Amino Acid‐Modulated Chirality Evolution and Highly Enantioselective Chiral Nanogap‐Enhanced Raman Scattering

Abstract

Controlling the growth and selection of chiral inducers is crucial for the generation of chiral inorganic structures as observed in nature. Herein, the plasmonic chirality evolution from the Au cube seed under the presence of L‐ or D‐amino acid as a chiral inducer is reported. The 432 Helicoid I structure is obtained using tryptophan (Trp), identical to the result with cysteine (Cys). The use of tyrosine (Tyr) produced a Helicoid IV‐type structure. However, no distinctive chiral structures can be obtained using phenylalanine (Phe), valine (Val) and leucine (Leu), which indicates the critical role of amino acids in chirality evolution. In particular, Trp‐Helicoid I nanoparticles (NPs) showed excellent enantioselective response toward L‐ or D‐Cys in the colorimetric assay and Raman analysis in the presence of Trp. Furthermore, the chiroptical property with a nanogap of 23.78 ± 0.82 nm in the Helicoid I structure further expands its applications for highly sensitive and quantitative chiral analysis for small molecules such as R/S‐epichlorohydrin (ECH), R/S‐limonene (LM), and R/S‐2‐butanol (BuOH) using a non‐polarized light source. The finding of amino acid‐dependent chirality evolution can widen the current understanding of chirality evolution in nature, and the use of helicoid structures with nanogaps incorporated with surface‐enhanced Raman scattering (SERS) can open a new avenue for chiral spectroscopic analysis.

Homochiral Optical Fibers Coated with Nanoscale Films of Metal–Organic Frameworks and Double-Plasmonic Ag and Au for In Situ Enantioselective Detection

“…As an alternative to the above-mentioned analytical approaches, a few more simple procedures based on electrochemical or optical approaches have been proposed. ,− In one of the common designs, the electrochemically or optically active surface is equipped with some chiral-sensitive features, which ensure its specific interaction with one of the targeted enantiomers. − In enantiomer presence, changes in the surface chemical or physical state occur, which can subsequently be detected through optical or electrochemical signal output. − Just a few examples of such approaches are the chiral-imprinted metal electrodes or plasmon-active substrates with voltammetry, impedance, or Raman spectroscopies used for enantioselective detection. − Among the various “chiral anchors”, the so-called HMOFs should be specially mentioned. − Due to their specific pore structure, these compounds can efficiently and selectively entrap various organic molecules, allowing their subsequent detection. − Simpler UV–vis optical spectroscopy can also be considered a useful tool for enantioselective recognition. In another simple approach, plasmon-active optical fibers created by the deposition of a nanometer-thick layer of noble metal(s) were used.…”

Chiroplasmonic DNA Scaffolded “Fusilli” Structures

“…In the ever-developing field of chiral nanomaterials, ,− we presented an exquisite example of large chiroplasmonic nanostructures synthesized by a simple self-assembly process, comprising a DNA scaffold and plasmonic nanoparticles. Noteworthy, a novel synthetic strategy was optimized for obtaining DNA nanotubes in the micrometer range.…”