Seminarium Optyczne

Noble metal nanoclusters (NCs) are ultra-small nanomaterials exhibiting optical properties intermediate to those of discrete molecules and bigger nanoparticles [1]. They possess exceptional linear and nonlinear optical characteristics, including tunable photoluminescence (UV-NIR), large Stokes shifts (>0.5 eV), high photostability, and significant two-photon absorption [2]. Importantly, many NCs display chirality, arising from chiral surface ligands, helical core motifs, or inherent kernel asymmetry [3]. These attributes make NCs excellent models for structure-property relationship studies and versatile tools in catalysis, bioimaging, and sensing.This work investigates the linear and nonlinear optical properties of NCs with diverse chirality origins. We synthesized and characterized NCs stabilized by: 1) chiral ligands within primary or secondary ligand shells (captopril, glutathione, arginin, single stranded DNA), and 2) achiral ligands where chirality was induced by the arrangement of staple motifs. To quantitatively assess chiral nonlinear optical properties, specifically two-photon circular dichroism (2PCD), we developed and employed two distinct methodologies: z-scan-based two-photon absorption measurements and fluorescence-detected two-photon excited luminescence measurements utilizing circularly polarized light [4, 5]. Our findings reveal that the 2PCD of these NCs is approximately 300 times stronger than their one-photon anisotropy factor. Furthermore, we successfully demonstrated the facile detection of both 2PCD and three-photon circular dichroism (3PCD) in chiral gold NCs [6]. This research provides critical insights into the interplay between chirality and nonlinear optical phenomena in NCs, opening new avenues for their application in advanced photonics and chiroptical technologies.References[1] I. Chakraborty et al., Chem. Rev. 2017, 117, 8208.[2] J. Olesiak-Banska et al., Chem. Soc. Rev. 2019, 48, 4087.[3] I. Dolamic, S. Knoppe, A. Dass et al. Nat. Commun. 2012, 3, 798.[4] J. Olesiak-Banska et al., RSC Adv., 2016, 6. 98748.[5] A. Pniakowska et al. Nanoscale 2023; 15, 8597-8602.[6] P. Obstarczyk et al. J. Am. Chem. Soc. 2024, 146, 51, 35011–35015.