Your question is not completely clear to me. Are you talking about graphene quantum dots (GQD) grown on a metal surface? In that case there is only the single layer of graphene, so no interplanar spacing. There is a spacing between the GQD on the metal surface that is more or less depenedant on the way you prepare your sample. This spacing is best tuned using the temperature programmed growth (TPG) technique, or a mix between TPG and CVD. For more info on these techniques I suggest you read the following reference: http://iopscience.iop.org/1367-2630/11/2/023006.