Unlocking Two-Photon Chiral Signatures in DNA-Stabilized Silver Nanoclusters: Two-Photon Circular Dichroism and...

Near-infrared (NIR) emitters with chiroptical properties are a novel class of materials with significant promise for chiral sensing and optoelectronic applications. Chiral nanoparticles, in particular, offer distinct advantages over molecular chiral agents. However, their practical applications remain significantly hindered due to challenges to precisely control nanoparticle chirality and reduce heterogeneity. Here, we investigate one-photon (1P) and two-photon (2P) chiroptical properties of DNA-stabilized silver nanoclusters (DNA-Ag_N) as atomically defined, water-soluble chiral nanoprobes. We perform a detailed analysis of 1P and 2P circular dichroism (1P-CD and 2P-CD, respectively) and circularly polarized luminescence (CPL) of (DNA)₂[Ag₁₆Cl₂]⁸⁺ , a NIR emissive DNA-Ag_N with solved crystal structure, over a broad wavelength range. We observe that (DNA)₂[Ag₁₆Cl₂]⁸⁺ exhibits 2P-CD two orders of magnitude higher than 1P anisotropy factor, with additional CD bands in the NIR range. Interestingly, (DNA)₂[Ag₁₆Cl₂]⁸⁺ also presents CPL with high anisotropy factors, upon both 1P and 2P excitation, with significant 2P CPL brightness. These findings demonstrate that DNA-Ag_N exhibits significant 1P- and 2P- excited chiroptical properties, highlighting their potential for chiral sensing and bioimaging at NIR wavelengths in the tissue transparency window.