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

Ganyaporn WONGWAEN; Koranut DECHSRI; Praneet  OPANASOPIT; Montri  AIEMPANAKIT; Cheewita SUWANCHAWALIT

doi:10.55713/jmmm.v35i4.2355

Authors

Ganyaporn WONGWAEN Department of Chemistry, Faculty of Science, Silpakorn University, Nakorn Pathom, 73000, Thailand
Koranut DECHSRI Pharmaceutical Development of Green Innovations Group (PDGIG), Department of Industrial Pharmacy, Faculty of Pharmacy, Silpakorn University, Nakhon Pathom, 73000, Thailand
Praneet OPANASOPIT Pharmaceutical Development of Green Innovations Group (PDGIG), Department of Industrial Pharmacy, Faculty of Pharmacy, Silpakorn University, Nakhon Pathom, 73000, Thailand
Montri AIEMPANAKIT Department of Physics, Faculty of Science, Silpakorn University, Nakhon Pathom, 73000, Thailand
Cheewita SUWANCHAWALIT Department of Chemistry, Faculty of Science, Silpakorn University, Nakorn Pathom, 73000, Thailand

DOI:

https://doi.org/10.55713/jmmm.v35i4.2355

Keywords:

Carbon dot, Caffeine, Solvothermal, Photocatalysts, Sulfur doped-carbon dots

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.

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