The Synthesis of Near-Infrared Carbon Dots Based On Polyethyleneimine-Methylene Blue

Fluorescent carbon dots have shown significant potential for biomedical applications such as bioimaging, sensing, and theranostics, owing to their remarkable properties, including superior optical characteristics, good biocompatibility, low toxicity, and facile preparation.In this report, near-infrared fluorescent carbon dots, termed PM-CDs, were synthesized by a simple hydrothermal method using branched polyethyleneimine (bPEI) and methylene blue (MB) as raw materials.The optimal reaction conditions for the carbon dots were determined by measuring their UV-visible absorption spectrum, fluorescence emission spectrum, and absolute quantum yield.The best preparation conditions were found to be a weight ratio of bPEI to MB of 1:10 in an alkaline NaOH medium, a reaction temperature of 210C, and a reaction time of 9 hours.Additionally, the synthesized carbon dots were characterized using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).This study provides an efficient method for synthesizing near-infrared carbon dots