Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Researchers synthesized Fe3O4/Fe2O3 nanoparticles and PVP-capped versions using a hydrothermal method, creating efficient photocatalysts. PVP reduced particle size, increased surface area, and improved dispersion while narrowing the bandgap for better light absorption. Under UV light, the capped nanocomposite degraded nearly 100% of Cr(III) in 105 min and organic pollutants in 120 min, outperforming the uncoated version due to enhanced charge separation and stability, enabling recyclable water purification.

ABSTRACT
In this study, Fe3O4/Fe2O3 and polyvinylpyrrolidone (PVP)-capped Fe3O4/Fe2O3@PVP nanocomposites were synthesized via a controlled hydrothermal route and evaluated as multifunctional photocatalysts for the degradation of inorganic and organic pollutants. Structural analyses confirmed the coexistence of magnetite and hematite phases, with PVP incorporation inducing compressive lattice strain, reducing crystallite size from 19.91 to 14.83 nm, and increasing the specific surface area from 55.84 to 68.8 m2 g−1. UV–Vis spectroscopy revealed a slight red shift in the optical bandgap (from 1.25 to 1.04 eV), attributed to enhanced polymer–oxide electronic coupling. Morphological studies showed that PVP effectively minimized nanoparticle agglomeration, leading to improved dispersion and surface accessibility. Photocatalytic evaluations under UV irradiation demonstrated nearly complete degradation (~99.9%) of Cr(III) within 105 min and of the organic pollutants 2,4-dinitroaniline and p-bromohydroxybenzene within 120 min. The PVP-capped Fe3O4/Fe2O3@PVP nanocomposite exhibited slightly superior efficiency and stability compared to the uncoated sample, owing to enhanced charge carrier separation, reduced electron–hole recombination, and improved interfacial contact with the pollutants. These findings highlight the potential of Fe3O4/Fe2O3@PVP nanocomposites as efficient, recyclable, and sustainable photocatalysts for water purification and environmental remediation.