Characterization of carbon quantum dots obtained through citric acid pyrolysis

Abstract

Carbon quantum dots (CQDs) were produced through citric acid (CA) pyrolysis. For the first time, we searched for the optimum CA pyrolysis duration and temperature. As a basic quality criterion of quantum dots, photoluminescence quantum yield (QY) was chosen. For this purpose, the pyrolysis products were analysed with UV–Vis spectroscopy and fluorescence (FL) spectroscopy. The optimum pyrolysis time was accepted to be 240 min, whereas the optimum pyrolysis temperature was approved as 200 °C. The pyrolysis products obtained at the optimum conditions were further subjected to dialysis. Finally, the purified CQDs were characterised with FL spectroscopy, transmission electron microscopy, dynamic light scattering, Raman spectroscopy, and Fourier transform infra-red spectroscopy. The produced CQDs were shown to be stable in water solution. Their PL QY (6.1%) was decreased to 1.2% after CQDs exposure to daylight for 90 days. Luminescent polymer composites were produced when CQDs were embedded in the poly(vinyl alcohol) and bacterial cellulose matrices. The prepared composites can be used for fabrication of transparent, flexible, and luminescent films and for production of anti-counterfeiting paper for confidential documents, labels, and banknotes.

Keywords:

• citric acid
• pyrolysis
• carbon quantum dots
• fluorescence
• quantum yield

Acknowledgements

The TEM study was performed using the equipment of the Shared Research Centre, ‘Crystallography and Photonics’ Federal Scientific Research Centre, Russian Academy of Sciences, and supported by the Ministry of Science and Higher Education within the State assignment of ‘Crystallography and Photonics’ Federal Scientific Research Centre, Russian Academy of Sciences.

Disclosure statement

The authors declare no potential conflict of interest.

Data availability statement

All the data generated and analysed during this study are included in this article and in Supplementary Information file.