Structural and optical properties of carbon nanodots based on citric acid doped with nitrogen atoms

Abstract

A study of the luminescent properties of carbon nanodots obtained by microwave and hydrothermal methods of synthesis from citric acid and urea was performed. The resulting nanoparticles were characterized using transmission electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. The sizes of the obtained carbon nanodots after dialysis was varied from 2 to 8 nm. FTIR spectra confirm the presence of oxygen-containing –OH, –CN and –NH groups in the resulting solutions. For all studied carbon nanodots, the maximum fluorescence intensity is observed upon excitation at a wavelength of 350 nm. The fluorescence spectrum does not change its position on the wavelength scale for the samples under study due to changes in the molar ratio of precursors and the method of synthesis. The highest fluorescence quantum yield was obtained for carbon nanodots with a ratio of citric acid and urea 1:4 obtained by the microwave synthesis method. The fluorescence lifetime of carbon nanodots doped with nitrogen atoms is ~7.4 ns. It is shown that a change in the ratio of precursors does not significantly affect the size and morphology of carbon nanodots.