XRD may work to identify your samples. If it was core-shell, XRD shows two groups of diffraction peaks from CdSe and CdS.

If the dots were very small---only a few nm---, the peaks become broad and hard to distinguish each peaks. But I think it's worth to try.   

Thanks a lot Yoshiki

Dear Nitin,

You can go for multiphase powder profile refinement if you know the cell parameters of the two phases.