Enhancement of Circular Dichroism of a Chiral Material by Dielectric Nanospheres

Abstract

Circular dichroism (CD) spectroscopy is very useful for studies of biomolecular conformation but suffers from very weak signals. Several theoretical and experimental papers reported schemes for CD enhancement using enhanced local fields produced by plasmonic nanostructures. Here we report enhancement of visible wavelength CD of chiral mercury sulfide (HgS) nanocrystals by Mie resonances of amorphous selenium nanospheres. The spatially averaged CD enhancement factor was estimated to be 4.7 ± 1.5 fold, while the peak enhancement at particular locations on the nanospheres is probably >10. This type of enhancement may be useful for increasing the sensitivity of CD measurements and in particular toward achievement of single chiral nanostructure CD measurements.