Au nanoparticles

I am interested in characterizing Au nanoparticles dispersed on flat surface. When using diffraction technique, e.g. X-ray or electron, I
realize that Au nanoparticles are often conjugated but not unconjugated in the literature. The surface of the substrate is also modified with, e.g. polymers. It could probably be to deposit charged Au particles by electric force to the substrate.
But if you simply want to disperse Au nanoparticles, you can disperse unconjugated ones on a substrate. Why do people do not do this? Does any one know why is this? At room temperature, do the nanoparticles move around, collide and form larger particles? Is there any literature I could not find for this?
If any one knows anything about this, it would be a great help for me.
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