▎ 摘　　要

Cobalt ferrite was co-doped with bismuth and silver of different concentrations via sol-gel combustion method. Citric acid was used as fuel. The powder product was calcined using an electric furnace at 1000 degrees C for 4 hrs. X-ray diffraction pattern of co-doped cobalt ferrite nanoparticles (CF-NPs) showed the formation of cubic crystalline structure. Few very small absorption bands were also observed. The crystallite sizes of these materials were - 40 nm to - 60 nm. As calculated using Scherrer's equation it has been observed that the crystallite size changed with change in doping and co-doping levels. This is a very pertinent observation showing that crystallite size can be controlled through doping and co-doping. Since properties of particles largely depend on the sizes of the particles this also imply that particles of desired properties can be synthesised using this method. The results obtained through X-ray diffraction were further deeply analysed using Rietveld Refinement using FullProf suite. Fourier Transform Infrared (FTIR) Spectroscopic studies confirmed the formation of spinel structures. Few very small absorption bands were also observed in FTIR. Particle sizes as observed using Zeta potential and Particle Size Analyser (ZS) was approximately 675 nm. Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscope (TEM) showed that the particles were agglomerated. Composites of co-doped CFNPs with ZnO/Ag were prepared manually by grinding them in a mortar and pestle. Starch was used as a binder. All these samples including composites showed antibacterial activities. The results revealed that co-doped cobalt ferrite nanoparticles of higher dopant concentration exhibit higher antibacterial activity. These materials can be used in various biomedical applications.