  Detection of enantiomers is a challenging problem in drug development as well
as environmental and food quality monitoring where traditional optical
detection methods suffer from low signals and sensitivity. Application of
surface enhanced Raman scattering (SERS) for enantiomeric discrimination is a
powerful approach for the analysis of optically active small organic or large
biomolecules. In this work, for enantio-selective sensing we proposed the
coupling of disposable chiral plasmonic shurikens supporting the chiral
near-field distribution with SERS active silver nanoclusters. As a result of
the plasmonic coupling significant difference in SERS response of optically
active analytes is observed. This is hypothesized and confirmed by numerical
simulations to be a consequence of the silver particles being excited by
superchiral fields generated at the surface or the probe molecules achieving
additional polarization. The plasmon coupling phenomena was found to be
extremely sensitive to slight variations in shuriken geometry, silver
nanostructured layer parameters, and SERS excitation wavelength(s). Designed
structures were able to discriminate cysteine enantiomers at concentrations in
the nanomolar range and probe biomolecular chirality, using a common Raman
spectrometer within several minutes. The combination of disposable plasmonic
substrates with specific near-field polarization can make the SERS enantiomer
discrimination a commonly available technique using standard Raman
spectrometers.
