posted on 2023-08-29, 15:09authored byZhongyu Liu, Meng Zhou, Lianshun Luo, Yitong Wang, Ellen Kahng, Rongchao Jin
More than a decade
of research on the photoluminescence (PL) of
classic Au25(SR)18 and its doped nanoclusters
(NCs) still leaves many fundamental questions unanswered due to the
complex electron dynamics. Here, we revisit the homogold Au25 (ligands omitted hereafter) and doped NCs, as well as the Ag25 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 Au25 leads
to weak PL in the near-infrared region (∼1000 nm, quantum yield
QY = 1% in solution at room temperature). Heteroatom doping of Au25 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 MAu24 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 Ag25 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 Ag25) in AuAg24 (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 MAu24 NCs, hence, counteracting the radiative enhancement
effect and giving rise to only 5% QY for AuxAg25–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.