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3 April 2020 Visualization of molecular trapping at plasmonic metal nanostructure by surface-enhanced Raman scattering imaging
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Optical manipulation has been used for the trapping of micrometer-scaled objects, but it is still difficult to control the motion of small molecules on the nanometer scale at room temperature. Plasmonic metal nanostructures are expected to be useful for the optical manipulation of nanoscale molecules using a highly localized electric field. We use the plasmonic Ag nanostructure for a demonstration of optical trapping through the observation using surface-enhanced Raman scattering (SERS) imaging. The optical measurements were conducted under electrochemical potential control to stabilize the nanostructure with target molecules, 4,4′-bipyridyl (44 bpy). Upon increasing the concentration of 44 bpy molecules in an electrolyte solution at room temperature, the blinking frequency of the SERS signal was different in both the spectra and imaging. The dwell time of the SERS signals was increased from several tens of milliseconds to a few seconds, which suggested the successful observation of plasmonic trapping of small molecules through the surface diffusion control. The observed results prove the importance for the control of the surface coverage of the molecules and its influence on surface diffusion under plasmonic molecular trapping.

© 2020 Society of Photo-Optical Instrumentation Engineers (SPIE) 1934-2608/2020/$28.00 © 2020 SPIE
Tomohiro Fukushima, Akira Miyauchi, Nobuaki Oyamada, Hiro Minamimoto, Toshinori Motegi, and Kei Murakoshi "Visualization of molecular trapping at plasmonic metal nanostructure by surface-enhanced Raman scattering imaging," Journal of Nanophotonics 14(2), 026001 (3 April 2020).
Received: 14 January 2020; Accepted: 20 March 2020; Published: 3 April 2020

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