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

Fh Alkallas,Sa Mansour,Km Elshokrofy

doi:10.1177/1847980419847806

Abstract

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.

Highlights

Metal oxides in their nanosized form play a crucial role in optical, acoustic, luminescent, electronic and optoelectronic applications
For pure TiO2 sample (TC0), the obtained diffraction pattern did not include any characteristic diffraction lines. Such pattern has a pronounced stepped-hump that identifies the amorphous feature of such pure TiO2 sample. This result is in agreement with that obtained elsewhere[1,11] for amorphous TiO2 which is prepared by the hydrolysis of titanium (IV) isopropoxide (TTIP)
It is worth to mentioning that the acid concentration has a major impact on the formed crystal phase type of TiO2, anatase, brookite and rutile, during hydrolysis process due to its effect on the variation of the kinetics of the reaction as a result of the changing in OHÀ amount.[12]

Summary

Introduction

Metal oxides in their nanosized form play a crucial role in optical, acoustic, luminescent, electronic and optoelectronic applications. TiO2 may be formed in three crystalline phases: anatase, brookite and rutile.[4] anatase phase has a higher photocatalytic activity compared to rutile and brookite phases.[5] the rutile phase is considered the most thermodynamically stable phase with the highest reflectivity to near-infrared (NIR) radiation This leads to obtaining high-performance cool white pigments due to the effective light scattering property of such phase structure.[6] the applications based on the brookite phase is still ongoing, which need much work due to difficulties in obtaining the pure brookite structure. Diffuse reflectance measurements were done in the wavelength range from 200 nm to 2500 nm using a JASCO (Japan) spectrophotometer of type UV/Vis/NIR V570

Results and discussion

A BÞ ð1Þ

Conclusions