Shape control of highly crystallized titania nanorods based on formation mechanism
- PDF / 371,112 Bytes
- 8 Pages / 584.957 x 782.986 pts Page_size
- 83 Downloads / 138 Views
Katsuya Yoshida and Takehiro Kurata Department of Chemical Engineering and Materials Science, Doshisha University, Kyotanabe 610-0321, Japan
Jun Adachi National Institute of Biomedical Innovation, Ibaraki 567-0085, Japan
Katsumi Tsuchiya and Yasushige Mori Department of Chemical Engineering and Materials Science, Doshisha University, Kyotanabe 610-0321, Japan
Fumio Uchida Fuji Chemical Co., Ltd., Hirakata 573-0003, Japan (Received 8 April 2011; accepted 11 October 2011)
A strategic scheme for controlling the shape of titania nanorods while maintaining their highly crystallized state was investigated in terms of the effects of reactant concentration and temperature change on the formation mechanism. Lowering the temperature from 433 to 413 K markedly slowed down the reaction rate and resulted in the coexistence of amorphous-like films and crystalline titania nanorods due to the concurrence of nucleation out of the amorphous phase and particle growth by crystallization. Based on these findings, a strategy for shape control was proposed and long, high aspect ratio titania nanorods in a highly crystallized state were successfully synthesized.
I. INTRODUCTION
The shape, size, and crystallinity of nanoparticles have significant influences on their electrical and optical properties and hence it is essential to be able to control particle size and shape, as well as their distributions and crystallinity,1–5 which requires a detailed understanding of the mechanisms of nucleation and growth, as well as such processes as aggregation and coarsening. Although the movement of electrons and holes in semiconductor materials is primarily dominated by the well-known quantum confinement, the transport properties related to phonons and photons are largely influenced by the size, geometry, and crystallinity of the materials.6–11 A variety of ideas for morphological control have been introduced12–31 based on: (i) a mixture to bind them selectively to the crystallographic faces for CdS,12 (ii) monomer concentration and ligand effects for CdSe,13 (iii) growth rate with controlled heating rate for CoFe2O4,14 (iv) biological routes in peptide sequence for FePt,15 (v) controlled removal of protecting organic stabilizer for CdTe,16–18 (vi) anodic alumina used as a template,19,20 (vii) anodic oxidation of titanium metal for producing a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.393 440
J. Mater. Res., Vol. 27, No. 2, Jan 28, 2012
http://journals.cambridge.org
Downloaded: 24 Feb 2015
nanotube arrays,21–24 (viii) the “oriented attachment” mechanism for nanoparticles,25,26 (ix) electrospun nanorods,27 (x) utilization of supercritical carbon dioxide,28 and (xi) synthesis of high-purity anatase TiO2 single crystals with a large percentage of reactive {001} facets.29,30 On the basis of the above strategies, a number of methods have been developed to control the shape of nanocrystals. Titanium dioxide has great potential for effective utilization of solar energy with photovoltaics32–38 and
Data Loading...
