Fields-Zinna Christina A, Crowe Matthew C, Dass Amala, Weaver Joshua E F, Murray Royce W
Kenan Laboratories of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Langmuir. 2009 Jul 7;25(13):7704-10. doi: 10.1021/la803865v.
Monolayer-protected clusters were prepared by procedures like those yielding Au25L18 (where L=-SCH2CH2Ph=-SC2Ph) but using, instead, mixtures of Au and Pd salts, as starting materials, with the intent of creating and characterizing Au25-xMxL18 clusters. Isolation of small nanoparticle product followed by partial ligand exchange to introduce thiolated poly(ethylene glycol) (SPEG=-S(CH2CH2O)5CH3) into the nanoparticle ligand shell enabled characterization of the Au25-xMxL18 content by positive mode electrospray ionization mass spectrometry (ESI-MS). For synthetic feed mole ratios of Au:Pd of 9:1 and 13:12, electrospray spectra of the PEGylated MPCs showed that the reaction and isolation produce a mixture of Au25(SC2Ph)18 and a mono-Pd nanoparticle Au24Pd(SC2Ph)18. A higher proportion of the mono-Pd nanoparticle is produced by the 13:12 mole ratio, and also when the thiol:metal ratio was lowered, according to ESI-MS and MALDI-TOF-MS. As the nanoparticle mixture is enriched, by solvent fractionations, in Au24Pd(SC2Ph)18 relative to Au25(SC2Ph)18, the distinctive optical and electrochemical signatures of Au25(SC2Ph)18 are replaced by Au24Pd(SC2Ph)18 nanoparticle responses, which are very different, even though only one Au atom is replaced by a Pd atom.
通过类似于制备Au25L18（其中L = -SCH2CH2Ph = -SC2Ph）的程序来制备单层保护簇，但使用金和钯盐的混合物作为起始材料，以制备和表征Au25 - xMxL18簇。分离出小的纳米颗粒产物，然后进行部分配体交换，将硫醇化聚乙二醇（SPEG = -S(CH2CH2O)5CH3）引入纳米颗粒配体壳中，从而能够通过正模式电喷雾电离质谱（ESI-MS）对Au25 - xMxL18的含量进行表征。对于金与钯的合成进料摩尔比为9:1和13:12的情况，聚乙二醇化MPC的电喷雾光谱表明，反应和分离产生了Au25(SC2Ph)18和单钯纳米颗粒Au24Pd(SC2Ph)18的混合物。根据ESI-MS和基质辅助激光解吸电离飞行时间质谱（MALDI-TOF-MS），13:12的摩尔比以及硫醇与金属比例降低时，会产生更高比例的单钯纳米颗粒。随着通过溶剂分馏使纳米颗粒混合物相对于Au25(SC2Ph)18富集Au24Pd(SC2Ph)18，Au25(SC2Ph)18独特的光学和电化学特征被Au24Pd(SC2Ph)18纳米颗粒的响应所取代，尽管仅一个金原子被钯原子取代，但它们的差异很大。
