Abstract

New class of nanocarbon materials, such as luminescent carbon quantum dots (CQDs) has gained a great deal of interest in the area of electrocatalysis, solar cells, bioimaging nanomedicine, a chemical sensor and a light-emitting diode. CQDs exhibit good physio-chemical properties, such as photoluminescence, high crystallization and good dispersibility. The rapid electron transfer, small size and superconductivity of CQDs provide the CQDs-based composite offering enhanced catalytic activity and electric conductivity. However, additional active moieties are present on the surface, which might aid in the formation of multi-component electrically activated catalysts. Additionally, the multi-component catalysts' internal interactions promote charge transfer and catalytic efficiency, both of which are essential for electrochemistry. Therefore, keeping in mind the importance of CQDs, they are synthesized on the basis of two approaches: Top-down and Bottom-up. The bulk material is reduced in size by utilizing chemical and physical processes in the top-down approach. On the contrary, in the bottom-up method, the atoms are assembled and converted into CQDs using polymerization and carbonization through a chemical reaction. Hence, in this chapter, we will discuss the synthesis techniques for CQDs, such as hydrothermal/solvothermal method, laser ablation, arc-discharge method, acidic oxidation, thermal/combustion routes, electrochemical method and microwave pyrolysis method.