Gold nanoparticles fluorescence enhancement

Kuhn et al. observed the fluorescence enhancement and fluorescence decay rate of a single terrylene molecule when a spherical gold nanoparticle was approached to the... 

Kiihn, S., Hakanson, U., Rogobete, L., and Sandoghdar, V. (2006). Enhancement of ingle-Molecule Fluorescence Using a Gold Nanoparticle as an Optical Nanoantenna. Phys. Rev. Lett. 97 017402-1-4 see also Supplementary info. 

Nakamura, Y., and Hayashi, S. (2005). Enhancement of dye fluorescence by gold nanoparticles analysis of particle size dependence. Jap. J. Appl. Phys. 44, 9A 6833-6837. 

Metal nanoparticles have attracted considerable interest due to their properties and applications related to size effects, which can be appropriately studied in the framework of nanophotonics [1]. Metal nanoparticles such as silver, gold and copper can scatter light elastically with remarkable efficiency because of a collective resonance of the conduction electrons in the metal (i.e., the Dipole Plasmon Resonance or Localized Surface Plasmon Resonance). Plasmonics is quickly becoming a dominant science-based technology for the twenty-first century, with enormous potential in the fields of optical computing, novel optical devices, and more recently, biological and medical research [2]. In particular, silver nanoparticles have attracted particular interest due to their applications in fluorescence enhancement [3-5]. 

Figure 20.3 Enhanced optical properties of gold nanoparticles resulting from the interaction of light with a gold nanoparticle including absorption, Mie scattering, fluorescence and surface nhanced Raman scattering of adsorbed molecules. Reprinted with permission from ref 3. Copyright 2007 Future Medicine.

The excitation of the surface plasmon effect also induces strongly enhanced fluorescence properties of gold nanoparticles due to the enhanconent in the radiative rate of the inter-band electronic transitions relative to that in bulk metals. Metal nanoparticles, especially gold nanorods exhibit enhanced two-photon luminescence (TPL) and multi-photon luminescoice (MPL) [7, 8]. Strongly-enhanced TPL has been observed from individual particles [9, 10] and particle solutions [11] under femtosecond NIR laser excitation. This observation raises the possibility of nonlinear optical imaging in the NIR region, where water and biomolecules have... 

The nanoparticles can be incorporated into cells by incubation the nanoparticies suspended in DMEM medium with the cells for 12 to 48 hours. From dark field light scattering imaging [54], it has been established that gold nanoparticies are taken intracellulariy into these cell lines. The nanoparticies are accumulated inside cytoplasm of live cells by receptor-mediated endocytosis processes. Figure 20.16 shows that for most of samples gold nanospheres quench the protein fluorescoice at 12 h incubation time. However, in some samples fluorescence enhancement is observed. 

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