Enantioselective SERS detection using chiral Au helicoids

The interaction between light and matter can be significantly enhanced through the excitation of surface plasmons and related nanospace-restricted focusing of light energy.The local enhancement of light energy is especially pronounced in the case of so-called plasmonic hotspots, which have found wide application in surface-enhanced Raman spectroscopy (SERS).This work focuses on the preparation and utilization of ordered array of chiral gold nanoparticles.The nanoparticles used have unique helical shapes with chirality encoded in each individual nanoparticle.An ordered layer of Au helices with a consistent gap between nanoparticles on a plasmon-active gold grating was fabricated.The created structure was able to support the excitation and propagation of surface plasmon-polaritons and local plasmons.Chiral molecules of the analyte(s) were placed between Au helicoids (i.e., in the place of the plasmonic hot spots).The influence of the chiral dielectric "spacer" (i.e., added chiral molecules) on the intensity of the local electric field and the SERS response of the enantiomers was investigated.A significant difference in the enhancement of SERS signal from enantiomers was observed, depending on the interplay of helicoids chirality and analytes chirality.