Structural and diffuse reflectance characterization of cobalt-doped titanium dioxide nanostructured powder prepared via facile sonochemical hydrolysis technique

This present study was carried out to synthesize cobalt-doped and undoped titanium dioxide nanosized particles using sonochemical hydrolysis technique. The microstructure and morphological characteristics of the synthesized samples have been studied using X-ray diffractometer and high-resolution transmission electron microscope, respectively. The obtained results of characterization have confirmed the amorphous nature of the undoped sample. However, cobalt-doped titanium dioxide samples are in anatase phase. The obtained phase structure proposed the effect of acidity level during the hydrolysis process at relatively low temperature. Anatase phase is the predominant phase for the doped samples with small traces of brookite phase depending on the concentration of cobalt nitrate as the precursor salt in the hydrolysis process. The estimated crystallite sizes of the doped samples are ranging from 6.1 nm to 6.8 nm. The diffuse reflectance measurement revealed high near-infrared solar reflectance (R*), 85.3%, for amorphous nanosized titanium dioxide which is a white (non-coloured) sample. Moreover, cobalt-doped titanium dioxide, coloured samples, showed reasonable high values of R* with respect to their coloured feature and were found to be 53% and 51% for the synthesized samples at molecular weight percentage ratios between cobalt and titanium precursors; 5% and 10%, respectively.