Influence of Dopant Types on the Morphological Transformation of Green-Synthesised Tungsten Trioxide Nanoparticles

Abstract

WO3 nanoparticles were synthesized by green method involving the interaction between ammonium paratungstate precursor and aqueous leaves extract of Spondias mombim. The effect of calcination temperature and dopant types on the phase types of WO3 were examined. Subsequently, doping of WO3 with Boron, Aluminium, Phosphorus and Iodine were achieved via a wet impregnation method to evaluate their influence on the size and shape of WO3. The characterization was done using HRSEM, BET and XRD The HRSEM micrograph demonstrated morphological transformation from spherical to thin and thick rods, bamboo- bundles and platelet-like structure depending on the dopant type and calcination temperature. The XRD pattern of undoped WO3 nanoparticles showed the formation of purely monoclinic phase at calcination temperature 550°C while mixed phase were noticed in the samples prepared at other temperatures. The BET analysis showed that as-prepared WO3 nanoparticles doped with B, Al, I and P possessed higher surface area in the order of B-WO3 (399.50 m2/g) > 1-W03 (392.50 m2/g) > AI-WO3 (388.46 m2/g) > P-W03 (356.76 m2/g) > undoped WO3 (352.49 m2/g). The study demonstrated that temperature influenced the morphological characteristics of WO3 while the four elements played a dual of a dopant as well as structure-directing agent.