Local Field Effect on Luminescent Properties of Organic Molecule-doped Silica Nanoparticles

Abstract The local field effect involves the modification of the spontaneous emission rate of an emitting center in a nanoparticle (NP) due to its environment which modifies the photon density of states and the electric field acting within the NP. We are unaware of reports of this effect for organic molecules so that we encapsulated a green dye and a porphyrin in a silica shell and dispersed these in media of different refractive index. The emission decays were monoexponential so that the calculated lifetimes could be fitted by a model recently employed for the local field effect. It was found that a good fit was achieved for the smaller NPs employed, indicating the importance of the effect, but the effect was not important for the larger NPs where different behavior was observed due to agglomeration.