Effect of Amino and Carboxyl Functionalization on the Photoluminescence Properties of Rice Husk-Derived Carbon Quantum Dots (RH-CQDs)

In this work, carbon quantum dots (CQDs) are synthesized using rice husk as a natural precursor. The effect of amino and carboxyl functionalization is studied by adjusting the amount of ethylenediamine (EDA) as the amino source and ascorbic acid as the carboxyl source. HRTEM analysis show the formation of spherical carbon quantum dots. FTIR analysis confirms the presence of OH and CO bonding, indicating formation of CQDs. The addition of EDA and ascorbic acid quenches the fluorescence and shifts the emission wavelength from blue region (450-485 nm) to green region (500-565 nm). Based on the results, N-RHCQDs (0.6 ml) and C-RHCQDs (2.5ml) are chosen as the best samples as they give the highest quantum yield of 0.37% and 3.26% respectively. This implies that the fluorescence intensity is higher at a more basic and less acidic condition. This study suggests that the addition of different functionalization agents can tune the photoluminescence properties of CQDs that will be beneficial for its application.