The plasmonic effect is the interaction between free electrons in metal nano particles and incident light. Why is this effect possible in metal nano-particles? Is it observable in bulk metals rather than metal nano-particles? What is the reason behind it?
Dear Shamjid,
maybe in this review you will find answer to your questions: http://turroserver.chem.columbia.edu/surfaceplasmons/pdf/20_csr_35_209_plasmonreview.pdf
In bulk metals, you need to irradiate it with incident light so that the TM-polarized light will propogate along the bulk surface. These waves moving along the surface will cause the surface electrons in the material to move back and forth along the surface, hence plasmon resonance. You need special configurations of bulk materials to acheive this, the most conventional way being putting a thin film of gold on a prism and shining a laser light through at an oblique angle (IE krestchmann configuration: https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&es_th=1&ie=UTF-8#safe=off&q=kretschmann+configuration&spell=1)
For nanoparticles smaller than the wavelengths of the light, the free electrons can move all around the particle. Consider spherical particles: the free electrons can move along the surface of the sphere in any manner. Thus, they can couple to any incoming electromagnetic field and move with it along the component of its electric field polarization projected on the sphere.
In both metal and metal nanoparticles. free electrons are there. Then why the plasmonic effect is in metal nanoparticles only
Plasmonics effects are found in both cases, bulk as well as metal nanoparticles. However, It is a matter of the desired effect which can be different in two cases. For example if you're concerned for localised surface plasmon resonance, hotspots generations, nanoparticle case is better. In a nutshell if you are looking for volume plasmonic responses, you would look for bulk metals and if for surface plasmonic effects you would look for nanomaterial. For clear understanding, You can go through the book,Kreibig U, Vollmer M (1995) Optical properties of metal clusters.Springer, New York.
Other papers on experimental side: J Appl Phys 109: 044311 (2011), Phys Status Solidi B 246: 2232–2237 (2009), Physica E 43:470–474 (2010), Plasmonics 9:129-136 (2014)
Shamjid,
Manish is right. Both bulk and surface plasmons (or surface plasmon polaritons) do exist. Bulk plasmons have the same nature and occur in the bulk of metals. I suggest you review any textbook on Solid State Physics, like Kittel on this subject.
Surface plasmons require an interface. Hence, an evanescent wave is confined to such metal-dielectric interface. As a result, one can observe surface plasmon resonance (SPR) in thin film structures or localized SPR (LSPR) in metal nanoparticles.
In (metal) nano-particles the interpretations of surface and volume (bulk) plasmons are more cumbersome then in the macroscopic metals. Think about the fact that due to quantum effects is not entirely correct to define the surface of such a particle since the electron density is not sharp, but falls exponentially towards infinity. Therefore, it is hard to say that an oscillation is localized on the surface (interface) of the nano-particle.
Instead, there have been theoretical studied that showed how a volume plasmons can be excited only by non-uniform electric fields, i.e. Electron Loss Spectroscopy experiments, so that is how you can separate in the spectrum the volume plasmon from a surface one
Plasmonic effect is observable in both nano particles and bulk metal, but because of large surface area and favorable conditions for plasma generation in metal nano particles it achieves greater plasmonic effect. For plasmonic effect generation there are two main conditions first is free electron and second dielectric properties. both conditions present when we use nano metal particles compared to bulk metal.
plasmonic effects are more prominent in Nanoparticles and thin films than in bulk material because of localized effects are generated by same number of photons for less number of particles(electrons) to oscilate for genration of plasma oscillation.
Shamjid Palappra I can't see any satisfactory answer here. Pls check the link below:
https://www.researchgate.net/post/Is_there_any_differences_between_Surface_plasmon_polariton_and_surface_plasmon_resonance
100% sure you will have better understanding once you check Dr. Peter's answer.
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