Synthesis and characterization of well-dispersed amorphous LnBO 3 ·3H 2 O (Ln: Dy, Tb) nanoparticles

Lanthanide nanoborates (LnBO 3 ·3H 2 O (Ln: Dy, Tb)) were prepared in the presence of polyethylene glycol (PEG) using a buffered-precipitation method. The same procedure was performed without adding PEG to expose the chemical formulations of the samples. X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Fourier transform infrared spectrum (FTIR) strongly supported amorphous lanthanide orthoborates having LnBO 3 ·3H 2 O structure. From TEM images, the mean particle size and standard deviation for Dy and Tb were calculated as 15.2 ± 6.3 nm and 15.4 ± 6.1 nm, respectively. The percentages of PEG molecules in the samples were determined as 7.5% for Dy and 4.31% for Tb by TGA. The average hydrodynamic sizes and surface charges of DyBO 3 ·3H 2 O and TbBO 3 ·3H 2 O nanoparticles in the distilled water were measured as 150.7 nm (PDI 0.152) + 40.9 ± 8.8 mV and 151.3 nm (PDI 0.105) + 41.9 ± 6.8 mV, respectively. The energy band gaps of both lanthanide nanoborates were determined as 5.3 eV by applying the Kubelka–Munk function to the measured UV–Vis diffuse reflectance spectra. The amorphous DyBO 3 ·3H 2 O and TbBO 3 ·3H 2 O nanoparticles exhibited strong paramagnetic behavior with μ eff / μ B values of 8.57 for Dy and 8.73 for Tb, respectively, at room temperature. The characteristic photoluminescence emission corresponding to the transition from 5 D 4 , 5 D 4 and 5 D 4 excited states to 7 F j ( j = 6, 5, 4, 3, 2, 1, 0) of the Tb +3 ions was observed in the wavelength range of 370–700 nm. Similarly, the emission spectrum of Dy +3 ions composed of peaks of different strength extends in the wavelength range of 370–850 nm. Although the emission peaks were found to be nearly temperature independent for both samples, the normalized integrated intensity of full spectrum corresponding to TbBO 3 ·3H 2 O sample decreased by %25, and increased by %10 for DyBO 3 ·3H 2 O over the temperature range of 10–300 K.