368 Bull. Korean Chem. Soc. 2006, Vol. 27, No. 3 Guo-Wei Zhou et al. Preparation and Spectroscopic Characterization of Ilmenite-Type C0T1O3 Nanoparticles Guo-Wei Zhou/ Don Keun Lee, Young Hwan Kim, Chang Woo Kim, and Young Soo Kang* ^'School of Chemical Engineering, Shandong Institute ofLight Industry, Jinan 250100, P. R. China Department of Chemistry, Pukyong National University, Busan 608-737, Korea. ^E-mail: yskang@pknu.ac.kr Received August 15, 2005 The cobalt titanate, CoTiOa nanoparticles have been prepared by calcinations of precursor obtained from a mixture of T1O2 and Co(OH)2 in aqueous cetyltrimethylammonium bromide (CTAB) solution. The nanoparticles were investigated with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric/differential thermal analysis (TGA/ DTA) to determine the crystallite size and the phase composition. The spectroscopic characterizations of these nanoparticles were also done with UV-Vis spectroscopy and FT-Raman spectroscopy. XRD patterns show that CoTiOa phase was formed at calcinations temperature above 600 °C. UV-Vis absorption spectra indicate that the CoTiOa nanoparticles have significant red shift to the visible region (400-700 nm) with =500 nm compared to pure T1O2 powder ( =320 nm). The new absorption peaks (absorption at 696,604, 520,478, 456, 383, 336, 267, 238, 208 cm-1), which were not appeared in FT-Raman spectra of P-25, also confirm the formation of Ti-O-Co bonds at above 600 °C and just not the mixtures of titanium dioxide with cobalt oxides. Key Words : Cobalt titanate CoTiOa, Nanoparticles, CTAB micelle solution Introduction The titanium dioxide (T1O2) powder (P-25), which is a standard material in the field of photocatalytic reactions, includes anatase and rutile phase. It has been widely investigated since it can be used in many important fields such as in the environmental photocatalytic degradation of organic compound in waste water,1-4 and utilization of solar energy?-11 The effect of doping other transition metals is to change the equilibrium concentration of electrons or holes. It has been known that the advantage of the doping of the metal ions in T1O2 is the temporary trapping of the photo- generated charge carriers by the dopant and the inhibition of their recombination during migration from inside of the material to the surfece or the enhanced association of the functionalized organic pollutants to the doping ion surface sites. The doping of transition metal ions may significantly influence the optical properties of T1O2 photocatalyst, and the light absorption band of M-T1O2 can be shifted into the visible regionJ 2-18 Ilmenite-type mixed oxides, such as FeTiOs (ilmenite) and the iso-structural compound CoTiOs can come from ABO& which is the corundum-type structure of A2O3 sesquioxides when half of the A cations of a corundum-type sesquioxide are substituted by a B cation. Obviously, A and B cations can be both trivalent, or A divalent and B tetravalent (as in ilmenite-type titanates), or, finally, A monovalent and B pentavalent, respectively There have been several papers on the applications of TiO2-supported Co oxide investigated previously owing to their potential industrial applications as catalysts and catalyst supports in recent years<19?20 but the synthesis and the characterization of ilmenite-type cobalt titanate in micelle solutions have not been reported so far. In the present work, we report the synthesis and charac- terization of cobalt titanate, CoTiOs nanoparticle produced by commercial titania powder (P-25) support with transition metal hydroxide in cetyltrimethylammonium bromide (CTAB) micelle template, followed by calcination. Here the CTAB has a role of microreactor for the suppression of particle size and shape control The morphology was studied with TEM and the structure and physical properties of nanoparticles were investigated by XRD, XPS, TGA/DTA, UV-Vis and FT Raman spectroscopic techniques. Experimental Section Materials. Titanium dioxide powder P-25 is predominant- ly anatase (70% anatase, 30% rutile), it was purchased from Degussa Co, (Germany) and was used without any further treatment. Cetyltrimethylammonium bromide (CTAB) and cobalt nitrate hexahydrate (Co(NO3)2-6H2O) were purchased from Aldrich Chemical Co, and were used as received. H se distilled de-ionized water was passed through a four- cartridge Bamsted Nanopure II purification train consisting of macropure treatment. Preparation of CEO3 nanoparticles. In a typical synthesis, 0.01 mol Co(NO3)2-6H2O was dissolved into 30 ml distilled de-ionized water After stirring for 30 minutes, an aqueous solutions of 0.02 mol NaOH in 10 mL distilled de-ionized water were added drop by drop with stirring, which reacts to produce precipitation of Co(OH)2. Then 0.01 mol of P-25 powder was added to the above solution. An aqueous micelle solution of CTAB (0.01 mol CTAB in 30 mL distilled de-ionized water) was added to the mixed solution under magnetic stirring at 75 °C and the suspension was refluxed for 12 hours at 75 °C. The supernatant was then