Detection of Co2+ via fluorescence resonance energy transfer between synthesized nitrogen-doped carbon quantum dots and Rhodamine 6G

The doping of carbon quantum dots with nitrogen gives a promising role to improve fluorescence performance. In the present study, nitrogen-doped carbon quantum dots (NCQDs) were synthesized through a facile and economically cheap hydrothermal method from Nerium Oleander L. petals as carbon source and ethylenediamine as nitrogen source. The quantum yield of NCQDs was found to be 3.5%. Here we have studied FRET between NCQDs and Rhodamine 6G (Rh6G) dye. The lifetime of NCQDs decreases from 2.70 to 1.90 ns on addition of Rh6G. The lifetime of acceptor increases from 5.2 ns (in the absence of donor) to 5.5 ns in the presence of donor. FRET process was hindered in the presence of Co2+ only and deactivated the excitation energy of Rh6G. As a consequence, the fluorescence quenching rates increase. So, the FRET between NCQDs and Rh6G allowed enhancing the selectivity and sensitivity of detection of Co2+ ion with limit of detection of 6.45 nM. The method was successfully applied for the detection of Co2+ ions in real water.