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10 October 2012 Plasmonic optical trapping of metal nanoparticles for SERS by utilizing gold nano-ring structure
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The derivate of surface plasmon and optical tweezers, so-called plasmonic nano-optical tweezers (PNOT), has attracted much research interest due to its powerful ability for immobilizing nano-objects in the nanoscale, and its potential application in chemo/biosensing and life science. In this work, we use gold nano-rings to construct PNOT, and demonstrate the feasibility to trap metal nanoparticles (Au-NPs) for SERS application from the numerical standpoint. 3D finite-difference time-domain (FDTD) and the Maxwell stress tensor (MST) were used in our simulation study. We show that the interactions of the localized surface plasmon (LSP) excitation and the plasmonic interferences of the nano-ring arrays contribute to a narrow spectral feature around 785 nm, resulting in strong local near-field enhancement and thus intensive field gradient forces. The trapping potential well is as high as 1.31×10-19 J under a low illuminating power density of 1.0 mW/μm2, which makes the trapping events effective enough to overcome Brownian motion of the Au-NPs. Moreover, the existence of multiple potential wells results in a very large active volume of ~106 nm3 for trapping the target particles. The trapped Au-NPs further lead to the formation of nano-gaps that offer a field enhancement of 160 times. Our proposal shows promising applications for sensing and microfluidic integrations.
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Zhiwen Kang and Ho-Pui Ho "Plasmonic optical trapping of metal nanoparticles for SERS by utilizing gold nano-ring structure", Proc. SPIE 8458, Optical Trapping and Optical Micromanipulation IX, 84583A (10 October 2012);


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