Coupling of metal nanoparticles causes a red-shift in extinction spectrum. So the extinction spectrum of a metallic dimer is not equal to sum of isolated nanoparticles extinction spectra. To determine the contribution of each nanoparticle in coupling, it is necessary to decompose the extinction spectrum of coupled nanoparticles (specially in asymmetric coupling of nanoparticles). How is it possible to decompose extinction spectrum of coupled particles to its components?
Let me ask you a question. Assume that you have the spectrum of e.g. GaAs, a semiconductor. Do you think you can obtain its spectrum if you investigate the spectra of elemental Ga and elemental As?
Thank you for your reply Thomas.
Obviously, the answer of your question is: no, because the electronic band structure of GaAs is completely different in comparison with Ga and As. In the case of coupled nanoparticles, no electron is exchanged and scattered electromagnetic field causes the coupling.
My question was formed as I was reading this paper:
Surface Plasmon Coupling of Compositionally Heterogeneous Core–Satellite Nanoassemblies
In Fig. 1(b) you can see the decomposed extinction spectrum of Au-Ag assembly. Based on this analysis, the author have determined the contribution of each component in extinction.
You may refer to the attached documents for details.
Sincerely,
Hossein
Actually my comparison with GaAs was poor in hindsight, since in the case that interests you, all particles are the same, right?! On the other hand, it might be correct to compare the properties of a material in the solid state and in the gas phase. Assuming that it is not Van-der-Vaals interactions that holds the material together in the solid state, the interaction changes the properties dramatically compared to the isolated moieties. Since all of them are the same, how will you attribute the interaction to the individuals? If they are all the same, you can only divide the interaction symmetrically and you end up with attributing the same spectrum to each individual particle, so there is no sense in doing so, or do I miss something?! Maybe the quantum chemistry analogon of having a bonding and an antibonding state (resonance hybridization) will help you to understand what is going on if metallic dimers, trimers or even oligomers interact. See e.g.
Article A Hybridization Model for the Plasmon Response of Complex Na...
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