Iron oxide nanoparticles–cellulose: a comprehensive insight on nanoclusters formation

Due to unique nanoscale properties, as superparamagnetism, iron oxide nanoparticles (IONPs) hybridized with cellulosic matrixes are an attractive material for environmental purposes. Previous studies obtained IONPs–cellulose clusters by the coprecipitation route. Nevertheless, the forces which bind IONPs and cellulosic matrixes and allow the nanocluster formation have not been well described. This study investigated the nanoclustering formation of superparamagnetic (SPM) IONPs and cellulosic materials. IONPs nanoclusters and hybrids were coprecipitated with microcrystalline cellulose (MC) in mass proportions of 1:0.5, 1:2, and 1:8. Lignocellulosic residues (LR) were also used as an organic matrix in mass proportions of 1:2. Dynamic light scattering analyses revealed that the obtained IONPs-organic clusters present sizes between 1.46 ± 0.49 and 6.84 ± 3.15 µm. The MC and LR organic matrix size were decisive for the hybrids’ final cluster size. Scanning electron microscopy images of the materials show an irregular morphology due to particle aggregation, while hybrids showed fibril character and the presence of crystal IONPs deposition at their surfaces. Micro-Raman spectra showed assignments of hematite (α-Fe2O3), goethite (α-FeOOH), magnetite (Fe3O4), and wustite (FeO), as a result of the coprecipitation process. Magnetization assays showed that the obtained clustered hybrids present SPM behavior at room temperature, despite to the cellulosic backbone presence and size. X-ray photoelectron spectroscopy brings light over the nanoclusters surface binding energies, evidencing the hydrogen bonding of the IONPs over the hydroxyl groups of MC and LR, clarifying the nanoclustering formation among heterogeneous IONPs and cellulosic matrixes.