Bright NIR‐II Photoluminescence in Rod‐Shaped Icosahedral Gold Nanoclusters

Abstract

Fluorophores with high quantum yields, extended maximum emission wavelengths, and long photoluminescence (PL) lifetimes are still lacking for sensing and imaging applications in the second near‐infrared window (NIR‐II). In this work, a series of rod‐shaped icosahedral nanoclusters with bright NIR‐II PL, quantum yields up to ≈8%, and a peak emission wavelength of 1520 nm are reported. It is found that the bright NIR‐II emission arises from a previously ignored state with near‐zero oscillator strength in the ground‐state geometry and the central Au atom in the nanoclusters suppresses the non‐radiative transitions and enhances the overall PL efficiency. In addition, a framework is developed to analyze and relate the underlying transitions for the absorptions and the NIR‐II emissions in the Au nanoclusters based on the experimentally defined absorption coefficient. Overall, this work not only shows good performance of the rod‐shaped icosahedral series of Au nanoclusters as NIR‐II fluorophores, but also unravels the fundamental electronic transitions and atomic‐level structure‐property relations for the enhancement of the NIR‐II PL in gold nanoclusters. The framework developed here also provides a simple method to analyze the underlying electronic transitions in metal nanoclusters.

Fluorescent carbon-dots enhance light harvesting and photosynthesis by overexpressing PsbP and PsiK genes

“…In previous reports, semiconductor quantum dots (SQDs) [ 9 ], silicon quantum dots [ 10 ], lanthanide-doped up-conversion phosphors [ 11 ] and noble metal nanoclusters [ 12 ] were exploited on the plant growth and development. However, toxicity of the heavy metal ions, high cost and low fluorescence quantum yield greatly limit their further applications [ 13 , 14 ]. Therefore, it is meaningful and challenging to seek new LNMs with the features of low cost, good biocompatibility and outstanding optical properties [ 15 ].…”

Tailoring the SWIR emission of gold nanoclusters by surface ligand rigidification and their application in 3D bioimaging

“…12 Other studies have demonstrated how increasing the rigidity of the organic shell surrounding the gold core of Au NC led to a striking enhancement and a blue-shift of the PL signal in the red window (650-850 nm). 14,15 The origin of the multiple SWIR PL bands observed for various Au NCs 12,13,[16][17][18] is still unclear and there is still a lack of information on their sensitivity to the environment such as pH, salt concentration, temperature, and viscosity.…”

Source of Bright Near-Infrared Luminescence in Gold Nanoclusters

“…It is worth noting that previous theoretical work from the Zhu group found that C and H have negligible contributions to the frontier orbitals in Au 21 (S-Adm) 15 . The calculated fluorescence energy was taken as the sum of the excitation energy and the total energy in the optimized excited state geometry of S 1 , minus the total energy of the optimized ground-state geometry, which corresponds to the E 0–0 transition. , Such methods were shown in previous work to give accurate and predictive fluorescence energies . This gave a wavelength of fluorescence of 928 nm, which corresponds to a Stokes shift of 0.23 eV.…”