Sulfur-doped carbon dots derived from caffeine: A highly efficient photocatalyst for organic dye degradation

Authors

• Ganyaporn Wongwaen
• Koranut Dechsri
• Praneet Opanasopit
• Montri Aiempanakit
• Cheewita Suwanchawalit

Publication Date

2025

Abstract

Sulfur-doped carbon dots (S-doped CDs) were synthesized via a solvothermal method using caffeine as a carbon precursor and sodium sulfide as a sulfur source. Characterization using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet -visible (UV-Vis) spectroscopy, and photoluminescence spectroscopy (PL) confirmed successful sulfur incorporation. TEM revealed a uniform size distribution and graphitic structures, while UV-Vis analysis showed a reduction in the bandgap from 3.29 eV to 3.10 eV, improving light absorption and charge carrier separation. The photocatalytic activity of S-doped CDs was evaluated for indigo carmine (IC) dye degradation under UV irradiation, where 2S-CDs exhibited the highest degradation efficiency (~90% within 240 min) due to enhanced charge carrier separation, defect-state-mediated electron transfer, and the generation of reactive oxygen species (ROS). Radical scavenger experiments confirmed that superoxide radicals (•O2‒), hydroxyl radicals (•OH), and photogenerated holes (h+) played key roles in dye degradation. This study demonstrates that S-doped CDs derived from caffeine are efficient and sustainable photocatalysts for wastewater treatment.

DOI

10.55713/jmmm.v35i4.2355

First Page

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Last Page

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Recommended Citation

Wongwaen, Ganyaporn; Dechsri, Koranut; Opanasopit, Praneet; Aiempanakit, Montri; and Suwanchawalit, Cheewita (2025) "Sulfur-doped carbon dots derived from caffeine: A highly efficient photocatalyst for organic dye degradation," Journal of Metals, Materials and Minerals: Vol. 35: No. 4, Article 4.
DOI: 10.55713/jmmm.v35i4.2355
Available at: https://digital.car.chula.ac.th/jmmm/vol35/iss4/4