Ferrite nanoparticles (NPs) with composition MFe$_2$O$_4$ (M $=$ Mg/Co) were synthesized by a facile combustion method. NPs were characterized employing various physico-chemical techniques. X-ray diffraction patterns confirmed the phase purity, transmission electron micrographs indicated that NPs are spherical and average diameter of maximum fraction of NPs was in the range of 20–30 nm. Magnetic studies revealed that the saturation magnetization values for MgFe$_2$O$_4$ and CoFe$_2$O$_4$ NPs were 13.17 and 41.12 emu g$^{−1}$, respectively. The Brunauer–Emmett–Teller surface area of CoFe$_2$O$_4$ and MgFe$_2$O$_4$ NPs was 22.98 and 34.39vm$^2$ g$^{−1}$, respectively. Synthesized ferrite NPs and activated charcoal were comparatively analysed as adsorbents for removal of Pb(II) ions. The factors influencing uptake behaviour of Pb(II) ions viz. adsorbent dose,pH, concentration, temperature and contact time were quantified.The adsorption data showed good correlationwith Langmuir and Freundlich models as compared to Dubinin–Radushkevich model. The maximum adsorption capacity displayed a twofold increase for NPs as compared to activated charcoal. The easy magnetic separation of ferrite NPs from the solution and their regeneration with 0.1 N NaOH for reuse without any loss make them potential adsorbents. The trend in ascending order for the elimination of Pb(II) ions from the solution was activated charcoal < CoFe$_2$O$_4$ NPs < MgFe$_2$O$_4$ NPs. The observed differences in the adsorption potential of NPs are explained on the basis of structural and magnetic properties and the surface area of NPs.

Single and co-doped ZnO thin films are currently under intense investigation and development for optoelectronic applications. Here in this study, pristine, indium-doped (IZO), gallium-doped (GZO) and co-doped (IGZO) ZnO thin filmswere deposited on a glass substrate using radio frequency magnetron sputtering. A comparative study of all the films was carried out on the basis of their various properties. The effect of single and co-doping on the structural (X-ray diffraction(XRD) studies and Raman studies), morphological (field emission scanning electron microscopy and energy dispersiveX-ray spectroscopy studies) and optical properties (ultraviolet–visible (UV–Vis) and photoluminescence (PL)) of the deposited films was investigated. X-ray photoelectron spectroscopy (XPS) characterization was employed to analyse the surface chemical composition and bonding of the deposited film. From the XRD patterns, it was found that the films were highly crystalline in nature and preferentially oriented along the (002) direction with a hexagonal wurtzite structure, consistent with Raman analysis. IGZO films displayed a dramatic improvement in the surface morphology as compared with the single dopant films due to the compensation effect of gallium and indium doping which reduced the lattice strain. The XPS analysisconfirmed the presence of the oxidized dopants in each film. All thin films have shown excellent optical properties with more than 90% transmission in the visible range of light. The blue-shift of the absorption edge accompanied by the increase of the optical band gap confirmed the Burstein–Moss effect. The UV PL peak originated from the near band edge emission of crystalline ZnO, while the visible PL was associated with the radiative transition related to oxygen interstitial (Oi) defects in the ZnO structure.