Green Synthesis of Highly Fluorescent Carbon Dots from Groundnut Shell Biomass for Bioimaging Applications

Carbon dots from alternative renewable carbon sources are emerging as alternatives to metal-based quantum dots. These nature-derived carbon dots exhibit excellent optical and fluorescent properties, which enable their use in several applications, including bioimaging. This work presents a facile and green approach to synthesizing highly fluorescent carbon dots from groundnut shells (GNS), an abundantly available agricultural residue. HRTEM analysis confirmed the synthesis of Groundnut shell Carbon Dots (GCDs) with a lattice spacing of around 0.22 nm, corresponding to low dimensional graphitic structures. The observed intense absorption at around 278 nm can be ascribed to the л – л* transitions resulting from the hybridization of sp2/sp3 orbitals in carbon dots. The fluorescence spectroscopy of GCDs displayed pronounced emission characteristics that varied depending on the excitation wavelength, which ranges from 280 to 480 nm. The quantum yield of these GCDs was estimated to be 17.1%. The biocompatibility of GCDs is confirmed by the cell viability test, which indicates their suitability for yeast cell imaging.

Groundnut shells are subjected to hydrothermal carbonization (HTC) at 220 ⁰C to obtain GCDs. The GCDs have been demonstrated as excellent bioimaging agents for live cell imaging