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Chemical strategies towards understanding electronic processes in zero-dimensional materials.

机译：理解零维材料中电子过程的化学策略。

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To the first approximation, nanocrystals are considered to be a spherical fragment of a perfect semiconductor. While such assumptions allow a simple treatment of electronic structure and the prediction of gross optical properties. In reality nanometer scale semiconductors are not perfect spheres. Such a small size scale inevitably introduces a large surface to volume ratio. A large number of surface atoms can lead to a plethora of dangling bonds. With these issues in mind, processes involving surface charges, inherent charge separation, induced charge separation and charge transfer are considered in colloidal semiconductor nanocrystals with a combination of chemical modifications and intraband spectroscopy.; Large permanent dipole moments are measured in semiconductor nanocrystals of hexagonal and cubic internal lattice symmetry. This unexpected finding may be explained by surface charges and irregular shapes. The presence of a large permanent dipole moment in nearly spherical semiconductor nanocrystals implies a careful reconsideration of the electronic structure, especially that of the hole states.; Infrared intraband spectroscopy of strongly confined electrons in semiconductor nanocrystals has been carried out from picosecond time regime to the static limit. The elongation of lifetimes of electrons in the lowest quantum confined conduction band states of semiconductor nanocrystals is shown to be possible by charge separation enhanced by surface modification. Electrons can also be placed in these confined states by charge transfer from strongly reducing species resulting in n-type colloidal semiconductor nanocrystals. This new type of material exhibits unique size and charge-dependent properties.
机译：对于第一近似，纳米晶体被认为是完美半导体的球形碎片。尽管这样的假设允许对电子结构进行简单处理并预测总体光学性能。实际上，纳米级半导体不是完美的球体。如此小的尺寸比例不可避免地引入了大的表面体积比。大量的表面原子可导致过多的悬空键。考虑到这些问题，在胶体半导体纳米晶体中结合化学修饰和带内光谱研究了涉及表面电荷，固有电荷分离，感应电荷分离和电荷转移的过程。在具有六方和立方内部晶格对称性的半导体纳米晶体中测量到大的永久偶极矩。这种意外发现可以用表面电荷和不规则形状来解释。在接近球形的半导体纳米晶体中存在大的永久偶极矩意味着对电子结构，尤其是空穴态的电子结构进行了仔细的重新考虑。从皮秒时间范围到静态极限，已经对半导体纳米晶体中的强约束电子进行了红外带内光谱分析。通过表面修饰增强的电荷分离，显示出在半导体纳米晶体的最低量子限制导带状态下电子的寿命延长是可能的。还可以通过强还原物种的电荷转移将电子置于这些受限状态，从而产生n型胶体半导体纳米晶体。这种新型材料具有独特的尺寸和电荷依赖性。

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