Photoemission Spectroscopy of Tethered CdSe Nanocrystals: Shifts in Ionization Potential and Local Vacuum Level As a Function of Nanocrystal Capping Ligand
Photoemission Spectroscopy of Tethered CdSe Nanocrystals: Shifts in Ionization Potential and Local Vacuum Level As a Function of Nanocrystal Capping Ligand
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DOI：
10.1021/am900834y
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发表时间：
2010-03-01
影响因子：
9.5
通讯作者：
Armstrong, Neal R.
中科院分区：
文献类型：
--
作者：
Munro, Andrea M.;Zacher, Brian;Armstrong, Neal R.
本文报道了利用He(l)和He（II）紫外光谱学表征了连接在光滑金衬底上的3.6和6.0 nm直径的裸CdSe纳米晶体（NC）的前沿轨道能量和界面偶极子效应。研究了纳米碳的电离势（IP）和薄膜的局部有效功函数随纳米碳盖配体偶极性质的变化。在两种尺寸的纳米碳纳米管中加入巯基覆盖配体1-己硫醇、1-苯硫醇和4-氟噻吩，可以忽略CdSe纳米碳纳米管的高动能边缘和金底物费米能之间的能量偏移。然而，纳米晶体层的局部真空度和IP变化高达0.3 eV。我们证明了确定局部真空水平和拴系NC样品的高动能边缘的重要性。这些研究证明了一种方法，可以在未来用于表征修饰或未修饰纳米晶体薄膜的前沿轨道能量偏移，其中nc被纳入宿主材料，应用范围从光伏到发光二极管。
We report the characterization of the frontier orbital energies and interface dipole effects for bare and ligand-capped 3.6 and 6.0 nm diameter CdSe nanocrystals (NC) tethered to smooth gold substrates, using He(l) and He(II) UV photoemission spectroscopy. Changes in the ionization potential (IP) of the NCs and local effective work function OF the films were explored as a function of the dipolar nature of the NC capping ligands. The addition of thiol-capping ligands 1-hexanethiol, I-benzenethiol, and 4-fluorothiophenol to both sizes OF NCs produces negligible shifts in energy offset between the high kinetic energy edge of the CdSe NCs and the gold substrate Fermi energy. However, the local vacuum level and IP of the nanocrystal layer are altered by as much as 0.3 eV. We demonstrate the importance of determining both the local vacuum level and the high kinetic energy edge of a tethered NC sample. These studies demonstrate a method that can be used in the future to characterize the frontier orbital energy offsets for modified or unmodified nanocrystalline films, in which the NCs are incorporated into host materials, for applications ranging from photovoltaics to light-emitting diodes.