Gyromagnetic imaging: Dynamic optical contrast using gold nanostars with magnetic cores

Qingshan Wei, Hyon Min Song, Alexei P. Leonov, Jacob A. Hale, Dongmyung Oh, Quy K. Ong, Kenneth Ritchie, Alexander Wei

Research output: Contribution to journalArticlepeer-review

110 Scopus citations


Plasmon-resonant nanoparticles with optical scattering in the near-infrared (NIR) are valuable contrast agents for biophotonic imaging and may be detected at the single-particle limit against a dark background, but their contrast is often limited in environments with high noise. Here we consider gyromagnetic imaging as a dynamic mode of optical contrast, using gold nanostars with superparamagnetic cores. The nanostars exhibit polarization-sensitive NIR scattering and can produce a frequency-modulated signal in response to a rotating magnetic field gradient. This periodic "twinkling" can be converted into Fourier-domain images with a dramatic reduction in background. We demonstrate gyromagnetic imaging of nanostars inside of tumor cells, using broadband excitation: while their time-domain signals are obscured by incoherent scattering, their Fourier-domain signals can be clearly resolved in less than a second. The gyromagnetically active nanostars do not cause a loss in viability, and can even have a mild stimulatory effect on cell growth.

Original languageEnglish (US)
Pages (from-to)9728-9734
Number of pages7
JournalJournal of the American Chemical Society
Issue number28
StatePublished - Jul 22 2009
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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