Which excitation wavelength is most suitable for subdiffraction limited Gold (Au) nanoparticle (NP) to excite its surface plasmons??
If we are using a series excitation wavelength from NUV to IR (325, 456, 488, 532, 632 and 785) what will be the most suitable laser for the excitation of surface plasmons in the subdiffraction limited Gold NPs (d=100 nm). If there exist a particular suitable wavelength, what is the value of it? and what will be the physical reason for choosing that particular wavelength for exciting SPPs ??
if it possible please help me by giving an answer.......
It depends on the nature of the surrounding medium, and if you are interested in the photothermal properties or the near-field enhancement, but 532 nm will certainly be the best option. The resonance of a 100-nm spherical gold nanoparticle in water is around 570 nm (extinction cross section).
dear Dr. Guillaume Baffou
thank you for kind attention and valuable suggestions...
Actually we are planning to do all of our experiments in open air itself.....
actually still, we have some doubts on how the Resonance will varies with particle size and excitation wavelength...
or in simple words... may I know the exact criteria for to observe surface plasmon resonance on noble metals....
will it purely depend on excitation wavelength ??
All your questions could be the basis of a whole textbook's chapter. So I'm not sure I can explain you everything in this reply.
Your nanoparticles will certainly not be completely surrounding by air, they will be at least deposited on a substrate. The permittivity of the substrate will affect the resonance and will have to be taken into account in simulations.
I don't have a reference in mind that simply explain how the resonance shifts as a function of the particle size and excitation wavelength. But you can keep in mind that enlarging or distorting a nanoparticle from an initial spherical shape tends to red-shift the resonance.
All your questions could be the basis of a whole textbook's chapter. So I'm not sure I can explain you everything in this reply.
Your nanoparticles will certainly not be completely surrounding by air, they will be at least deposited on a substrate. The permittivity of the substrate will affect the resonance and will have to be taken into account in simulations.
I don't have a reference in mind that simply explain how the resonance shifts as a function of the particle size and excitation wavelength. But you can keep in mind that enlarging or distorting a nanoparticle from an initial spherical shape tends to red-shift the resonance.
All your questions could be the basis of a whole textbook's chapter. So I'm not sure I can explain you everything in this reply.
Your nanoparticles will certainly not be completely surrounding by air, they will be at least deposited on a substrate. The permittivity of the substrate will affect the resonance and will have to be taken into account in simulations.
I don't have a reference in mind that simply explain how the resonance shifts as a function of the particle size and excitation wavelength. But you can keep in mind that enlarging or distorting a nanoparticle from an initial spherical shape tends to red-shift the resonance.
thank you for your suggestions Dr . Guillaume Baffou
but if you are finding some good explanatory articles or books you can inform me..
thank you...!
The plasmon resonance frequency will depend upon the size of your gold nanoparticles (and their shape) and the surrounding medium. If you have access to a simple UV-Visible spectrometer (either transmission or reflectance mode), you might take a spectrum to directly determine the absorption frequency of your particular gold nanoparticle sample. In work I did with gold nanoparticles used as catalysts, the UV-Vis spectrum agreed very well with XPS values--and x-ray photoelectron spectroscopy can also be used to determine the plasmon frequency. An excerpt from one of my reports: "Preferred catalysts utilized nanogold with crystallite size distribution
You might also do a quick search using key words: "UV visible spectra nanogold".
This should bring up many examples showing absorption frequencies of nanogold plasmons.
If you search using key words: "UV-visible spectra gold nanoparticles", you should find many examples with maximum absorption near your laser frequency of 532 nm. I am not certain of your applications, but as an alternative, you may wish to modify your gold nanoparticle synthesis procedure (or its surrounding medium) so that their plasmon absorption frequency closely matches the frequency of your available lasers.
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