High quantum yield nitrogen-doped carbon dots: green synthesis and application as "off-on" fluorescent sensors for the determination of Fe3+ and adenosine triphosphate in biological samples

In this work, for the first time, natural bauhinia flower was adopted as a carbon source to prepare nitrogen-doped carbon dots (N-CDs) through facile and green microwave method without further passivation or modification. The fluorescent quantum yield (QY = 27.00%) of the as-synthesized N-CDs was higher than most of CDs prepared from other natural sources. The N-CDs was proved to be an effective "turn-off" fluorescent sensor for detection of Fe3+ exhibiting excellent sensitivity with the detection limit of 0.01 mu M. The fluorescence of N-CDs-Fe3+ system would be recovered when ATP was added mainly due to high affinity of the adenosine triphosphate (ATP) for Fe3+ through Fe-O-P bonds. Therefore, a sensitive and reliable "turn-on" fluorescent ATP sensor was developed, the limit detection was calculated to be 0.005 mu M. In addition, the fluorescent sensors could act as a good candidate to determine Fe3+ and ATP in biological samples with satisfying results. What's more, the application of the fluorescent sensors for imaging Fe3+ and ATP in living cells, which suggested that the systems had great potential applications in biosensing and bioimaging.