A novel carbon quantum dot (CQD) synthesis method with cost-effective reactants and a definitive indication: Hot bubble synthesis (HBBBS)

Carbon quantum dots (CQDs) are carbon-based biocompatible quantum dots that have low toxicity, are more soluble in water, have broad application areas, and the surface modification of these can be performed easily. In this study, we present a new CQD synthesis method with cost-effective reactants that can be easily found in laboratories are used. Besides, there is a definitive indication (bubble) for CQD production, unlike the other methods in the literature. The purification method of the CQDs was also optimized in this study. In the beginning of the synthesis, 3 times centrifugation (x3 CF) of the mixture was performed and the optimization of the purification method indicated that x3 CF before 3 days of dialysis membrane tubing (x3 CF & 3 DM) resulted in the formation of the purest CQDs. The characterization of the CQDs was done utilizing UV–VIS spectrophotometer, Fourier Transfer Infrared Spectroscopy (FT-IR), Zetasizer, fluorescence microscopy, Dynamic Light Scattering (DLS), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), and Transmission Electron Microscopy (TEM). It was concluded that the CQD formation depended on the mixing of sulphuric acid:acetone (2:1) ratio in a hot (140–165 °C) and an inert environment, and bubble coverage of the mixture surface (30–60 s). The bubble formation due to the reaction between sulphuric acid and pure acetone at high temperatures gives the developed method’s name of “Hot Bubble Synthesis” (HBBBS). • CQDs were prepared by bubble formation of acetone and sulfuric acid mixture at high temperatures ( ≈ 165 °C). • A definitive indication (bubble formation) was determined to predict CQDs production and the time alongside heat parameters for CQD production were optimized. • Synthesized CQDs had high fluorescence intensity determined by fluorescent image analysis.