Facile hydrothermal synthesis of the colloidal hierarchical Volborthite (Cu₃V₂O₇(OH)₂·2H₂O) hollow sphere phosphors

Colloidal hierarchical self-assembled Cu₃V₂O₇(OH)₂·2H₂O hollow spheres were synthesized using a facile hydrothermal synthesis route without using PS hollow sphere template. Powder x-ray diffraction (XRD) of the obtained Cu₃V₂O₇(OH)₂·2H₂O sample demonstrated that the sample well-indexed to the monoclinic phase with high purity and well crystallinity. Fourier Transform infrared (FT-IR) of the sample proved hydrophilicity of the as-synthesized sample. Moreover, scanning electron microscopy (SEM) analysis indicated that the product consist of a large amount of the colloidal hierarchical Cu₃V₂O₇(OH)₂·2H₂O hollow spheres with a mean diameter of about 2–4 µm, in which an individual self-assembled spherical structure was composed of a large number of the 50–90 nm nanoparticles. The optical properties of the sample was studied by ultraviolet–visible spectroscopy (UV–Vis) and emission/excitation spectra analyses (PL). The results showed that the sample has photo absorption ability in the visible region and an energy band-gap of 2.44 eV was estimated from UV–Vis absorption spectrum. Also, the as-prepared nanostructures has a very red-shifted PL emissions with high intensity under the excitation wavelength of 237 nm in their photoluminescence spectra.