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Nanoparticles of cobalt ferrite are doped with multiple lanthanum (La) amounts up to an unusually high level of doping. They are synthesised using a soft chemical approach. The structural characterisation is conducted using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystallite size, micro strain, crystal density, deformation and twin fault probability are found out by Rietveld analysis. Room temperature Mössbauer spectroscopy is performed for determination of spin aberration due to La doping. The values of isomeric shift are obtained in the range of 0.33–0.41 mm/s for different samples as compared to the standard range of 0.32–0.34 mm/s. Large and narrow hysteresis are observed in 5 K and 300 K magnetic measurements, respectively with coercivities in the range 0.2–2 kOe at room temperature. The coercivity is in the range of 0.8–15 kOe at 5 K. The results from magnetic measurement show deviation from standard which is also seen from the inferences from Photoluminescence (PL) which hint at the increased versatility of the ferrite material by doping with rare earth (RE) metals. However, there is an upper limit to this inclusion in the ferrite matrix. As such there is also the existence of wasp-waist hysteresis which is indicative of antiferromagnetic (AFM) to ferromagnetic (FM) interaction but from the Rietveld analysis it is seen that this coupling does not have an undesirable effect on the stability of the nanoferrite. [ABSTRACT FROM AUTHOR]

We explore the solventless synthesis of iron oxide nanomaterials obtained on thermal conversion of iron(III)citrate in presence of malonic acid and glucose as co-precursors in varying weight ratios and physical characterization of the materials obtained. Pure phase of hematite was found only for a particular combination of precursor and co-precursor and else a mixture of hematite and magnetite. Significant effect of the co-precursors on the nature and size of the synthesized materials was noticed. Gradual conversion of hematite to magnetite with increasing amount of co-precursor was established. Morin transition was observed in the temperature dependent magnetization study for the hematite materials. Absorption spectroscopy exhibited three different electronic transitions that take place within the 3d5 shell of the octahedrally coordinated Fe3+ ions for hematite materials. The optical (direct and indirect) band gaps estimated from the Tauc's plot showed particle size dependence. From photoluminescence study the transitions of trapped electrons in various defect states of oxygen vacancies were observed which led to the appearance of nonradiative peaks. In the Raman spectra the significant bands of hematite (A1g and Eg bands) were noted. From morphology study the hematite nanomaterials appear as clusters of large irregular shaped particles of various sizes. Formation of hematite nanomaterials as observed by XRD studies was supplemented by the SAED patterns obtained in the HRTEM study. Present study established that nano-sized pure hematite materials can be thermally synthesized at comparatively lower temperature on thermal decomposition of iron(III)citrate by varying the weight ratio of suitable co-precursors. [ABSTRACT FROM AUTHOR]

Ubiquitous nanomaterials have been extensively involved in multifarious biotransformation of diverse organic and synthetic techniques. This research study describes the robust immobilization of α-amylase on magnetic nanoparticles of magnesium ferrite (MgFO) functionalized with silane. The XRD patterns, FESEM and HRTEM images were analysed to study structural and morphological features. The crystallite size of MgFO is found to be 12 nm. The FTIR results confirmed the covalent attachment of the enzyme with the MgFO and VSM and Mössbauer spectrometric graphs were evaluated to study the magnetic behaviour of the prepared samples. The Kinetic parameters, reusability, storage capacity and catalytic activity of the enzyme at various reaction time, pH and temperature conditions before and after attachment with MgFO were examined to confirm the successful immobilization process. The reusability of the enzyme on modified MgFO is found to be good (> 50%) even after 12 consecutive usability cycles and also retain 50% catalytic efficiency over 30 days storage period. [ABSTRACT FROM AUTHOR]

In this investigation, we have used the thermal treatment method for the preparation of nickel and manganese ferrite nanoparticles. All the samples were calcined at different temperatures from 420 to 570 °C. The results of XRD demonstrated the variation of average nanocrystallite size as a function of calcination temperature. Mossbauer spectra of calcined NiFe2O4 nanoparticles at 570 °C exhibit two sextets, indicating the samples are ferromagnetic, while calcined MnFe2O4 nanoparticles at 420 °C reveal simultaneous presence of two paramagnetic doublets with a central magnetic sextet. The Mossbauer spectroscopy is also applied here for investigating the magnetic hyperfine characteristics and cation distribution of the above-mentioned ferrite nanoparticles. Mossbauer results demonstrate that higher calcination temperature assistances M2+ ions enter into the octahedral sites, while simultaneously Fe3+ ions transfer from the octahedral (B) sites to the tetrahedral (A) sites. As the results indicate, magnetic properties of the samples can be attributed to the hyperfine parameters such as hyperfine field and cation distribution. The results of Mossbauer showed the change in hyperfine parameters along with changing temperature and nanocrystallite size. [ABSTRACT FROM AUTHOR]