Highly Efficient Antioxidant F- and Cl-Doped Carbon Quantum Dots for Bioimaging
Zoran Marković, Martina Labudová, Martin Danko, Danka Matijašević, Matej Mičušík, Vojtěch Nádaždy, Mária Kováčová, Angela Kleinová, Zdenko Špitálský, Vladimir B. Pavlović, Dušan Milivojević, Mina Medić, Biljana M. Todorović Marković
Abstract
The addition of heteroatoms to pristine carbon quantum dots (CQDs) change their structure and optical properties. In this study, fluorine (F)- and chlorine (Cl)-doped CQDs are prepared by the one-step green hydrothermal route from sodium fluoride, sodium chloride, urea, and citric acid as the starting precursors. Microscopy analysis reveals that the average size of these quantum dots is 5 ± 2 nm, whereas the chemical study shows the existence of C–F and C–Cl bonds. The produced F- and Cl-doped CQDs have fluorescence quantum yields of 0.151 and 0.284, respectively, at an excitation wavelength of 450 nm. Charge transfer resistance of F- and Cl-doped CQDs films is 2 orders of magnitude higher than in the pristine CQD films. Transport band gap of the doped CQDs is 2 eV bigger than that of pristine CQDs. Radical scavenging activity shows very good antioxidant activity of doped CQDs. Antibacterial testing reveals poor antibacterial activity against Staphylococcus aureus and Escherichia coli. The F- and Cl-doped CQDs are successfully used as fluorescent probes for cell imaging as shown by confocal microscopy.