Chiral Metafilms and Surface Enhanced Raman Scattering for Enantiomeric Discrimination of Helicoid Nanoparticles

摘要

Chiral nanophotonic platforms provide a means of creating near fields withboth enhanced asymmetric properties and intensities. They can be exploitedfor optical measurements that allow enantiomeric discrimination at detectionlevels > 6 orders of magnitude than is achieved with conventional chirallysensitive spectroscopic methods based on circularly polarized light. Hereit is shown that surface enhanced Raman spectroscopy (SERS) is such alocal probe of the near field environment. It is used to achieve enantiomericdiscrimination of chiral helicoid nanoparticles deposited on left- and righthandedenantiomorphs of a chiral metafilm using an achiral molecule asa probe. “Hotter” electromagnetic (EM) hotspots are created for matchedcombinations of helicoid and metafilms (left-left and right-right), whilemismatched combinations leads to significantly “cooler” electromagnetichotspots. This large enantiomeric dependency on hotspot intensity is readilydetected using SERS with the aid of an achiral Raman reporter molecule. Ineffect SERS is used to distinguish between the different EM environments ofthe plasmonic diastereomers produced by mixing chiral nanoparticles andmetafilms. The work demonstrates that by combining chiral nanophotonicplatforms with established SERS strategies new avenues in ultrasensitivechiral detection can be opened.