Properties of non-IPR fullerene films versus size of the building blocks.
Properties of non-IPR fullerene films versus size of the building blocks.
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非 IPR 富勒烯薄膜的特性与构件尺寸的关系。
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发表时间：
2010
期刊：
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通讯作者：
M. Kappes
中科院分区：
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作者：
D. Löffler;S. Ulas;S. Jester;P. Weis;A. Böttcher;M. Kappes
该观点重点关注通过在超高真空条件下将质量选择的C(n)(+)（48、50、52、54、56、58、62、64、66和68）软着陆到室温石墨表面上而生长的新型固体富勒烯纳米膜的笼尺寸依赖性特性。这种非孤立五边形环（非IPR）富勒烯材料无法通过标准富勒烯制备方法获得。非 IPR 薄膜的组成分子构件是通过升华 IPR-C(70)(D(5h)) (-->C(n) (n = 68, 66, 64, 62)) 或 IPR-C(60)(I(h)) (-->C(n) (n = 58, 56, 54, 52) 的电子碰撞诱导电离/碎裂产生的50））。石墨上的非 IPR 富勒烯薄膜通过形成树枝状 C(n) 聚集体而生长，而 IPR 富勒烯在类似条件下的沉积（通过沉积未碎片的 C(60)(+) 和 C(70)(+)）会形成致密的岛。后者受弱范德华笼-笼相互作用控制。相反，前者通过非 IPR 位点（主要是相邻的五边形对，AP）介导的共价笼间键来稳定。沉积的非 IPR C(n) 笼的很大一部分可以通过加热完整地（再）升华。相应的平均解吸活化能 E(des) 从 C(68) 的 2.1 eV 增加到 C(50) 的 2.6 eV。测量了半导体非 IPR 薄膜的价带区 (DOS)、表面电离势 (sIP) 和 HOMO-LUMO 能隙 (Delta) 中的态密度，发现它们随笼尺寸的变化而变化很大。总体而言，这些性质的 n 依赖性可以用包含最稳定（中性）C(n) 异构体的共价互连寡聚结构来解释，如密度泛函理论 (DFT) 计算所确定的。非 IPR 富勒烯薄膜是元素簇材料的第一个已知示例，其中簇构建块共价但可逆地互连。
This perspective focuses on the cage size dependent properties of novel solid fullerene nanofilms grown by soft-landing of mass-selected C(n)(+) (48, 50, 52, 54, 56, 58, 62, 64, 66 and 68) onto room temperature graphite surfaces under ultra-high vacuum conditions. Such non-isolated-pentagon-ring (non-IPR) fullerene materials are not accessible to standard fullerene preparation methods. The component molecular building blocks of non-IPR films were generated by electron impact induced ionization/fragmentation of sublimed IPR-C(70)(D(5h)) (-->C(n) (n = 68, 66, 64, 62)) or IPR-C(60)(I(h)) (-->C(n) (n = 58, 56, 54, 52, 50)). Non-IPR fullerene films on graphite grow via formation of dendritic C(n) aggregates, whereas deposition of IPR fullerenes under analogous conditions (via deposition of unfragmented C(60)(+) and C(70)(+)) leads to compact islands. The latter are governed by weak van der Waals cage-cage interactions. In contrast, the former are stabilized by covalent intercage bonds as mediated by the non-IPR sites (primarily adjacent pentagon pairs, AP). A significant fraction of the deposited non-IPR C(n) cages can be intactly (re)sublimed by heating. The corresponding mean desorption activation energies, E(des), increase from 2.1 eV for C(68) up to 2.6 eV for C(50). The densities of states in the valence band regions (DOS), surface ionization potentials (sIP) and HOMO-LUMO gaps (Delta) of semiconducting non-IPR films were measured and found to vary strongly with cage size. Overall, the n-dependencies of these properties can be interpreted in terms of covalently interconnected oligomeric structures comprising the most stable (neutral) C(n) isomers-as determined from density functional theory (DFT) calculations. Non-IPR fullerene films are the first known examples of elemental cluster materials in which the cluster building blocks are covalently but reversibly interconnected.