Hi,

There are several approaches by how you can do this.

For example, simple soaking procedure- soak the graphite disk in the colloidal Ag or Cu medium for some time. Selection of solvents can help in achieving homogenity for some extent. You can play with a binary solvent system for better result.

Another approach is to mix the graphite powder (if possible) with the Cu or Ag colloidal solution under ultrasonication. You can then spin or dip coat into a suitable substrate. Time and adequate solvent (viscosity is a factor) selection can help. 

I hope it helps. Good luck.

What Aswin proposes makes sense of course, but I am afraid the amount of coated metals will not be high because there is no "glue" on the graphite surface which would hold metals. I am not a synthetic chemist, therefore just wondering about 2 possibilities: 1) either to grow graphite around metal nanoparticles in solution, so that graphite walls embrace metal particles and trap them physically; 2) here is one PhD thesis when functionalisation of carbon nanotubes surface was done. https://depositonce.tu-berlin.de/handle/11303/4402   (file on the down part as pdf).  Would it be possible to modify graphite surface as well?   Sorry about not suggesting something concrete, just some ideas 

Probably, This publication will be helpful for you:

https://www.researchgate.net/publication/276415611_Nanostructuring_of_the_carbon_macrofiber_surface

Good luck!

Article Nanostructuring of the carbon macrofiber surface