Improvement of the thermal stability of nanomaghemite by functionalization with type 5A zeolite and magnetic properties studied by in-field 57Fe Mössbauer measurements

In Situ and after Synthesis of Magnetic Nanoarchitectures Grown onto Zeolite Type 5A/CTAB Frameworks and Their Ecotoxicological Properties

“…In general, this oxidation that leads from Fe 3 O 4 to γ-Fe 2 O 3 can occur in the first 2 weeks at which the NPs were synthesized and usually occurs first at the surface. 8,9,14, 20,35,38 In our work, we were able to detect the initial Fe 3 O 4 phase by Raman microscopy because this method was applied immediately after the sample synthesis. In addition, the surface oxidation of the assynthetized Fe 3 O 4 NPs was monitored by the after-burning protocol when the γ → α transformation has occurred, yielding a gradual formation first of the γ-Fe 2 O 3 phase, which obviously started at the surface, and finally the α-Fe 2 O 3 , as also found in the literature.…”

“…However, low-temperature Mössbauer measurements (e.g., below 20 K) can be suitable to differentiate the contribution from either Fe 3 O 4 or γ-Fe 2 O 3 NPs. We must also highlight that the initial state of the iron oxide by co-precipitation is usually Fe 3 O 4 , but several scientific reports have shown that a simple air exposition of the Fe 3 O 4 NPs can cause total oxidation of the surface without additional chemical treatment. ,,,,, The oxidation effect can be due to the high surface chemical reactivity, and it is really important for applications in nanoremediation processes because the surface adsorption depends on Fe 2+ and Fe 3+ coordination and, of course, the adsorption efficiency can be severely affected depending of the phase found in the sample. In general, this oxidation that leads from Fe 3 O 4 to γ-Fe 2 O 3 can occur in the first 2 weeks at which the NPs were synthesized and usually occurs first at the surface. ,,,,, In our work, we were able to detect the initial Fe 3 O 4 phase by Raman microscopy because this method was applied immediately after the sample synthesis.…”

“…We must also highlight that the initial state of the iron oxide by co-precipitation is usually Fe 3 O 4 , but several scientific reports have shown that a simple air exposition of the Fe 3 O 4 NPs can cause total oxidation of the surface without additional chemical treatment. ,,,,, The oxidation effect can be due to the high surface chemical reactivity, and it is really important for applications in nanoremediation processes because the surface adsorption depends on Fe 2+ and Fe 3+ coordination and, of course, the adsorption efficiency can be severely affected depending of the phase found in the sample. In general, this oxidation that leads from Fe 3 O 4 to γ-Fe 2 O 3 can occur in the first 2 weeks at which the NPs were synthesized and usually occurs first at the surface. ,,,,, In our work, we were able to detect the initial Fe 3 O 4 phase by Raman microscopy because this method was applied immediately after the sample synthesis. In addition, the surface oxidation of the as-synthetized Fe 3 O 4 NPs was monitored by the after-burning protocol when the γ → α transformation has occurred, yielding a gradual formation first of the γ-Fe 2 O 3 phase, which obviously started at the surface, and finally the α-Fe 2 O 3 , as also found in the literature.…”

“…These 15 K spectra were then fitted with two magnetic components (except the NPD2 sample), and their refined hyperfine parameters are also presented in Table . In all samples, the two static asymmetric sextets of the FI γ-Fe 2 O 3 phase allowed fixing the A/B ratio at 0.6, a fraction expected for a well-defined crystallographic γ-Fe 2 O 3 phase. ,,,, Also, the mean hyperfine values are strongly related to the bulk γ-Fe 2 O 3 phase. However, the 15 K spectrum for the 4.7 nm NP2D sample confirms the two secondary antiferromagnetic phases of 6LFh and AK (also found in X-ray data) and smaller crystallites conserving superparamagnetic relaxation (representing 57% of the total relative absorption area, R.A.A.).…”

Zn-=SUB=-x-=/SUB=-Fe-=SUB=-3-x-=/SUB=-O-=SUB=-4-=/SUB=- (0 ≤ x≤ 1.0) magnetic nanoparticles functionalized with polyacrylic acid (PAA)

“…It was found that MFs are extremely promising materials for practical applications, such as magnetic fluid seals, magnetic lubricants, visualization systems for the structure of constant magnetic fields and the domain structure of magnetics, magnetically controlled light filters, hydromechanical transducers, sound emitters and spintronic devices, etc. [5][6][7].…”