Green synthesis of carbon dots by celery leaves for use as fluorescent paper sensors for the detection of nitrophenols

Herein, natural celery leaves and glutathione were used as the precursors to prepare carbon dots (CDs) as novel fluorescent paper sensors, which exhibited high sensitivity and selectivity for the detection of explosive nitrophenols (including 2-nitrophenol (2-NP), 3-nitrophenol (3-NP) and 4-nitrophenol (4-NP)). The prepared CDs featured blue fluorescence emission under irradiation using an UV lamp, and the fluorescence quantum yield was as high as 53%. As fluorescent probes, the CDs showed a particular response to 2-NP, 3-NP and 4-NP, and the detection limits of 2-NP, 3-NP and 4-NP were determined to be 39 nM, 43 nM and 26 nM, respectively. Due to the multiple advantages including good water solubility, low toxicity and excellent stability, CDs are expected to be widely used. Meanwhile, a CD-based test paper was exploited and it displayed a distinctive quenching response when exposed to 3-NP and 4-NP, with the visual detection limits of 0.5 mu M and 0.1 mu M, respectively. Furthermore, the low toxicity and biocompatibility of CDs were also demonstrated by evaluating cell culture experiments, and CDs showed good potential applications in imaging. In summary, the prepared CDs are promising for fluorescent paper sensors and bioimaging.