Manipulating Magneto-Optic Properties of a Chiral Polymer by Doping with Stable Organic Biradicals

Chang Keun Lim, Min Ju Cho, Ajay Singh, Qi Li, Won Jin Kim, Hong Sub Jee, Kathlyn L. Fillman, Stephanie H. Carpenter, Michael L. Neidig, Alexander Baev, Mark T. Swihart, Paras N. Prasad

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


We report the first example of tuning the large magneto-optic activity of a chiral polymer by addition of stable organic biradicals. The spectral dispersion of Verdet constant, which quantifies magneto-optic response, differs substantially between the base polymer and the nanocomposite. We employed a microscopic model, supported by atomistic calculations, to rationalize the behavior of this nanocomposite system. The suggested mechanism involves magnetic coupling between helical conjugated polymer fibrils, with spatially delocalized helical π-electron density, and the high density of spin states provided by the biradical dopants, which leads to synergistic enhancement of magneto-optic response. Our combined experimental and theoretical studies reveal that the manipulation of magnetic coupling in this new class of magneto-optic materials offers an opportunity to tailor the magnitude, sign, and spectral dispersion of the Verdet constant over a broad range of wavelengths, from the UV to the near-IR. This provides a new strategy for creating conformable materials with extraordinary magneto-optic activity, which can ultimately enable new applications requiring spatially and temporally resolved measurement of extremely weak magnetic fields. In particular, magneto-optic materials, presently employed in technologies like optical isolators and optical circulators, could be used in ultrasensitive optical magnetometers. This, in turn, could open a path toward mapping of brain activity via optical magnetoencephalography.

Original languageEnglish
Pages (from-to)5451-5455
Number of pages5
JournalNano Letters
Issue number9
Publication statusPublished - Sep 14 2016
Externally publishedYes


  • biradicals
  • chirality
  • Faraday rotation
  • polymers

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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