Ultrathin SmVO4 nanosheets: ionic liquid-assisted hydrothermal synthesis, characterization, formation mechanism and optical property.

We report on the synthesis of ultrathin SmVO(4) nanosheets through a simple and facile ionic liquid-assisted hydrothermal approach and their application in luminescence properties. The as-prepared products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy/high-resolution TEM, energy dispersive X-ray microanalysis, Fourier transform infrared spectrometry and photoluminescence technique. The SmVO(4) nanosheets had a tetragonal (t-) structure with the thickness of 10-20 nm and the size in the range of 10-12 microm. We found that the amount of ionic liquid, pH value and synthesizing temperature played crucial roles in controlling the structure and morphology of as-prepared samples. Particularly, the amount of ionic liquid [BMIM]Br can effectively control the shape of t-SmVO(4) nanostructures by adsorption on the (001) plane of the crystals, resulting in their preferential growth along the [100] and [010] directions via hydrogen bond-co-pi-pi stack interaction. A dissolution-recrystallization process was reasonably proposed to understand the formation mechanism of t-SmVO(4) nanosheets based on the experimental results. In addition, the photoluminescence spectra reveals that the as-prepared t-SmVO(4) nanosheets exit red emission related to (4)G(5/2)-->(6)H(7/2) transition.