Luminescence properties of hierarchical CaMoO4 microspheres derived by ionic liquid-assisted process

Hierarchical calcium molybdate (CaMoO4) nanostructured microspheres were synthesized via a facile room-temperature route assisted by an ionic liquid, 1-n-butyl-3-methylimidazolium chloride. The product was characterized by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that micro-scaled CaMoO4 powders were assembled by nanoparticles with diameters ranging from 10 to 20 nm. The optical absorbance, photoluminescence emission (PL), and luminescence excitation (PLE) were investigated. The PL spectra excited at 273 nm have a strong green emission band maximum at 511 nm, which is attributed to the charge-transfer transitions within the MoO42− complex, and the luminescence intensity indicated a good luminescence quality of the CaMoO4 materials. By varying the amount of this assisted agent, we found that the ionic liquid played a crucial role as a surfactant in the formation of CaMoO4 materials with uniform hierarchical structure, which may be beneficial to the luminescence performance. This study presented a promising preparation strategy towards other luminescent materials.