Gold Quantum Rods Emit in the Shortwave Infrared (1000–2200 nm) with 10 4–5 M –1 cm –1 Ultrabrightness

Fluorescence in the near-infrared-II (NIR-II) region (1000-2500 nm, also called shortwave infrared, SWIR) is highly attractive for advanced optical applications, including quantum photonics, biomedicine, and environmental sensing, yet the development of bright, stable, and tunable SWIR emitters remains a significant challenge. Here, we report ultrabright, subnanosecond fluorescence emission spanning 1000 to 2200 nm from a periodic series of atomically precise gold quantum rods (Au QRs) with quantum yields reaching up to ∼21% by suppressing singlet-to-triplet exciton conversion and electron-vibration coupling. The high quantum yields, together with high absorption coefficients (εpeak ∼ 105-6 M-1 cm-1) of Au QRs, offer unprecedented brightness (104-5 M-1 cm-1), exceeding the state-of-the-art SWIR organic dyes by more than 2 orders of magnitude in the 1100-1400 nm region and 4 orders of magnitude in the >1500 nm region. Furthermore, Au QRs are successfully transferred into aqueous phase using a Pluronic F-127 amphiphilic polymer wrapping method. The results establish atomically precise Au QRs as a new benchmark platform that redefines the brightness and spectral reach attainable in SWIR fluorescence, providing a foundation for next-generation SWIR photonic and biorelated technologies.