Enhancing the Sensitivity of Single-Particle Photothermal Imaging with Thermotropic Liquid Crystals.
Individual molecules and nanoparticles can be imaged based on their absorption using photothermal microscopy. This technique relies on the heating-induced changes in the refractive index of the surrounding medium. Here, we demonstrate an order of magnitude larger enhancement of the signal-to-noise ratio in photothermal imaging of 20 nm gold nanoparticles when using a thermotropic liquid crystal (5CB). We show quantitatively that this increase is due to the large change in the thermo-optical properties of 5CB mainly along the nematic director. Enhancing the sensitivity is important for the further development of absorption-based single-molecule spectroscopy techniques.
†Department of Chemistry and §Department of Electrical and Computer Engineering, Laboratory for Nanophotonics, Rice University, Houston, Texas 77005, United States.
Wei-Shun
WS
Chang
†Department of Chemistry and §Department of Electrical and Computer Engineering, Laboratory for Nanophotonics, Rice University, Houston, Texas 77005, United States.
Stephan
S
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gold nanoparticles; liquid crystals; photothermal imaging; single-particle spectroscopy; surface plasmon resonance