Optimization of extraction conditions to synthesize green carbon nanodots using the Maillard reaction

Abstract

Carbon nanodots (CNDs) are a class of nanoparticles with unique optical properties with broad applications in various fields. However, synthesizing CNDs with high fluorescence intensity and small size using a green solvent and low temperature remains challenging. In this study, we investigated the use of the Maillard reaction for synthesizing CNDs and optimized the reaction conditions at 120 °C for 12 h to achieve CNDs with desirable properties. The results showed that glycine was the most effective amino acid for CNDs formation when combined with sucrose. A molar ratio of 1 : 1 for glycine : sucrose resulted in the highest fluorescence intensity. The fluorescence intensity increased remarkably with 40% ethanol as the extraction solvent. However, a high ethanol concentration (above 60%) had an inverse relationship with CNDs’ fluorescence intensity, indicating that a high concentration of ethanol solution prevented the Schiff base formation. The purified CNDs (M-CNDs) were characterized using fluorescence spectrophotometry, UV-Vis spectroscopy, Raman spectroscopy, and TEM techniques. These findings provide a purification process of sustainable CNDs using the Maillard reaction and green solvents with optimized conditions and low temperatures.