SOLVENT-DEPENDENT SYNTHESIS AND OPTICAL CHARACTERIZATION OF IRON OXIDE (Fe2O3) NANOPARTICLES VIA COPRECIPITATION METHOD

Abstract

Nanostructured metal oxides, particularly iron oxide (Fe₂O₃), have attracted considerable interest because of their unique optical and magnetic properties and due to their wide applications in catalysis, sensors, magnetic devices, and environmental remediation. This study investigates the solvent-dependent synthesis of iron oxide (Fe₂O₃) nanoparticles via a co-precipitation method using distilled water, ethanol, and a water–ethanol (1:1) mixture, with a focus on tailoring structural and optical properties for advanced applications. Iron chloride precursors were co-precipitated under alkaline conditions (pH 10), followed by filtering and drying at 80 °C to yield crystalline Fe₂O₃. Fourier-transform infrared (FTIR) spectroscopy confirmed Fe–O vibrational modes (550–700 cm⁻¹) and solvent-specific surface chemistry: water-synthesized nanoparticles exhibited strong O–H stretching (3400 cm⁻¹) and bending (1630 cm⁻¹) modes, indicative of hydroxylation, while ethanol-derived samples showed minimal surface hydration but residual C–H/C–O bands (2800–2900 cm⁻¹). UV-Vis spectroscopy revealed solvent-mediated bandgap tuning, with ethanol producing smaller nanoparticles (≈30 nm) and a reduced bandgap of 2.1 eV due to quantum confinement, compared to water-synthesized particles (≈37 nm, 2.58 eV). The water–ethanol mixture yielded intermediate properties, balancing nucleation kinetics and colloidal stability. These findings underscore the critical role of solvent polarity in modulating crystallinity, particle size, and surface chemistry. Ethanol’s low dielectric constant minimized agglomeration and enhanced optical absorption in the visible spectrum, positioning ethanol-derived Fe₂O₃ as a promising candidate for photocatalysis and solar energy harvesting. Conversely, water-synthesized nanoparticles, with hydroxyl-rich surfaces, show potential for biomedical applications. This work advances solvent engineering as a sustainable, tunable strategy for optimizing Fe₂O₃ nanomaterials, offering insights into scalable synthesis routes for targeted technological applications.