Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet Geneva 4, Genève, 1211, Switzerland.
Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet Geneva 4, Genève, 1211, Switzerland.
Small. 2021 Oct;17(39):e2101855. doi: 10.1002/smll.202101855. Epub 2021 Aug 18.
Distinct Raman spectroscopic signatures of the metal core of atomically precise, ligand-protected noble metal nanoclusters are reported using Au (PET) and Au Ag (PET) (PET = 2-phenylethanethiolate, -SC H C H ) as model systems. The fingerprint Raman features (occurring <200 cm ) of these clusters arise due to the vibrations involving metal atoms of their Au or Au Ag cores. A distinct core breathing vibrational mode of the Au core has been observed at 90 cm . Whereas the breathing mode shifts to higher frequencies with increasing Ag content of the cluster, the vibrational signatures due to the outer metal-ligand staple motifs (between 200 and 500 cm ) do not shift significantly. DFT calculations furthermore reveal weak Raman bands at higher frequencies compared to the breathing mode, which are associated mostly with the rattling of two central gold atoms of the bi-icosahedral Au core. These vibrations are also observed in the experimental spectrum. The study indicates that low-frequency Raman spectra are a characteristic fingerprint of atomically precise clusters, just as electronic absorption spectroscopy, in contrast to the spectrum associated with the ligand shell, which is observed at higher frequencies.
本文报道了使用 Au(PET)和 AuAg(PET)（PET=2-苯乙硫醇盐，-SC H C H ）作为模型体系，对原子精确、配体保护的贵金属纳米团簇的金属核心具有独特拉曼光谱特征。这些团簇的指纹拉曼特征（出现在<200 cm ）是由于其 Au 或 AuAg 核中金属原子的振动引起的。在 90 cm 处观察到 Au 核的明显核呼吸振动模式。而呼吸模式随着簇中 Ag 含量的增加而向更高频率移动，而由于外层金属-配体钉扎基元（在 200 至 500 cm 之间）引起的振动特征并没有显著移动。DFT 计算还表明，与呼吸模式相比，在更高频率处存在较弱的拉曼带，这些带主要与双二十面体 Au 核中两个中心金原子的晃动有关。这些振动也在实验光谱中观察到。该研究表明，低频拉曼光谱是原子精确团簇的特征指纹，就像电子吸收光谱一样，与配体壳相关的光谱不同，它出现在更高的频率。
