In-situ synthesis of ionic liquid-based-carbon quantum dots as fluorescence probe for hemoglobin detection

Carbon quantum dots (CQDs) have emerged as a potential fluorescent probe in bio/analytical chemistry in the present decade. The optical characteristics of CQDs may be tuned by their functional groups, which can also be used to selectively produce stable bonds with target molecules. Along with them, ionic liquids (ILs) are now demonstrating their important relevance in the field of pharmaceuticals for the creation of potent therapeutics. In the article, we have discussed the use of high fluorescent ILs-decorated-CQDs (CQDs-IM@OTf) as a straightforward and quick-acting fluorescence probe for sensitive and precise hemoglobin (Hb) determination with minimum detectability of 6.7 nM. The proposed mechanism behind this involves static mode of quenching which leads to the formation of a ground state complex [CQDs-IM@OTf-Hb complex] between the Hb protein and the drug. Despite the fact that Hb can quench the fluorescence of CQDs due to the inner filter effect (IFE) of the protein, which effects both the excitation and emission spectra of the CQDs, the addition of H₂O₂ improved the sensitivity of Hb detection. The present assay predicated on Hb interaction with H₂O₂, which produces reactive oxygen species such as hydroxyl (OH^.) and superoxide (O₂^.-) radicals under heme degradation and/or iron release from Hb. The subsequent reaction of hydroxyl radicals with CQDs, which acts as a strong oxidising agent, causes a high fluorescence quenching. The designed fluorescence probe was used to measure Hb in the concentration range of 3-90 nM with a precise detection limit of 0.33 nM. The quantification of hemoglobin (Hb) in diluted human blood samples is done using this observation.