Modeling the Chiral Imprinting Response of Oriented Dipole Moments on Metal Nanostructures

Chiral plasmonics is a growing field because of its potential to produce high-performance biomolecule sensors and negative refractive index materials. Understanding and controlling molecular properties and their effect on the chiroptical coupling between chiral molecular films and metal nanostructures is thus vital for the future design of devices. Here we develop and apply a theoretical method to study that coupling. We first extend the three-dimensional finite-difference time-domain method to include chiral molecular layers with arbitrarily oriented induced dipole moments relative to the nanostructure's surface. We then use the methodology to investigate the chiral imprinting response from molecularly coated nanospheres as a test of the method. Finally we study a gold nanocross array to understand how long- and short-range interactions between the chiral molecular layer and the nanoparticles affect their optical response.