Anomalous enhancement of fluorescence of carbon dots through lanthanum doping and potential application in intracellular imaging of ferric ion

An anomalous enhancement of fluorescence of carbon dots (CDs) was observed via lanthanum (La) doping. La-doped CDs (La-CDs) were prepared through microwave pyrolysis within 4 min. With La3+ doping, the emission band shifted from blue to green although La3+ is non-fluorescent. The quantum yield and fluorescence lifetime improved by about 20% and 35%, respectively. All experiment results indicate that La3+ doping is an effective way to tune fluorescence and improve the performance of CDs. Another unique attribute of La-CDs is high sensitivity to Fe3+. The La-CD-based fluorescence probe was established and used for sensitive and selective detection of Fe3+ with a limit of detection of 91 nmol/L. The proposed fluorescence probe also was successfully employed to visualize intracellular Fe3+ in live HeLa cells through cell imaging. It was also shown that yttrium exhibited the same fluorescence enhancement effect as La. The results may provide a new route for preparing CDs with special properties.