Elucidating the Near-Infrared Photoluminescence Mechanism of Homometal and Doped M₂₅(SR)₁₈ Nanoclusters

Abstract

More than a decade of research on the photoluminescence (PL) of classic Au 25 (SR) 18 and its doped nanoclusters (NCs) still leaves many fundamental questions unanswered due to the complex electron dynamics. Here, we revisit the homogold Au 25 (ligands omitted hereafter) and doped NCs, as well as the Ag 25 and doped ones, for a comparative study to disentangle the influencing factors and elucidate the PL mechanism. We find that the strong electron–vibration coupling in Au 25 leads to weak PL in the near-infrared region (∼1000 nm, quantum yield QY = 1% in solution at room temperature). Heteroatom doping of Au 25 with a single Cd or Hg atom strengthens the coupling of the exciton with staple vibrations but reduces the coupling with the core breathing and quadrupolar modes. The QYs of the three MAu 24 NCs (M = Hg, Au, and Cd) follow a linear relation with their PL lifetimes, suggesting a mechanism of suppressed nonradiative decay in PL enhancement. In contrast, the weaker electron–vibration coupling in Ag 25 leads to higher PL (QY = 3.5%), and single Au atom doping further leads to a 5× enhancement of the radiative rate and a suppression of nonradiative decay rate (i.e., twice the PL lifetime of Ag 25 ) in AuAg 24 (hence, QY 35%), but doping more Au atoms results in gold distribution to staple motifs and thus triggering of strong electron–vibration coupling as in the MAu 24 NCs, hence, counteracting the radiative enhancement effect and giving rise to only 5% QY for Au x Ag 25– x ( x = 3–10). The obtained insights will provide guidance for the design of metal NCs with high PL for lighting, sensing, and optoelectronic applications.

Solvent-Mediated Hetero/Homo-Phase Crystallization of Copper Nanoclusters and Superatomic Kernel-Related NIR Phosphorescence

“…The Cu26 demonstrates a large Stocks shift of 1.196 eV (i.e., 1239.83/933 to 1239.83/491), indicating obvious structural changes in the excited state . The photoluminescence excitation (PLE) spectrum detected at an emission of 933 nm closely resembles the UV/vis absorption spectrum, while no dependence on emission wavelength was observed in the 2D PL/PLE map (Figure S12) excited between 300 and 560 nm, suggesting the emission of Cu26 is only related to the first excited state after the relaxation of the hot exciton . The NIR PL dynamic was studied using the time-correlated single-photon counting technique, which reveals that two-microsecond magnitude components (τ 1 , 2.53 μs, f = 36.95%; τ 2 , 9.54 μs, f = 63.05%) were required to fit the decay curve.…”

Tailoring Carbon Tails of Ligands on Au52(SR)32 Nanoclusters Enhances the Near-Infrared Photoluminescence Quantum Yield from 3.8 to 18.3%

“…These values are lower in energy than the PL spectral blue-shift (from 899 to 838 nm, or ∼100 meV blue-shift) during the temperature decrease, suggesting that a change in the emission proportion (TADF/phosphorescence) occurred in a narrow temperature range. The temperature-dependent PL line width (full-width at half-maximum, fwhm) of Au 52 ( p -MBT) 32 is further extracted and plotted in Figure f, which presents a nearly linear relationship to the temperature (from 80 to 280 K), suggesting a weak electron–phonon interaction represented by eq , in which Γ 0 is the PL line width at 0 K, γ ac and γ LO are the coupling coefficients of the excited electron with acoustic phonon (ac) and longitudinal optical (LO) phonon, respectively, and E LO represents the average energy of the LO phonon. Data fitting to eq gives the fitted parameters (Figure f, inset).…”

Staggered Assembly of a Dimeric Au13 Cluster: Impacts on Coupling of Geometric Isomerism

“…[11,55] Recently, Mitsui et al also demonstrated that the emission from Au 25 -E is triplet-statedominated. [56] Theoretical Calculations DFT calculations were performed to elucidate the electronic structures of Au 25 -E and Au 25 -S. According to previous reports, 16 free electrons distributed on the Au 25 9 + cluster core has the configuration (1Σ) 2 (1Σ*) 2 (2Σ) 2 (1Π) 4 (1Π*) 4 -(2Σ*) 2 . [23,57] The calculation of Au 25 -S cluster with ligands shows that the orbital energy of 1Π* (highest occupied molecular orbital (HOMO) and HOMO-1) was higher than that of 2Σ* (HOMO-2) (Figure 5).…”

“…Metal nanoclusters as the initial product of the nanoparticle nucleation stage, the structure can be precisely determined. [1][2][3][4][5] The directional assembly of the building blocks of sub-nanometer metal clusters can serve as nanoelectronic devices such as single-electron transistors. [6][7][8][9][10][11][12] The linear assembly of icosahedral M 13 (8e) with I h symmetry is of great interest because the effective coupling between the M 13 units makes them promising candidates for nextgeneration electronics.…”