Raluca Ivan

Hybrid nanocomposite layers consisting of core−shell magnesium oxynitride/ nanocarbon nanoparticles and nitrogen doped reduced graphene oxide platelets were synthesized through reactive, matrix assisted pulsed laser evaporation technique, by laser induced photochemical processes, through the irradiation of commercial Mg(NO3)2 and GO platelets precursors’ dispersions. The eco-friendly laser-based technique allows for the synthesis and deposition of the complex nanocomposite layers in a single processing step, at room temperature. The hybrid nanocomposites are able to decompose nucleic acid, RNA molecules extracted from yeast Saccharomyces cerevisiae cells through advanced oxidation processes both under UV and simulated solar radiation, by generation of reactive oxygen species (ROSs). The energy band structure of the hybrid nanocomposite indicates that H2O2 is the main ROS responsible for the decomposition of RNA, besides the photogenerated h+ and free e-. Photocatalytic tests performed in the presence of scavenger molecules confirm the limited role of superoxide O2•- and hydroxyl •OH radicals in the light induced decomposition process.

Nanocomposite films of rGO/MFeO₃ (M = Bi, La) nanofibers were grown by matrix-assisted pulsed laser evaporation of frozen target dispersions containing GO platelets and MFeO₃ nanofibers. Electron microscopy investigations confirmed the successful fabrication of MFeO₃ nanofibers by electrospinning Part of nanofibers were broken into shorter units, and spherical nanoparticles were formed during laser processing. Numerical simulations were performed in order to estimate the maximum temperature values reached by the nanofibers during laser irradiation. X-ray diffraction analyses revealed the formation of perovskite MFeO₃ phase, whereas secondary phases of BiFeO₃ could not be completely avoided, due to the high volatility of bismuth. XPS measurements disclosed the presence of metallic bismuth and Fe²⁺ for BiFeO₃, whereas La₂(CO₃)₃ and Fe²⁺ were observed in case of LaFeO₃ nanofibers. High photocatalytic efficiencies for the degradation of methyl orange were achieved for nanocomposite films, both under UV and visible light irradiation conditions. Degradation values of up to 70% after 400 min irradiation were obtained for rGO/LaFeO₃ nanocomposite thin layers, with weights below 10 µg, rGO platelets acting as reservoirs for photoelectrons generated at the surface of MFeO₃.