Summary: This study aims at the effect of Zinc ferrite nanoparticles of particle size (14 AE 2) nm prepared by sol-gel technique on chlorella pyrenoidosa at two different concentrations (1.0 mM and 2.0 mM). The structural characterizations of the prepared sample (ZnFe 2 O 4 ) were carried out by XRD, TEM, and XRF. XRD analysis revealed single phased cubic spinel structure having space group Fd3m. XRF analysis confirmed the purity of the sample. The negative effect of ZnFe 2 O 4 on chlorella pyrenoidosa was manifested by the progressive depletion of cell count. It was found that the algal growth was inhibited by 47% even at a low concentration of 2 mM indicating that zinc ferrite nanoparticles are promising agent for the control of unwanted algal growth. To the best of our knowledge, the effect of ferrite nanoparticles on algae has not been reported elsewhere.

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The present article investigates the effect of different dopants on manganese based mixed nano ferrites synthesized through sol-gel method.MnF, MnCoF and MnCoMgF (MnFe2O4, Mn0.5Co0.5Fe2O4andMn0.5Co0.25Mg0.25Fe2O4) were synthesized by Sol-gel method. The structural, magnetic and optical properties of the samples were analysed through XRD(X-RayDiffractometer), VSM (Vibrating Sample Magnetometer,) and UV-Visible Spectroscopy. The phase identification and lattice parameter determination were carried out by using X-RayDiffraction and hence the crystallite size and X-Ray density were calculated. Peaks (220), (311), (400), (511), and (440) were obtained from the XRDpattern of the samples, which confirmed their single-phase cubic spinel structure. It was observed that because of the large ionic radius of Co2+ (0.745 Å) ions as compared to that of Fe3+ (0.645 Å) ions, lattice parameter of MnCoF increased in comparison with that of MnF but, the substitution of Mg2+ to MnCoF sample decreased the lattice constant. By investigating the hysteresis loops produced by the samples in the VSM analyses, it was found that the MnF have low coercivity and moderate saturation magnetization amongst the three. The substitution of Mg2+ in MnCoF sample decreased the value of saturation magnetization. UV-Visible analysis was used to determine bandgap energy of three samples.From the Tauc plot, we can observe bandgap energies of 3.202 eV, 3.180 eV and 3.239 eV, for MnF, MnCoF and MnCoMgF respectively.On substituting with the Co2+ in MnF the band gap of sample decreases indicating quantum confinement phenomenon.When substitution was done both Co2+ and Mg2+, the band gap energy value increases.

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Nanoparticles of gadolinium substituted Mg-Zn ferrite, Mg 0.75 Zn 0.25 Gd x Fe 2-x O 4 (where x = 0.00, 0.05, 0.10, 0.15) have been prepared by the sol-gel technique. The lattice constant is found to increase with increase in the Gd 3? ion concentration. The observed variation of dielectric constant with frequency is explained on the basis of the MaxwellWagner two layer model and the electron hopping mechanism. The dielectric constant and dielectric loss decrease with Gd 3? ion substitution. The variation of AC conductivity with frequency suggests that the conduction is due to small polaron hopping. It is also noticed that the dielectric constant and the AC conductivity increase with temperature and it is explained in terms of the thermally enhanced drift mobility of the charge carriers. The observed low value of dielectric constant and also the dielectric loss factor obtained for gadolinium substituted ferrites make them desirable for high frequency applications.