Synthesis and Single‐Particle Optical Detection of Low‐Polydispersity Plasmonic‐Superparamagnetic Nanoparticles

The synthesis, magnetic characterization, and optical properties of nanoparticles with iron oxide cores and gold shells are presented. The nanoparticles are superparamagnetic at room temperature and can be reversibly collected by a permanent magnet. They display a localized surface plasmon resonance peak at 605 nm, and their large scattering cross-section allows them to be individually resolved in darkfield optical microscopy as they undergo Brownian motion in aqueous suspension. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2089/2008/adma200702196_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.