Inducing superparamagnetic behavior and enhancing antibacterial efficiency of ZnO nanopowders through Mn + F doping

Doubly doped (Mn + F) zinc oxide nanopowders were synthesized using a simple soft chemical route. The F doping level was varied from 0 to 20 at.% in steps of 5 at.% and the Mn doping level was kept constant at 10 at.%. Structural, optical, surface morphological and magnetic properties of the synthesized nanopowders were investigated. The antibacterial activity was studied using well diffusion method as a function of F doping level against the Bacillus subtilis bacteria. XRD analysis ensures that the synthesized material has hexagonal wurtzite structure with preferential orientation along the (101) plane and no secondary phases were observed. Crystallite sizes were found to be increasing up to 10 at.% of F doping level and then decreasing with further doping. The shift in the NBE peak of the PL spectra and the absorption edge of the optical absorbance spectra confirmed the variation in the band gap which in turn indicated the variation in the carrier concentration caused by F doping. The SEM and TEM images showed that the size and shape of the grains are remarkably influenced by F doping. The magnetic measurements performed at room temperature showed that Mn + F doped ZnO nanopowders exhibits super paramagnetic behavior. Moreover, it was found that the antibacterial activity of doubly doped ZnO nanopowders was enhanced remarkably up to 10 at.% of F doping level and then slightly decreased with further increase in the F doping level.