and initial pollutant concentration, with alkaline conditions favoring degradation. Radical scavenger experiments indicated that superoxide radicals played a dominant role in the degradation mechanism. In adsorption studies, the composite achieved 90.5% MB removal at an initial concentration of 10&#xa0;mg/L within 60&#xa0;min, significantly outperforming bulk and thermally exfoliated g-C₃N₄. Adsorption behavior followed the Langmuir isotherm and pseudo-second-order kinetic model, suggesting predominantly chemisorption-driven interactions. The findings demonstrate that macroalgae-derived CQD-modified TE-g-C₃N₄ composites represent a sustainable and multifunctional platform for the efficient removal of emerging organic contaminants from water systems.</p> Graphical Abstract <p></p>

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Carbon Quantum Dots (CQDs)-Infused Exfoliated g-C₃N₄ Composites for Enhanced Photocatalytic and Adsorptive Performance against Carbamazepine and Methylene Blue

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • Sibel Barisci,
  • Meral Dükkancı,
  • Gamze Turan,
  • Ayse Merve Unsur,
  • Fatma Kuş,
  • Elif Sinav,
  • Ezgi Altunkaynak,
  • Beyza Cengiz,
  • Işılsu Karadayı,
  • Ceyda Güven,
  • Aslı Naz Toy

摘要

Carbon quantum dots (CQDs) have attracted increasing attention in environmental remediation due to their tunable optical properties, high surface functionality, and sustainable synthesis potential. In this study, biomass-derived CQDs were synthesized using the green macroalgae Ulva rigida and incorporated into thermally exfoliated graphitic carbon nitride (TE-g-C₃N₄) to fabricate a sustainable UCQD/TE-g-C₃N₄ composite with enhanced photocatalytic and adsorptive performance. Structural, morphological, and optical characterization confirmed the successful integration of CQDs onto the TE-g-C₃N₄ framework and revealed improved charge separation behavior, enhanced visible-light absorption, lower photoluminescence intensity, and higher photocurrent response compared to pristine g-C₃N₄. The environmental applicability of the composite was evaluated through the photocatalytic degradation of carbamazepine (CBZ), a persistent pharmaceutical contaminant, and the adsorption of the methylene blue (MB) dye in aqueous media. The UCQD/TE-g-C₃N₄ composite increased CBZ removal efficiency from 16.2% to 32.7% under visible-light irradiation within 6 h. Photocatalytic performance was influenced by operational parameters such as solution pH, catalyst dosage, and initial pollutant concentration, with alkaline conditions favoring degradation. Radical scavenger experiments indicated that superoxide radicals played a dominant role in the degradation mechanism. In adsorption studies, the composite achieved 90.5% MB removal at an initial concentration of 10 mg/L within 60 min, significantly outperforming bulk and thermally exfoliated g-C₃N₄. Adsorption behavior followed the Langmuir isotherm and pseudo-second-order kinetic model, suggesting predominantly chemisorption-driven interactions. The findings demonstrate that macroalgae-derived CQD-modified TE-g-C₃N₄ composites represent a sustainable and multifunctional platform for the efficient removal of emerging organic contaminants from water systems.

Graphical Abstract