From bulk to nano: Size-induced variations in the structural, magnetic, optical and photocatalytic properties of CoCrFeO4

Abstract

Abstract

CoCrFeO 4 ferrites with nano (CFN) and bulk (CFB) morphologies were synthesized via a facile Sol-gel route by calcination at 400 and 1250 °C, respectively, to investigate the influence of particle size on their structural, optical, magnetic, and photocatalytic properties. Rietveld refinement of X-ray diffraction data confirmed the formation of a single-phase cubic spinel structure for both the samples. FESEM and HRTEM analyses revealed agglomerated nanosized particles for CFN and densely packed grains for CFB. Nitrogen adsorption–desorption studies demonstrated a remarkable increase in specific surface area from 0.496 m 2 /g for CFB to 92.7 m 2 /g for CFN, together with the development of a mesoporous structure. UV–visible diffuse reflectance measurements indicated band gap energies of 1.51 and 1.64 eV for CFN and CFB, respectively, while photoluminescence studies revealed suppressed electron–hole recombination in the nanocrystalline sample. Magnetic investigations performed at 10 and 300 K showed a strong particle-size dependence. The bulk sample exhibited higher saturation magnetization owing to improved crystallinity and reduced surface spin disorder, whereas the nano sample displayed significantly enhanced coercivity and magnetic anisotropy arising from finite-size effects and surface spin pinning. ZFC–FC measurements revealed blocking temperatures of approximately 185 and 280 K for CFN and CFB, respectively, while T c was only observed for CFB. The photocatalytic performance was evaluated through the visible-light degradation of Acridine Orange (AO). Under optimized conditions, CFN achieved 99% degradation within 16 min, whereas CFB exhibited only ~5% degradation. Radical trapping experiments identified hydroxyl radicals as the dominant reactive species responsible for dye degradation. The superior photocatalytic activity of CFN is attributed to its high surface area, mesoporosity, narrow band gap, and efficient charge separation. The present study establishes a clear correlation between particle size, magnetic behaviour, and photocatalytic performance in CoCrFeO 4 ferrites and highlights the potential of nanocrystalline CoCrFeO 4 for environmental remediation applications.