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Open Access Nano Express

Ordered mesoporous silica prepared by quiescent interfacial growth method - effects of reaction chemistry

Hatem M Alsyouri1*, Malyuba A Abu-Daabes2, Ayah Alassali2 and Jerry YS Lin3

Author Affiliations

1 Department of Chemical Engineering, The University of Jordan, Amman 11942, Jordan

2 Department of Pharmaceutical and Chemical Engineering, German-Jordanian University, Amman 11180, Jordan

3 School of Engineering for Matter, Transport and Energy, Arizona State University, Tempe AZ 85287, USA

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Nanoscale Research Letters 2013, 8:484  doi:10.1186/1556-276X-8-484

Published: 16 November 2013

Abstract

Acidic interfacial growth can provide a number of industrially important mesoporous silica morphologies including fibers, spheres, and other rich shapes. Studying the reaction chemistry under quiescent (no mixing) conditions is important for understanding and for the production of the desired shapes. The focus of this work is to understand the effect of a number of previously untested conditions: acid type (HCl, HNO3, and H2SO4), acid content, silica precursor type (TBOS and TEOS), and surfactant type (CTAB, Tween 20, and Tween 80) on the shape and structure of products formed under quiescent two-phase interfacial configuration. Results show that the quiescent growth is typically slow due to the absence of mixing. The whole process of product formation and pore structuring becomes limited by the slow interfacial diffusion of silica source. TBOS-CTAB-HCl was the typical combination to produce fibers with high order in the interfacial region. The use of other acids (HNO3 and H2SO4), a less hydrophobic silica source (TEOS), and/or a neutral surfactant (Tweens) facilitate diffusion and homogenous supply of silica source into the bulk phase and give spheres and gyroids with low mesoporous order. The results suggest two distinct regions for silica growth (interfacial region and bulk region) in which the rate of solvent evaporation and local concentration affect the speed and dimension of growth. A combined mechanism for the interfacial bulk growth of mesoporous silica under quiescent conditions is proposed.

Keywords:
Self assembly; Quiescent growth; Interfacial synthesis; Ordered mesoporous silica; Synthesis-structure relationship