Carbon quantum dots by submerged arc discharge in water: Synthesis, characterization, and mechanism of formation

Abstract

Carbon quantum dots (CQDs) are novel nanostructures that have great potential as fluorescent markers due to their multi-fluorescence, down and up converted emission, resistance to photobleaching, and biocompatibility. Here, we report the synthesis of fluorescent CQDs by the submerged arc discharge in water method. We discuss the method's simplicity, natural phases’ separation, and scalability. The produced CQDs size distribution was in the range of 1–5 nm. High-resolution transmission electron microscopy images and their fast Fourier transformation allowed the analysis of the CQDs’ internal structure. The absorption and fluorescence spectra of the as-produced CQDs were analyzed. The UV-Vis spectrum shows a single band with a maximum located at 356 nm. The photoluminescence emission presents two consistent bands with maxima located in the ranges of 320–340 nm (band A) and 400–410 nm (band B). To these emission bands correspond two bands in the excitation spectra located at 275 nm (band A) and 285 nm (band B). The fluorescence quantum yield was assessed as ∼16% using Rhodamine 6G as reference. The capabilities of the produced CQDs as fluorescent markers for in vitro studies were also evaluated by setting them in contact with a cell culture of L929 murine fibroblasts. Control and CQD-treated cell cultures were visualized under a fluorescence microscope. Finally, the mechanism of formation of these nanostructures by top-down methods is discussed, and a general model of formation is proposed.

Recent Advances on Synthesis and Potential Applications of Carbon Quantum Dots

“…The obtained CQDs have exhibited a quantum yield of 16% and emitted two consistent bands in the spectrum of 320-340 nm (band A) and 400-410 nm (band B) with excitation wavelengths of 275 nm (band A) and 285 nm (band B), respectively. These CQDs were utilized as a fluorescent biomarker for in-vitro investigations on L929 murine fibroblasts in a cell culture (Chao-Mujica et al, 2021). This approach can provide CQDs that can be used in bio-imaging applications.…”

Carbon Dots: Classification, Properties, Synthesis, Characterization, and Applications in Health Care—An Updated Review (2018–2021)

“…Currently, macroscopic carbonaceous materials including activated carbon, CNTs, and graphite are being extensively employed for the production of CDs by top-down approaches such as arc discharge method, laser ablation method, ultrasonic treatment, and electrochemical methods [45,80,108]. Nonetheless, these techniques are generally conducted under conditions such as high acidity, high potential, as well as high energy.…”

Research Progress in the Synthesis of Carbon Dots and Their Application in Food Analysis

“…Cui et al [ 28 ] fabricate CDs and applied them in biomedical imaging by the dual-beam laser ablation method. Chao et al [ 29 ] synthesize CDs with a quantum yield (QY) of 16%, and the wavelengths were 275 nm (A band) and 285 nm (B band) by arc discharge, as shown in Figure 1 a. The CDs obtained by arc discharge have good water solubility but contain many impurities that are difficult to extract and purify.…”