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Proc Natl Acad Sci U S A. 2011 Apr 12;108(15):5976-9. doi: 10.1073/pnas.1017962108. Epub 2011 Mar 28.

High sensitivity nanoparticle detection using optical microcavities.

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Department of Applied Physics, MC 128-95, California Institute of Technology, Pasadena, CA 91125, USA.


We demonstrate a highly sensitive nanoparticle and virus detection method by using a thermal-stabilized reference interferometer in conjunction with an ultrahigh-Q microcavity. Sensitivity is sufficient to resolve shifts caused by binding of individual nanobeads in solution down to a record radius of 12.5 nm, a size approaching that of single protein molecules. A histogram of wavelength shift versus nanoparticle radius shows that particle size can be inferred from shift maxima. Additionally, the signal-to-noise ratio for detection of Influenza A virus is enhanced to 381 from the previously reported 31. The method does not use feedback stabilization of the probe laser. It is also observed that the conjunction of particle-induced backscatter and optical-path-induced shifts can be used to enhance detection signal-to-noise.

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