Cuttlefish ink-based N and S co-doped carbon quantum dots as a fluorescent sensor for highly sensitive and selective para-nitrophenol detection

Para-nitrophenol (PNP) is an important raw material for organic synthesis and its extensive use has produced a series of environmental problems. Here, we develop a highly sensitive and selective fluorescent detection method for PNP with cuttlefish ink-based carbon quantum dots (CQDs). The cuttlefish ink, which is rich in eumelanin, is utilized as the only precursor to synthesize the CQDs via a one-step hydrothermal method. The resultant CQDs were co-doped with nitrogen and sulfur and exhibited excellent fluorescence properties. Two optimal emissions can be observed at the excitation/emission wavelengths of 320/385 nm and 390/465 nm, respectively. In the presence of PNP, the two emissions are remarkably quenched. PNP can be measured in the linear detection concentration range of 1.25-50 mu M (Em = 385 nm and R-2 = 0.9884) or 1.25-27.5 mu M (Em = 465 nm and R-2 = 0.9818) with a detection limit of 0.05 mu M. Significantly, it is found that a much wider linear detection range of 0.05-125 mu M with a lower detection limit of 0.039 mu M (3 sigma/k) can be achieved when log(I-385 nm + I-465 nm) was utilized to quantify PNP. The investigations of the sensing mechanism suggested that the inner filter effect and photoinduced electron transfer of PNP and N,S-CQDs leads to fluorescence quenching. The sensing method is successfully applied for PNP detection in real water samples with satisfactory recoveries (91.18-103.14%). A new sustainable waste-prevention strategy of cuttlefish ink and a feasible alternative to PNP detection methods is provided in this article.

Automated summary

The highly sensitive and selective fluorescent detection method for PNP was developed using cuttlefish ink-based carbon quantum dots. The method achieved successful detection of PNP in real water samples with satisfactory recoveries, offering a new sustainable waste-prevention strategy and a feasible alternative to traditional PNP detection methods.