Au₇₆(SC₆H₄-p-CH₃)₄₂ Square Quantum Platelet: One-Dimensional Growth of Quantum Rods Turns 90 Degrees.

Area of Science:

• Nanomaterials Science
• Photochemistry
• Solid-State Chemistry

Background:

• Atomically precise nanoclusters (NCs) are crucial for optoelectronic and biomedical applications due to their second near-infrared (NIR-II) photoluminescence (PL).
• Nonradiative processes often limit the PL performance of NIR-II emitters, necessitating structural optimization for enhanced luminescence.
• Understanding NC growth patterns is fundamental to controlling structural properties and their impact on photoluminescence.

Purpose of the Study:

• To investigate the growth pattern of atomically precise gold nanoclusters and its effect on photoluminescence.
• To discover new NIR-II emitting nanoclusters with improved quantum yields.
• To elucidate the structure-property relationships governing the enhanced luminescence in gold nanoclusters.

Main Methods:

• Synthesis and characterization of atomically precise gold nanoclusters, specifically Au76(p-MBT)42 (Au76).
• Photoluminescence (PL) spectroscopy to measure emission spectra and quantum yields (PLQY).
• X-ray crystallography and time-resolved spectroscopy to determine structural parameters and luminescence mechanisms.

Main Results:

• Discovery of a novel square-shaped Au76 nanocluster with a face-centered cubic (fcc) core.
• Au76 exhibits bright emission at 970 nm with a PLQY of 30% in solution, enhanced to 40% when deaerated.
• Shorter Au-Au bond lengths (2.835 Å) in Au76 compared to Au52 (3.04 Å) result in nearly doubled PLQY (40% vs 18.3%).

Conclusions:

• The square growth facet of Au76 nanoclusters significantly enhances photoluminescence quantum yield.
• Shorter metal-metal bond lengths are critical for reducing nonradiative decay pathways and improving NIR-II emission.
• This study provides insights for designing highly luminescent nanoclusters for photovoltaics, photocatalysis, and optoelectronics.