Synthesis of Porous Silica Nanotubes using Rosette Nanotubes as Templates
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Synthesis of Porous Silica Nanotubes using Rosette Nanotubes as Templates Christophe Danumah, Usha D. Hemraz, and Hicham Fenniri National Institute for Nanotechnology, Chemistry Department, University of Alberta, 11421 Saskatchewan Drive, Edmonton AB, T6G 2M9, Canada ABSTRACT Rosette nanotubes (RNTs) were used as structure-directing agents for the synthesis of microporous and/or mesoporous silica nanotubes. The silica nanomaterials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and CO2 and nitrogen physisorptions. The results show that the mode of the obtained porous systems as well as the surface areas and volume of micro- and/or mesopores depend on the nature of the pendant attached to the rosette nanotubes surface. INTRODUCTION Supramolecular assemblies of surfactant molecules and block copolymers have previously been used as templates for the synthesis of a variety of ordered mesoporous materials with a wide range of pore sizes [1-3]. Mesoporous materials have attracted considerable interest for applications in catalysis, sorption, separation, fine chemicals synthesis [4], and host–guest chemistry [5], because of the ability to tune their framework composition and structure, surface chemistry, morphology, and pore sizes. Here we present preliminary studies demonstrating the versatility of a new structure directing system based on the rosette nanotube scaffold [6, 7]. The RNTs used in this study were obtained through a hierarchical self-assembly process of a twin G∧C base (Figure 1A). Of particular note and relevance to this study is the functional group tolerance of the RNTs. In principle, any functional group attached to the twin G∧C base (Figure 1A) will end up being expressed on the surface of the RNTs (Figure 1C).
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Figure 1. Hierarchical self-assembly process of a twin G∧C base (A) into twin rosette assemblies (B) maintained by 36 hydrogen bonds, followed by their stacking to form a nanotubular architecture (C) with a predefined diameter. Herein we report how the nature of RNTs’ pendants leads to silica materials with microand/or mesoporous system. The characterization techniques show the templating effect of RNTs in the synthesis of silica nanotubes and also demonstrate that the specific surface area, pore volume, and pores size distribution of the final silica nanotubes are greatly affected by the nature of the pendant attached to the RNTs’ surface.
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Synthesis of Silica nanotubes. Silica nanotubes were synthesized using a sonicated mixture of RNTs (1.6 mL, 0.25 mg/mL of 1 or 2 from a 1 mg/mL stock solution in water) and absolute ethanol (2.4 mL, Commercial Alcohols Inc.) as template. To this mixture, tetraethyl orthosilicate (TEOS, 0.01 mL, 98%, Aldrich) was added followed by 1 to 2 minutes ultrasonic agitation. The mixture was allowed to s
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