Pressure-Activated Efficient Near-Infrared Luminescence in Atomically Precise Gold Nanoclusters

Achieving efficient near-infrared (NIR) luminescence in atomically precise gold nanoclusters is challenging due to the strong vibrational freedom of the gold core. Herein, we synthesized two gold nanoclusters, [Au₁₁(PPh₃)₈Cl₂]Cl (Au₁₁-1) and Au₁₁(PPh₃)₇Cl₃ (Au₁₁-2), with comparable initial NIR photoluminescence quantum yields (PLQY, 0.3% and 0.32%, respectively), and systematically investigated their NIR piezoluminescence behaviors based on the hydrostatic pressure effect. Under high pressure, Au₁₁-1 exhibits a significant NIR piezoluminescence enhancement. When the pressure increases to 3.6 GPa, the NIR-PLQY of Au₁₁-1 amplifies from the initial 0.3% to 75.6%, which is the highest PLQY reported for solid-state gold nanoclusters. However, Au₁₁-2 exhibits only monotonic pressure-induced luminescence quenching under compression. In situ high-pressure angle-dispersive X-ray diffraction experiments and theoretical calculations confirm the existence of distinct anisotropic compressions in Au₁₁-1 and Au₁₁-2, which induce differential structural distortion of the gold core. The faster shrinkage along the a-axis exacerbates the structural distortion of the Au₁₁-1 core, whereas the more rapid compression along the b-axis in Au₁₁-2 suppresses the structural distortion of the gold core. High-pressure femtosecond transient absorption and Raman spectra synergistically demonstrate that pressure-driven directional structural distortion significantly suppresses nonradiative losses caused by low-frequency vibrations of the Au₁₁-1 core along the a-axis, resulting in NIR piezoluminescence enhancement of Au₁₁-1. Our study deeply reveals the intrinsic correlation between NIR-PLQY and metal core vibration relaxation at the atomic scale and provides a new approach to design and develop high-performance NIR luminescent materials.