Fields-Zinna Christina A, Sampson Jason S, Crowe Matthew C, Tracy Joseph B, Parker Joseph F, deNey Alexander M, Muddiman David C, Murray Royce W
Kenan Laboratories of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
J Am Chem Soc. 2009 Sep 30;131(38):13844-51. doi: 10.1021/ja905787y.
We report the first collision-induced dissociation tandem mass spectrometry (CID MS/MS) of a thiolate-protected Au nanoparticle that has a crystallographically determined structure. CID spectra assert that dissociation pathways for the mixed monolayer Na(x)Au(25)(SC(2)H(4)Ph)(18-y)(S(C(2)H(4)O)(5)CH(3))(y) centrally involve the semi-ring Au(2)L(3) coordination (L = some combination of the two thiolate ligands) that constitutes the nanoparticle's protecting structure. The data additionally confirm charge state assignments in the mass spectra. Prominent among the fragments is Na(2)AuL(2), one precursor of which is identified as another nanoparticle fragment in the higher m/z region. Another detected fragment, Na(2)Au(2)L(3), represents a mass loss equivalent to an entire semi-ring, whereas others suggest involvement (fragmentation/rearrangement) of multiple semi-rings, e.g., NaAu(3)L(3) and NaAu(4)L(4). The detailed dissociation/rearrangement mechanisms of these species are not established, but they are observed in other mass spectrometry experiments, including those under non-CID conditions, namely, electrospray ionization mass spectrometry (ESI-MS) with both time-of-flight (TOF) and FT-ICR analyzers. The latter, previously unreported results show that even soft ionization sources can result in Au nanoparticle fragmentation, including that yielding Au(4)L(4) in ESI-TOF of a much larger thiolate-protected Au(144) nanoparticle under non-CID conditions.
我们报道了首例具有晶体学确定结构的硫醇盐保护的金纳米颗粒的碰撞诱导解离串联质谱（CID MS/MS）。CID光谱表明，混合单层Na(x)Au(25)(SC(2)H(4)Ph)(18 - y)(S(C(2)H(4)O)(5)CH(3))(y)的解离途径主要涉及构成纳米颗粒保护结构的半环Au(2)L(3)配位（L = 两种硫醇盐配体的某种组合）。这些数据还证实了质谱中的电荷态归属。碎片中突出的是Na(2)AuL(2)，其前体之一在较高m/z区域被鉴定为另一个纳米颗粒碎片。另一个检测到的碎片Na(2)Au(2)L(3)，代表相当于整个半环的质量损失，而其他碎片表明多个半环参与（碎片化/重排），例如NaAu(3)L(3)和NaAu(4)L(4)。这些物种的详细解离/重排机制尚未确定，但在其他质谱实验中也有观察到，包括在非CID条件下的实验，即使用飞行时间（TOF）和傅里叶变换离子回旋共振（FT-ICR）分析仪的电喷雾电离质谱（ESI-MS）。后者以前未报道的结果表明，即使是软电离源也会导致金纳米颗粒碎片化，包括在非CID条件下对一个大得多的硫醇盐保护的Au(144)纳米颗粒进行ESI-TOF分析时产生Au(4)L(4)。
