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

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-SeCys(2)) as a chiral inducer. While L-SeCys(2) generates GNAs with a weak PCD signal, the irradiated L-SeCys(2) (irr-L-SeCys(2)) leads to GNAs with featured helical grooves (HeliGNAs) accompanying with a strong PCD signal. It is revealed that when L-SeCys(2) 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-SeCys(2) 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.