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Updated: Jun 4, 2025
Synthesis of Near-Infrared Emitting Gold Nanoclusters for Biological Applications
Published on: March 22, 2020
Two-photon brightness of NIR-emitting, atomically precise DNA-stabilized silver nanoclusters
Agata Hajda1, Rweetuparna Guha2, Stacy Marla Copp2,3,4,5
1Institute of Advanced Materials, Wroclaw University of Science and Technology Wrocław Poland joanna.olesiak-banska@pwr.edu.pl.
DNA-stabilized silver nanoclusters show promise as near-infrared (NIR) two-photon absorbers for in vivo imaging. These Ag-DNAs exhibit high two-photon absorption (2PA) cross-sections, enabling brighter NIR-to-NIR imaging probes.
Area of Science:
- Materials Science
- Nanotechnology
- Biophotonics
Background:
- Near-infrared (NIR) emitters with high two-photon absorption (2PA) are crucial for deep tissue imaging due to reduced light scattering.
- DNA-stabilized silver nanoclusters (Ag-DNAs) are explored as potential water-soluble probes for biological applications.
- Understanding the photophysical properties of Ag-DNAs, including their 2PA behavior, is essential for their development.
Purpose of the Study:
- To investigate the two-photon absorption (2PA) properties of various DNA-stabilized silver nanocluster (Ag-DNA) species.
- To evaluate the potential of these Ag-DNAs as NIR-to-NIR two-photon probes for in vivo imaging.
- To correlate nanocluster composition and ligand environment with 2PA cross-sections and emission characteristics.
Main Methods:
- Synthesis and characterization of four distinct atomically precise Ag-DNA species.
- Determination of 2PA cross-sections (σ₂) using the two-photon excited luminescence (2PEL) technique across a broad wavelength range (810–1400 nm).
- Analysis of the relationship between one-photon and two-photon absorption spectra to understand photophysical complexities.
Main Results:
- Ag-DNAs demonstrated reversed transition strengths in the two-photon regime compared to one-photon absorption, indicating complex photophysics.
- A maximal 2PA cross-section of ~582 GM was observed for (DNA)₃[Ag₂₁]¹⁵⁺.
- (DNA)₂[Ag₁₆Cl₂]⁸⁺ exhibited unique 2PA behavior with a high cross-section of 176 GM at 1050 nm, distinct from Ag-DNAs without chlorido ligands.
Conclusions:
- Ag-DNAs are promising water-soluble NIR-to-NIR two-photon probes with high 2PA cross-sections and fluorescence quantum yields.
- The observed two-photon brightness (up to ~10² GM) surpasses that of many water-soluble organic fluorophores.
- These findings support the utility of Ag-DNAs for advanced bioimaging applications requiring efficient NIR excitation and emission.
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