Chitosan coating by mechanical milling of MnFe₂O₄ and Mn_0.5Co_0.5Fe₂O₄: Effect of milling

Abstract

Manganese ferrite (MnFe2O4) and manganese-cobalt ferrite (Mn0.5Co0.5Fe2O4) fine powders were produced by glycol-thermal technique. Fine powders were then milled with chitosan for different times ranging from 5 hours to 60 hours. XRD patterns of the as-prepared and milled oxides confirm cubic phase structure with an average crystallite size of 11 nm. The observed values of lattice parameter decrease with milling due to the inversion of cations induced by milling. TEM results reveal nanoparticles with spherical shape and average particle sizes correlating to XRD data. No aggregation of particles was observed after milling suggesting effective chitosan coating. Magnetization studies performed at room temperature in fields up to 14 kOe revealed the superparamagnetic nature of both naked and coated nanoparticles with spontaneous and saturation magnetizations decreasing with milling. Larger coercive fields observed in Mn-Co oxides were attributed to higher magnetic anisotropy associated with Co ions. A reduction of coercive field due to milling duration was observed. 57Fe Mössbauer spectra of Mn0.5Co0.5Fe2O4 samples show ordered magnetic states, while paramagnetic nature is revealed in MnFe2O4 samples. Hence, current results suggest that chitosan coating can be successfully achieved through mechanical milling resulting in nanoparticles with potential for biomedical applications. The differences in the magnetic properties of the samples are discussed based on Stoner-Wohlfarth theory.

Evolution of the Magnetic and Structural Properties with the Chemical Composition in Oleate-Capped MnxCo1–xFe2O4 Nanoparticles

“…The observed saturation magnetization values appeared higher than those usually observed in the literature for Co/Mn mixed ferrite NPs ,,,,,,,,,, from about 30 to 70 Am 2 /kg, due to differences in the particle size and particle size distribution, the presence of dead layers of canted surface spins, and cation distribution. However, the values are close to those observed for other spinel ferrite systems produced by the same oleate-based solvothermal method …”

“…Indeed, in the literature, few studies reported a discussion of the magnetic properties together with the chemical composition obtained by quantitative analytical methods, such as atomic absorption spectroscopy (AAS) 55 or inductively coupled plasma optical emission spectrometry (ICP−OES), 34 or semi-quantitative ones, such as scanning electron microscopy (SEM)−energy dispersive X-ray (EDX) analysis. 29,34,39,40,51,59 The crystallite size in the studied samples was found to change as a function of the Co/Mn ratio in the range of 14−22, 51 16−34, 29 23−33, 34,59 and 3.0−31.0 nm. 55 Some studies focused on a single intermediate chemical composition.…”

“…In the beginning, attention was devoted to Co/Zn or Co/Fe mixed ferrites . Co/Mn chemically mixed ferrites were first proposed in 2009, in the form of spheroidal NPs or nanowires, , but the attention on these systems is still vivid with many recent studies published. − Indeed, manganese ferrite has 2 orders of magnitude lower anisotropy constant but higher saturation magnetization with respect to cobalt ferrite, and the co-presence of Co and Mn ions may lead to interesting physical and chemical properties exploitable for different applications, from magnetic stress sensoring to catalysis. − …”

“…Indeed, in the literature, few studies reported a discussion of the magnetic properties together with the chemical composition obtained by quantitative analytical methods, such as atomic absorption spectroscopy (AAS) or inductively coupled plasma optical emission spectrometry (ICP–OES), or semi-quantitative ones, such as scanning electron microscopy (SEM)–energy dispersive X-ray (EDX) analysis. ,,,,, The crystallite size in the studied samples was found to change as a function of the Co/Mn ratio in the range of 14–22, 16–34, 23–33, , and 3.0–31.0 nm . Some studies focused on a single intermediate chemical composition. ,, Most commonly, a study of the magnetic field ,,,,,,,,,− and/or temperature dependence ,,,,,,, of the magnetization is reported, whereas only rarely an investigation of the interparticle interactions is provided . In one case, the Co/Mn mixed ferrite NPs were used for comparison with bimagnetic core–shell NPs …”

“…55 Some studies focused on a single intermediate chemical composition. 34,39,40 Most commonly, a study of the magnetic field 24,26,31,34,35,39,40,52,57,59−61 and/or temperature dependence 28,30,49,51,52,55,60,62 of the magnetization is reported, whereas only rarely an investigation of the interparticle interactions is provided. 28 In one case, the Co/Mn mixed ferrite NPs were used for comparison with bimagnetic core−shell NPs.…”