Unveiling the quenching mechanism of metal ions using solvent-driven N, S-doped carbon quantum dots

Carbon quantum dots (CQDs) hold great potential as fluorescence probes due to their tunable optical properties, but remain challenges in tailoring surface functionalization for selective metal ion detection, which is essential for environmental monitoring and water quality analysis. This work, synthesized nitrogen and sulfur co-doped carbon quantum dots (N, S-CQDs) were via a one-pot solvothermal method with two different solvents, N, N-dimethylformamide (DMF) and acetone. The influences of solvent selectivity on the surface functionality of CQDs and their fluorescence quenching mechanisms were evaluated in both experimental and computational methods. To represent CQDs surfaces, density functional theory (DFT) calculations of the total density of states (TDOS) and partial density of states (PDOS) were conducted. Our findings revealed that synthesized CQDs in DMF and acetone exhibited fluorescence quenching as static and dynamic. We have achieved the highest quantum yields of 37.85 % and 28.59 %. This shows excellent sensitivities of Fe³⁺ at 0.82 μM and 1.19 μM for Co²⁺. Furthermore, the study extended to validated in real water sample analysis. This approach enabled the development of a novel strategy for the selective and sensitive detection of Fe³⁺ and Co²⁺ ions.