Chiral plasmonic nanosensors

Abstract

Plasmonic nanoparticles hold great interest as extremely local sensors that promise to deliver modular and low-cost sensing with high-detection thresholds [1]. However their sensing performance, including sensitivity and figure of merit (FOM), has been so far insufficient for the practical use in medical applications [2]. Here we introduce dispersion and shape engineered chiral plasmonic particles that lead to record refractive index sensitivity (1,091 nm RIU-1 at λ = 921 nm) and FOM (42,800 RIU-1) [3]. The chiral particle shows polarizationdependent extinction rich in spectral features. In particular zero-crossing serves as a natural point for tracking with very small effective line-widths and thus results in high FOM. Moreover, we for the first time show that it is possible to engineer the dielectric function of individual nanoparticles by the physical shadow growth [4], which allows us to achieve remarkable sensitivity. 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, even in complex biological media with limited transmission (e.g. optical density, ~3 OD). In this presentation, the fabrication of designer nanocolloids that are shape and dispersion engineered will be presented and it will be shown how their spectral analysis enables new sensing tasks in complex biological fluids. [1] Mayer KM, Hafner JH. Localized Surface Plasmon Resonance Sensors. Chemical Reviews 111, 3828-3857 (2011). [2] D. Howes P, Rana S, M. Stevens M. Plasmonic nanomaterials for biodiagnostics. Chemical Society Reviews 43, 3835-3853 (2014). [3] Jeong H-H, Mark AG, Alarcón-Correa M, Kim I, Oswald P, Lee T-C, and Fischer P. Dispersion and shape engineered plasmonic nanosensors. Nat Commun, DOI: 10.1038/ncomms11331 (2016). [4] Mark AG, Gibbs JG, Lee T-C, Fischer P. Hybrid nanocolloids with programmed three-dimensional shape and material composition. Nat Mater 12, 802-807 (2013).