Putri Pramana Arnum, Naomi Rahma Dania Jounza, Syamsi Aini, Umar Kalmar Nizar, Sherly Kasuma Warda Ningsih, Krismadinata Krismadinata, Remon Lapisa, Ali Amran, Deski Beri
Nitrogen-doped carbon dots (N-CDs) were synthesized via a simple and metal-free solvothermal route using citric acid and urea as carbon and nitrogen precursors, respectively. The urea-to-citric-acid molar ratio was systematically varied to investigate its influence on the optical properties and photocatalytic performance of the resulting N-CDs. UV–Vis absorption and photoluminescence (PL) analyses reveal tunable emission in the range of 491–510 nm with corresponding optical band gaps between 2.53 and 2.43 eV. Particle size analysis confirms an average particle diameter of approximately 4.3 nm. An exceptionally high PL quantum yield (PLQY) of 92.88% was achieved at an optimal urea-to-citric-acid ratio of 1:5, attributed to balanced nitrogen doping and effective surface-state passivation. The optimized N-CDs exhibit efficient photocatalytic degradation of methylene blue and rhodamine B under 405 nm UV irradiation, achieving degradation efficiencies of 87.99% and 85.36% after 240 min, respectively. Kinetic analysis indicates pseudo-first-order behavior consistent with the Langmuir–Hinshelwood model. These results demonstrate that metal-free N-CDs synthesized through a green and scalable approach are promising photocatalysts for dye-contaminated wastewater treatment. © 2026 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the https://creativecommons.org/licenses/by/4.0/. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Chemistry Department, Faculty of Mathematics and Natural Sciences, Universitas Negeri Padang, Kampus UNP Air Tawar, Jl. Prof. Dr Hamka, Padang, Indonesia; Electrical Engineering Department, Faculty of Engineering, Universitas Negeri Padang, Kampus UNP Air Tawar, Jl. Prof. Dr Hamka, Padang, Indonesia; Mechanical Engineering Department, Faculty of Engineering, Universitas Negeri Padang, Kampus UNP Air Tawar, Jl. Prof. Dr Hamka, Padang, Indonesia
