The aligned array and thin film of zeolites and molecular sieves possess a variety of potential applica- tions in membrane separation and catalysis, chemical sensors, and microelectronic devices. There are two main synthesis methods for manufacturing the aligned arrays and thin films of zeolites and mo- lecular sieves, i.e. in situ hydrothermal reaction and self-assembly of crystal grains on substrates. Both of them have attracted much attention in the scientific community worldwide. A series of significant progress has been made in recent years. By the in situ hydrothermal synthesis, the oriented nucleation and growth of zeolite and molecular sieve crystals can be achieved by modifying the surface properties of substrates or by changing the composition of synthesis solutions, leading to the formation of uni- formly oriented multicrystal-aligned arrays or thin films. On the other hand, the crystal grains of zeo- lites and molecular sieves can be assembled onto the substrate surface in required orientation using different bondages, for instance, the microstructure in the array or thin film can be controlled. This review is going to summarize and comment the significant results and progress reported recently in manufacturing highly covered and uniformly aligned arrays or thin films of zeolites and molecular sieves. It involves (1) in situ growth of highly aligned zeolite arrays and thin films via embedding func- tional groups on the substrate surface, modifying the surface microstructure of substrates, as well as varying the composition of synthesis solutions; (2) assembly of zeolite and molecular sieve crystals on various substrates to form aligned arrays and thin films with full coverage by covalent, ionic, and in- termolecular coupling interactions between crystals and substrates; (3) coupling surface assembly with microcontact printing or photoetching technique to produce patterned zeolite arrays and thin films. Finally, the functionality and applications of zeolite arrays and thin films are briefly introduced.
The b-oriented TS-1 films on α-Al2O3 substrates were synthesized by using in situ crystallization by the inducing effect of the chitosan thin film.The synthesized TS-1 films were characterized with XRD and SEM.The functional groups on the chitosan film surface and the interactions between the chitosan film and synthesis solution were described by using diffuse-reflectance FT-IR and contact angle measurements.It was shown that the b-oriented TS-1 film could be synthesized with the help of the chitosan thin film,whereas the randomly oriented TS-1 film was obtained on the α-Al2O3 substrate without chitosan induction.The XRD patterns of the synthesized films revealed that the crystals possessed TS-1 zeolite structure.The diffuse-reflectance FT-IR spectrum and contact angle measurements exhibited that the functional groups were abundant on the surface of the chitosan thin film,which could attract organic and inorganic compounds.Therefore,a transitional layer could be formed on the chitosan film,with nucleation and crystal growth to sheet-shaped TS-1 crystal grains,eventually leading to the formation of the multilayer b-oriented TS-1 film.
