Surface-enhanced chiroptical spectroscopy with superchiral surface waves.

We study the chiroptical properties of one-dimensional photonic crystals supporting superchiral surface waves by introducing a simple formalism based on the Fresnel reflection matrix. We show that the proposed framework provides useful insights on the behavior of all the relevant chiroptical quantities, allowing for a deeper understanding of surface-enhanced chiral sensing platforms based on one-dimensional photonic crystals. Finally, we analyze and discuss the limitations of such platforms as the surface concentration of the target chiral analytes is gradually increased.

Electromagnetic Enantiomer: Chiral Nanophotonic Cavities for Inducing Chemical Asymmetry.

Chiral molecules, a cornerstone of chemical sciences with applications ranging from pharmaceuticals to molecular electronics, come in mirror-image pairs called enantiomers. However, their synthesis often requires complex control of their molecular geometry. We propose a strategy called "electromagnetic enantiomers" for inducing chirality in molecules located within engineered nanocavities using light, eliminating the need for intricate molecular design. This approach works by exploiting the strong coupling between a nonchiral molecule and a chiral mode within a nanocavity. We provide evidence for this strong coupling through angular emission patterns verified by numerical simulations and with complementary evidence provided by luminescence lifetime measurements. In simpler terms, our hypothesis suggests that chiral properties can be conveyed on to a molecule with a suitable chromophore by placing it within a specially designed chiral nanocavity that is significantly larger (hundreds of nanometers) than the molecule itself. To demonstrate this concept, we showcase an application in display technology, achieving efficient emission of circularly polarized light from a nonchiral molecule. The electromagnetic enantiomer concept offers a simpler approach to chiral control, potentially opening doors for asymmetric synthesis.

Chiral Quantum Metamaterial for Hypersensitive Biomolecule Detection.

Chiral biological and pharmaceutical molecules are analyzed with phenomena that monitor their very weak differential interaction with circularly polarized light. This inherent weakness results in detection levels for chiral molecules that are inferior, by at least six orders of magnitude, to the single molecule level achieved by state-of-the-art chirally insensitive spectroscopic measurements. Here, we show a phenomenon based on chiral quantum metamaterials (CQMs) that overcomes these intrinsic limits. Specifically, the emission from a quantum emitter, a semiconductor quantum dot (QD), selectively placed in a chiral nanocavity is strongly perturbed when individual biomolecules (here, antibodies) are introduced into the cavity. The effect is extremely sensitive, with six molecules per nanocavity being easily detected. The phenomenon is attributed to the CQM being responsive to significant local changes in the optical density of states caused by the introduction of the biomolecule into the cavity. These local changes in the metamaterial electromagnetic environment, and hence the biomolecules, are invisible to "classical" light-scattering-based measurements. Given the extremely large effects reported, our work presages next generation technologies for rapid hypersensitive measurements with applications in nanometrology and biodetection.

Programmable Multicomponent Self-Assembly Based on Aromatic Amino Acids.

Construction of integrated self-assembly with ordered structures from two or more organic building blocks is currently a challenge, since it suffers from intrinsic systematic complexity and diverse competitive pathways. Here, it is reported that aromatic amino acid building units can be incorporated into two- or three-component coassembly driven primarily by hydrogen bonding interactions without the assistance of metal-ligand and macrocycle-based host-guest interactions. The key strategy is to employ a C3 -symmetric molecule with alternative hydrogen bonding donor/acceptor sites that are able to bind either carboxylic acid or pyridine appended building units. Aromatic amino acids, C3 -symmetric compound, and bipyridine unit constitute a unique ternary mutual binding system, where three coassembly pathways including two pairwise formations and one ternary combination are unveiled, giving rise to two- and three-component self-assemblies with ordered structures, respectively. The pathway complexity lies in the structural parameter of aromatic amino acids, which can be programmable by controlling substituents at the α-position of amino acids.