Berlin 2024 – scientific programme

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BP: Fachverband Biologische Physik

BP 27: Single Molecule Biophysics

BP 27.8: Talk

Thursday, March 21, 2024, 11:45–12:00, H 0112

Cavity-enhanced ultrafast sensing of single nanosystems — •Shalom Palkhivala, Larissa Kohler, and David Hunger — Karlsruhe Institute of Technology, Karlsruhe, Germany

The investigation of single unlabelled nanosystems is of interest in branches of science such as biophysics and chemistry, where sensors are needed which can detect nanosystems in aqueous environments. We demonstrate an open-access optofluidic platform for the high-speed label-free sensing of nanoparticles in aqueous suspension. The heart of the sensor is a fibre-based Fabry-Perot microcavity with high finesse (5 × 10⁴ in water) integrated into a microfluidic system. By monitoring the cavity resonance as the optical field interacts with a nanoparticle, the particle can be detected and characterised. We have demonstrated three-dimensional tracking of a single diffusing nanoparticle by measuring the resonance frequency shifts of several transverse modes [1]. Now, our cavity-locked detection scheme allows measurement of fast nanoparticle dynamics with a temporal resolution (∼ 10 ns) orders of magnitude better than most other techniques. Additionally, orthogonal polarisation eigenmodes of the cavity are interrogated to yield orientational information of anisotropic particles. Thus, the rotation of single nanorods 20 nm long could be tracked with high measurement bandwidth, and the diffusion dynamics used to determine the dimensions of individual nanorods. We shall report progress towards using our sensor to investigate the dynamics of biological nanosystems, such as the folding of DNA "origami".

[1] Kohler, L. et al. Nat Commun 12, 6385 (2021).

Keywords: optical microcavity; single nanoparticles; high-speed sensing