Modeling of Radiation-Molecule Interaction in Nanophotonic Environments

Chirality, the property characterized by broken mirror symmetry, is a widespread trait of nature, manifested in the twist of galaxies to the handedness of molecules. Enantiomers, the two mirror counterparts of a chiral molecule, exhibit distinct biochemical properties, making chiral sensing crucial in pharmaceutical and biomedical industries. Current state-of-the-art techniques are effective for macroscopic operational volume; however, they lack real-time compatibility and are inefficient for lab-on-a-chip integration platforms. This work advances a step forward toward improving the sensitivity of enantiomeric excess detection by exploring chiroptical interactions in nanophotonic environments, utilizing realistic pharmaceutical drugs. The radiation-molecule interactions are demonstrated through a perturbative theory in the density matrix formalism, and the microscopic molecular observables are evaluated through a robust computational method combining Molecular Dynamics (MD), Time-Dependent Density Functional Theory (TDDFT) and quantum chemical calculations. We observe that Surface-Plasmon Polariton (SPP)s at the noble metal interface can significantly enhance circular dichroism differential absorption by chiral samples. Additionally, we investigate enhanced vibrational circular dichroism offered by Localised Surface Plasmon Resonance (LSPR)s in plasmonic nanostructures embedding chiral mixtures. Thanks to intense nearfields produced by SPPs and LSPRs, we attain significant enhancement of chiroptical signal in an nl-volume chiral sample, paving a way to design highly sensitive, laboratory-friendly, innovative chiral sensors.