A possible formation mechanism and photocatalytic properties of CoFe2O4/PVA-SiO2 nanocomposites

The paper presents the synthesis of CoFe2O4 nanocrystallites embedded in PVA-SiO2 hybrid matrix by a modified sol-gel method. The paper is focused on two aspects: (1) formation of cobalt and iron carboxylate-type precursors (oxalate, lactate, malonate and succinate) in the presence of tetraethylorthosilicate, polyvinylalcohol (PVA) and different diols: 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and (2) possible decomposition mechanism of carboxylate-type precursors into CoFe2O4 within the pores of PVA-SiO2 hybrid matrix. The formation and decomposition of carboxylate-type precursors was studied by thermal analysis coupled with mass spectrometry, while the formation of CoFe2O4/PVA-SiO2 nanocomposites (NCs) was investigated by X-ray diffraction and Fourier transformed infrared spectroscopy. The particle size and shape were studied by transmission electron microscopy. At 1000 degrees C, well-crystallized CoFe2O4 was evidenced as single phase in G1,2ED and G1,4BD and together with Co2SiO4 in G1,2 PD and G1,3 PD. Based on UV-vis absorption spectra, the band gaps of the NCs were evaluated. The photocatalytic activities of the NCs were evaluated by degrading Rhodamine B under UV vis light irradiation. The reactive radical species produced at the solid-liquid interface were evidenced using electron spin resonance coupled with spin trapping.