Heterogeneous nanostructures that possess multiple properties as a result of their differing constituent materials have
attracted significant interest in the last few years. In particular, fluorescent-magnetic nanostructures have potential
applications in imaging, separations, and single molecule tracking as a result of their fluorescent and magnetic
properties. Here we report the synthesis of fluorescent-magnetic nanocomposites composed of fluorescent
semiconductor quantum dots or graphitic carbon nanoparticles and magnetic iron oxide nanoparticles. We have
developed synthetic strategies using either micellular or polymer encapsulation, yielding composites from ~10 - 100s of
nms. Composites maintain the fluorescent and magnetic properties of their constituent materials. These composites can
be used for in vitro and in vivo imaging using fluorescent or magnetic (e.g., MRI) modalities. Additionally, we describe
the manipulation of these composites using magnetic instrumentation. In particular, we have designed a magnetic needle
that can be used to manipulate nanocomposites. Particles as small as 30 nm can be manipulated while simultaneous
observed through their fluorescent property. Single particle status can be confirmed through quantum dot blinking,
demonstrating the potential of these composites for single molecule tracking.
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