Samarium doped cerium oxide nanoparticles under extreme temperatures and its photocatalysis activity on tetracycline

Abstract

In this work, we report the characterization and application of cerium oxide (CeO2) doped with samarium (Sm). The physical and chemical properties of these Sm-CeO2 are discussed in comparison with their pure cerium oxide counterparts. Raman spectroscopy measurements under extreme temperature conditions showed that the vibrational optical modes at 267 cm−1, 458 cm−1, 555 cm−1 and 603 cm−1, except for the mode 555 cm−1, exhibited a red shift with increasing temperature with different temperature coefficients θ = ∂ω/∂T. The first-order temperature coefficient θ of the mode 458 cm−1 is ∼ (−0.01154 ± 4.4 × 10−4 cm−1/K). In contrast, the second-order mode coefficient at ∼267 cm−1 which equal ∼ (−0.04949 ± 2 × 10−3 cm−1/K) is higher, as well as that of modes 555 cm−1 and 603 cm−1 which are equivalent to ∼ (−0.01339 ± 2.6 × 10−3 cm−1/K) and (−0.00575 ± 1.89 × 10−3 cm−1/K). If based on the evolution of the analyzed Raman spectra that no structural phase transition of the crystal was observed for high and low temperatures, only a conformational change at temperatures of 553 and 733 K, which may be associated with the formation of oxygen vacancies in the lattice of Sm-CeO2. We also show the efficiency of the Sm-CeO2 sample for applications in Photocatalysis demonstrated through the removal of the Tetracycline (TC) drug in comparison with the pure CeO2 sample. The photocatalytic experiments showed a significant increase in TC removal efficiency in a remarkable synergistic effect between adsorption and photocatalysis, leading to approximately 83 % TC removal for Sm-CeO2.