Prof. Bogdan G. Dragnea Profile

Prof. Bogdan G. Dragnea

Professor at Indiana Univ

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Publications (3)

Proceedings Article | 17 September 2018 Presentation

A virus assembly experimental approach to the plasmonic Dicke effect (Conference Presentation)

Bogdan Dragnea

Proceedings Volume 10722, 1072210 (2018) https://doi.org/10.1117/12.2321176

KEYWORDS: Chromophores, Plasmonics, Luminescence, Natural surfaces, Proteins, Atmospheric particles, Metals, Nanoparticles, Antennas, Plasmons

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We introduce preliminary work aiming at developing a new generation of bio-enabled nanoscopic antennas which relies on quantum coherence to transform light energy into collective electronic excitations. The idea of super-radiant coupling between plasmons and molecular excited states has been discussed before, theoretically, in simplified contexts, e.g two state systems, in absence of geometric spatial symmetry considerations. Symmetry of molecular electronic states, and mesoscopic geometric constraints are factors that for the time being are easier to tackle experimentally. In our experiments, we decorate the surface of an icosahedral virus protein cage with organic dyes which interact strongly with the virus surface via intermolecular forces. We study the fluorescence emission under ultrafast pumping, in terms of intensity and lifetime as we increase the number of chromophores per particle. We find that, the initial increase in the number of chromophore, is accompanied by concentration quenching as one would expect from a dense chromophore system near thermodynamic equilibrium. However, above a threshold value (N = 135, 75% coverage), the intensity of fluorescence emission suddenly increases several times. The fluorescence lifetime is shorter than what we could measure with the current setup. We believe this to be a strong indication that collective relaxation tends to dominate emission when reaching near complete coverages. Control experiments that perturb the shell-chromophore interaction also destroy the suppression of fluorescence quenching effect. To study the near-field energy transfer between the chromophores excited state and the surface plasmon of a metal nanoparticle we encapsulate the later into a chromophore studded virus protein shell. Preliminary results show that the ratio of the integrated spectral density of emission from virus-like particles containing metal to the spectral density of emission from free dye depends on pump power. The same ratio is independent of pump power in the nanoparticle absence.