State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China.
Phys Chem Chem Phys. 2013 Feb 14;15(6):1815-20. doi: 10.1039/c2cp43763e. Epub 2013 Jan 4.
Theoretical understanding of the surface modification of Cl-passivated silicon nanocrystals (Si NCs) is rather limited, in stark contrast to that for H-passivated Si NCs. We now investigate four surface-modification schemes (silanization, alkylation, alkoxylation and aminization) that have been experimentally adopted for Cl-passivated Si NCs in the framework of density functional theory. It is found that aminization most significantly affects the electronic structures of Si NCs by raising the highest occupied molecular orbital (HOMO). The effect of aminization depends on the substituents of amines, rather than the coverage of amine-derived ligands at the NC surface. The lowest unoccupied molecular orbital (LUMO) is more sensitive to the NC size than the HOMO. Only the HOMO is sensitive to surface modification. All the aminization leads to the decrease of the HOMO-LUMO gap despite that the dominant role of quantum confinement effect is maintained in most cases. The current results contribute to the understanding of the optical behavior of Si NCs derived from the surface modification of Cl-passivated ones.
理论上对 Cl 钝化硅纳米晶体（Si NCs）的表面改性的理解相当有限，这与 H 钝化 Si NCs 形成鲜明对比。我们现在在密度泛函理论的框架内研究了四种已被实验采用的 Cl 钝化 Si NCs 的表面改性方案（硅烷化、烷基化、烷氧基化和氨化）。结果发现，氨化通过提高最高占据分子轨道（HOMO），最显著地影响 Si NCs 的电子结构。氨化的效果取决于胺的取代基，而不是 NC 表面上衍生的胺配体的覆盖率。最低未占据分子轨道（LUMO）比 HOMO 对 NC 尺寸更敏感。只有 HOMO 对表面改性敏感。尽管在大多数情况下仍保持量子限域效应的主导作用，但所有氨化都会导致 HOMO-LUMO 能隙减小。目前的结果有助于理解源自 Cl 钝化 Si NCs 的表面改性的 Si NCs 的光学行为。
