Synthesis, characterization, shape-preserved transformation, and optical properties of La(OH)3, La2O2CO3, and La2O3 nanorods

A simple method to directly synthesize stable and crystalline pure phase La(OH)3 nanorods, with a diameter of around 15 nm and lengths in the range of 120–200 nm, was developed using cationic surfactant (cetyltrimethylammonium bromide, CTAB). The obtained La(OH)3 nanorods can be successfully converted to La2O2CO3 and La2O3 nanorods via calcination under appropriate conditions. Analytical methods such as X-ray diffraction (XRD) spectra, Fourier transformed infrared (FTIR) spectrum, differential scanning calorimetry and thermogravimetric analysis (DSC–TGA), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM) were employed to characterize the morphology and microstructure of the final products. The results reveal that La(OH)3 nanorods were shape-preserved and transformed to La2O2CO3 nanorods at 400 °C for 2 h and to La2O3 nanorods at 800 °C for 2 h, respectively. TEM images indicate that the as-obtained La2O2CO3 and La2O3 entirely consist of uniform nanorods in high yield with diameters of about 15 nm and 23 nm, lengths of 200–300 nm and 300–500 nm, respectively. The formation mechanism of the La(OH)3, La2O2CO3 and La2O3 nanorods was investigated. Room-temperature photoluminescence (RTPL) properties were investigated under the excitation of 275 nm. The 5D3 → 7Fj (j = 2–6) emission peaks at the wavelength below 500 nm were found in the RTPL spectra.

Research highlights▶ In this paper, stable and crystalline pure phase La(OH)3 nanorods of hexagonal structure with a diameter of around 15 nm and lengths in the range of 120–200 nm were successfully synthesized by a facile process at room temperature. ▶ La(OH)3 nanorods were shape-preserved and transformed to La2O2CO3 nanorods by calcination at 400 °C for 2 h and to La2O3 nanorods at 800 °C for 2 h, respectively. ▶ This is a new synthetical process to obtain the La(OH)3, La2O2CO3, and La2O3 nanorods. ▶ A possible formation mechanism of these nanorods was proposed. ▶ This is a new synthetical process to obtain the La(OH)3, La2O2CO3, and La2O3 nanorods. ▶ It is considered that this simple method can be applied as a general method for the preparation of rare-earth hydroxides with 1D nanostructures.