Upon a resonant excitation by a specific wavelength, the collectively oscillating electrons in the conduction band of a noble metal nanoparticle, i.e. localized surface plasmon resonance (LSPR), prompt a strong light absorption in the UV/vis region. The wavelength coincidence of a chromophore with LSPR leads to an enhanced optical response of the system and could facilitate its study at low concentrations [1]. 

The state-of-the-art modeling of the resonance UV/vis spectroscopic properties relies on a specific hybrid discrete interaction/quantum model (QM/DIM) which describes the chromophore at TDDFT level, in presence of an electrodynamical treatment of the nanoparticle, including electrostatics and polarization of the atoms [2]. However, prior to applying such a complex model, the nanosystem under investigation has to be carefully chosen. Indeed, a resonant coupling between a large inorganic nanoparticle and a small organic chromophore can only occur in specific conditions, thereby necessitating the design of both nanosized systems. We propose here to investigate the optical properties of a new class of versatile chromophores [3] whose first singlet-singlet absorption energy can be tuned to be in resonance with the surface plasmon of a noble metal nanoparticle. At lower size scale, we further show that the coupling between an organic chromophore and an inorganic metal cluster is a methodological challenge. We thus demonstrate how our last developments in DFT can provide some answers to that specific issue [4].

[1] M. A. El-Sayed Annu. Rev. Phys. Chem. 54, 331 (2003).

[2] J. L. Payton, S. M. Morton, J. E. Moore and L. Jensen J. Chem. Phys. 136, 214103 (2012).

[3] R. Gueret, L. Poulard, M. Oshinowo, J. Chauvin, M. Dahmane, G. Dupeyre, P. P. Lainé, J. Fortage, M.-N. Collomb ACS Catal. 8, 3792 (2018).

[4] É. Brémond, A. J. Pérez-Jiménez, J. C. Sancho-Garcia and C. Adamo J. Chem. Phys. 150, 201102 (2019).