Metal nanoparticle scattering

Wlrile tire Bms fonnula can be used to locate tire spectral position of tire excitonic state, tliere is no equivalent a priori description of the spectral widtli of tliis state. These bandwidtlis have been attributed to a combination of effects, including inlromogeneous broadening arising from size dispersion, optical dephasing from exciton-surface and exciton-phonon scattering, and fast lifetimes resulting from surface localization 1167, 168, 170, 1711. Due to tire complex nature of tliese line shapes, tliere have been few quantitative calculations of absorjDtion spectra. This situation is in contrast witli tliat of metal nanoparticles, where a more quantitative level of prediction is possible. 

The optical properties of metal nanoparticles have traditionally relied on Mie tlieory, a purely classical electromagnetic scattering tlieory for particles witli known dielectrics [172]. For particles whose size is comparable to or larger tlian tire wavelengtli of the incident radiation, tliis calculation is ratlier cumbersome. However, if tire scatterers are smaller tlian -10% of tire wavelengtli, as in nearly all nanocrystals, tire lowest-order tenn of Mie tlieory is sufficient to describe tire absorjDtion and scattering of radiation. In tliis limit, tire absorjDtion is detennined solely by tire frequency-dependent dielectric function of tire metal particles and the dielectric of tire background matrix in which tliey are... 

To summarize, we have shown here that enhanced electric-field distribution in metal nanoparticle assemblies can be visualized on the nanoscale by a near-field two-photon excitation imaging method. By combining this method and near-field Raman imaging, we have clearly demonstrated that hot spots in noble metal nanoparticle assemblies make a major contribution to surface enhanced Raman scattering. 

Cade NI, Ritman-Meer T, Kwaka K, Richards D (2009) The plasmonic engineering of metal nanoparticles for enhanced fluorescence and Raman scattering. Nanotechnology 20 285201... 

Fig. 9.1.7 Image of the colloidal dispersions of the envelopes with and without metal nanoparticles. Light scattering can measure the average size of both envelopes, and the Taylor dispersion method can do only the size of the envelopes with metal nanoparticles.

Metal nanoparticles have been intensively studied due to their potential for both fundamental and applied research. They give a possibility to examine the material properties in transient conditions between the bulk material and separated atoms. Some phenomena, such as surface plasmon resonance transitions, electron-electron or electron-phonon scattering have special character in metal nanoparticles. 

Gold nanoparticles have large second- and third-order nonlinear susceptibilities and are therefore a promising class of nonlinear optical materials.214 We will briefly discuss several nonlinear optical processes from metal nanoparticles, such as multiphoton luminescence, hyper-Rayleigh scattering, and multiharmonic generation. 

The versatility of the crosslinked structures opens a new broad avenue for their application in several areas. As mentioned above, corona-crosslinked PFS assemblies demonstrate excellent shape retention upon pyrolysis and permit the formation of ceramic replicas. We have also recently shown that in a common good solvent, the PFS chains in the microgel interior of xPMVS can serve as a microreactor forthe localized production of metal nanoparticles [25], We are also about to begin light scattering studies of PMVS micelles, before and after corona crosslinking, and hope to use these experiments to learn more about the self-assembled structures formed in dilute solution. 

Johansson, P., Xu, H., and Kail, M. (2005). Surface-enhanced Raman scattering and fluorescence near metal nanoparticles. Phys. Rev. B 72 035427-1-17. 

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