One-Pot Synthesis of Magnetic Nanocellulose/Fe₃O₄ Hybrids Using FeCl₃ as Cellulose Hydrolytic Medium and Fe₃O₄ Precursor

A facile one-pot method was reported for synthesizing magnetic cellulose nanocrystals (CNC) loaded with iron tetroxide (Fe3O4) nanoparticles. Initially, microcrystalline cellulose (MCC) was treated with a 1 M solution of ferric chloride (FeCl3) and hydrolyzed into CNCs. The FeCl3 played a dual role, acting both as a cellulose hydrolytic medium and as an Fe3O4 precursor. Subsequently, CNCs served as a stabilizing and sole reducing agent for the in situ formation of Fe3O4 nanoparticles during the solvothermal reaction. The impact of the cellulose substrate, reaction solvent, solvothermal time, and MCC solid-to-liquid ratio on the growth, morphology, and crystal structure of ferrite was investigated. Pure and small sphere-like Fe3O4 (similar to 30 nm) nanoparticles were successfully immobilized and reduced on the CNC surface when ethanol was used, and the solvent heating time was extended to 3-30 h. Complete reduction of Fe3+ to Fe3O4 was achieved when the MCC solid to FeCl3 solution ratio was higher than 1 g:75 mL. Under optimized conditions, the resulting CNC/Fe3O4 hybrid contained 33.3% Fe3O4 and exhibited a maximum saturation magnetization (Ms) value of 22.0 emu/g with low coercivity, making it promising for a wide range of applications.