Deterministic placement of plasmonic nanoparticles in so-called metasurfaces enables tailored modulation of light amplitude, phase and polarization state. Here, we introduce a scalable colloidal approach to construct a chiral arrangement of cross-stacked particle chains. The intrinsic chirality of the structure and strong inter-particle coupling produce pronounced circular dichroism (CD) of up to 11 degrees at visible and near-infrared wavelengths. Surpassing other colloidal strategies by two orders of magnitude, our system can easily compete with lithographic approaches.<br/><br/>As unique benefit of the particle-based, re-stackable design, superchiral plasmonic near fields are accessible for ultrasensitive, enantio-selective detection of analytes. Moreover, the chiroptical response is fully tunable in a post-fabrication manner. Changing the stacking angle tunes CD magnitude and sign (i.e., chiral handedness), while compression normal to the interface yields a reversible 160 nm spectral shift.<br/><br/>The simple design combined with exceptionally high and fully tunable CD offers various applications including tunable, planarized polarization optics, strain sensors and chiral molecular detection. Moreover, inscribing local optical properties by complex mechanical strain fields represents an intriguing direction for future nanoplasmonic devices.

Dynamic tuning of giant circular dichroism in chiral colloidal assemblies

ACS Spring Meeting 2021

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