The cyanide aqueous solution selectively leaches native gold and in solution it already exists in the form of a complex compound with CN ions. There will be no gold nanoparticles on the surface of your solution. It will be in the form of a complexing ion in the solution. On the surface there may be nanoparticles of other elements and compounds that do not dissolve in a cyanide solution. However, crushing the ore is difficult to achieve nano-sized material.