Assembling polyoxometalate microcrystals into thin films with preferential [110]-orientation

Abstract

Rhombic dodecahedral Keggin type (NH4)3PW12O40 microcrystals selected as a protype were fabricated on plane glass substrates by using a horizontal deposition method and characterized. It was found that experimental parameters such as concentration of microcrystals in a solvent and character (polarity, volatility) of the solvent affected significantly the quality of the resulting films. The adopted approach allowed the microcrystals to be assembled into single-crystal-like 2D and/or 3D structure with preferential [110] orientation under optimal conditions. Compared with those films produced by other methods reported in the literature, the resulting films fabricated under optimal conditions are superior in view of the easy-to-fabrication, thickness controllability, and remarkable preferential orientation, which are vital for device fabrication in nano-, micro- and macro-scale.