Deep Eutectic Solvent-Assisted Preparation of Nitrogen/Chloride-Doped Carbon Dots for Intracellular Biological Sensing and Live Cell Imaging

Abstract

A novel approach for the preparation of dual-functional carbon dots, i.e., nitrogen- and chloride-doped carbon dots, abbreviated as N/Cl-CDs, is developed with the assistance of a choline chloride-glycerine deep eutectic solvent (DES). The carbon source is provided by urea and the DES serves as a solvent for controlling the preparation of CDs in the absence of water. The dual-element doped carbon dots are oxygen-rich with hydroxyl and amine groups. They exhibit an average particle size of ca. 3.88 nm and give rise to strong and pH-sensitive fluorescent emission at λ/λ = 340/430 nm with a quantum yield of 16.15 ± 1.36%. It is particularly interesting to see that the fluorescence of N/Cl-CDs remains stable in a high-salinity matrix, providing vast potentials for treating real biological sample matrixes with high salinity. The N/Cl-CDs provide an optical probe for intracellular pH sensing and multicolor imaging in HeLa cells. In addition, the N/Cl-CDs show obvious fluorescence response to cytochrome c (cyt- c) with a detection limit of 3.6 mg L (ca. 0.29 μmol L) within in a range of 10-500 mg L, providing potentials for fluorescence detection of cyt- c as well as facilitating intracellular cyt- c imaging.

Blue light-emitting carbon dots (CDs) from a milk protein and their interaction with Spinacia oleracea leaf cells

“…The value obtained was quite similar to that reported by Tabaraki and Sadeghinejad who synthesized carbon dots from citric acid, urea, and thiourea by microwave-assisted method and reported QY of 19.2% [26]. Similarly, Wang et al obtained dual functional carbon dots, designated as N/ Cl-CDs, with the assistance of a choline chloride-glycerine deep eutectic solvent (DES) and reported a QY of 16.15 [27].…”

“…Amino acids, due to their low cost and abundance, are frequently used as carbon and nitrogen sources. In addition, primary amines not only provide nitrogen, but they also passivate the carbon dots surface [17]. Indeed, there are several reports in recent past about the synthesis of N-doped carbon dots.…”

Boron Doped Carbon Dots with Unusually High Photoluminescence Quantum Yield for Ratiometric Intracellular pH Sensing

“…It would also be worthwhile to pursue composite formation based on differently emitting carbon dots. In other words, contrary to previous reports, [26,27] fabrication of a composite based on carbon dots with widely separate emission maxima may have greater application potential where emission characteristics of the component peaks are affected by the change in the environmental parameters. For example, if the emission profiles of the carbon dots are affected by pH of the medium then the composite could be used for ratiometric pH sensing.…”

Interfacial engineering of carbon dots with benzenediboronic acid for fluorescent biosensing

“…15 Specically, the unique optical features of CDs make them particularly attractive for biosensors. 16,17 In order to develop novel biological sensing platforms, one of the fundamental factors is the surface modication and engineering CDs to initiate biorecognition events or biocatalytic transformations. Different synthetic strategies including both top-down and bottom-up synthesis are developed to control functional groups on the surface.…”