[Nature Nanotechnology] Monitoring the orientation of rare-earth-doped nanorods for flow shear tomog
Rare-earth phosphors exhibit unique luminescence polarization features originating from the anisotropic symmetry of the emitter ion's chemical environment. However, to take advantage of this peculiar property, it is necessary to control and measure the ensemble orientation of the host particles with a high degree of precision. Here, we show a methodology to obtain the photoluminescence polarization of Eu-doped LaPO4 nanorods assembled in an electrically modulated liquid-crystalline phase. We measure Eu3+ emission spectra for the three main optical configurations (σ, π and α, depending on the direction of observation and the polarization axes) and use them as a reference for the nanorod orientation analysis. Based on the fact that flowing nanorods tend to orient along the shear strain profile, we use this orientation analysis to measure the local shear rate in a flowing liquid. The potential of this approach is then demonstrated through tomographic imaging of the shear rate distribution in a microfluidic system.
Jongwook Kim, Sébastien Michelin, Michiel Hilbers, Lucio Martinelli, Elodie Chaudan, Gabriel Amselem, Etienne Fradet, Jean-Pierre Boilot, Albert M. Brouwer, Charles N. Baroud, Jacques Peretti & Thierry Gacoin AffiliationsContributions Nature Nanotechnology (2017) doi:10.1038/nnano.2017.111 Received 04 August 2015 Accepted 05 May 2017 Published online 19 June 2017