DES-N-doped oxygenated carbon dot colloidal solutions for light harvesting and bio-imaging applications

Abstract

A novel colloidal system comprising choline oleate in deep eutectic solvent (DES: choline chloride–ethylene glycol) is developed and utilized for in situ generation and stabilization of nanosized (1 to 3 nm) N-doped oxygenated, crystalline CDs via dissolution of gelatin. Self-assembly of choline oleate in DES has been characterized using surface tension, DLS and 2D NMR NOESY methods. The stability of colloidal CDs was examined using FTIR and Raman spectroscopy. TEM, HR-TEM, and PXRD techniques have been used to characterize CDs. Optical properties have been investigated using UV, fluorescence and time-resolved photoluminescence (TrPL) spectroscopy. Colloidal CDs possess bright blue to red luminescence and short fluorescence lifetime with exceptionally high quantum yield (ca. 82%), and exhibited excellent biocompatibility as bioimaging agents towards labeling of bacterial cells (both Gram positive and Gram negative), thus indicating a potential benign system for disease detection, drug delivery and light harvesting applications.