Low temperature hydrothermal synthesis, evaluation of band gap energies and catalytic performance for Biginelli reactions of Sr2-xAxNb2O7+δ (A=Eu3+ and Nd3+) (x = 0.01 and 0.05) nanomaterials

Document Type: Original Research Paper

Authors

1 Department of Inorganic Chemistry, Faculty of Chemistry, Semnan University, Semnan 35351-19111, Iran

2 Department of Inorganic Chemistry, Faculty of Chemistry, Semnan University, Semnan, Iran

Abstract

Nano powders Eu3+ and Nd3+ - doped Sr2Nb2O7 were prepared by a low temperature hydrothermal
method at 120 ºC for 48 h followed by annealing at 400 ᵒC for 3 h among Sr(NO3)2
and Nb2O5, Eu2O3 and Nd2O3 raw materials at stoichiometric 1:1 Sr:Nb molar ratio. Characterization
of the synthesized materials was performed by X-ray powder diffraction (XRPD)
technique. FullProf program employing profile matching with constant scale factors was employed
for structural analysis. The results showed that the patterns had a main Sr2Nb2O7 orthorhombic
crystal structure with space group . FESEM images showed that the synthesized
nanomaterials had flower morphologies. Ultraviolet-visible spectra analysis showed that the
synthesized Eu3+ and Nd3+ - doped Sr2Nb2O7 nanomaterials had light absorption in the ultraviolet
light region. The direct optical band gap energies obtained from UV-Vis absorption spectra
were 3.45, 3.50 and 3.80 eV for pure Sr2Nb2O7, S2 and S4, respectively. The catalytic activity of
the obtained materials in the one-pot synthesis of the heterocyclic compounds 3,4-dihydropyrimidin-
2(1H)-ones (DHPMs) in Biginelli reaction is investigated. The optimized 0.03 g of the
catalyst, 95 ºC reaction temperature, and 60 min reaction time are used for the other Biginelli
reactions in this work.

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