Table 3.

Advantages and limitations of the major synthesis techniques of graphene–gold nanocomposites.

Synthesis Techniques	Advantages	Limitations	References
In situ reduction	One-pot synthesis. Efficient, easy to perform, and cost effective. Generally, no need of protecting surfactant or extra linker molecule. Can be employed by a lot of physical and chemical synthesis methods.	Hard to control the size and morphology of AuNPs in the resulting composite.	[25,83,84]
Ex situ	Prior synthesis of nanoparticles ensures good control over morphology, size, distribution and density of AuNPs on graphene.	Requires more time and steps.	[76,82,84]
Hydro-thermal	Synthesis of nanoparticles with high crystallinity and narrow size distribution. High production efficiency.	Requires high temp. and long reaction times, which may cause partial or complete reduction of GO.	[85,86,87]
Electro-chemical	Cost effective, robust and in most cases it’s a green approach. Morphology and size of the AuNPs can be fine-tuned by adjusting the electrodeposition potential, time and concentration of precursor solution.	Normally involves multiple steps.	[41,88,89,90,91,92]