Tanaka Katsumi, Komatsu Yuhko, Choo Cheow-Keong
Department of Human Communication and Graduate School of Electronic Engineering, The University of Electro-Communications, 1-5-1 Chofu, Tokyo 182-8585, Japan.
J Phys Chem B. 2005 Jan 20;109(2):736-42. doi: 10.1021/jp047355f.
Photoluminescence (PL) spectra of Si species encapsulated in zeolite supercages are studied. It is reported that the chained Si species terminated partially with phenyl groups and with some unsaturated bonds are formed in zeolite supercages by the reaction with phenylsilane and they show PL around 4 eV (J. Phys. Chem. 2004, 108, 2501-2508). In the present paper they are reduced with hydrogen to prepare Si chained species terminated and saturated with hydrogen atoms. The PL spectra are deconvoluted to be four components at 1.9, 2.2, 2.6, and 3.7 eV, which can tentatively be assigned to Si nanocrystals and Si quantum wires in addition to defects in SiO2 and uncontrolled organic impurities in zeolite, respectively. At elevated temperatures the Si quantum wires in zeolite pores seem to change the Si nanocrystals with the size larger than that of the zeolite pore diameter. It is the first case in which the PL decay lifetime of oxygen vacancies in zeolite can be detected to be quite short to be about 16 ns. The detected lifetimes of Si quantum wires are significantly very short, about 12 ns. The Si species encapsulated zeolite is solvated with hydrofluoric acid solution to separate the Si quantum wires by dissolving zeolite lattice. The Si quantum wires in the HF solution show intense PL spectra peaked at 2.33 eV and broad UV spectra around 2.8-3.5 eV. They will have different shapes and lengths. The HF solvated zeolite shows still PL spectra characteristic of oxygen vacancies and the absorption edge at 3.6 eV. The result means that zeolite lattice is solvated in HF solution as clusters with a band gap of 3.6 eV and they can still have some oxygen vacancies. Oxygen vacancies situate about 1.0 eV below the zeolite conduction band minimum, and the absorbed energy can be dissipated as PL between the valence band maximum and the oxygen vacancies. It is concluded that the excitation photon energy can be absorbed in zeolite and the Si quantum wires and then the absorbed energies are competitively relaxed in zeolite and the Si quantum wires.
对封装在沸石超笼中的硅物种的光致发光（PL）光谱进行了研究。据报道，通过与苯基硅烷反应，在沸石超笼中形成了部分以苯基和一些不饱和键终止的链状硅物种，它们在4 eV左右显示出PL（《物理化学杂志》2004年，108卷，2501 - 2508页）。在本文中，它们用氢气还原以制备被氢原子终止并饱和的硅链物种。PL光谱被解卷积为1.9、2.2、2.6和3.7 eV的四个组分，这四个组分可初步分别归因于硅纳米晶体和硅量子线，此外还分别归因于二氧化硅中的缺陷和沸石中未控制的有机杂质。在升高的温度下，沸石孔中的硅量子线似乎会转变为尺寸大于沸石孔径的硅纳米晶体。这是首次检测到沸石中氧空位的PL衰减寿命非常短，约为16 ns。检测到的硅量子线的寿命明显非常短，约为12 ns。用氢氟酸溶液溶剂化封装有硅物种的沸石，通过溶解沸石晶格来分离硅量子线。氢氟酸溶液中的硅量子线显示出在2.33 eV处有峰值的强PL光谱以及在2.8 - 3.5 eV附近的宽紫外光谱。它们将具有不同的形状和长度。氢氟酸溶剂化的沸石仍显示出氧空位的PL光谱特征以及3.6 eV处的吸收边。结果表明，沸石晶格在氢氟酸溶液中以带隙为3.6 eV的团簇形式被溶剂化，并且它们仍然可以有一些氧空位。氧空位位于沸石导带最小值以下约1.0 eV处，吸收的能量可以作为PL在价带最大值和氧空位之间耗散。得出的结论是，激发光子能量可以被沸石和硅量子线吸收，然后吸收的能量在沸石和硅量子线中竞争性地弛豫。
Zotero 插件