Source of Bright Near-Infrared Luminescence in Gold Nanoclusters
Source of Bright Near-Infrared Luminescence in Gold Nanoclusters
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DOI：
10.1021/acsnano.1c04759
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发表时间：
2021-10-06
期刊：
影响因子：
17.1
通讯作者：
Gu, X. Wendy
中科院分区：
文献类型：
--
作者：
Li, Qi;Zeman, Charles J.;Gu, X. Wendy
具有近红外（NIR）光致发光（PL）特性的金纳米团簇在生物医学和生物成像领域作为传感和成像材料具有巨大的应用潜力。在这项工作中，Au-21（S-Adm）（15）和Au 38 S2（S-Adm）（20）被用来解开金纳米团簇中提高量子产率（QY）、大斯托克斯位移和长PL寿命的潜在机制。两种纳米团簇都显示出良好的PL QY。特别地，Au 38 S2（S-Adm）20纳米团簇在环境条件下在正常溶剂（例如甲苯）中在900 nm处显示出明亮的NIR PL，QY高达15%。与Au 38 S2（S-Adm）（20）相比，Au-21（S-Adm）（15）（4%）的QY相对较低，这归因于最低激发态是不允许的，如与PL相比吸收光谱的压力依赖性反光谱位移所证明的，但Au-21（S-Adm）（15）由于附近的不允许激发态而保持了一些发射性质。此外，我们的研究结果表明，由于表面“锁环”，它包围了Au内核和表面“锁原子”，它桥接了基本的Au内核单元（例如，四面体、二十面体等），是在金纳米团簇中获得高QY的关键。复杂的激发态过程和带边跃迁的小吸收系数导致了金纳米团簇中广泛观察到的大的Stokes位移和长的PL寿命。
Gold nanoclusters with near-infrared (NIR) photoluminescence (PL) have great potential as sensing and imaging materials in biomedical and bioimaging applications. In this work, Au-21(S-Adm)(15) and Au38S2(S-Adm)(20) are used to unravel the underlying mechanisms for the improved quantum yields (QY), large Stokes shifts, and long PL lifetimes in gold nanoclusters. Both nanoclusters show decent PL QY. In particular, the Au38S2(S-Adm) 20 nanocluster shows a bright NIR PL at 900 nm with QY up to 15% in normal solvents (such as toluene) at ambient conditions. The relatively lower QY for Au-21(S-Adm)(15) (4%) compared to that of Au38S2(S-Adm)(20) is attributed to the lowest-lying excited state being symmetry-disallowed, as evidenced by the pressure-dependent antispectral shift of the absorption spectra compared to PL, yet Au-21(S-Adm)(15) maintains some emissive properties due to a nearby symmetry-allowed excited state. Furthermore, our results show that suppression of nonradiative decay due to the surface "lock rings", which encircle the Au kernel and the surface "lock atoms" which bridge the fundamental Au kernel units (e.g., tetrahedra, icosahedra, etc.), is the key to obtaining high QYs in gold nanoclusters. The complicated excited-state processes and the small absorption coefficient of the band-edge transition lead to the large Stokes shifts and the long PL lifetimes that are widely observed in gold nanoclusters.