Photothermal Circular Dichroism of Single Nanoparticles Rejecting Linear Dichroism by Dual Modulation

Patrick Spaeth, Subhasis Adhikari, Martin Dieter Baaske, Sergii Pud, Jacco Ton, Michel Orrit*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Circular dichroism (CD) is the property of chiral nanoobjects to absorb circularly polarized light of either handedness to different extents. Photothermal microscopy enables the detection of CD signals with high sensitivity and provides a direct absorptive response of the samples under study. To achieve CD measurements at the single-particle level, one must reduce such artifacts as leakage of linear dichroism (LD) and residual intensity modulation. We have simulated our setup with a simple model, which allows us to tune modulation parameters to obtain a CD signal virtually free from artifacts. We demonstrate the sensitivity of our setup by measuring the very weak inherent CD signals of single gold nanospheres. We furthermore demonstrate that our method can be extended to obtain spectra of the full absorptive properties of single nanoparticles, including isotropic absorption, linear dichroism, and circular dichroism. We then investigate nominally achiral gold nanoparticles immersed in a chiral liquid. Carefully taking into account the intrinsic chirality of the particles and its change due to heat-induced reshaping, we find that the chiral liquid carvone surrounding the particle has no measurable effect on the particles' chirality, down to g-factors of 3 × 10-4.

Original languageEnglish
Pages (from-to)16277-16285
Number of pages9
JournalACS nano
Volume15
DOIs
Publication statusPublished - 22 Sep 2021
Externally publishedYes

Keywords

  • chirality
  • circular dichroism
  • linear dichroism
  • nanoparticles
  • nanophotonics
  • photothermal microscopy
  • single-particle spectroscopy

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