Opto-thermophoretic separation and trapping of plasmonic nanoparticles

Optical tweezers are powerful tools to trap, transport, and analyse individual nano-objects at dilute concentrations. However, it is still challenging to manipulate isolated single nano-objects in dense target environments with various kinds of materials, such as in living cells and mixtures of nano...

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Bibliographic Details
Published in:Nanoscale 2019-11, Vol.11 (44), p.2193-2112
Main Authors: Setoura, Kenji, Tsuji, Tetsuro, Ito, Syoji, Kawano, Satoyuki, Miyasaka, Hiroshi
Format: Article
Language:English
Subjects:
Continuous radiation
Depletion
Drag
Gold
Histograms
Infrared lasers
Lasers
Mathematical analysis
Nanoparticles
Optical trapping
Photoluminescence
Separation
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Summary:Optical tweezers are powerful tools to trap, transport, and analyse individual nano-objects at dilute concentrations. However, it is still challenging to manipulate isolated single nano-objects in dense target environments with various kinds of materials, such as in living cells and mixtures of nanocolloids. In the present work, we have succeeded in the selective trapping of a few gold nanoshells with specific sizes and sweeping others out completely, only by irradiating the dense colloidal suspension of gold nanoshells with a focused near infrared continuous-wave (CW) laser. This was achieved by an interplay between optical gradient- and thermophoretic forces: while the gradient force traps the targets at the focal spot, the thermophoretic force pushes others out from the focal spot. The distance between the trapped targets and the separated others was longer than 20 μm, allowing us to measure plasmonic scattering spectra of the trapped targets at a single-nanoparticle level. The present method paves a way for manipulating and analysing single nano-objects in dense mixtures of targets and various kinds of materials. We have succeeded in the selective trapping of single gold nanoshells with specific sizes and sweeping others out completely, only by irradiating the dense colloidal suspension of gold nanoshells with a focused near infrared continuous-wave laser.
ISSN:2040-3364
2040-3372
DOI:10.1039/c9nr05052c