Lactoferrin-assisted synthesis of zinc ferrite nanocrystal: Its magnetic performance and photocatalytic activity

Lactoferrin (LF) was used to assist the synthesis of zinc ferrite (ZnFe₂O₄, ZFO) semiconductor photocatalysts in this study, and superparamagnetic ZFO nanocrystals with an average crystallite size ranging from 11.3 nm to 20.1 nm were successfully obtained via the hydrothermal method. It was found that LF was conducive to fast formation of ZFO nuclei, which resulted in remarkable crystallinity enhancement of the as-prepared ZFO nanocrystals. The saturation magnetization (M_s) of the as-prepared ZFO crystals would be greatly improved with increasing the LF content, and the M_s of the as-prepared ZFO crystals synthesized with 50 mg of LF (ZFO-50LF) could reach 19.9 emu/g, whereas the M_s of the as-prepared ZFO crystals synthesized in the absence of LF (ZFO-0LF) was only 8.8 emu/g. In addition, although the specific surface area of ZFO-0LF nanocrystals (127.2 m²/g) was larger than that of ZFO-50LF nanocrystals (101.6 m²/g), and ZFO-0LF exhibited a higher absorption of methyl orange (MO) molecules in contrast with ZFO-50LF, but ZFO-50LF possessed a larger optical absorption coefficient, smaller band gap and higher photocatalytic degradation efficiency per unit area. After being irradiated under UV light for 3 h, ZFO-50LF almost could make MO molecules completely degrade. Therefore, the LF-assisted synthesized ZFO nanocrystals have a promising application prospect to be used as a new high-efficiency recyclable photocatalyst. - Highlights: • We report a novelty method to prepare ZnFe₂O₄ nanocrystals. • ZnFe₂O₄ nanocrystals with a size ranging from 11.3 nm to 20.1 nm are obtained. • Lactoferrin-assisted synthesized ZnFe₂O₄ nanocrystals show good superparamagnetism. • Lactoferrin helps to enhance the saturation magnetization of ZnFe₂O₄ nanocrystals. • ZnFe₂O₄ nanocrystal synthesized with lactoferrin has good photocatalytic activity.