Zinc oxide nanostructures of controlled morphology prepared from single source precursors by wet chemical route

Controlled and reproducible synthesis of ZnO nanoparticles with uniform size and shape is highly desirable for tuning its physico-chemical properties. Metal β-diketonates have many advantages as precursors in sol gel process over the conventional metal salts. Exploiting the advantageous characteristics of Zn(tmhd)₂ (where tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate), we have synthesized ZnO nanoparticles by wet chemical (sol gel) method in acidic (pH 3) and basic (pH 9) media, and subsequently annealed at 250°C and 550°C. The resulting particles exhibited Wurtzite (hexagonal) crystal structure. The variation in pH and temperature has shown appreciable impact on the crystallite size and the morphology of the final product. The increase in particle size with increasing sintering temperature was reflected in the band gap energy, IR spectra and surface area measurements. Cylindrical, rod like nanoparticles were obtained at acidic pH 3 while spherical particles were achieved at basic pH 9 when sintered at 250°C. However, the particles obtained at sintering temperature of 250°C and 550°C were morphologically different. The lower pH 3 particles have elongated and flat shapes, while the higher pH 9 have hexagonal rod like particles when sintered at 550°C.