Plasmon–Excitation Coupling for Dithienylethene/Gold Nanoparticle Hybrid Systems: A Theoretical Study

Abstract

We present a theoretical study dedicated to the optical response properties of a photochromic dithienylethene molecule physisorbed on gold nanoparticles (NPs). The absorption spectra are obtained with the discrete interaction model/quantum mechanics scheme recently developed by Jensen and coworkers. This hybrid scheme relies on an atomistic electrodynamics model of the metal NP and a time-dependent density functional theory description of the molecule. The first two absorption bands, S1 and S2, of the closed-ring dithienylethene, overlap with the plasmon resonance band of the metallic part. These bands are found to be highly impacted by the localized enhanced electric field generated by the external field applied (the plasmon band) and, to a lesser extent, by the dipolar environment created by the gold atoms. The coupling between the molecular excitations and the plasmon is observed up to distances of the order of the NP diameter. This coupling is highly dependent on the orientation of the molecule with r...