Russier-Antoine Isabelle, Bertorelle Franck, Vojkovic Marin, Rayane Driss, Salmon Estelle, Jonin Christian, Dugourd Philippe, Antoine Rodolphe, Brevet Pierre-François
Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex, France.
Nanoscale. 2014 Nov 21;6(22):13572-8. doi: 10.1039/c4nr03782k.
By developing a new method for synthesizing atomically monodisperse Au15 nanoclusters stabilized with glutathione molecules and using the current state-of-the-art methods for synthesizing monodisperse protected Au25 nanoclusters, we investigated their nonlinear optical (NLO) properties after two-photon absorption. The two-photon emission spectra and the first hyperpolarizabilities of these particles were obtained using, in particular, a hyper-Rayleigh scattering technique. The influence on NLO of the excitation wavelength, the size as well as the nature of the ligands is also explored and discussed. Au15, the smallest stable thiolated gold nanocluster, presents remarkable nonlinear properties with respect to two-photon processes. The two-photon absorption cross-section at 780 nm for Au15 is ∼65,700 GM. This experimental cross-section value points to a quantum yield for two-photon emission of about 3 × 10(-7) at 475 nm for Au15. The first hyperpolarizability β for Au15 clusters (509 × 10(-30) esu), as compared to Au25 clusters (128 × 10(-30) esu), is larger considering the difference in the number of gold atoms. Also, 10(30) β per atom values reported for Au15 and Au25 clusters are more than two orders of magnitude larger than the values reported for Au NPs in the size range 10-50 nm, outlining the quantum cluster regime.
通过开发一种合成由谷胱甘肽分子稳定的原子单分散Au15纳米团簇的新方法，并使用当前合成单分散受保护Au25纳米团簇的最先进方法，我们研究了它们在双光子吸收后的非线性光学（NLO）性质。特别是使用超瑞利散射技术获得了这些粒子的双光子发射光谱和第一超极化率。还探索并讨论了激发波长、尺寸以及配体性质对NLO的影响。Au15是最小的稳定硫醇化金纳米团簇，在双光子过程方面呈现出显著的非线性特性。Au15在780nm处的双光子吸收截面约为65700 GM。该实验截面值表明Au15在475nm处的双光子发射量子产率约为3×10^(-7)。与Au25团簇（128×10^(-30) esu）相比，Au15团簇的第一超极化率β（509×10^(-30) esu）考虑到金原子数量的差异更大。此外，Au15和Au25团簇报道的每原子10^30β值比尺寸范围为10 - 50nm的金纳米颗粒报道的值大两个数量级以上，勾勒出量子团簇区域。
