Abstract
In this study, an on–off–on fluorescence probe for the detection of trace Cu(ii) and ascorbic acid (AA) based on biomass-derived sulfur and nitrogen double heteroatom-doped carbon dots (N,S-CDs) was designed. For the first time, the probe (N,S-CDs) was prepared from grape seeds and thiourea as the precursor. Cu(ii) was added to the carbon point solution, the fluorescence intensity (FL) of N,S-CDs was strongly quenched (switch OFF) and the fluorescence probe turned to “ON” (switch ON) with the addition of AA. Under the optimal conditions, the as-synthesized N,S-CDs had a good detection performance for Cu(ii) and AA assay with the linearity ranges from 150–500 μg mL−1 and 0.1–400 μg mL−1, and the LODs were 0.048 mg L−1 and 0.036 mg L−1, respectively. The as-prepared N,S-CDs exhibited a low cytotoxicity and a good biocompatibility, which show their potential for application in the biological imaging of living cells.
Highlights
Carbon dots (CDs) have been applied in pharmaceutical analysis, bio-imaging and other elds due to their advantages of high photostability, good biocompatibility, low toxicity, and excellent optical properties.[1]
The grape seeds were ground into powder and used as the carbon source for synthesising N,S-CDs. 2.50 g of this powder and 3.0 g of thiourea were mixed into a 25.0 mL aqueous solution under magnetic stirring for 30 min
The above observations indicated that N,S-CDs had crystalline properties, as evidenced by a clear fringe distance of 0.22 nm, which was similar to the (1120) characteristic lattice fringes of graphene.[21]
Summary
Carbon dots (CDs) have been applied in pharmaceutical analysis, bio-imaging and other elds due to their advantages of high photostability, good biocompatibility, low toxicity, and excellent optical properties.[1] The carbon source is one of the important conditions that directly affects the properties of the CDs.[2] Carbon sources mainly include organic chemicals (citric acid,[3] etc.) and biomass (plants,[4] animals[5] and their derivatives[6]). Due to the high nitrogen content,[7] low cost, and good biocompatibility of biomass,[8] more and more biomass-derived carbon dots were synthesized, such as soy milk[9] (Yu 1⁄4 8.6%, Yu is the uorescence quantum yield) and bamboo leaves[10] (Yu 1⁄4 7.1%). Its seeds contain numerous polyphenols,[19] which can be used as a good carbon and nitrogen source for CD production.
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