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arXiv · 1209.5918

Nanoscale Thermotropic Phase Transitions Enhance Photothermal Microscopy Signals

A. Nicholas G. Parra-Vasquez·Laura Oudjedi·Laurent Cognet·Brahim Lounis
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Abstract

The photothermal heterodyne imaging technique enabled studies of individual weakly absorbing nano-objects in various environments. It uses a photo-induced change in the refractive index of the environment. Taking advantage of the dramatic index of refraction change occurring around a thermotropic liquid crystalline phase transition, we demonstrate a 40-fold signal-to-noise ratio enhancement for gold nanoparticles imaged in 4-Cyano-4'-pentylbiphenyl (5CB) liquid crystals over those in a water environment. We studied the photothermal signal as a function of probe laser polarization, heating power, and sample temperature quantifying the optimal enhancement. This study established photothermal microscopy as a valuable technique for inducing and/or detecting local phase transitions at the nanometer scales.

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A. Nicholas G. Parra-Vasquez, Laura Oudjedi, Laurent Cognet, Brahim Lounis. 2012-09-26. Nanoscale Thermotropic Phase Transitions Enhance Photothermal Microscopy Signals. https://doi.org/10.1021/jz300369d

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