| Institution: | 1. Department of Chemistry and Pharmacy, Laboratory of Materials Science and Nanotechnology, CR-INSTM, Via Vienna 2., 07100 Sassari, Italy;2. Department of Physics, University of Cagliari, Campus of Monserrato, sp n.8, km 0.700, 09042 Monserrato, Italy;3. Department of Organic Chemistry, Semmelweis University, 1092 Budapest, Hogyes Endre St. 7., Hungary
MTA TTK Lendület Artificial Transporter Research Group, Institute of Materials and Environmental Chemistry, Research Center for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Magyar Tudósok krt. 2., Hungary;4. Materials Characterization Facility, Istituto Italiano di Tecnologia, Via Morego, 30., 16163 Genova, Italy;5. Department of Chemical Sciences, University of Padua, Via Marzolo 1, 35131 Padova, Italy |
| Abstract: | Thermal decomposition of citric acid is one of the most common synthesis methods for fluorescent carbon dots; the reaction pathway is, however, quite complex and the details are still far from being understood. For instance, several intermediates form during the process and they also give rise to fluorescent species. In the present work, the formation of fluorescent C-dots from citric acid has been studied as a function of reaction time by coupling infrared analysis, X-ray photoelectron spectroscopy, liquid chromatography/mass spectroscopy (LC/MS) with the change of the optical properties, absorption and emission. The reaction intermediates, which have been identified at different stages, produce two main emissive species, in the green and blue, as also indicated by the decay time analysis. C-dots formed from the intermediates have also been synthesised by thermal decomposition, which gave an emission maximum around 450 nm. The citric acid C-dots in water show short temporal stability, but their functionalisation with 3-aminopropyltriethoxysilane reduces the quenching. The understanding of the citric acid thermal decomposition reaction is expected to improve the control and reproducibility of C-dots synthesis. |
