Ligand exchange in chiral gold nanorods synthesized with 1,12- binaphthyl-2,22-diamine for subsequent cationic dye attachment

Abstract

Metal nanoparticles exhibit a property known as localized surface plasmon resonance (LSPR) that leads to very strong visible light-matter interactions. When these nanomaterials are synthesized with a chiral morphology, the introduced asymmetry enables selective interaction with left- or right-circularly polarized light. Chiral metal nanoparticles, at the forefront of nanotechnology, offer unique optical properties, making them attractive for applications in biosensing, surface-enhanced spectroscopy, photochemistry, and more. Recent advancements involve the development of hybrid nanostructures by functionalizing gold nanoparticles with organic chiral and achiral molecules, enhancing their versatility. Some studies have showed that gold chiral nanoparticles functionalized with achiral dyes modulated the dye photoactivity and triggered a selective response to left- or right-circularly polarized light. Based on these findings, this proposal focuses on the synthesis of chiral gold nanorods (AuNRs) functionalized with (R)-(+)/(S)-(-)1,12-binaphthyl-2,22-diamine (R-/S-BINAMINE), as a primary chiral inducer, followed by ligand exchange processes to produce three distinct hybrid chiral nanomaterials. Ultimately, the presence of the chiral ligand R-/S-BINAMINE and an achiral ligand such as 11-mercaptoundecanoic acid (MUA) contributes to the formation of a hydrophobic microenvironment at the nanorod surface. Additional ligand exchange with D-cysteine and MUA introduces negative charges, thereby facilitating interactions with cationic aromatic dyes. This study aims to create a nanomaterial that can help deepen the understanding of synergistic effects between chiral interfaces and achiral photoactive materials, and exploring their potential applications, particularly in the fields of photochemical and photophysical processes.