Microscopic Origin of Surface-Enhanced Circular Dichroism

Seojoo Lee, Seokjae Yoo, Q Han Park

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Circular dichroism (CD), the difference in absorption of two opposite circularly polarized light sources by chiral molecules, can be significantly enhanced when molecules are adsorbed on the surface of nanostructures. We present a theory based on Poynting's theorem adapted for chiral media to analyze the surface-enhanced CD of a chiral molecule/nanostructure coupled system. Our theory clarifies the microscopic origin of surface-enhanced CD signals by showing that the enhanced CD has two forms, inherent and induced. The inherent CD is the direct molecular CD that becomes enhanced due to the strongly localized optical helicity density near the nanostructure. The induced CD, previously ignored, derives from asymmetric excitation and absorption of electromagnetic fields inside the nanostructures surrounded by chiral molecules upon the injection of two oppositely circularly polarized light sources. Moreover, it is demonstrated that the induced CD can contribute significantly to the CD signals measured by surface-enhanced chiroptical spectroscopy.

Original languageEnglish
Pages (from-to)2047-2052
Number of pages6
JournalACS Photonics
Volume4
Issue number8
DOIs
Publication statusPublished - 2017 Aug 16

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Keywords

  • biosensing
  • chiral molecule
  • chirality
  • circular dichroism
  • metamaterial
  • plasmonics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biotechnology
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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