Synthesis of Multi-Color Fluorescent Carbon Dots From Mint Leaves: A Robust Bioimaging Agent with Potential Antioxidant Activity.

Carbon dots (C-dots), a promising luminescent nanomaterial with exceptional physico-chemical properties gaining enormous attention in recent years. Carbon dots having enhanced biocompatibility and multiple routes of synthesis offers a promising substitute to luminescent quantum dots (QD). Further, wavelength-controlled emission features of C-dots proved as a good candidate in the biolabeling applications. Herein, we are reporting a facile and one-step hydrothermal synthesis of biocompatible multi-color, Polyethyleneimine (PEI) surface passivated C-dots (CDP) from mint leaves as a green source. The morphological and optical properties of C-dots have been extensively studied by Zeta-sizer, Transmission electron microscopy (TEM), X-ray diffraction (XRD) pattern, Ultra violet (UV)-visible spectroscopy and fluorescence spectroscopic analysis. Furthermore, Fourier transform infrared (FT-IR) and X-Ray Photoelectron Spectroscopic (XPS) analysis have been performed for the understanding of surface states and chemical composition of C-dots. A comparative analysis in the biolabeling potentials of non-passivated C-dots (CD) and CDP was conducted in the breast cancer (MCF-7) cells and the concentration dependent cytotoxicity was estimated. Further, an enhanced antioxidant property was showed by CDP as compared to CD. In the present study, a practical implication of C-dots synthesized from a herbal source (mint) to serve as a novel agent for various biolabeling applications and antioxidant activity have been experimentally resolved. As synthesized CD and CDP can be, serve as better alternatives for imaging probe with improved biocompatibility.