Second-Order Nonlinear Optical Scattering Properties of Phosphine-Protected Au₂₀ Clusters

Abstract

We report the first hyperpolarizability of the [Au20(PP3)4]­Cl4 cluster (PP3: tris­(2-(diphenylphosphino)­ethyl)­phosphine) using the Hyper-Rayleigh Scattering technique. This is the first determination of nonlinear optical properties of a phosphine-protected “superatomic” gold cluster. Weak contributions of multiphoton-excited fluorescence were observed in the spectral dispersion of the generated light upon excitation at 1300 and 1064 nm. The first hyperpolarizability of the intrinsically chiral cluster is weaker than that of thiolate-protected gold clusters of similar size and inherent chirality.

Role of Donor and Acceptor Substituents on the Nonlinear Optical Properties of Gold Nanoclusters

“…Our results indicate that donor/acceptor systems could potentially be exploited for optimizing second-order NLO responses using thiolate-protected gold 15 clusters. While the static first hyperpolarizability has not been calculated for many monolayer-protected gold clusters, 80,81,93 the value computed for 17 is the largest thus far.…”

“…80 In phosphine-protected gold clusters, a change from PRH 2 to PRPh 3 also leads to a significant change of β HRS . 81 This indicates that second-order nonlinear optical properties might be very sensitive to slight changes in the electronic demand of the ligands. Due to the conjugated systems, changes in substituents of thiophenol derivatives are expected to show a very pronounced effect.…”

Au10(SG)10: A Chiral Gold Catenane Nanocluster with Zero Confined Electrons. Optical Properties and First-Principles Theoretical Analysis

“…[8] In addition to promising radiotherapy properties, noble metal NCs may display NIR emission, [9,10]and in particular can allow for imaging within the tissue transparency window which, along with their multiphoton excitation properties, may permit deep tissue penetration while minimizing background fluorescence and scattering problems. While recent efforts have been done on the nonlinear optical (NLO) properties determination of small gold and silver NCs, [11][12][13][14][15][16][17][18][19] the NLO activity of ultra-small gold or silver NCs (with a number of metal atoms lower than [10][11][12] has not yet been investigated. Note that the 1:1 [Au]: [GS] NCs chemical stoichiometry suggests that Au10-remarkable structural and chiroptical properties.…”

Excited-State Behaviors of M1Au24(SR)18 Nanoclusters: The Number of Valence Electrons Matters

“…Atomically precise metal nanoclusters offer exciting opportunities in fundamental research owing to their well-defined structures and unique properties. − Significant advances in gold nanocluster research have made it possible to correlate the optical properties with structures, − which allows for rational design and functionalization of these ultrasmall gold nanoparticles for specific applications. The optical properties of metal nanoclusters, including photoluminescence, , nonlinear absorption, − and a long-lived excited-state lifetime, , differentiate such nanoclusters from those larger counterpartsplasmonic nanoparticles .…”

“…Atomically precise metal nanoclusters offer exciting opportunities in fundamental research owing to their well-defined structures and unique properties. − Significant advances in gold nanocluster research have made it possible to correlate the optical properties with structures, − which allows for rational design and functionalization of these ultrasmall gold nanoparticles for specific applications. The optical properties of metal nanoclusters, including photoluminescence, , nonlinear absorption, − and a long-lived excited-state lifetime, , differentiate such nanoclusters from those larger counterpartsplasmonic nanoparticles . Understanding the optical properties, especially the excited-state dynamics of gold nanoclusters, will help to develop new applications in energy storage and conversion. − In recent research, ultrafast spectroscopy has been employed to (i) probe the evolution from metallic to molecular behavior, − (ii) correlate the electron dynamics with the structure of nanoclusters, − and (iii) understand the excited-state interactions between clusters and dye molecules as well as solvents. − Nevertheless, understanding of the excited-state process as well as correlation with structures of metal nanoclusters is still far from complete; for instance, it still remains elusive how the electron and phonon dynamics are affected by the type of crystal structure, metal composition, and surface-protecting ligands of metal nanoclusters.…”