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Electronic excitations and resonance energy transfer in hybrid nanosystems

Giovedì 2 novembre 2017 alle ore 15:00, aula Seminari, S3 Cnr Nano, edificio Fisica, Modena

Relatore: Gabriel Gil Perez (CNR - NANO S3, Modena, Italy
Abstract: Hybrid nanosystems, composed of organic dyes and a semiconductor nanoparticle (NP), belong to a class of nanomaterials with great prospects in a number of biological and medical applications as well as in optoelectronic devices. The underlying advantage of the latter is that one can profit especially from both a) the possibility to tailor specific electronic and optical properties by controlling the size and composition of NPs, as well as from b) the abundance of dyes in Nature, their solubility, biocompatibility, and the fact that they can be functionalized.
Many of the envisaged applications for hybrid nanosystems rely on the interaction with light, and the intrasystem processes promoted by such interaction. One of these processes is the resonance energy transfer (RET) from the NP to the dye (or vice versa), consisting of the simultaneous and radiationless de-excitation of one of the subsystems (the donor, e.g., the NP) and the excitation of the other (the acceptor, e.g., a dye).
Since the NPs may be composed of millions of atoms, there is a theoretical and computational challenge in treating RET processes within hybrid nanosystems. In the seminar, I will present a new multi-scale approach to treat electronic excitations of the whole hybrid nanosystem -as well as RET between its fragments-, whose computational cost is independent of the size of the NP. In our method, optical excitations of each subsystem are accurately described within a quantum-mechanical approach at the appropriate level of description, i.e., a state-of-the-art first-principles for the molecule (e.g., Time-Dependent Density Functional Theory) and an accurate -yet semi-empirical- envelope-function based Configuration Interaction of excited electron-hole pairs (excitons) for the nanoparticle. Taking into account realistic systems involved in applications, our multi-scale approach allows us to incorporate and study the effect of all transition multipole moments of the NP, a development beyond the standard Förster theory, as well as the inherent anisotropy in dye-NP RET, typically neglected in experimental analyses. Finally, I will show preliminary results on how NP antennas could enhance the light-harvesting ability of protein-pigment complexes taking part in the photosynthesis of bacterial organisms.

[Ultimo aggiornamento: 27/10/2017 10:38:07]