The interaction of glucose-derived carbon quantum dots (CQDs) with silver (Ag) and gold (Au) nanoparticles (NPs) was explored by fluorescence spectroscopy. Both metal NPs cause an efficient quenching of CQD fluorescence, which is likely due to the energy transfer process between CQDs as donors and metal NPs as acceptors. The Stern-Volmer plots were evaluated and corresponding quenching constants were found to be 1.9 × 1010 and 2.2 × 108 M-1 for AgNPs and AuNPs, respectively. The analytical applicability of these systems was demonstrated for turn-on fluorescence detection of the anti-cancer drug, 6-thioguanine. Because the CQD-AgNP system had much higher sensitivity than the CQD-AuNP system, we used it as a selective fluorescence probe in a turn-on assay of 6-thioguanine. Under optimum conditions, the calibration graph was linear from 0.03 to 1.0 μM with a detection limit of 0.01 μM. The developed method was applied to the analysis of human plasma samples with satisfactory results.
Keywords: 6-thioguanine; carbon quantum dots; fluorescence quenching; gold nanoparticles; silver nanoparticles.
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