Considering the significant impact of heavy metals on environment and food safety inspection in trace determination, the orange photoluminescent carbon dots (O-CDs) was innovative designed by promoting the co-hydrothermal reaction of polyethyleneimine and resazurin. The produced O-CDs exhibit exceptional optical performance, advantageous water solubility and outstanding photostability. It is worth emphasizing that the proposed O-CDs has significant advantages in constructing sequential sensing platform for sensitive determination of Ni 2+ and morin. Simultaneous taking Ni 2+ for analytes and fluorescence quenching agents on the O-CDs sensing platforms, a good linear relationship can be received in the range of 5–50 μM with satisfactory sensitivity. Subsequently, morin can effectively promote the fluorescence recovery of O-CDs@Ni 2+ on account of stronger binding force between morin and Ni 2+ . Based on the above results, effective recovery of 97.26 %-100.90 % and 98.24 %-101.99 % is observed towards nickel ion and morin in real food samples. These findings provide an original strategy for the construction of long-wavelength emission carbon dots, which provides a pathway for the determination of typical pollutants based on efficient and robust nanosensors in the field of food safety.
Herein, a facile approach for highly sensitive and selective detection of tannic acid (TA) was proposed with the nitrogen-doped fluorescent carbon dots (NCDs) as a novel fluorescent probe , using sodium citrate and aminopyrazine as precursors. The as-synthesized NCDs exhibited multiple advantages including high quantum yield (11.8%), good water solubility and satisfactory stability. In addition, the NCDs displayed excitation-independent emission behavior with fluorescence emission peak remaining at 389 nm under excitation of 270–350 nm. Significantly, the fluorescence quenching of as-fabricated NCDs was observed with the increasing TA concentration, and the calibration curve displayed a wide linear region ranging from 0.40 to 9.0 μmol L −1 with a detection limit of 0.12 μmol L −1 . This fluorescent probe also performed well in determining TA in beer samples with average recoveries of TA ranging from 96.1% to 104.4% and the relative standard deviation less than 5%, which provided a reliable, rapid and simple method to determine TA in real samples. Thus, this method offered a valuable insight for its practical applications.
Iodine ion is one of the most indispensable anions in living organisms, particularly being an important substance for the synthesis of thyroid hormones. Curcumin is a yellow-orange polyphenol compound derived from the rhizome of Curcuma longa L. , which has been commonly used as a spice and natural coloring agent, food additives, cosmetics as well as Chinese medicine. However, excess curcumin may cause DNA inactivation, lead to a decrease in intracellular ATP levels, and trigger the tissue necrosis. Therefore, quantitative detection of iodine and curcumin is of great significance in the fields of food and life sciences. Herein, we develop nitrogen-doped fluorescent carbon dots (NCDs) as a multi-mechanism detection for iodide and curcumin in actual complex biological and food samples, which was prepared by a one-step solid-phase synthesis using tartaric acid and urea as precursors without adding any other reagents. An assembled NCDs-Hg 2+ fluorescence-enhanced sensor for the quantitative detection of I − was established based on a fluorescence “turn-off-on” mechanism in a linear range of 0.3–15 μM with a detection limit of 69.4 nM and successfully quantified trace amounts of I − in water samples and urine sample. Meanwhile, the as-synthesized NCDs also can be used as a fluorescent quenched sensor for curcumin detection based on the synergistic internal filtration effect (IFE) and static quenching, achieving a good linear range of 0.1–20 μM with a satisfactory detection limit of 29.8 nM. These results indicate that carbon dots are potential sensing materials for iodine and curcumin detection for the good of our health.
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