Authors: R. Bacsa, M. Verelst, J. Dexpert, W. Bacsa, P. Serp
Affilation: CEMES CNRS Univ Toulouse, France
Pages: 666 - 668
Keywords: ZnO, nanorods, tetrapods, UV absorption, aerosol
ZnO is a direct band gap semiconductor that finds applications in varistors and arrestors. Efficient luminescence in the UV of high purity nanocrystalline ZnO nanoparticles (20-50nm) is used in medicine and in the cosmetic industry as an effective UV screen. Gas phase chemistry has the advantage of producing high purity crystalline particles in a single step reaction and is often preferred due to its low cost. We present results on the synthesis and characterization of ZnO nanorods, tetrapods and nanospheres prepared by the gas phase oxidation of zinc vapor followed by the collection of the oxide particles in an aerosol. Spherical nanoparticles or fine nanorods of ZnO consisting principally of tetra pod like structures are obtained selectively depending on the process parameters. Intermediate structures can also be synthesized. Transmission electron microscopy of the particles and rods shows that these are single crystals with diameters in the 5-50nm range. We find that the tetrapods have high absorption in the UV and nearly 100% reflectivity in the visible. UV absorption coefficients for suspensions of tetrapods are found to be higher than for commercial nanocrystalline powders by one order of magnitude.