ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis and characterization of well-dispersed amorphous LnBO₃·3H₂O (Ln: Dy, Tb) nanoparticles

Seda Beyaz, Berna Bulbul, Remziye Tulek, and Ali Teke

Department of Chemistry, Faculty of Science and Literature, Balikesir University, Balıkesir, Turkey

E-mail: sedacan@balikesir.edu.tr

Received: 11 November 2019  Accepted: 28 January 2020

Abstract:

Lanthanide nanoborates (LnBO₃·3H₂O (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 LnBO₃·3H₂O 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 DyBO₃·3H₂O and TbBO₃·3H₂O 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 DyBO₃·3H₂O and TbBO₃·3H₂O 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 ⁵D₄, ⁵D₄ and ⁵D₄ excited states to ⁷F_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 TbBO₃·3H₂O sample decreased by %25, and increased by %10 for DyBO₃·3H₂O over the temperature range of 10–300 K.

Keywords: Lanthanide orthoborate; Nanoparticles; Co-precipitation method; Well dispersed

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01081-w

Chemical Papers 74 (8) 2449–2459 (2020)