DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai-600 036, India.
Nanoscale. 2013 Oct 7;5(19):9404-11. doi: 10.1039/c3nr03463a. Epub 2013 Aug 20.
Clusters composed of a 32 silver atom core, protected with thiolates of glutathione (GSH) and N-(2-mercaptopropionyl)glycine (MPGH), were synthesized by a solid-state route in milligram scale. They do not exhibit surface plasmon resonance unlike their larger sized nanoparticle analogues but show molecule-like features in absorption and luminescence spectra, falling in the visible window. The compositions Ag₃₂SG₁₉ (SG: thiolate of glutathione) and Ag₃₂MPG₁₉ (MPG: thiolate of MPGH) were identified from electrospray ionization mass spectrometry (ESI MS). Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) was not successful for -SG protected clusters as reported before, but for Ag₃₂MPG₁₉ a peak at 6.1 kDa was seen at a threshold laser intensity. This peak shifted to low mass region with increasing laser intensity due to systematic losses of Ag₂S. Further confirmation of the composition Ag₃₂SG₁₉ was made using various studies such as XPS and EDAX. One-dimensional (1D) and two-dimensional (2D) NMR spectroscopic investigations of Ag₃₂SG₁₉ provided interesting spectral features which indicated the dominant -[SR-Ag-SR]- structural motif. This structural motif as the predominant entity is found for the first time in silver clusters.
通过固态路线在毫克规模上合成了由 32 个银原子核心组成的簇，这些簇由谷胱甘肽（GSH）和 N-（2-巯基丙酰基）甘氨酸（MPGH）的硫醇保护。与较大尺寸的纳米粒子类似物不同，它们没有表现出表面等离子体共振，但在吸收和发光光谱中表现出类似分子的特征，落在可见光窗口中。通过电喷雾电离质谱（ESI MS）确定了 Ag₃₂SG₁₉（SG：谷胱甘肽的硫醇）和 Ag₃₂MPG₁₉（MPG：MPGH 的硫醇）的组成。如前所述，基质辅助激光解吸/电离质谱（MALDI MS）对 -SG 保护的簇不成功，但对于 Ag₃₂MPG₁₉，在阈值激光强度下观察到 6.1 kDa 的峰。由于 Ag₂S 的系统损失，该峰随着激光强度的增加而向低质量区域移动。通过 XPS 和 EDAX 等各种研究进一步证实了 Ag₃₂SG₁₉ 的组成。Ag₃₂SG₁₉ 的一维（1D）和二维（2D）NMR 光谱研究提供了有趣的光谱特征，表明主要的 -[SR-Ag-SR]-结构基序。这种结构基序作为主要实体首次在银簇中发现。
