Hollow BN microspheres constructed by nanoplates: Synthesis, growth mechanism and cathodoluminescence property

Hollow microspheres constructed by single-crystalline hexagonal boron nitride (h-BN) nanoplates have been synthesized via a facile chemical vapour reaction route employing ammonia borane as a starting material. The as-synthesized products are extensively characterized by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), and electron energy loss spectroscopy (EELS). The hollow microspheres are in nest-like morphology with diameters of ∼3 μm and are composed of numerous single-crystalline h-BN nanoplates of 200-500 nm in diameter and 10-30 nm in thickness. The dependence of the morphology of the BN hollow microspheres on experimental parameters, such as reaction temperature, holding time and gas pressure, is systematically investigated. The reaction temperature and holding time are proved to be key parameters to tailor the morphology of the final products. Controlled experiments indicate that the growth process of the BN hollow microspheres involves the formation of smooth bowl-shaped hollow microspheres and their subsequent growth into the hierarchical ones. The BN hollow microspheres exhibit intense cathodoluminescence emissions in the region of 200 to 400 nm, indicating that they could be potentially used as compact ultraviolet (UV) laser emitters.