Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
Department of Chemistry, Georgia State University, Atlanta, GA, 30302, USA.
Angew Chem Int Ed Engl. 2017 Dec 18;56(51):16257-16261. doi: 10.1002/anie.201709095. Epub 2017 Nov 22.
The transition from molecular to plasmonic behaviour in metal nanoparticles with increasing size remains a central question in nanoscience. We report that the giant 246-gold-atom nanocluster (2.2 nm in gold core diameter) protected by 80 thiolate ligands is surprisingly non-metallic based on UV/Vis and femtosecond transient absorption spectroscopy as well as electrochemical measurements. Specifically, the Au nanocluster exhibits multiple excitonic peaks in transient absorption spectra and electron dynamics independent of the pump power, which are in contrast to the behaviour of metallic gold nanoparticles. Moreover, a prominent oscillatory feature with frequency of 0.5 THz can be observed in almost all the probe wavelengths. The phase and amplitude analysis of the oscillation suggests that it arises from the wavepacket motion on the ground state potential energy surface, which also indicates the presence of a small band-gap and thus non-metallic or molecular-like behaviour.
随着尺寸的增加，金属纳米粒子从分子态向等离子体态的转变仍然是纳米科学中的一个核心问题。我们报告说，由 80 个硫醇配体保护的巨大的 246 金原子纳米团簇（金核直径为 2.2nm）在基于紫外/可见和飞秒瞬态吸收光谱以及电化学测量的情况下出人意料地是非金属的。具体来说，金纳米团簇在瞬态吸收光谱和电子动力学中表现出多个激子峰，而与金属金纳米粒子的行为相反，电子动力学与泵浦功率无关。此外，在几乎所有的探测波长都可以观察到一个明显的具有 0.5THz 频率的振荡特征。该振荡的相位和振幅分析表明，它是由基态势能表面上的波包运动引起的，这也表明存在一个小的带隙，因此表现出非金属或类似分子的行为。
