Screw dislocation-driven t-Ba2V2O7 helical meso/nanosquares: microwave irradiation assisted-SDBS fabrication and their unique magnetic properties

Triclinic (t-) Ba2V2O7 helical-like meso/nanosquares assembled from self-spiraling nanosheets have been controllably synthesized by a high-efficiency microwave irradiation-assisted surfactant process. The microstructure and morphology of the as-prepared t-Ba2V2O7 products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results show that the spirals of stacked nanosheets grow along the z-axis of microsquares, leading to the formation of a helical shape. Based on parallel experiments and theoretical analysis of t-Ba2V2O7 helical mesosquares at different reaction stages, the formation mechanism has been proposed to be a ''self-assembly-dissolution-recrystallization-Ostwald-ripening'' mechanism. The helical structures with uniform morphology and size may find promising applications in a variety of fields. The SDBS-assisted microwave irradiation method offers an easy path to the controllable fabrication of helical Ba2V2O7 meso/nanomaterials, which can be readily extended to the development of functional structures of other alkaline earth vanadates. Moreover, it is found that the helical-like materials exhibit unique magnetic properties, corresponding to shape evolutions with different particle sizes at continuous reaction time.