Synthesis of transparent aqueous solutions of colloidal layered tungstate nanocrystals at room temperature

Abstract

The synthesis of aqueous solutions of colloidal layered tungstate nanocrystals was examined by reacting H₂WO₄ and alkylamines at room temperature. The use of alkylamines with short alkyl groups resulted in transparent colloidal solutions, whereas alkylamines with long alkyl groups provided the formation of precipitates. This suggested that the hydrophilicity of the amines played an important role in the formation of tungstate colloidal aqueous solutions. Moreover, WO₃ thin films were fabricated by the sol-gel method using the tungstate colloidal solutions. The WO₃ thin films had a high orientation, which may derive from the layered structure of the tungstate colloids.