Abstract
In the 1960s, experimental studies and modeling showed that electrodynamics based on flat metal surfaces can cause decrease in the fluorescence signal of chromophores when these molecules are close to the surface. Moreover, it was found that rough surfaces and nanoparticles can amplify the optical properties, especially the Raman scattering, which gave rise to technical Surface-Enhanced Raman Scattering (SERS). It was shown that it is possible to switch between brightness enhancement and quenching of fluorescence only by varying the distance metal chromophore and therefore to determine the conditions under which each effect is favored. These properties are useful for many areas, such as analytical, biosensors, electronics and materials science. However, there is still no systematic study in the literature, including various compositions, sizes and shapes of nanoparticles. On the other hand, computer simulations are a natural way for in-depth study of fluorophore-nanoparticle interaction, and there are already some papers in the literature. Instead of that, there are computational limitations to treat nanoparticles, and clusters usually replace them. The validity of this substitution has been little explored. So, this project aims to determine how to make changes in the fluorescence spectra of dyes in the presence of metal nanoparticles, using a computer simulations in two main approaches: (a) using "discrete" metal clusters, for which will be evaluated the minimum number of metal atoms that we have to include to obtain the effects on fluorescence spectra, and (b) using a polarizable dielectric to simulate the effects of a nanoparticle. We intend also to conduct systematic experimental studies, in which fluorophores and nanoparticles (composition, shape and size) will be evaluated. (AU)
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