Carbon dots with polarity-tunable characteristics for the selective detection of sodium copper chlorophyllin and copper ions

Abstract

Compared to water-soluble carbon dots (CDs) the properties and applications of hydrophobic CDs are rarely addressed. In this study, a one-pot, simple chemical oxidation approach has been applied to synthesize hydrophobic carbon dots (TO-CDs) at room temperature from triolein (TO) in concentrated sulfuric acid solution. Sodium copper chlorophyllin (SCC) quenches the fluorescence of TO-CDs by a photoinduced electron transfer process. Upon excitation at 400 nm, the fluorescence intensity of TO-CDs probe at 500 nm shows a linear response against the SCC concentration ranging from 1.0 to 10 mu M, with a limit of detection (LOD) of 0.61 mu M. Quantitation of SCC in flavored drinks shows percentage recovery (% R) vaues of 98-103% and relative standard deviation (RSD) values less than 6.5%. The hydrophobic TOCDs can be converted into hydrophilic TO-CDs through hydrolysis in NaOH solution. The presence of sulfonyl groups on the hydrophilic TO-CDs enhances the coordination ability of the CDs toward Cu2+ ions, leading to fluorescence quenching which allows for the detection of Cu2+ ions with LOD of 0.21 mu M and a linear range of 0.5-10 mu M. The hydrophilic TO-CD probe possesses high selectivity toward Cu2+ ions (tolerance at least ten-fold comparative to other metal ions). The assay has been validated with the analysis of spiked soil samples, with %R values of Cu concentration of 97.8-99.0% and RSDs below 2.0%. The surface tunable CD probes demonstrate their potential for the rapid screening of Cu2+ ions in environmental samples and SCC in foods. (C) 2021 Elsevier B.V. All rights reserved.