The maximum absorption wavelength increases with the increasing of larger size AgNPs percentage volume. Such a red-shift is characteristic for an increased NPs size. The position of the absorption maximum of poly disperse colloid does not give information about the size of nanoparticles, because it is not possible to observe peaks separation form specific populations in these colloids. The plasmon resonance will be redshifted to a longer wavelength for a multi-nanoparticle aggregate than the resonance of an individual nanoparticles. Thus the aggregation is observable as an intensity increase in the near infrared region of the spectrum