So, what's the exactly components substance of the plastic scintillators we are looking for ? which...(and after all this time researching...) is in fact the radioactive source of the x ray machines...produced by nuclear reactors.

Ytterbium Fluoride Nanoparticles

http://www.getnanomaterials.com/nanoparticles/ytterbiumfluoride/

1. 

   Ytterbium Fluoride (YbF3, 99 %, 40-80 nm)

   Size:	40-80 nm
   Purity:	99%
   Nanoparticles:	Ytterbium Fluoride
   Morphology:	nearly spherical
   Type:
   GNM ID:	#5670YD
   Properties:	Ytterbium Fluoride Nanoparticles: #5670YD