A combined X-ray spectroscopic study on the multicolored pattern formation in gels containing FeCl3 and K3[Fe(CN)6]
A combined X-ray spectroscopic study on the multicolored pattern formation in gels containing FeCl3 and K3[Fe(CN)6]
复制标题
含 FeCl3 和 K3[Fe(CN)6] 凝胶中多彩图案形成的组合 X 射线光谱研究
DOI：
10.1039/c5ja00481k
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Hisashi Hayashi and Hitoshi Abe
中科院分区：
文献类型：
--
作者：
M. Asami;S. Nishida;N. Furuta;Hisashi Hayashi and Hitoshi Abe
我们考察了两种X射线光谱方法--时间分辨X射线荧光(XRF)光谱和位置相关X射线吸收近边结构(XANES)光谱--相结合用于研究无机化合物在凝胶介质中复杂的反应-扩散过程的潜力。为了验证这种方法，我们制备了含有琼脂糖凝胶和水玻璃凝胶的玻璃管，其中琼脂糖凝胶与FeCl3溶液混合，水玻璃凝胶与K3[Fe(CN)6]溶液和盐酸混合。在水玻璃凝胶中形成了宽棕色和窄蓝色的条带，彩色图案的完全显影大约需要25天。用XRF和XANES光谱分别研究了色带中铁的浓度分布和微观局域结构随时间的变化规律。这些分析表明，棕色带是由局部结构主要为[Fe(Cl)2O4]的Fe物种的稳定积累形成的，而蓝色带(来源于普鲁士蓝(PB)类化合物)的形成在很大程度上对带中主要Fe物种(主要是[Fe(Cl)O5])的铁浓度分布和局部结构不敏感。这种不敏感性归因于PB(∼10−41)极小的溶度积，这使得即使在非常低的Fe~(2+)和[Fe(CN)6]~(3+)浓度下也能形成PB/PB类化合物。结果是，当高浓度的Fe2+、[Fe(CN)6]3+和/或[Fe(CN)6]4+存在时，棕色带被蓝色的类PB化合物遮盖，但在很低的浓度下，棕色带变得可见，显示出五颜六色的图案。
We examined the potential of the combined use of two X-ray spectroscopic methods, time-resolved X-ray fluorescence (XRF) spectroscopy and position-dependent X-ray absorption near-edge structure (XANES) spectroscopy, for the study of intricate reaction–diffusion processes of inorganic compounds in gel media. To test this approach, we prepared a glass tube containing agarose gel mixed with FeCl3 solution and water-glass gel mixed with K3[Fe(CN)6] solution and hydrochloric acid. Wide brown and narrow blue bands formed in the water-glass gel, and the full development of the colored patterns took approximately 25 days. XRF and XANES spectroscopies were then used to study the time dependence of the Fe concentration distributions and the microscopic local structures of the Fe species formed in the colored bands, respectively. From these analyses, it was deduced that the brown bands were formed by the stable accumulation of Fe species whose local structure was mainly [Fe(Cl)2O4]; in contrast, the formation of the blue bands (originating from Prussian blue (PB) like compounds) was largely insensitive to both the Fe concentration distribution and the local structure of the dominant Fe species (mainly [Fe(Cl)O5]) in the bands. Such insensitivities are attributable to the extremely small solubility product of PB (∼10−41), which allows PB/PB-like compounds to form even under very low concentrations of both Fe2+ and [Fe(CN)6]3+. As a result, the brown bands were obscured by the blue colored PB-like compounds when high concentrations of Fe2+, [Fe(CN)6]3+, and/or [Fe(CN)6]4+ were present, but became visible to reveal multicolored patterns under very low concentrations of these ions.