start-ver=1.4 cd-journal=joma no-vol=117 cd-vols= no-issue=10 article-no= start-page=101103 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200909 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Super-chiral vibrational spectroscopy with metasurfaces for high-sensitive identification of alanine enantiomers en-subtitle= kn-subtitle= en-abstract= kn-abstract=Chiral nature of an enantiomer can be characterized by circular dichroism (CD) spectroscopy, but such a technique usually suffers from weak signal even with a sophisticated optical instrument. Recent demonstrations of plasmonic metasurfaces showed that chiroptical interaction of molecules can be engineered, thereby greatly simplifying a measurement system with high sensing capability. Here, by exploiting super-chiral field in a metasurface, we experimentally demonstrate high-sensitive vibrational CD spectroscopy of alanine enantiomers, the smallest chiral amino acid. Under linearly polarized excitation, the metasurface consisting of an array of staggered Au nano-rods selectively produces the left- and right-handed super-chiral fields at 1600 cm−1, which spectrally overlaps with the functional group vibrations of alanine. In the Fourier-transform infrared spectrometer measurements, the mirror symmetric CD spectra of D- and L-alanine are clearly observed depending on the handedness of the metasurface, realizing the reliable identification of small chiral molecules. The corresponding numerical simulations reveal the underlying resonant chiroptical interaction of plasmonic modes of the metasurface and vibrational modes of alanine. Our approach demonstrates a high-sensitive vibrational CD spectroscopic technique, opening up a reliable chiral sensing platform for advanced infrared inspection technologies. en-copyright= kn-copyright= en-aut-name=IidaTakumi en-aut-sei=Iida en-aut-mei=Takumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=IshikawaAtsushi en-aut-sei=Ishikawa en-aut-mei=Atsushi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TanakaTakuo en-aut-sei=Tanaka en-aut-mei=Takuo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MuranakaAtsuya en-aut-sei=Muranaka en-aut-mei=Atsuya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=UchiyamaMasanobu en-aut-sei=Uchiyama en-aut-mei=Masanobu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=HayashiYasuhiko en-aut-sei=Hayashi en-aut-mei=Yasuhiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=TsurutaKenji en-aut-sei=Tsuruta en-aut-mei=Kenji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil=Department of Electrical and Electronic Engineering, Okayama University kn-affil= affil-num=2 en-affil=Department of Electrical and Electronic Engineering, Okayama University kn-affil= affil-num=3 en-affil=Metamaterials Laboratory, RIKEN Cluster for Pioneering Research kn-affil= affil-num=4 en-affil=Advanced Elements Chemistry Laboratory, RIKEN Cluster for Pioneering Research kn-affil= affil-num=5 en-affil=Advanced Elements Chemistry Laboratory, RIKEN Cluster for Pioneering Research kn-affil= affil-num=6 en-affil=Department of Electrical and Electronic Engineering, Okayama University kn-affil= affil-num=7 en-affil=Department of Electrical and Electronic Engineering, Okayama University kn-affil= END