A single-gold-atom addition regulates sharp redshift in the fluorescence of atomically precise nanoclusters

Area of Science:

• Nanomaterials Science
• Atomic-Level Manipulation
• Fluorescence Spectroscopy

Background:

• Controlling emission peaks at the atomic level is crucial for understanding fluorescence mechanisms.
• Gold nanoclusters (AuNCs) are promising for optical applications due to their unique photoluminescence.

Purpose of the Study:

• To synthesize a novel gold nanocluster with modified structural and optical properties.
• To investigate the origin of near-infrared-II (NIR-II) fluorescence and the emission peak red-shift mechanism.

Main Methods:

• Phosphine-mediated modification of Au36(TBBT)24 nanocluster to synthesize Au37(TBBT)21(TPP)2.
• Structural characterization using X-ray crystallography.
• Photoluminescence spectroscopy and Density Functional Theory (DFT) calculations.

Main Results:

• A new gold nanocluster, Au37(TBBT)21(TPP)2, was synthesized with a red-shifted emission peak into the NIR-II window (1152 nm).
• The modified nanocluster exhibited a quantum yield of 1.5%.
• DFT calculations revealed that the 37th gold atom insertion enhanced HOMO orbital contribution and shifted fluorescence origin from Local Excitation (LE) to Inter Fragment Charge Transfer (IFCT).

Conclusions:

• The structural modification of gold nanoclusters can precisely tune their optical properties, enabling NIR-II emission.
• The study elucidates the mechanism behind the red-shifted fluorescence, attributing it to atomic rearrangement and altered electronic transitions.