Time- and Synthesis-Solvent-Dependent Luminescence of Citric Acid–Urea Carbon Dots and Their Alkylamine-Tunable Interfacial Activity
Abstract
Citric acid–urea carbon dots are widely used fluorophores, but the influence of reaction duration and solvent on their structural and optical evolution remains underexplored. Here, citric acidurea carbon dots were prepared in water and N,N-dimethylformamide at 200 °C with reaction times ranging from 10 min to 72 h, and selected samples were subsequently functionalized with butylamine, hexylamine, or octylamine via carbodiimide-mediated amide coupling. Structural analysis showed that DMF-derived particles were nitrogen-rich and amide-dominated, whereas water-derived particles were more hydrophilic and carboxyl/hydroxyl-rich, with nonmonotonic compositional changes over time. These differences were mirrored in the photoluminescence behavior: DMF-based synthesis produced gradually red-shifted emission, while aqueous synthesis favored blue-shifted emission and higher quantum yields at specific excitation windows. Alkylamine grafting converted surface carboxyl groups into amides, reduced ζ-potential magnitude, and produced chain-length-dependent interfacial activity, lowering the air–water surface tension from about 70 mN·m −1 to approximately 34 mN·m −1 . The results show that solvent choice and reaction time provide a practical route to tune the core composition, surface chemistry, emission properties, and interfacial behavior of citric acid–urea carbon dots.
Related
- Gd3+-Doped NaYF4:Yb,Er Upconversion Nanoparticles: Synthesis, Luminescence Enhancement, and Anti-Counterfeiting Applications
- Excitation-Dependent Visible and Near-Infrared Luminescence of Dy3+/Pr3+ Co-Doped Borate Glasses
- Multi-wavelength optical encoding enabled by excitation-dependent luminescence in rare-earth activated La2O3 phosphors
- Synthesis, Structural and Luminescence Properties of Mn4+-Activated Medium-Entropy Perovskites (La1/3Gd1/3Y1/3)1−xMxAlO3−δ (M = Ca, Sr)
- A grinding-free synthesis strategy of persistent luminescence nanoprobes with enhanced optical performance for PSA detection
BibTeX
@misc{fulop2026time,
title = {{Time- and Synthesis-Solvent-Dependent Luminescence of Citric Acid–Urea Carbon Dots and Their Alkylamine-Tunable Interfacial Activity}},
author = {Dániel Fülöp and Adél Sarolta Rácz and Dániel Olasz and Gergő Gyulai},
howpublished = {ChemRxiv},
year = {2026},
month = aug,
doi = {10.26434/chemrxiv.15008099/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008099/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Time- and Synthesis-Solvent-Dependent Luminescence of Citric Acid–Urea Carbon Dots and Their Alkylamine-Tunable Interfacial Activity
AU - Dániel Fülöp
AU - Adél Sarolta Rácz
AU - Dániel Olasz
AU - Gergő Gyulai
PY - 2026
DA - 2026/08/31
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008099/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008099/v1
AB - Citric acid–urea carbon dots are widely used fluorophores, but the influence of reaction duration and solvent on their structural and optical evolution remains underexplored. Here, citric acidurea carbon dots were prepared in water and N,N-dimethylformamide at 200 °C with reaction times ranging from 10 min to 72 h, and selected samples were subsequently functionalized with butylamine, hexylamine, or octylamine via carbodiimide-mediated amide coupling. Structural analysis showed that DMF-derived particles were nitrogen-rich and amide-dominated, whereas water-derived particles were more hydrophilic and carboxyl/hydroxyl-rich, with nonmonotonic compositional changes over time. These differences were mirrored in the photoluminescence behavior: DMF-based synthesis produced gradually red-shifted emission, while aqueous synthesis favored blue-shifted emission and higher quantum yields at specific excitation windows. Alkylamine grafting converted surface carboxyl groups into amides, reduced ζ-potential magnitude, and produced chain-length-dependent interfacial activity, lowering the air–water surface tension from about 70 mN·m −1 to approximately 34 mN·m −1 . The results show that solvent choice and reaction time provide a practical route to tune the core composition, surface chemistry, emission properties, and interfacial behavior of citric acid–urea carbon dots.
ER -