Controlled synthesis of europium-doped lutetium compounds: nanoflakes, nanoquadrels, and nanorods

Abstract

In this contribution, we report the successful preparation of large-scale and uniform europium-doped lutetium compounds with the varied morphologies of nanoflakes, nanoquadrels and nanorods, using colloidal Lu(OH)₃–Eu at different concentrations as a precursor for the hydrothermal method (170 °C and pH = 13 for 24 h). The as-made products have different crystalline structures as well as different morphologies. The as-synthesized nanoflakes have a “perfect” square shape with side lengths of 220–400 nm and thicknesses of 50 nm or below. On the basis of the observed “non-perfect” nanoflakes, we have deduced a mechanism of “side wrapping” to describe the growth of the “perfect” square nanoflakes. The as-made nanoquadrels possess a sandwich-like nanostructure and they are all composed of several square nanoflakes via face-to-face “self-reorganization”. The formation of nanorods is due to the high chemical potential resulting from the high precursor concentration. At the same time, the pH value of the precursor and the method of mixing of the lanthanide nitrate solution with the NaOH solution have a great effect on the morphology of the as-synthesized products. The shapes of the as-made products were sustained after thermal decomposition to europium-doped Lu₂O₃. The crystalline structure, morphology and thermal behavior of as-synthesized products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TG) and differential scanning calorimetric analysis (DSC), respectively.