State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang, 310027, PR China.
Phys Chem Chem Phys. 2011 Dec 7;13(45):20255-61. doi: 10.1039/c1cp21366k. Epub 2011 Oct 12.
We report the synthesis of silicon nanocrystals via a one-step route, namely, femtosecond laser ablation in 1-hexene under ambient conditions. The size of these silicon nanocrystals is 2.37 ± 0.56 nm as determined by transmission electron microscopy. Fourier transform infrared spectra and X-ray photoelectron spectra indicate that the surface of the silicon nanocrystals is passivated by organic molecules and is also partially oxidized by O(2) and H(2)O dissolved in the solution. These silicon nanocrystals emit stable and bright blue photoluminescence. We suggest that the photoluminescence originates from the radiative recombination of electron-hole pairs through the oxide-related centers on the surface of the silicon nanocrystals. The decay rate of the oxide-related surface recombination can be comparable to that of the direct band gap transition. In the excitation and emission spectra, a vibrational structure with nearly constant spacings (0.18 eV) is observed. We propose that the strong electron-phonon coupling between excitons and the longitudinal optical (LO) phonons of the Si-C vibration is responsible for this vibrational structure. The fluctuations in the peak resolution, about ±0.01 eV, are ascribed to the size distribution and presence of Si-O vibrations. These silicon nanocrystals offer stable luminescence and are synthesized through a "green" and simple route. They may find important applications in many fields, such as bioimaging and environmental science.
我们报告了一种通过一步途径，即在环境条件下用飞秒激光烧蚀 1-己烯来合成硅纳米晶体的方法。通过透射电子显微镜确定这些硅纳米晶体的尺寸为 2.37 ± 0.56nm。傅里叶变换红外光谱和 X 射线光电子能谱表明，硅纳米晶体的表面被有机分子钝化，并且部分被溶解在溶液中的 O(2)和 H(2)O 氧化。这些硅纳米晶体发出稳定而明亮的蓝色光致发光。我们认为，光致发光源于通过硅纳米晶体表面的氧化物相关中心的电子-空穴对的辐射复合。氧化物相关表面复合的衰减速率可以与直接带隙跃迁的速率相媲美。在激发和发射光谱中，观察到具有几乎恒定间距（0.18eV）的振动结构。我们提出，激子与 Si-C 振动的纵光学（LO）声子之间的强电子-声子耦合是导致这种振动结构的原因。峰分辨率的波动约为 ±0.01eV，归因于尺寸分布和 Si-O 振动的存在。这些硅纳米晶体提供了稳定的发光，并且通过“绿色”和简单的途径合成。它们可能在许多领域有重要的应用，例如生物成像和环境科学。
