Synthesis of Chitosan-Mediated Silver Coated γ-Fe2O3 (Ag-γ-Fe2O3@Cs) Superparamagnetic Binary Nanohybrids for Multifunctional Applications

The coating of chitosan on gamma-Fe2O3 (IO) nanoparticles (NPs) produces the biocompatible nanohybrids (CIO) with enhanced functionalities and optical features associated with a reduction in the average size of IO nanoclusters from 11.3 to 9.3 nm as was estimated by transmission electron microscopy (TEM). The effective capping by chitosan was shown by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), TEM, and Brunauer-Emmett-Teller (BET) analyses. The in situ generation of Ag on the surface of CIO displays characteristic surface plasmonic resonance band resulting in a further decrease in the average size of IO nanoclusters in these binary nanohybrids (CIOMAg) to 8.1 nm involving supramolecular binding through IO and chitosan functionalities. The identification of the phases of iron oxide and Ag NPs and the effective capping of chitosan in binary nanohybrids have been analyzed by XRD, AFM, FESEM, and infrared (IR) analyses. The phase of iron oxide and the presence of Ag NPs in the binary nanohybrids are evidently revealed by X-ray photoelectron spectroscopy (XPS) analysis and also supported by Raman spectroscopy. The interactions among IO, chitosan, and Ag moieties in the binary nanohybrids have been analyzed by IR and XPS. These binary nanohybrids demonstrated superparamagnetic behavior with relatively higher saturation magnetization (72.5-75.5 emu/g) at room temperature compared to those of CIO (69.2 emu/g), which provides an important feature for their catalytic, SERS, and biomedical applications. As-synthesized binary nanohybrids exhibited fairly high catalytic efficiency for the reduction of methyl orange even at low Ag concentration (30 nM) and could be recycled up to ten cycles without any loss of efficiency. It demonstrated the antibacterial activity for model bacteria E. coli with MIC and MBC at 1.1 and 4.2 g/mL Ag, respectively, and SERS activity for model dye p-ATP with a detection limit at 10 pM, evidently suggesting their environmental and biomedical potential.