In Situ Atomic-Level Tracking of Heterogeneous Nucleation in Nanocrystal Growth with an Isocyanide Molecular Probe
In Situ Atomic-Level Tracking of Heterogeneous Nucleation in Nanocrystal Growth with an Isocyanide Molecular Probe
复制标题
DOI：
10.1021/jacs.8b04824
复制
发表时间：
2018-07-04
影响因子：
15
通讯作者：
Qin, Dong
中科院分区：
文献类型：
--
作者：
Wu, Yiren;Qin, Dong
用2，6-二甲基苯基异氰酸酯(2，6-DMPI)作为光谱探针，用表面增强拉曼光谱研究了不同条件下钯在银纳米立方体上的非均相成核和沉积。作为一个主要的优点，光谱分析可以在反应溶液中仍然悬浮的纳米颗粒的情况下进行原位和实时的分析。这种方法的成功依赖于2，6-DMPI中异氰基分别通过S施主和pi-Back施主与银和钯原子键合时独特的伸缩频率(nU(Nc))。值得注意的是，我们发现Nu(NC)对Pd吸附原子在Ag表面的排列很敏感。例如，当异氰基与一个、两个和三个Pd原子结合时，我们会在不同的Nu(Nc)频率下分别观察到顶部、桥和中空的构型。因此，Nu(NC)带可以作为Pd吸附原子沉积到银纳米立方体上不同类型的小平面上的特征报告，具有原子级的灵敏度。当2，6-DMPI分子被引入到反应溶液中时，我们通过监测银和钯表面原子的Nu(NC)带随反应时间的变化，进一步展示了Pd在银纳米立方体上的异相成核和早期沉积的原位跟踪。这种原位技术为研究反应温度和Pd(II)前驱体类型在影响双金属纳米晶非均相成核和生长中所起的作用提供了机会。异氰基对Pd原子的敏感性有助于解释异相成核过程中还原、沉积和扩散过程的一些细节。
We report the use of 2,6-dimethylphenyl isocyanide (2,6-DMPI) as a spectroscopic probe to study the heterogeneous nucleation and deposition of Pd on Ag nanocubes under different conditions by surface-enhanced Raman scattering. As a major advantage, the spectroscopic analysis can be performed in situ and in real time with the nanoparticles still suspended in the reaction solution. The success of this method relies on the distinctive stretching frequencies (nu(NC)) of the isocyanide group in 2,6-DMPI when it binds to Ag and Pd atoms through s donation and pi-back-donation, respectively. Significantly, we discovered that nu(NC) was sensitive to the arrangement of Pd adatoms on the Ag surface. For example, when the isocyanide group bound to one, two, and three Pd atoms, we would observe the atop, bridge, and hollow configurations, respectively, at different nu(NC) frequencies. As such, the nu(NC) band could serve as a characteristic reporter for the Pd adatoms being deposited onto different types of facets on Ag nanocubes with atomic-level sensitivity. When 2,6-DMPI molecules were introduced into the reaction solution, we further demonstrated in situ tracking of heterogeneous nucleation and early stage deposition of Pd on Ag nanocubes by monitoring the evolution of nu(NC) bands for both Ag and Pd surface atoms as a function of reaction time. This in situ technique opens up the opportunity to investigate the roles played by reaction temperature and the type of Pd(II) precursor in influencing the heterogeneous nucleation and growth of bimetallic nanocrystals. The sensitivity of isocyanide group to Pd atoms helps elucidate some of the details on the reduction, deposition, and diffusion processes involved in heterogeneous nucleation.