Boosting chiral amplification in plasmon-coupled circular dichroism using discrete silver nanorods as amplifiers

Biomimetic Chiral Nanomaterials with Selective Catalysis Activity

Chiral nanomaterials with unique chiral configurations and biocompatible ligands have been booming over the past decade for their interesting chiroptical effect, unique catalytical activity, and related bioapplications. The catalytic activity and selectivity of chiral nanomaterials have emerged as important topics, that can be potentially controlled and optimized by the rational biochemical design of nanomaterials. In this review, chiral nanomaterials synthesis, composition, and catalytic performances of different biohybrid chiral nanomaterials are discussed. The construction of chiral nanomaterials with multiscale chiral geometries along with the underlying principles for enhancing chiroptical responses are highlighted. Various biochemical approaches to regulate the selectivity and catalytic activity of chiral nanomaterials for biocatalysis are also summarized. Furthermore, attention is paid to specific chiral ligands, materials compositions, structure characteristics, and so on for introducing selective catalytic activities of representative chiral nanomaterials, with emphasis on substrates including small molecules, biological macromolecule, and in-site catalysis in living systems. Promising progress has also been emphasized in chiral nanomaterials featuring structural versatility and improved chiral responses that gave rise to unprecedented chances to utilize light for biocatalytic applications. In summary, the challenges, future trends, and prospects associated with chiral nanomaterials for catalysis are comprehensively proposed.

Reshaping and induction of optical activity in gold@silver nanocuboids by chiral glutathione molecules

Core-shell gold-silver cuboidal nanoparticles were produced, with either concave or straight facets. Their incubation with a low concentration of chiral l-glutathione (GSH) biomolecules was found to produce near UV plasmonic extinction and induced circular dichroism (CD) peaks. The effect is sensitive to the silver shell thickness. The GSH molecules were found to cause redistribution of silver in the shell, removing silver atoms from edges/corners and re-depositing them at the nanocuboid facets, probably through some redox and complexation processes between the silver and thiol group of the GSH. Other thiolated chiral biomolecules (and drug molecules) did not show this effect. The emerging near UV surface plasmon resonance is a silver slab resonance, which might also possess some multipolar resonance nature. The concave-shaped nanocuboids exhibited stronger induced plasmonic CD relative to the nanocuboids with straight facets.

Trace detection of chiral J-aggregated molecules adsorbed on single Au nanorods

Trace detection of chiral molecules, which is of great significance in chemical, biological, medical and pharmaceutical sciences, requires microscopic techniques at the single-particle or single-molecule level. Although ensemble experiments show that the circular dichroism of chiral molecules can be amplified by plasmonic nanocrystals, trace detection of small chiral molecules remains challenging due to weak signals that are far below the detection limit. Herein, we demonstrate trace detection of chiral J-aggregated molecules adsorbed on individual Au nanorods (NRs) using single-particle circular differential scattering (CDS) spectroscopy. Through measuring the single-particle CDS spectra, we identified dip-peak bisignatures and further determined the chirality by matching them with calculations modelled with chiral media. We therefore find that plasmonic nanocrystals can dramatically amplify the circular dichroism of strongly coupled molecules to a detectable level so that the detection limit is as low as 3.9 × 10³ molecules on an individual plasmonic nanoparticle, whereas 2.5 × 10¹² molecules free in solution are barely detectable using a commercial circular dichroism instrument, suggesting a significant amplification factor of 10⁸. Our method provides a promising strategy with a high amplification factor, shedding light on the trace detection of chiral molecules using optical microscopic methods.