State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
Langmuir. 2010 Apr 20;26(8):5895-900. doi: 10.1021/la903850r.
The microstructure control and optimization of zeolite films and membranes is an indispensable challenge for various innovative applications. It can be steered by understanding the formation process. Here we design an unprecedented strategy to uncover direct evidence via the hydrothermal synthesis of chitosan-supported zeolite monolayers. The chitosan-supported layer involved in the hydrothermal reaction is observed using SEM, AFM, EPMA, and HRTEM while nucleation and crystal growth in the bulk synthesis solution are pursued with HRTEM, DLS, and SEM. The direct HRTEM observation is achieved on the chitosan-supported layer by peeling chitosan from its support. It reveals that a gel layer is initially formed on the chitosan layer where the subsequent crystal growth is fatally restrained. Our own experimental evidence and the literature reports clearly demonstrate that the formation mechanism is homogeneous for severely reduced crystal growth on the substrate but is heterogeneous when crystal growth on the substrate is significantly enhanced.
沸石膜的微观结构控制和优化是各种创新应用不可或缺的挑战。通过了解其形成过程，可以对其进行控制。在这里，我们设计了一种前所未有的策略，通过水热合成壳聚糖负载沸石单层来揭示直接证据。通过 SEM、AFM、EPMA 和 HRTEM 观察参与水热反应的壳聚糖负载层，通过 HRTEM、DLS 和 SEM 研究体相合成溶液中的成核和晶体生长。通过从其载体上剥离壳聚糖，在壳聚糖载体上进行直接 HRTEM 观察，结果表明，在壳聚糖层上最初形成了一层凝胶层，随后的晶体生长受到严重限制。我们自己的实验证据和文献报道清楚地表明，当基底上的晶体生长显著增强时，其形成机制是不均匀的，但当基底上的晶体生长受到严重抑制时，其形成机制是均匀的。
