Synthesis and Comparative Analysis of Carbon Dots: A Study on Continuous Flow, Microwave, and Furnace Methods

Since the discovery in 2004, Carbon Dots (CDs) have gained significant attention due to their unique properties, making them suitable for a wide range of applications. This study investigates the synthesis and properties of CDs using three different methods: continuous flow (CF), a microwave synthesizer, and a furnace. Additionally, it assesses the potential advantages of the CF technique compared to conventional batch methods.

The CD synthesis involves simple precursors and environmentally friendly solvents, aiming to optimize reaction parameters like temperature, flow rate, and reactant concentration to enhance quality and yield. Detailed characterization of the CDs includes Fluorescence spectroscopy, UV-vis spectroscopy, FT-IR spectroscopy, TEM imaging, Raman spectroscopy, and Dynamic Light Scattering (DLS).

Ideally, CF setups offer precise control over reaction conditions, scalability, and efficient mixing. The results suggest minor differences among CDs synthesized using the different methods, accompanied by common challenges such as incomplete carbonization, particle aggregation, and purification difficulties.

There is a need for standardization of purification and work-up techniques, requiring further optimization, including the use of dialysis as chosen in this study.

Although CF synthesis shows promise for automation and scalability, it faces obstacles concerning gas evolution and pressure control.

Certain trends were evident. For instance, nitrogen content enhanced the fluorescence of particle solutions. Prolonged residence times in cascade experiments correlated with decreased FL intensity, indicating more defined carbon cores. UV-vis spectra exhibited distinct absorption peaks at 332 nm, while FT-IR analyses depicted broad peaks indicative of complex molecular environments.

Both Raman and DLS measurements faced challenges due to interference from sample fluorescence. TEM imaging confirmed the heterogeneous nature of CD samples, with larger particle sizes than previously reported.

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