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18 March 2014 An imaging magnetometer for bio-sensing based on nitrogen-vacancy centers in diamond
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We present a widefield microscopy system for imaging super-paramagnetic nanoparticles (SPNs), and propose to use it as a bio-sensing system wherein SPNs are used as tags. Potential advantages of magnetic tags over conventional fluorescent tags include the elimination of noise from auto-fluorescence, optical isolation of the biological system from the measurement apparatus, and the potential for magnetic removal of non-specifically bound material. The microscope magnetic sensing surface is composed of a thin layer of nitrogen-vacancy defect centers in the top 200 nm of a diamond substrate. Nitrogen-vacancy centers in diamond have been shown to be suitable for use as highly sensitive magnetometers due to their long spin-coherence time at room temperature. Furthermore, spin-dependent photoluminescence allows for simple far-field optical readout of the spin state, which in turn allows for opticallydetected magnetic resonance measurements. We will present our results detecting a single, lithographically defined 50 nm diameter by 100 nm thick iron nanodot. With the current sensitivity of 9 μT⋅Hz-1/2, we expect to be able to detect single 20 nm magnetite SPNs, our proposed tags, in less than one minute. By further optimizing the sensor surface, we predict DC magnetic sensitivities as low as 1 μT⋅Hz-1/2.
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Michael Gould, Russell Barbour, Chris Chen, Zhiting Zhu, and Kai-Mei Fu "An imaging magnetometer for bio-sensing based on nitrogen-vacancy centers in diamond", Proc. SPIE 8933, Frontiers in Biological Detection: From Nanosensors to Systems VI, 89330L (18 March 2014);

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