Preparation of Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites and their adsorption of bovine serum albumin

The magnetic nanocomposites of (1-x)Ni0.5Zn0.5Fe2O4/xSiO(2) (x = 0-0.2) were synthesized by the citrate-gel process and their absorption behavior of bovine serum albumin (BSA) was investigated by UV spectroscopy at room temperature. The gel precursor and resultant nanocomposites were characterized by FTIR, XRD, TEM and BET techniques. The results show that the single ferrite phase of Ni0.5Zn0.5Fe2O4 is formed at 400 degrees C, with high saturation magnetization and small coercivity. A porous, amorphous silica layer is located at the ferrite nanograin boundaries, with the silica content increasing from 0 to 0.20, the average grain size of Ni0.5Zn0.5Fe2O4 calcined at 400 degrees C reduced from about 18-8 nm. Consequently, the specific surface area of the nanocomposites ascends clearly with the increase of silica content, which is largely contributed by the increase in the thickness of the porous silica layer. The Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites demonstrate a better adsorption capability than the bare Ni0.5Zn0.5Fe2O4 nanoparticles for BSA. With the increase of the silica content from 0 to 0.05 and the specific surface area from about 49-57 m(2)/g, the BSA adsorption capability of the Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites calcined at 400 degrees C improve dramatically from 22 to 49 mg/g. However, with a further increase of the silica content from 0.05 to 0.2, the specific surface area increase from about 57-120 m(2)/g, the BSA adsorption for the nanocomposites remains around 49 mg/g, owing to the pores in the porous silica layer which are too small to let the BSA protein molecules in. (C) 2011 Elsevier B.V. All rights reserved.