Volume 89 Issue 47 | p. 31 | Concentrates
Issue Date: November 21, 2011

Nanomagnets Under The Microscope

Fluorescent molecules illuminate the strength of magnetic fields around nanoparticles
Department: Science & Technology
News Channels: Analytical SCENE, Materials SCENE
Keywords: nanomagnets, magnetic fields, fluorescent molecules, quantum computing, nanoparticles, SQUID microscopy
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The brightness of light emitted by a fluorescent indicator varies with the magnetic field strength of a 100-micrometer-diameter iron particle (left), as predicted by a simulation (right).
Credit: Nano Lett.
A fluorescent molecule glows with variable intensity based on the strength of a 100 µm-diameter iron nanostructure’s magnetic field (left), as predicted by a simulation (right).
 
The brightness of light emitted by a fluorescent indicator varies with the magnetic field strength of a 100-micrometer-diameter iron particle (left), as predicted by a simulation (right).
Credit: Nano Lett.

A fluorescent molecule that glows brighter in the presence of weak magnetic fields can help map the fields around nanoparticles, according to a study in Nano Letters (DOI: 10.1021/nl202950h). When scientists design new magnetic nanoparticles, such as those in memory chips, they have to collect detailed information about the magnetic fields in the vicinity of the particles. Adam E. Cohen, a chemist at Harvard University, and his colleagues developed a simple method for making those measurements based on the properties of an indicator molecule consisting of phenanthrene tethered to N,N-dimethylaniline. The team showed that by applying a magnetic field, they could increase the intensity of light that the molecule emitted after UV radiation excited it. For example, in a magnetic field of 0.15 tesla—slightly higher than typical refrigerator-magnet strength—the compound glowed about 80% brighter than it did in the absence of a field. When the chemists used that property to map magnetic fields around iron particles, they found that they could detect field strengths as small as about 0.1 millitesla.

 
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ISSN 0009-2347
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