Modeling Atomistic Nanoplasmonics: Classical and Hybrid Quantum Mechanical/Classical Schemes

Nanoplasmonics is characterized by complex physical phenomena that give rise to enhanced optical properties of plasmonic substrates. Furthermore, the interaction of nanoplasmonic devices with molecular systems can significantly influence the molecular response, leading to either enhanced or quenched physicochemical properties, such as their spectroscopic signals. Therefore, understanding the theoretical foundations of nanoplasmonics is essential for the experimental optimization of these devices, prior to their commercialization. In this context, we have developed theoretical approaches grounded in classical physics to evaluate realistic, large-scale nanoplasmonic substrates. These classical approaches retain the atomistic characteristics of the plasmonic profile, which strongly influences the material’s response. The results obtained have been benchmarked and validated against ab initio and experimental data, thus confirming the robustness of our calculations. Furthermore, we have extended these approaches to evaluate plasmon-mediated molecular properties. With this aim, we have coupled these classical methodologies to analyze nanoplasmonic materials with a Time-Dependent Density Functional Theory description of the molecule. More in detail, we have applied this multiscale framework to evaluate Surface-Enhanced Raman Scattering and Surface-Enhanced Fluorescence spectroscopies. Our findings demonstrate that preserving the atomistic profile of plasmons is crucial, as spectroscopic signals are highly sensitive to the morphology of the plasmonic substrates.