Selenocystine and Photo‐Irradiation Directed Growth of Helically Grooved Gold Nanoarrows

Abstract

The fabrication of discrete nanostructures with both plasmonic circular dichroism (PCD) and chiral features is still a challenge. Here, gold nanoarrows (GNAs) with both chiroptical responses and chiral morphologies are achieved by using L‐selenocystine (L‐SeCys2) as a chiral inducer. While L‐SeCys2 generates GNAs with a weak PCD signal, the irradiated L‐SeCys2 (irr‐L‐SeCys2) leads to GNAs with featured helical grooves (HeliGNAs) accompanying with a strong PCD signal. It is revealed that when L‐SeCys2 is photo‐irradiated, the emergence of selenyl radicals plays an important role in the formation of HeliGNAs and enhancement of the chiroptical signal. In comparison with L‐SeCys2 and the other kinds of sulfur‐containing amino acids, the formation mechanism of helical grooves on the surface of GNAs is proposed. Both HeliGNAs and GNAs are used to discriminate amino acids by utilizing surface enhanced Raman scattering (SERS) effect. In the presence of either GNAs or HeliGNAs as the substrate, Fmoc‐L‐Phe shows more significant SERS than Fmoc‐D‐Phe. This study may advance the design of discrete plasmonic nanomaterials with both chiral morphology and potential applications in discrimination of chiral molecules.

Tunable Reversal of Circular Dichroism in the Seed-Mediated Growth of Bichiral Plasmonic Nanoparticles

“…However, no signal reversal in CD spectra of chiral Au NRs was observed and propeller geometry with bichiral centers was undistinguishable from the structural feature, which is in line with recent work on anisotropic chiral NRs. 41,[46][47][48]53,55,79 To further investigate the effect of Au seeds with different crystal structures, we replaced the singlecrystalline Au seeds with the polycrystalline Au nanospheres (NSs), which was prepared by a citrate-based reduction method (Figure S40). 80 Also, no CD reversal was observed when using polycrystalline Au NSs as seeds (Figure 7F), and random distortions and twists were observed from the structures in the as-prepared chiral Au NPs (Figure S41).…”

“…Seed-mediated growth provides a robust and versatile wet-chemical approach to chiral plasmonic NPs with precisely controlled structures and finely tailored chiroptical properties. ,,− The enantioselective interaction between chiral molecules and surfaces was found to be the key factor that facilitates the chirality transfer from molecules to particles during the chiral overgrowth process. Notably, biomolecules including amino acids, peptides, and single-stranded oligonucleotides have been deliberately designed and employed as chiral inducers for synthesizing the chiral plasmonic NPs. − By changing the structure of chiral molecules, the geometry of seed, and other synthetic parameters, chiral plasmonic NPs with tunable morphologies, compositions, and chiroptical properties can be obtained. ,,,− In particular, the geometric chirality of the resulting chiral NPs can be inverted by changing the handedness of chiral molecules, resulting in the signal reversal of plasmonic CD. ,, The signal reversal of plasmonic CD is a distinct spectroscopic signature and has promising applications in chiral biosensing and optical switches. ,− However, only inverting the geometric chirality using chiral molecules with opposite handedness can achieve the signal reversal of CD so far in the seed-mediated growth of chiral NPs. Also, the relationship between the geometric chirality of NPs and the sign of plasmonic CD is mechanistically complex.…”

Generation and reactivity of vinyltelluryl radical

“…24 Moreover, very recently, the vinylsulfinyl radical CH 2 QC(H)SO was isolated in cryogenic matrixes and characterized with IR and UV/Vis spectroscopy. 25 The vinylselenyl radical (4) and vinyltelluryl radical (5) remain elusive (Scheme 1(B)), despite the fact that selenyl and telluryl radicals are highly relevant in synthesis, 26,27 biological processes, 28 as well as living radical polymerizations. 29,30 The parent H-Te radical was first observed by Radford via electron paramagnetic resonance (EPR) in 1964.…”

Gold-Nanoparticle-Based Chiral Plasmonic Nanostructures and Their Biomedical Applications

“…In the absence of pre-irradiation, GNAs showed no observable helical grooves and produced weak PCD responses. In contrast, adding pre-irradiated L-SeCys 2 , the obtained GNAs exhibited obvious helical grooves and produced 10-fold stronger PCD responses compared to GNAs with an opposite sign [ 83 ]. The generation of selenyl radicals upon photo-irradiation was suggested as crucial for the formation of helical grooves.…”

“…Copyright 2020, American Chemical Society. ( b ) HeliGNAs as SERS substrates for recognition of Fmoc-L/D-Phe [ 83 ]. Copyright 2021, Wiley.…”