Hydrothermal synthesis of Cs0.3WO3 with uniform morphology and size via a dynamic balance of pH

Abstract

Nanoscale tungsten bronze, MxWO3 (M: alkali elements or NH4+, 0 < x < 1), is a kind of functional material with a property of near-infrared absorption that is closely related to its morphology and size. A change of pH corresponds to a shift in composition and structure of tungstate polyanion, along with the resultant mutations in the morphology and size related with the properties of nano-MxWO3. Consequently, a reversible imine reaction was conducted to create a dynamic balance of pH system, in where uniform CsxWO3 was expected to synthesize in this study. The results show that an initial nucleation stage, morphology directing of CH3CH2COO−, and Oswald ripening work synergistically to evolve both morphology and size of Cs0.3WO3. Under a moderate pH level, chemical reaction inhibits growth of Cs0.3WO3 nuclei and gains uniform particles. Under a higher pH, Oswald ripening following the nucleating period ultimately dominates uniform Cs0.3WO3.