Synthesis of silica–ammonium chloride macrofibers generated by anionic surfactant templated nanotubes

Abstract

Silica-ammonium chloride nanotubes, generated by the condensation of sodium silicate onto ammonium cation-modified anionic sodium dodecyl sulfate (SDS) micellular templates, readily create hierarchical structures through the self-assembly into thicker nanotubes, belts, and ultimately into centimetre long macrofibers. The resulting fibers possess a remarkable range of tubular dimensions (i.e., nanometre to micrometre diameters, and micrometre to centimetre lengths) within a single assembly. The silica-ammonium chloride nanotubes have a high organic content as a result of the surfactant template. The nanotubes lose structural integrity in aqueous solution, but demonstrate retention of structure in organic solvents or when dried. The dependence on each of the component reagents for the generation of these nanotube structures has been investigated. The silica-ammonium chloride nanotubes have been characterized by SEM, TEM, XRD, XPS, and TGA. The creation of three-dimensional mineral structures using anionic surfactants more closely mimics biomineralization processes than prior approaches with cationic or non-ionic organic templates.