N-doped carbon quantum dots from osmanthus fragrans as a novel off-on fluorescent nanosensor for highly sensitive detection of quercetin and aluminium ion, and cell imaging

In this work, fluorescent N-doped carbon quantum dots (N-CQDs) have been synthesized by simple hydrothermal heating of natural osmanthus fragrans, without any toxic ingredients or surface chemical modifications. The N-CQDs possess a high quantum yield of 21.9 %, outstanding blue fluorescence, good water dispersity, and excellent optical stability. Because the favorable inner filter effect (IFE) between N-CQDs and quercetin (QT) occurs, the addition of QT to N-CQDs can cause their fluorescence quenching. When Al3+ was added to the N-CQDs/QT system solution, it was found that the inhibition of IFE leads to the fluorescence intensity of N-CQDs/QT system enhancement by virtue of a specific binding of QT to aluminum ion (Al3+). Therefore, we used the N-CQDs as a novel off-on fluorescent nanosensor to detect QT and Al3+. Under optimal conditions, the fluorescent nanosensor can detect QT within the wide linear response in the range of 0.003-80 mu mol/L with as low as 1 nmol/L detection limit. For the detection of Al3+, the N-CQDs/QT system showed linearity response toward Al3+ in a range of 0.1 similar to 100 mu mol/L and the limit of detection was found at 26 nmol/L. In addition, N-CQDs have been successfully used to efficient quantification QT in human plasma and monitor Al3+ in serum samples. Noteworthy, the N-CQDs demonstrated low toxicity toward T24 cells, which realized sensing QT and Al3+ in the living cells. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Fluorescent N-doped carbon quantum dots were synthesized from natural osmanthus fragrans through a simple hydrothermal method, showing high quantum yield and excellent performance. They were utilized as novel fluorescent nanosensors for the detection of quercetin and aluminum ion, with potential applications in various fields.