Properties of Zeolite Nanopowder Coated with Titanium Dioxide by Atomic Layer Deposition

Abstract

Nanosized zeolites were prepared in an autoclave using tetraethoxysilane (TEOS), tetrapropylammonium hydroxide (TPAOH), and H-2O, at various hydrothermal synthesis temperatures. Using transmission electron microscopy and particle size analysis, the nanopowder particulate sizes were revealed to be 10-300 nm. X-ray diffraction analysis confirmed that the synthesized nanopowder was silicalite-1 zeolite. Using atomic layer deposition, the fabricated zeolite nanopowder particles were coated with nanoscale TiO2 films. The TiO2 films were prepared at 300 degrees C by using Ti[N(CH3)(2)](4) and H2O as precursor and reactant gas, respectively. In the TEM analysis, the growth rate was similar to 0.7 angstrom/cycle. Zeta potential and sedimentation test results indicated that, owing to the electrostatic repulsion between TiO2-coated layers on the surface of the zeolite nanoparticles, the dispersibility of the coated nanoparticles was higher than that of the uncoated nanoparticles. In addition, the effect of the coated nanoparticles on the photodecomposition was studied for the irradiation time of 240 min; the concentration of methylene blue was found to decrease to 48%.