Synthesis of nanocomposites based on Fe₃O₄ nanoparticles and nitrogen-doped reduced graphene oxide aerogel by ex-situ approach and their magnetic properties

In this study, were synthesised hybrid nanocomposites (Fe3O4@NrGO) using magnetite nanoparticles (Fe3O4-NPs) and nitrogen-doped reduced graphene oxide (NrGO) aerogel through ex-situ approach, which is simple and easily scalable. The NrGO exhibited 7.96 at% N, demonstrated efficient doping and a high content of active nitrogen sites within the composite matrix. Structural, morphological, and elemental analyses of the obtained nanocomposites confirmed the successful incorporation of Fe3O4-NPs into both doped and undoped aerogel matrices (rGO). The presence of nitrogen sites greatly influenced the interaction and incorporation of nanostructures, as evident from the well-distributed and denser nanoparticle arrangement in Fe3O4@NrGO. The impact of matrix doping was also highlighted through porosity analyses, revealing increases in both; pore volume and surface area. Porosity analysis emphasised the efficacy of the ex-situ strategy and the use of aerogel as the matrix, enabling the achievement of a surface area of 1456 m(2) g(-1) for Fe3O4@NrGO, owing to the particular swelling mechanism of the "spongy" structure. Vibrating-sample magnetometry and electron paramagnetic resonance spectroscopy techniques were employed to investigate the influence of nitrogenous sites on magnetic properties. The higher nanoparticle density in Fe3O4@NrGO resulted in a saturation magnetisation of 0.7219 emu g(-1), more than double that of Fe3O4 @rGO. Resonant peaks at low magnetic fields, characterised by a g-factor of 4.4219, were attributed to paramagnetic nitrogen centres that facilitated the efficient anchoring of Fe3O4-NPs in NrGO