2 research outputs found
Titania Condensation by a Bio-Inspired Synthetic Block Copolymer
Silicatein
α, an enzyme found at the center of silica spicules in marine
sponges, is known to play a role in silica condensation from seawater.
It has also been shown to catalyze the formation of silica from various
silica precursors such as tetraethyl orthosilicate (TEOS). Inspired
by the finding that the serine-26 and histidine-165 amino acids in
the enzyme are required for silica formation from TEOS, we synthesized
polyÂ(hydroxylated isoprene-<i>b</i>-2-vinylpyridine) block
copolymers to mimic these amino acid residues. Here, we present the
results of our investigation utilizing this biomimetic polymer to
condense titania from titanium <i>iso</i>-propoxide (TiP).
Our silicatein α mimic is shown to condense titania at neutral
pH and room temperature and is compared to material produced by standard
sol–gel methods. Heats of crystallization are observed to be
72% lower for the titania made from the mimic polymer, and indistinct
X-ray diffraction peaks, even after heating well above the crystallization
temperature, suggest a higher degree of titania condensation with
the silicatein α mimic. Results from thermogravimetric analysis
show that the mimic formed titania initially contains ∼15 wt
% polymer and that the surface area increases from less than 5 to
greater than 110 m<sup>2</sup>/g when heated to 400 °C. Titania
made from the silicatein α mimic also shows a higher catalytic
activity than does commercial Degussa P25 TiO<sub>2</sub> for the
photodegradation of N-nitrosodimethylamine (NDMA), degrading 73% of
the NDMA in two hours as compared to 62% with Degussa P25. The biomimetic
system presented here offers the promise of an environmentally friendlier
method of titania production and will enable applications requiring
neutral pH and low temperatures, such as titania composite synthesis,
surface coating, or catalyst design
Nonthermal Synthesis of Three-Dimensional Metal Oxide Structures under Continuous-Flow Conditions and Their Catalytic Applications
Continuous-flow synthesis of one-dimensional (1D) metal oxide nanostructures and/or their integration into hierarchical structures under nonthermal conditions is still a challenge. In this work, a nonthermal, continuous-flow approach for the preparation of γ-manganese oxide (γ-MnO<sub>2</sub>) and cerium oxide (CeO<sub>2</sub>) microspheres has been developed. By this technique, γ-MnO<sub>2</sub> materials with surface areas of 240, 98, and 87 m<sup>2</sup>/g and CeO<sub>2</sub> microspheres with a surface area of 1 m<sup>2</sup>/g have been fabricated successfully. Characterization of the materials was carried out using powder X-ray diffraction, infrared and inductively coupled plasma optical emission spectrometer (ICP/OES), nitrogen sorption, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The synthesized materials showed good catalytic activity in the oxidation of α-methyl styrene