Charge influences the binding of virus and other nano-particles to microcavity bio-sensors, although surprisingly there have been no reports of the determination of either cavity charge density σw or nanoparticle charge qp using these sensors. In this letter, we experimentally demonstrate an approach for the determination of both. We use an opto-mechanical Whispering Gallery Mode (WGM) Carousel trap to extract the electrostatic interaction energy versus separation s between the cavity surface and a nanoparticle from WGM frequency fluctuations induced by the orbiting particle. Next, we fit this interaction energy to linearized wall-colloid theory (Debye-Hückel theory) for a particle whose charge is known and determine σw. With this microcavity charge density in hand, a larger particle having unknown charge and orbiting the same microcavity has its charge measured from its associated electrostatic interaction energy. This charge is found to be smaller by 10% when compared to results from independent zeta potential measurements and outside of one standard deviation. However, non-linear Gouy-Chapman theory when applied to our measured data arrives at a charge that overlaps zeta potential measurements. Our method is non-destructive, enabling the same particle to be passed on for further characterization.
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29 January 2018
Research Article|
January 31 2018
Whispering gallery mode coulometry of the nanoparticle-microcavity interaction in aqueous solution
Jehovani R. Lopez;
Jehovani R. Lopez
Microparticle Photophysics Lab (MP3L), NYU Tandon School of Engineering
, Brooklyn, New York 11201, USA
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Eshan Treasurer;
Eshan Treasurer
Microparticle Photophysics Lab (MP3L), NYU Tandon School of Engineering
, Brooklyn, New York 11201, USA
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Kaitlynn M. Snyder;
Kaitlynn M. Snyder
Microparticle Photophysics Lab (MP3L), NYU Tandon School of Engineering
, Brooklyn, New York 11201, USA
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David Keng;
David Keng
Microparticle Photophysics Lab (MP3L), NYU Tandon School of Engineering
, Brooklyn, New York 11201, USA
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Stephen Arnold
Stephen Arnold
a)
Microparticle Photophysics Lab (MP3L), NYU Tandon School of Engineering
, Brooklyn, New York 11201, USA
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a)
Author to whom correspondence should be addressed: sarnold935@aol.com
Appl. Phys. Lett. 112, 051109 (2018)
Article history
Received:
November 23 2017
Accepted:
January 14 2018
Citation
Jehovani R. Lopez, Eshan Treasurer, Kaitlynn M. Snyder, David Keng, Stephen Arnold; Whispering gallery mode coulometry of the nanoparticle-microcavity interaction in aqueous solution. Appl. Phys. Lett. 29 January 2018; 112 (5): 051109. https://doi.org/10.1063/1.5017041
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