FAB mass spectrometry of Au25(SR)18 nanoparticles
FAB mass spectrometry of Au25(SR)18 nanoparticles
复制标题
DOI：
10.1021/ac801259j
复制
发表时间：
2008-09-15
影响因子：
7.4
通讯作者：
Murray, Royce W.
中科院分区：
文献类型：
--
作者：
Dass, Amala;Dubay, George R.;Murray, Royce W.
Au-25(SCH_2-CH_2Ph)(18)(A(25)(SR)(18))纳米粒子的快原子轰击(FAB，Xe原子)电离质谱仪在7394Da处观察到分子离子。在5225-7394Da的质量区间内有明显的正碎片离子模式，在该区间出现了相当于R2实体的连续质量损失的峰值。由于Au-25(SCH_2CH_2Ph)(18)纳米粒子结构在结晶学上是由六个Au-2(SR)(3)半环包围的以Au-13为中心的二十面体核心组成的，因此R2S损失被认为是半环结构的一系列重排和分解。相当于R2S2和R-2实体的质量损失也出现在该质量区间的下端。最强的光谱峰在m/z=5246Da处归属于片断Au25S10，从中解离了所有的CH2CH2Ph有机单元，但没有丢失金原子。在较低质量下观察到不同的碎裂模式，产生的离子对应于一个金原子和不同数量的硫原子的连续损失，一直持续到Au9S2碎片。Au纳米粒子的FAB质谱图比激光解吸/电离谱更容易解释，但它们显示的更多。比电喷雾和低激光脉冲强度的MALDI光谱有更广泛的碎裂。在FAB中R2S碎裂的损失是独特的，不像在其他电离模式中看到的那样。还报道了纳米Au-25(S(CH2)(9)CH3)(18)的FAB谱；其碎裂与Au-25(SCH_2CH2Ph)(18)的碎裂相似，这意味着该纳米粒子具有相同的令人惊讶的星状(钉)结构。
The molecular ion of the nanoparticle Au-25(SCH2-CH2Ph)(18) (A(25)(SR)(18)) is observed at 7394 Da in fast atom bombardment (FAB, Xe atoms) ionization mass spectrometry using a 3-nitrobenzyl alcohol matrix. A distinctive pattern of positive fragment ions is evident in the mass interval 5225-7394 Da, where peaks are seen for successive mass losses equivalent to R2S entities. Because the Au-25(SCH2CH2Ph)(18) nanoparticle structure is crystallographically known to consist of a centered Au-13 icosahedral core surrounded by six Au-2(SR)(3) semirings, the R2S loses are proposed to represent serial rearrangements and decompositions of the semiring structures. Mass losses equivalent to R2S2 and R-2 entities also appear at the lower end of this mass interval. The most intense spectral peak, at m/z = 5246 Da, is assigned to the fragment Au25S10, from which all of the CH2CH2Ph organic units have been cleaved but from which no gold atoms have been lost. A different pattern of fragmentation is observed at lower masses, producing ions corresponding to serial losses of one gold atom and varied numbers of sulfur atoms, which continues down to a Au9S2 fragment FAB mass spectra of the Au nanoparticle are much easier to interpret than laser desorption/ionization spectra, but they show more. extensive fragmentation than do electrospray and low laser pulse intensity MALDI spectra. The loss of R2S fragmentation in FAB is distinctive and unlike that seen in the other ionization modes. The FAB spectrum for the nanoparticle Au-25(S(CH2)(9)CH3)(18) is also reported; its fragmentation parallels that for Au-25(SCH2CH2Ph)(18), implying that this nanoparticle has the same surprising stellated (staples) structure.