Article pubs.acs.org/JAFC
Green Synthesis of Fluorescent Carbon Dots for Selective Detection of Tartrazine in Food Samples Hua Xu,† Xiupei Yang,*,† Gu Li,† Chuan Zhao,† and Xiangjun Liao*,§ †
College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637000, People’s Republic of China Exposure and Biomonitoring Division, Health Canada, 50 Colombine Driveway, Ottawa K1A 0K9, Canada
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J. Agric. Food Chem. 2015.63:6707-6714. Downloaded from pubs.acs.org by OPEN UNIV OF HONG KONG on 01/24/19. For personal use only.
S Supporting Information *
ABSTRACT: A simple, economical, and green method for the preparation of water-soluble, high-fluorescent carbon quantum dots (C-dots) has been developed via hydrothermal process using aloe as a carbon source. The synthesized C-dots were characterized by atomic force microscope (AFM), transmission electron microscopy (TEM), fluorescence spectrophotometer, UV−vis absorption spectra as well as Fourier transform infrared spectroscopy (FTIR). The results reveal that the as-prepared Cdots were spherical shape with an average diameter of 5 nm and emit bright yellow photoluminescence (PL) with a quantum yield of approximately 10.37%. The surface of the C-dots was rich in hydroxyl groups and presented various merits including high fluorescent quantum yield, excellent photostability, low toxicity and satisfactory solubility. Additionally, we found that one of the widely used synthetic food colorants, tartrazine, could result in a strong fluorescence quenching of the C-dots through a static quenching process. The decrease of fluorescence intensity made it possible to determine tartrazine in the linear range extending from 0.25 to 32.50 μM, This observation was further successfully applied for the determination of tartrazine in food samples collected from local markets, suggesting its great potential toward food routine analysis. Results from our study may shed light on the production of fluorescent and biocompatible nanocarbons due to our simple and environmental benign strategy to synthesize C-dots in which aloe was used as a carbon source. KEYWORDS: carbon quantum dots, tartrazine, aloe, fluorescence quench
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cellular imaging, and biomedicine.14,15 Over the past years, several methods have been developed for the synthesis of Cdots, including arc discharge,16 laser ablation,17,18 electrochemical oxidation,19 and microwave irradiation.20 However, hydrothermal carbonization has provided great advancement over existing physical methods, which is due to its simplicity and production of C-dots with good quantum yield. Recently, hydrothermal carbonization of chitosan, orange peels, coffee grounds, and grass has been successfully applied to synthesize fluorescent C-dots, which could be probes for recognizing various chemical species and cells in vitro and in vivo.21−24 All of these proved that hydrothermal carbonization is an ecofriendly, facile, and classical route for the synthesis of C-dots in aqueous media. From the point of material preparation, there is an urgent need to locate new carbon sources for simple, economical, and green synthesis of C-dots. In this work, a facile and green method for the preparation of fluorescent C-dots by hydrothermal treatment of aloe and the application has been proposed. On the basis of fluorescence quenching, the prepared C-dots can serve as an effective sensor for sensitive and selective determination of tartrazine. The use of the synthesized C-dots for detection has been validated by measuring the concentration of tartrazine in food samples collected from a local supermarket.
INTRODUCTION Tartrazine is a widely used synthetic food colorant that can be found in certain food products such as candies, beverages, bakery products, and dairy products.1,2 However, some studies have revealed that tartrazine may cause adverse health effects such as changes in hepatic and renal parameters and reproductive toxicity, as well as neurobehavioral poisonousness when it is excessively consumed.3,4 Therefore, the food industry must strictly control and regulate the content of tartrazine in foods, which necessitates an interest in the development of an efficient measurement technique to determine tartrazine in foods in terms of rapidity, simplicity, and sensitivity. Until now, various instrumental techniques that analyzed tartrazine in foodstuff products have been increasingly employed, which include thin-layer chromatography (TLC) method,5 electrochemical sensor,6 spectrophotometry,7 and high-performance liquid chromatography (HPLC).8 Nevertheless, these methods may not be suitable for routine monitoring because they require sophisticated equipment and time-consuming sample preparation. As a result, the development of a simple, economical, fast, and reliable assay of tartrazine has been a challenge for analytical researchers. Recently, carbon quantum dots (C-dots), which are a new class of fluorescent nanomaterials with a size of
