I just wanted to know the Joint Committee on Powder Diffraction Standards (JCPDS) card number for silver nanoparticles and whether it can be called as JCPDS or ICDD?
Silver is of A1 structure ("fcc") with a = 4.085 A. This info is sufficient to calculate your diffraction pattern, even if your material is nanocrystalline. ICDD/JCPDS is there to solve your technical problems, but it is not a scientific tool. So leave out ICDD from science. Refer to original works and not to databases when writing scientific papers.