The production of hierarchically ordered materials under non-equilibrium conditions is a widely unexplored area with profound potential for enormous applications. We report an experiment that establishes control over the growth velocities of macroscopic tubes in the reaction between polymerizable inorganic anion and non-alkali metal ion. Our approach is based on the injection of acidic metal salt solution into a large volume of basic sodium silicate solution. The forming tube is pinned to a gas bubble that is held at the end of a hollow glass rod. The tube's linear growth follows the speed of the glass rod while its radius is self-selected according to volume conservation of the injected solution. Magnetite-silica tubes are produced by injecting an iron (II,III) solution ([Fe(III)]/[Fe(II)]=2:1) into a large reservoir containing sodium silicate and ammonium hydroxide solutions. The iron oxide phase is characterized using powder X-ray diffraction, Raman and M�ssbauer spectroscopic techniques. The tubes exhibit superparamagnetic behavior at room temperature and the magnetic properties depend on the dynamics of the tube growth. Photoluminescent tubes are prepared by trapping quantum dots into the wall of silica-zinc hydroxide tubes during formation. They can provide a platform for sensing copper ions via photoluminescence quenching. The kinetics of fluorescence quenching is also studied.

Silica tubes with tunable magnetic and optical properties synthesized under actively controlled growth dynamics

244th National Meeting (2012)

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