Preparation and characterization of ultrafine TiO 2 particles in reverse micelles by hydrolysis of titanium di-ethylhexy
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Preparation and characterization of ultrafine TiO2 particles in reverse micelles by hydrolysis of titanium di-ethylhexyl sulfosuccinate Manjari Lal and Vishal Chhabra Department of Chemistry, University of Delhi, Delhi 110 007, India
Pushan Ayyub Materials Research Group, Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400 005, India
Amarnath Maitra Department of Chemistry, University of Delhi, Delhi 110 007, India (Received 13 January 1997; accepted 9 June 1997)
We describe the synthesis and characterization of ultrafine TiO2 particles (in both anatase as well as rutile form) produced by a chemical reaction within the aqueous core of a water-in-oil microemulsion. The microemulsion was stabilized and the Ti41 ions provided by a functionalized surfactant derived from the commercially available Aerosol-OT, i.e., sodium bis (2-ethylhexyl) sulfosuccinate (Na-DEHSS). The Na1 ions in Aerosol-OT were completely replaced by Ti41 through an ion-exchange reaction in nonaqueous solvents. Ultrafine TiO2 particles were produced by the hydrolysis of the Ti-containing surfactant in the water droplets. The dependence of the size of the precipitated TiO2 ? xH2 O particles on various structure parameters of the microemulsion was studied in detail. I. INTRODUCTION
Interest in atomic clusters, ultrafine particles, and nanophase materials has grown rapidly in the last decade.1–4 Nanometer-sized particles find technological applications in many different areas such as catalysis, magnetic recording, high performance ceramics, and microelectronic components. Nanophase materials may be composed of metals, ceramics, or composites. They have unique and often significantly improved mechanical, electronic, magnetic, and optical properties as compared to conventional polycrystalline material. Because of the substantial increase in the volume occupied by the grain boundaries and in the number of atoms residing at the interfaces, the use of nanoparticles often leads to a marked improvement in sintering rates as well as a reduction in sintering and solid state reaction temperatures. Of course, clusters and nanocrystalline materials are also very interesting from the point of view of basic research. Whether one is interested in the fundamental or the applied aspects of small solid systems, it is essential to produce samples with a narrow, reproducible, and controllable particle size distribution. Depending on the material of interest and the size range involved, a variety of synthesis techniques have been used. These include coprecipitation, sol-gel, complexation, spray-drying, spraypyrolysis, freeze-drying, evaporation-condensation, laser ablation, etc. Water-in-oil microemulsions (or reverse micelles) have been successfully utilized for the synthesis of J. Mater. Res., Vol. 13, No. 5, May 1998
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nanoparticles by a number of workers.5,6 A microemulsion7,8 is a thermodynamically stable, transparent nanodispersion of two immiscibl
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