The Preparation of Partially Oriented Zeolite Thin Films via Pulsed Laser Ablation
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The Preparation of Partially Oriented Zeolite Thin Films via Pulsed Laser Ablation Zhongsheng Deng, Thomas J. Pisklak, and Kenneth J. Balkus, Jr.* The University of Texas at Dallas, Department of Chemistry and the UTD NanoTech Institute, Richardson, TX 75080-0688 ABSTRACT Thin films of zeolites including silicalite-1, mordenite and UTD-18 have been prepared on stainless steel foil via pulsed laser deposition (PLD). Laser ablation of assynthesized zeolite targets onto stainless steel foil followed by a post hydrothermal treatment results in partially oriented zeolite thin films. SEM, XRD were used to characterize the zeolite thin films. Preliminary results for multilayercoatings of different zeolites will also be presented. INTRODUCTION The development of new methodologies for the preparation of zeolite and molecular sieve thin films enhances the potential application of these materials in optical and electronic devices [1], membrane separations, membrane catalysis [2-7] and molecular sensing [8-12]. There are a variety of methods that have been reported including the “in-situ” [13-17], “seed” [18-24] and the “VPT” (Vapor Phase Transport) [25] methods. The zeolite thin films prepared by these methods include MFI [13, 18], LTA [19], FAU [14, 20-21], MOR [15, 20], MWW [16], GIS [17] and FER [25] type molecular sieves. Our approach to fabricating thin zeolite films involves pulsed laser deposition (PLD). This technique involves striking a zeolite target with an excimer laser beam, which results in a plume of particles that deposit on a temperature-controlled substrate. The PLD film is then subjected to a post-hydrothermal treatment to reorganize the zeolite coating. This method has been employed to prepare a variety of molecular sieve thin films and membranes that have been used in chemical sensors, separations, and catalysis [9-11]. We have also demonstrated oriented film growth for several materials including NaX [26,27], UTD-1 [28,29], MCM-41 [30], MAPO-39 [31] and MCM-22 [32]. The laser ablation method of preparing zeolite thin films has several advantages, including an almost universal applicability to any zeolite structure and composition as well as the ability to coat both planar and non-planar substrates of various construction. Additionally, the PLD film thickness can be controlled and the membranes generally have good adhesion properties. In some cases, preferred orientations of zeolite films have been obtained that have yet to be duplicated by other methods. Herein , we report for the first time the fabrication of several molecular sieve thin films & membranes including partially oriented silicalite-1, mordenite & UTD-18 using the PLD method. Additionally multilayer films of zeolite NaX and UTD-18 prepared by successive PLD coatings will be briefly described. In this case, we also report for the first time that PLD coatings of different zeolites can be layered on top of each other to form composite membranes. EXPERIMENTAL Synthesis of the target zeolite material The all silica silicalite-1 target mat
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