Multifunctional hybrid films made from CoT₃OT_x4 and CoFeT₂OT₄ nanoparticles inside a poly 3-hydroxybutyrate matrix and study of their impact in methyl orange photodegradation

by Lan J. Bernal-Sánchez, América R. Vázquez-Olmos, Roberto Y. Sato-Berrú, Esther Mata-Zamora, Margarita Rivera, Vicente Garibay-Febles

This work aims to produce hybrid materials with potential applications in dye photodegradation. Therefore, hybrid films were obtained by incorporating cobalt (II, III) oxide (Co₃O₄) or cobalt ferrite (CoFe₂O₄) nanoparticles (NPs) with 18 ± 1.6 nm and 26 ± 1.3 nm, respectively, into a poly 3-hydroxybutyrate (P3HB) polymeric matrix. The Co₃O₄@P3HB and CoFe₂O₄@P3HB hybrid films were fabricated by solvent casting in a ratio of 85 mg to 15 mg (P3HB-NPs). Different spectroscopic and microscopy techniques characterized the Co₃O₄ and CoFe₂O₄ NPs and the P3HB, Co₃O₄@P3HB and CoFe₂O₄@P3HB films. The optical band gap for Co₃O₄ and CoFe₂O₄ NPs was estimated from their diffuse reflectance spectra (DRS) around 2.5 eV. X-ray diffraction (XRD) of the hybrid films revealed that the nanometric sizes of the Co₃O₄ and CoFe₂O₄ nanoparticles incorporated into the P3HB are preserved. The magnetic hysteresis curve of CoFe₂O₄ nanoparticles and CoFe₂O₄@P3HB film showed a ferromagnetic behaviour at 300 K. Transmission electron microscopy (TEM) confirmed the formation of nanocrystals, and scanning electron microscopy (SEM) provided evidence for the successful incorporation of the NPs into the P3HB matrix. The surface roughness and hydrophilicity of the hybrid films are increased compared to the P3HB film. The impact of the nanoparticles and the hybrid films on the photodegradation of methyl orange (MO) in its acidic form was studied. The photodegradation tests were carried out by direct sunlight exposure. The CoFe₂O₄@P3HB hybrid film achieved 85% photodegradation efficiency of a methyl orange solution of 20 ppm after 15 minutes of exposure to sunlight. After 30 minutes of exposure to sunlight, the nanoparticles and the hybrid films reached about 90% of the MO degradation. The results suggest that combining nanoparticles with the polymer significantly enhances photodegradation compared to isolated nanoparticles.