# Au20Ag32 Nanocluster Emitting Bright Near-Infrared-II Photoluminescence with Quantum Yield of 30% in Aerated Solution

## TL;DR

This paper reports a gold-silver nanocluster with high near-infrared-II photoluminescence efficiency, useful for optoelectronic applications.

## Contribution

The study introduces a new Au20Ag32 nanocluster with a record 30% quantum yield in aerated solution for NIR-II emission.

## Key findings

- Au20Ag32 nanocluster emits bright near-infrared-II photoluminescence at 980 nm.
- The nanocluster achieves a quantum yield of 30% in aerated and 33% in deaerated conditions.
- PL mechanism involves thermally activated delayed fluorescence and phosphorescence.

## Abstract

Atomically precise
metal nanoclusters (NCs) have emerged
as an
important class of materials for optoelectronic applications, owing
to their near-infrared-II (NIR-II) photoluminescence (PL) properties.
To fully realize their applications, the PL quantum yield (PLQY) of
NCs must be enhanced. In this regard, structure–property correlation
studies are of critical importance. Herein, we report an alkynide-protected
Au20Ag32 NC (charge neutral) protected by 36
ligands, including 12 Cl– and 24 p-tert-butylphenylacetylide (
t
BuPA–). Structural analysis shows that the
NC is a three-dimensional growth of a bi-icosahedral core. Theoretical
analysis reproduces the experimental optical absorption spectral features.
Interestingly, Au20Ag32 shows bright PL emission
centered at 980 nm, with a PLQY of 30% in aerated and 33% in deaerated
medium at room temperature, which is the highest among the reported
NIR-II NCs. Furthermore, cryogenic PL measurements and transient absorption
spectroscopy analysis reveal the PL mechanism, which involves both
thermally activated delayed fluorescence (TADF) and phosphorescence
(PH). This study is expected to motivate further research in expanding
the Au–Ag nanoclusters and studying their high NIR-II emission.