Table 1.

Summary of the advantages and disadvantages of different C-dot synthesis methods.

	Methods	Advantages	Disadvantages
Top-down	Electrochemical oxidation	High purity, high yield, controllable size, good reproducibility, low cost	Complicated operation, especially when doping with heteroatoms
	Laser ablation	Simple experimental setup, can produce particles with different sizes and controllable morphology by changing experimental parameters	Low yield and high cost
	Chemcial oxidation	Inexpensive equipment and can produce c-dots are a large scale	Numerous tedious steps, usually requires toxic reagents and strong acid/base. Non-uniform size distribution
	Ultrasonic synthesis	Easy operation	High energy cost and instrumental wastage
Bottom-up	Hydrothermal treatment	Low cost, with simple control of key parameters such as temperature, time and pressure of the reaction vessel. The produced c-dots also have a high quantum efficiency and are non-toxic.	Long synthesis duration and at a low yield
	Microwave synthesis	Short reaction time and it is easy to control the size of the particles with the c-dots produced being uniform in size distribution.	High energy cost
	Thermal decomposition	Easy operation, solvent-free, low cost and can produce c-dots at a large scale	Low yield