Sol-gel derived urea cross-linked organically modified silicates.: 2.: Blue-light emission
Sol-gel derived urea cross-linked organically modified silicates.: 2.: Blue-light emission
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DOI：
10.1021/cm980373n
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发表时间：
1999-03-01
影响因子：
8.6
通讯作者：
Assunçao, M
中科院分区：
文献类型：
--
作者：
Carlos, LD;Bermudez, VD;Assunçao, M
讨论了溶胶-凝胶衍生的有机-无机杂化物的光致发光和局部结构。它们的宿主基质是一个基于硅的网络，通过尿素键将不同数量的氧乙烯重复单元（U（600）、U（900）和U（2000）分别为8.5、15.5和40.5）共价接枝。小角x射线散射（SAXS）结果表明，硅畴和聚合物区局部相分离导致的杂化产物具有双相结构。U（600）的域间距离为27埃，U（2000）的域间距离为59 ~ 64埃，表明这三个区域在SAXS尺度上是均匀的。发光光谱在2.0 ~ 4.1 eV范围内具有较宽的发光光谱，在2.6 eV范围内呈蓝色，在2.8 ~ 3.0 eV范围内呈紫蓝色。这两种组分的能量与主无机骨架的尺寸有关。这些非晶硅质区域的局部结构被描述为一个平面结构，它结合了不同比例的6到8个硅基链（蓝色发射）和3到4个有机修饰的Si-O环境（紫蓝色发射）。计算得到的U（600）、U（900）和U（2000）硅质畴的相干衍射长度分别为16.6、16.1和20.5埃，表明随着氧乙烯链的数量从8.5增加到40.5，无机主链的总体无序度增加。
The photoluminescence and the local structure of sol-gel derived organic-inorganic hybrids, so-called ureasils, are discussed. Their host matrix is a silica-based network to which different numbers of oxyethylene repeat units-8.5, 15.5, and 40.5 for U(600), U(900), and U(2000), respectively-are covalently grafted by means of urea linkages. The small-angle X-ray scattering (SAXS) results suggest a diphasic structure for the morphology of the hybrids induced by local phase separation between siliceous domains and polymeric regions. The estimated interdomain distances, ranging from 27 Angstrom for U(600) to 59-64 Angstrom for U(2000), indicate that the three ureasils are greatly homogeneous on the SAXS scale. The luminescence spectra show a broad light emission (2.0-4.1 eV) with a blue band at similar to 2.6 eV and a purplish-blue one at similar to 2.8-3.0 eV, clearly distinguished by time-resolved spectroscopy. The energies of these two components are related to the dimension of the backbone inorganic skeleton. The local structure of these amorphous siliceous regions is depicted as a planar structure that combines different proportions of six to eight silica-based chains (blue emission) with three to four organically modified Si-O environments (purplish-blue emission). The calculated coherent diffraction lengths of the siliceous domains for U(600), U(900), and U(2000)-16.6, 16.1, and 20.5 Angstrom, respectively-points to an increase of the overall disorder of the inorganic backbone as the quantity of oxyethylene chains increase from 8.5 to 40.5.