Modification using additional NaOH for the preparation of γ‐Fe ₂ O ₃ nanoparticles by chemically induced transition

Abstract

γ-Fe 2 O 3 nanoparticles coated with a layer of FeCl 3 ·6H 2 O were prepared by chemically induced transition in FeCl 2 solution. NaOH was added to the reaction solution, to investigate the effect of alkalinity on the resulting particles. Vibrating sample magnetometry, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were used to characterise the products. Additional NaOH stimulated the epitaxial growth of γ-Fe 2 O 3 on the γ-Fe 2 O 3 crystallites and more FeCl 3 ·6H 2 O adsorbed on γ-Fe 2 O 3 . Under the experimental conditions, the increase in γ-Fe 2 O 3 content was larger than that of FeCl 3 ·6H 2 O, at ≤0.7 M NaOH. At >0.7 M NaOH, the increase in γ-Fe 2 O 3 content was less than that of FeCl 3 ·6H 2 O. The non-monotonic variation of the FeCl 3 ·6H 2 O/ γ-Fe 2 O 3 ratio was consistent with this result, and was consistent with the variation in apparent specific magnetisation with increasing NaOH concentration.

Cu(I) Modification duringγ-Fe2O3Nanoparticles Synthesis and Subsequent Characterization

“…Their O 1s spectra exhibited two peaks: the P1 peak at approximately 529.5 eV can be attributed to Fe 2 O 3 , and the P2 peak at approximately 532.2 eV is due to molecular H 2 O [19]. The Cl 2p 3/2 peak at approximately 198.7 eV corresponds to Cl 2p 3/2 in FeCl 3 (199 eV), which is in good agreement with the probable presence of FeCl 3 ⋅6H 2 O, as unmodified sample [14]. Thus, the Fe 2p 3/2 peak at ∼711.2 eV resulted from both Table 1: Atomic percentages of Fe, Cl, and Cu from energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) measurements for samples (1), (2), and (3).…”

“…Liquid-phase synthesis is often used to prepare inorganic nanoparticles [10]; the conventional aqueous synthesis of the -Fe 2 O 3 particles involves three or more steps [11,12]. We have proposed a method to synthesize -Fe 2 O 3 nanoparticles by thermally treating the FeOOH/Mg(OH) 2 precursor in FeCl 2 treating solution [13,14]. Through this method, known as chemically induced transition (CIT) method, FeOOH species were transformed into -Fe 2 O 3 nanocrystallites by dehydration and Mg(OH) 2 was dissolved to assist the precipitation of the nanoparticles.…”

“…Through this method, known as chemically induced transition (CIT) method, FeOOH species were transformed into -Fe 2 O 3 nanocrystallites by dehydration and Mg(OH) 2 was dissolved to assist the precipitation of the nanoparticles. Besides, the Fe 2+ ions in the FeCl 2 solution were oxidized to Fe 3+ to form a FeCl 3 ⋅6H 2 O coating on the -Fe 2 O 3 nanocrystallites [14]. During the synthesis of the -Fe 2 O 3 nanoparticles, the surface modification was performed by adding a salt solution composed of metal ions with a valency of two, such as Zn(II)Cl 2 [15,16] and Co(II)(NO 3 ) 2 [17], to fabricate Zn(II)Fe 2 O 4 and Co(II)Fe 2 O 4 epitaxial layers, respectively, on the -Fe 2 O 3 crystallites.…”

Preparation of magnetic nanoparticles via chemically induced transition

“…26 Recently, we proposed a method of liquid-phase synthesis to produce g-Fe 2 O 3 -based magnetic nanoparticles, which involved preparing an FeOOH/Mg(OH) 2 precursor having loose aggregation without regular edges and treating the hydroxide precursors in an Iron(II) chloride (FeCl 2 ) solution at 100 C. 27 For the preparation, FeOOH species dehydrated to transform it into the g-Fe 2 O 3 nanoparticles and Mg(OH) 2 dissolved to act as a precipitation agent. This method is referred to as chemically induced transition (CIT), 28 which is a novel reaction on a nanoscale and may provide a new route for the preparation of oxide nanoparticles. In the work presented here, we investigate the components and magnetization of the nanoparticles as a function of the concentration of FeCl 2 treating solution used.…”

“…27 For the preparation, FeOOH species dehydrated to transform it into the γ-Fe 2 O 3 nanoparticles and Mg(OH) 2 dissolved to act as a precipitation agent. This method is referred to as chemically induced transition (CIT), 28 which is a novel reaction on a nanoscale and may provide a new route for the preparation of oxide nanoparticles. In the work presented here, we investigate the components and magnetization of the nanoparticles as a function of the concentration of FeCl 2 treating solution used.…”