Photoluminescence plasmon-enhanced

Park HJ, Vak D, Noh YY, Lim B, Kim DY (2007) Surface plasmon enhanced photoluminescence of conjugated polymers. Appl Phys Lett 90 161107... 

DEVELOPMENT OF NANOTEXTURED METAL ASSEMBLIES FOR STRONG PLASMONIC ENHANCEMENT OF PHOTOLUMINESCENCE... 

As noted above, observations of large enhancements of the photoluminescence are insufficient to guarantee utility for application of plasmon-enhanced emission in OLEDs where the excited state is not photogenerated. In principle, increases in photoluminescence observed exfierimentally could be completely due to absorption enhancement. Even observation of reduced excited state lifetimes in conjunction with increased emission is insufficient to prove radiative rate enhancement since the lifetime reduction could be due to excited state quenching by the metallic surface and compensated by large absorption enhancements. 

Kochergin V, Christophersen M, Foil H (2004) Effective medium approach for calculations of optical anisotropy in porous materials. Appl Phys B 79(6) 731-739 Kochergin V, Christophersen M, Foil H (2005) Surface plasmon enhancement of an optical anisotropy in porous silicon/metal composite. Appl Phys B 80(l) 81-87 Kovalev D et al (1995) Porous Si anisotropy from photoluminescence polarization. Appl Phys Lett 67(11) 1585-1587... 

DUV spectroscopy includes several techniques, such as absorption and scattering spectroscopy, vibrational spectroscopy, photoluminescence, and plasmonically enhanced spectroscopy. This spectroscopic technique has been applied to materials that specifically interact with photons with DUV energies. The methods are not confined to component analysis, but have also been extended to microscopy (Chap. 7) and nanoscopy (near-field microscopy. Chap. 8), although the field is still in its infancy. 

N.E. Hecker, R.A. Hopfel, N. Sawaki, T. Maier, G. Strasser, Surface plasmon-enhanced photoluminescence from a single quantum well. Appl. Phys. Lett. 75,1577 (1999)... 

In principle, optical chemosensors make use of optical techniques to provide analytical information. The most extensively exploited techniques in this regard are optical absorption and photoluminescence. Moreover, sensors based on surface plasmon resonance (SPR) and surface enhanced Raman scattering (SERS) have recently been devised. 

Understanding the field enhancement of radiative rates is insufficient to predict how molecular photophysical properties such as enhancement of fluorescence quantum yield will be affected by interactions of the molecule with plasmons. A more detailed model of the photophysics that accounts for non-radiative rates is necessary to deduce effects on photoluminescence (PL) yields. Such a model must include decay pathways present in the absence of metal nanoparticles as well as additional pathtvays such as charge transfer quenching that are associated with the introduction of the metal particles. Schematically, we depict the simplest conceivable model in Figure 19. IB. Note that both the contributions of radiative rate enhancement and the excited state quenching by proximity to the metal surface will depend on distance of the chromophore from the metal assembly. In most circumstances, one expects the optimal distance of the chromophores from the surface to be dictated by the competition between quenching when it is too close and reduction of enhancement when it is too far. The amount of PL will be increased both due to absorption enhancement and emissive rate enhancement. Hence, it is possible to increase PL substantially even for molecules with 100 % fluorescence yield in the absence of metal nanoparticles. 

In the present paper, we report on observation of the pronounced enhancement of photoluminescence of semiconductor nanocrystals near nanostructured metal surfaces which is shown to depend essentially on nanocrystal-metal spacing. Unlike conventional SERS, the surface enhanced PL should exhibit non-monotonous character with distance between emitting dipole (QD) and metal surface (Au colloid). The reason is that at smallest distances when QDs and colloidal particles are in close contact, the QD emission should be damped due to resonant energy transfer (RET) from photoexcited QDs to metal colloidal nanoparticles. Enhancement of photoluminescence (PL) is possibly promoted by surface plasmons excited in the metal. So, at a certain distance the enhanced QD emission would exhibit a maximum. We use a polyelectrolyte multilayers as the most appropriate... 

Core-shell NPs exhibit unique properties with several possible applications. In the case of fluorescent saniconductor NPs, core-shell NPs help to increase the robustness and enhance the photoluminescence quantum yield as well as the probability of radioactive recombination. NPs with magnetic, plasmonic and semi-conducting properties can be used as cores or shells for manipulating the properties of these hybrid structures. Properties of either component within the hybrids (core-shell NPs) can be modulated through a conjugating component or interface. 

The interaction of RE with silver NPs was also used for increasing upconver-sion of infrared energy, which cannot be used for solar cells, to visible light where the solar cells are sensitive. Some examples can be foimd in Refs. [65,66] and in the recent paper by Sun et al. [67], where upconversion provides an additional example in this direction. Energy transfer enhanced by silver plasmons allowed a strong upconversion from infrared light absorbed by Yb to visible photoluminescence of Er. 

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