Hidden Chirality in Superficially Racemic Patchy Silver Films

Abstract

Chiral patchy particle films where morphological enantiomers exist in equal proportion are found to have significant circular dichroism. It is determined that the rotation direction during glancing angle deposition breaks the racemic symmetry, resulting in a distribution of material which enhances the chirality of one set of enantiomers relative to the other. Microscopic analysis and geometric chirality calculations reveal that the chirality of the bulk film results from incomplete cancellations of even stronger local chiralities.

Ultrabroadband Optical Superchirality in a 3D Stacked‐Patch Plasmonic Metamaterial Designed by Two‐Step Glancing Angle Deposition

“…Such ultrabroadband chiral resonance in the visible region has been rarely seen in previous studies and the measured CD strength is far more stronger than those reported previously for 3D helically stacked PCMs prepared by a similar GLAD method [3,36,37,40,41] (CD of ≈0.1 in ref. Such ultrabroadband chiral resonance in the visible region has been rarely seen in previous studies and the measured CD strength is far more stronger than those reported previously for 3D helically stacked PCMs prepared by a similar GLAD method [3,36,37,40,41] (CD of ≈0.1 in ref.…”

“…[40] and ≈0.04° at normal incidence in ref. [36,37]. More importantly, we would like to point out that such an ultrabroadband superchiral response observed in our SPPCMs is originated from the formation of definite handedness in all microscale domains in the same sample and therefore it eliminates the problem of random local chiralities reported in refs.…”

“…[37,45] However, the long-range disorder arrangement of a self-assembled microsphere array leads to random lattice orientations (i.e., azimuthal angle φ 1 , which refers to the azimuth angle of the first-step GLAD) for different micro-domains in the array, which as a result produces a racemic mixture over macroscopic sample areas and consequently causes strong cancellation of local chiralities. [37,45] However, the long-range disorder arrangement of a self-assembled microsphere array leads to random lattice orientations (i.e., azimuthal angle φ 1 , which refers to the azimuth angle of the first-step GLAD) for different micro-domains in the array, which as a result produces a racemic mixture over macroscopic sample areas and consequently causes strong cancellation of local chiralities.…”

“…[33][34][35] Although these bottom-up methods can produce chiral metamolecules in large amount and at low cost, the chiral performance and structure reproducibility of the samples made with these methods often are not comparable to that fabricated by the aforementioned top-down techniques. Sophisticated modifications based on symmetry considerations to the deposition parameters used in previous GLAD recipes [36,37] eliminate the undesirable yet unavoidable nature of racemic mixture induced by the long-range disorder arrangement of the microsphere array, resulting in SPPCMs with definite handedness over macroscopic areas and consequently an order of magnitude enhancement of CD over nearly the whole visible spectrum. [27][28][29][30][31][32] Here, we propose a novel fabrication solution to address all above-mentioned issues associated with the current plasmonic chiral metamaterials and metamolecules.…”

Scalable Fabrication of Quasi-Three-Dimensional Chiral Plasmonic Oligomers Based on Stepwise Colloid Sphere Lithography Technology

“…Particularly, our previous work also demonstrates that with the help of assembled polystyrene (PS) sphere array, a kind of shell-like chiral nanostructures can be achieved [29]. This kind of CPS can combine the magnetic or dielectric spheres to form chiral “Janus particles” [30] or “patchy particles” [31, 32] and will find potential applications in the colloid field. However, the cancellation effect originated from the PS array limited the related applications.…”