Modeling of multi-photon-induced photoluminescence from organic fluorophores and metal-coated semiconductor nanoparticles

In this talk I will describe some applications of multiphysics modeling of molecular and nano-particle materials that have been carried out at our department. Among the various multiphysics approaches, those that combine quantum mechanics with wave mechanics and quantum mechanics with statistical mechanics have turned out to be particularly powerful for predicting optical properties of organic fluorophores, respectively, nanoparticles. The first type of combined approach allows to estimate the optical transmission from cross sections of multi-photon absorption processes and from considerations of propagation and saturation effects. The other type of combined approach, quantum mechanics with statistical mechanics, allows to account for the spontaneous photon emission of two-photon excited quantum dots including the nonradiative energy dissipation process of phonon scattering. Multi-photon quantum dots offer the combined advantage of brilliance and photo- resistance of normal quantum dots with the 3-dimensional confocality and penetration of multi-photon excitation, something that can have a broad ramification on fluorescence based experiments in biology. We have in particular investigated multiphoton-induced photoluminescence from metal-coated coated quantum dots under the influence of electromagnetic field enhancement associated with surface plasmon resonances. It is argued that up-conversion luminescence of coated quantum dots is a promising approach for bio-imaging as it can generate the multiphoton excitation at reduced laser intensities.