Pressure-Induced Optical Transitions in Metal Nanoclusters
Pressure-Induced Optical Transitions in Metal Nanoclusters
复制标题
金属纳米团簇中的压力诱导光跃迁
DOI：
10.1021/acsnano.0c04813
复制
发表时间：
2020-09-22
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;Mosquera, Martin A.;Gu, X. Wendy
目前，对于直径在1 ~ 3nm之间的超小金属纳米团簇的原子结构与光学性质之间的关系还缺乏全面的认识。为了应对这一挑战，有必要开发工具来干扰原子结构和调制金属纳米团簇的光学性质，而不是使用合成化学可以实现的。在这里，我们对一系列原子精确配体保护的金属纳米团簇进行了系统的高压研究。金刚石砧细胞用作高压室来逐渐压缩金属纳米团簇，同时原位监测其光学特性。实验结果表明，在高达7 GPa的压力下，这些纳米团簇的光致发光（PL）提高了2个数量级。随着压力的增加，吸收开始红移，接近12 GPa。密度泛函理论计算表明，由于核心电子离域到碳配体上，团簇的离散能级之间的间距缩小，从而产生了红移。压力诱导的PL增强归因于(i)近带边缘跃迁强度的增强，（ii）非辐射振动的抑制，以及（iii）激发态结构畸变的阻碍。总之，我们的研究结果表明，高压是调制金属纳米团簇光学性质和提高其发光亮度的有效工具。本文所获得的对结构-性质关系的见解也有助于合理设计用于各种光学应用的金属纳米团簇。
Currently, a comprehensive understanding of the relationship between atomic structures and optical properties of ultrasmall metal nanoclusters with diameters between 1 and 3 nm is lacking. To address this challenge, it is necessary to develop tools for perturbing the atomic structure and modulating the optical properties of metal nanoclusters beyond what can be achieved using synthetic chemistry. Here, we present a systematic high-pressure study on a series of atomically precise ligand-protected metal nanoclusters. A diamond anvil cell is used as a high-pressure chamber to gradually compress the metal nanoclusters, while their optical properties are monitored in situ. Our experimental results show that the photoluminescence (PL) of these nanoclusters is enhanced by up to 2 orders of magnitude at pressures up to 7 GPa. The absorption onset red-shifts with increasing pressure up to , similar to 12 GPa. Density functional theory calculations reveal that the red-shift arises because of narrowing of the spacing between discrete energy levels of the cluster due to delocalization of the core electrons to the carbon ligands. The pressure-induced PL enhancement is ascribed to (i) the enhancement of the near-band-edge transition strength, (ii) suppression of the nonradiative vibrations, and (iii) hindrance of the excited-state structural distortions. Overall, our results demonstrate that high pressure is an effective tool for modulating the optical properties and improving the luminescence brightness of metal nanoclusters. The insights into structure-property relations obtained here also contribute to the rational design of metal nanoclusters for various optical applications.