Quenching nanoparticles

In Figure 5, the normalized emission spectra of the two solid hybrid materials, GFP/SBA-15 and GFP/Aerosil , are reported. The shape of the emission profile for GFP/SBA-15 follows closely that of the GFP in buffer solution, whereas the photoemission intensity of GFP/Aerosil is one order of magnitude lower and slightly different in its tale shape (spectra at the actual intensities not reported). This reduction in intensity could be explained by a multilayer arrangement of the protein molecules on the amorphous nanoparticles, which would explain both the difference in emission spectra ("self-quenching effect") and the difference in adsorption amount shown above. 

Much effort has been made to establish the optimum distance between the dye and the surface of the metal particle. If fluorescence from a molecule or nanoparticle is directly adsorbed onto the surface of a metallic particle, it is strongly quenched due to electron transfer, and if the distance is too large, the enhancement effect has again to vanish there should, therefore, be an optimal distance for the observation of the enhancement effect. Based on experiments with organic dyes [84, 85] and Quantum Dots [80], this distance should be 5-10 nm. 

Gouanve F, Schuster T, Allard E, Meallet-Renault R, Larpent C (2007) Fluorescence quenching upon binding of copper ions in dye-doped and ligand-capped polymer nanoparticles a simple way to probe the dye accessibility in nano-sized templates. Adv Funct Mater 17 2746-2756... 

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