Morphological Evolution of (NH4)0.5V2O5•mH2O Fibers into Belts, Triangles, and Rings

In this contribution, single-crystalline (NH4)(0.5)V2O5 center dot mH(2)O xerogels made of belts, rings, triangles, and ovals have been synthesized using a surfactant-free hydrothermal method. The analytical techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED) have been used to characterize the morphology, composition, and structure of the as-prepared products. On the basis of SEM and TEM observations, we suggested that the as-prepared (NH4)(0.5)V2O5 center dot mH(2)O rings, triangles, and ovals have been formed by connecting two ends of the vanadium oxide sheet made of edge and corner sharing VO5 square pyramids. The as-prepared (NH4)(0.5)V2O5 center dot mH(2)O nanobelts are up to several hundreds of micrometers long, 402-551 nm wide, and 235-305 nm thick. The thickness and width of the rings are respectively similar to 454 nm and similar to 1 mu m. Triangles with three unequal sides having a thickness of similar to 143 nm and a width of similar to 1 mu m were also formed. The crystalline orthorhombic phase of shcherbianite V2O5 was obtained on calcination of (NH4)(0.5)V2O5 center dot mH(2)O at 350 degrees C for 2 h. The SEM image of this V2O5 product retains the parent morphology of the preheated compound. A possible reaction mechanism and the growth process involved in the formation of belts/rings/triangles and ovallike microstructures are discussed.