Abstract
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.
Highlights
Carbon quantum dots or carbon dots, as a new class in carbonaceous nanomaterials have received much interest among researchers ever since its first discovery by Xu et al (2004) from the purification of carbon nanotubes [1]
For this study, rice husk is used as the precursor to synthesize carbon quantum dots due to its abundancy in environment, low cost, facile preparation method when compared to others biowaste precursors
C-rice husk-derived carbon quantum dots (RHCQDs) show the clearest image of spherical carbon dots among the samples
Summary
Carbon quantum dots or carbon dots, as a new class in carbonaceous nanomaterials have received much interest among researchers ever since its first discovery by Xu et al (2004) from the purification of carbon nanotubes [1]. Many studies have been done to investigate the synthesis process using different synthetic and natural precursors. Natural precursors are preferable among researchers due to their low-cost and high abundance advantages [4]. Rice husk is an agricultural waste and a by-product of rice milling processes [15]. For this study, rice husk is used as the precursor to synthesize carbon quantum dots due to its abundancy in environment, low cost, facile preparation method when compared to others biowaste precursors. Hydrothermal method, a bottom-up approach is commonly used in synthesizing the carbon quantum dots from natural precursor due to its facile synthesis, low cost and controlled morphology advantages [16]
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