Chiral plasmonic nanosensors

Abstract

Chiral nanoparticles show interesting polarization effects that are many orders of magnitude stronger than what is observed in biomolecules [1]. They are therefore able to amplify small polarization changes which hold tremendous potential in sensing applications [2-4]. However, most nanoparticles’ material composition and shape cannot be tuned and so functions have thus far been limited.

Here, we introduce multifunctional chiral nanocolloids that can be extremely sensitive plasmonic nanosensors and that can also be used as a nanomechanical probe for active nanorheology. We for the first time show that it is possible to engineer the shape and dielectric function of individual nanoparticles by the physical shadow growth [1], which allows us to achieve remarkable sensing performance (sensitivity 1091 nm/RIU and figure of merit 42800 /RIU) in local surface plasmon resonance (LSPR) sensing [2-3]. When the refractive index of the medium surrounding the particle is changed, the large shift is induced in the spectral features that can be readily tracked. Furthermore, we combine multiple functionalities within our nanocolloids, such as a chiral shape, plasmonic activity, and a magnetic moment. This has allowed us to use a suspension of these nanocolloids for active nanorheology [4]. A common feature of both the chiral spectroscopy for LSPR sensing and the nanorheology is that the chirality of the nanoparticle causes the polarization-dependent extinction spectrum with rich features that is background free and that can be precisely tracked. Importantly, this allows these nanosensors to be optically observable even in highly absorbing whole blood at an optical density of OD 3. It is thus possible to perform rheological measurements of the blood serum without the need to separate the blood cells.

In this presentation, the fabrication of designer nanocolloids will be presented and it will be shown how their spectral analysis enables new sensing tasks in complex biological fluids.

Keywords

Plasmonics, Nanoparticles, Chiral sensing, Nanorheology

References

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