Plasmon-Coupled Circular Dichroism of Cysteine-Embedded Ag Nanoparticles with Strong Chiral Amplification and Long-Term Stability

Plasmonic-coupled circular dichroism (PCCD) represents a versatile method to synthesize chiroplasmonic nanoparticles (NPs), which play irreplaceable roles in various fields such as enantioselective sensing, spectroscopies, and chiral catalysis. Nonetheless, two critical challenges are faced in the development of PCCD-based chiroplasmonic NPs: low chiral amplification and poor stability. To circumvent these restrictions, we herein performed a quantitative study of the enhancement and stability of PCCD by the embedment of chiral molecules in discrete Ag NPs. Our study reveals that the high chiral amplification is attributed to the chiral molecules embedded in NPs, rather than those adsorbed on the surface. The embedment of chiral molecules significantly increases the coupling between chiral molecules and Ag NPs, and thus, a record-high chiral amplification of over 4800 times is achieved. Moreover, the CD signals of the Cys-embedded Ag NPs are almost unchanged after 3 months of storage, also benefiting from the embedment strategy. These results will open up new possibilities for designing new PCCD systems with high chiral amplification and superior stability and lay the groundwork for the applications of PCCD-based chiral NPs.