Fluorescence of D-Glucose-Derived Carbon Dots: Effect of Process Parameters

The aim of this study was to synthesize highly fluorescent carbon dots (CDs) from glucose using a microwave hydrothermal method. It explored the impact of glucose concentration, process time, molar ratio of KH₂PO₄ to glucose, and homogenization time on the resulting CDs, employing a fractional plan 3^(k-1) with four independent parameters for twenty-seven synthesis. Results showed that longer process times at 200°C increased the fluorescence intensity of the CDs. The molar ratio of KH₂PO₄ to glucose, glucose concentration, and process time significantly influenced fluorescence. Homogenization was crucial for obtaining small particles, though an anti-aggregation agent might still be needed. UV-vis spectroscopy, spectrofluorimetry, and DLS were used to analyze the synthesized CDs. The UV-vis absorption maxima were observed around 230 nm and 282 nm, with peak shifts at different excitation wavelengths. Out of the twenty-seven samples, six CDs samples were identified to be below 10 nm and a total of twelve below 50 nm. Analyzing the results, the study concluded that the CDs possess strong fluorescence and are suitable for diverse applications. For enhanced fluorescence, longer process times at 200°C and the use of KH₂PO₄ were recommended, while shorter processes were preferred for obtaining smaller particles. Hierarchical clustering, the k-means method, Pareto charts, and profiles for predicted values and desirability were used to analyze the results. It was confirmed that higher fluorescence is favored by longer process time at 200°C and the use of KH₂PO₄. In order to obtain smaller particles, shorter processes should be used.