Effect of organic fuels on surface area and photocatalytic activity of scheelite CaWO₄ nanoparticles

Discrete nanoscale calcium tungstate (CaWO₄) nanoparticles with exquisite photocatalytic activities were synthesized through ultra-rapid solution combustion route. Here, we aim to study the effect of different fuels on the synthesis of CaWO₄ nanoparticles which lead to improve the characteristic properties and morphological evolution of the powders. From BET surface area measurement, it is observed that CaWO₄ nanoparticles synthesized by using citric acid as fuel exhibits relatively large surface area (31.78 m² g⁻¹) as compared to other fuels. The powder x-ray diffraction (PXRD) studies reveal that CaWO₄ nanoparticles belong to scheelite type tetragonal system. The morphology of CaWO₄ nanoparticles investigated using scanning electron microscopy (SEM) reveals that the powders are highly porous and agglomerated. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of the CaWO₄ nanoparticles show that a well-dispersed nearly oval-shaped nanoparticles with variable dimensions and lattice spacing that depends on the type of fuels used in the synthesis. The selected area electron diffraction (SAED) patterns of CaWO₄ nanoparticles exhibit several concentric rings with bright spots indicating the polycrystalline nature of the powders. Investigation on photocatalytic activity of CaWO₄ nanoparticles synthesized using citric acid shows highest (∼93%) degradation of methylene blue (MB). (paper)