Red-emission carbon dots-quercetin systems as ratiometric fluorescent nanoprobes towards Zn2+ and adenosine triphosphate

Carbon dots (CDs) emitting red fluorescence (610 nm) were synthesized by solvent thermal treatment of p-phenylenediamine in toluene. Upon 440 nm excitation, quercetin (QCT) alone endowed slight effects on the red fluorescence of CDs. Once Zn 2+ was further introduced, the QCT-Zn 2+ complex was quickly formed. This complex absorbs excitation light and emits bright green fluorescence at 480 nm. The red fluorescence of CDs was greatly quenched owing to the inner-filter effect. The ratio of fluorescence intensity at 480 nm and 610 nm (I 480 /I 610 ) gradually increases with increasing concentration ( c ) of Zn 2+ . Al 3+ exhibits the same phenomen like Zn 2+ . Fluoride ions form a more stable complex with Al 3+ than QCT-Al 3+ complex but have a negligible effect on the QCT-Zn 2+ complex. The possible interference of Al 3+ on Zn 2+ can thus be avoided by adding certain amount of F − . The CD-QCT-F − system was constructed as a ratio-metric fluorescent nanoprobe toward Zn 2+ with determination range of 0.14–30 μM and limit of detection (LOD) of 0.14 μM. Due to the stronger affinity of adenosine triphosphate (ATP) to Zn 2+ than QCT, the I 480 /I 610 value of CD-QCT-F − -Zn 2+ system gradually decreases with increasing c ATP . The ratiometric fluorescent nanoprobe toward ATP was established with detection ranges of 0.55–10 and 10–35 μM and a LOD of 0.55 μM. The above two probes enable the quantitative determination of Zn 2+ and ATP in tap and lake water samples with satisfactory recoveries. Schematic representation of the ratiometric fluorescent nanoprobes based on the carbon dots (CDs)-quercetin (QCT) system towards Zn 2+ and adenosine triphosphate (ATP) with high selectivity and sensitivity.