Controllable assembly of zeolite beta monolayers and bilayers on various substrates using the LangmuireBlodgett technique
Controllable assembly of zeolite beta monolayers and bilayers on various substrates using the LangmuireBlodgett technique
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使用 LangmuireBlodgett 技术在各种基材上可控组装 β 沸石单层和双层
DOI：
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发表时间：
2018
影响因子：
5.2
通讯作者：
Xiufeng Liu
中科院分区：
文献类型：
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作者：
Honghong Xu;Baoquan Zhang;Jian Li;Xiufeng Liu
采用LB技术在玻璃板、α-Al_2O_3圆盘、玻璃毛细管、铜丝、不锈钢管和g-Al_2 O_3管等基底上制备了纳米β（nano-beta）晶体的单层膜、双层膜和微米β（micro-beta）晶体的单层膜。相对于1重量%的甲醇悬浮液，用十六烷基三甲基溴化铵（CTAB）修饰的纳米β，得到两个区域的表面压力-面积等温线，导致在每个转移表面压力下形成具有令人满意的覆盖度（DOC）和紧密堆积（DCP）的纳米β单层和双层。当纳米β晶体被脱铝时，表面压力-面积关系降低到单区等温线，并且所得的L-B膜包含聚集区。对于微β晶体的组装，甲醇和仲丁醇都被用作分散剂。所得到的微β单分子层是随机取向的大截断方双锥晶体的沉降压缩通过使用甲醇悬浮液。使用仲丁醇作为分散剂，由于仲丁醇分子与表面硅烷醇的化学反应，导致微β晶体的疏水性增强，从而导致在各种衬底上形成c-取向的微β单分子膜，同时没有发生大的截方形双锥晶体的沉降。在晶种生长的c-取向的微β单分子层的结构方向下，可以制备致密且优先c-取向的β沸石膜，这不能在具有随机取向的纳米β单分子层或微β单分子层上形成。因此，可以得出结论，β晶体在籽晶层上的生长可以遵循外延生长机制。
The Langmuir-Blodgett (L-B) technique was employed to fabricate the monolayers and bilayers of nanosized beta (nano-beta) crystals, and the monolayers of micrometer-sized beta (micro-beta) crystals on various substrates including glass plate, alpha-alumina disk, glass capillary tube, copper wire, stainless-steel tube and g-Al2O3 tube. With respect to the methanol suspension of 1 wt.% nano-beta modified with cetyltrimethylammonium bromide (CTAB), a two-region surface pressure-area isotherm was obtained, leading to the formation of both nano-beta monolayers and bilayers with satisfactory degree of coverage (DOC) and close packing (DCP) under each transfer surface pressure. When nano-beta crystals were dealuminated, the surface pressure-area relation was reduced to the one-region isotherm, and the resulting L-B film contained aggregated areas. As for the assembly of micro-beta crystals, both methanol and sec-butanol were used as the dispersant. The resulting micro-beta monolayer was randomly oriented with the sedimentation of large truncated-square-bipyramid crystals on compression by using the methanol suspension. The use of sec-butanol as the dispersant resulted in the enhanced hydrophobicity of micro-beta crystals due to the chemical reaction of sec-butanol molecules with surface silanols, leading to the formation of c-oriented micro-beta monolayers over various substrates, and simultaneously the sedimentation of large truncated-square-bipyramid crystals did not occur. Under the structure direction of the c-oriented micro-beta monolayer in the seeded growth, the dense and preferentially c-oriented zeolite beta film could be fabricated, which could not be formed on either the nanobeta monolayer or the micro-beta monolayer with random orientation. Therefore, it would be concluded that the growth of beta crystals over the seed layer could be followed by the epitaxial growth mechanism.