Sub-nanometer scale size-control of iron oxide nanoparticles with drying time of iron oleate

Balakrishnan, Thiruparasakthi; Lee, Min-Jae; Dey, Jahar; Choi, Sung‐Min

doi:10.1039/c9ce00112c

Cited by 20 publications

(27 citation statements)

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“…Their M s values are in the range of typical values (30–50 emu/g) reported for nanosized iron oxide particles, even with very high-quality size and shape properties in several previous studies obtained by the thermal decomposition method. 12 , 13 , 20 , 49 , 104 , 105 It is well-known that the M s values in iron oxide nanoparticles are much lower than their bulk counterparts (86 and 76 emu/g for magnetite and maghemite at room temperature, respectively 102 , 106 ) and usually decrease with size. 49 , 107 However, iron oxide nanoparticles with small sizes have also been synthesized, which have shown M s values equal or close to those of bulk magnetite.…”

Section: Resultsmentioning

confidence: 99%

From Low to High Saturation Magnetization in Magnetite Nanoparticles: The Crucial Role of the Molar Ratios Between the Chemicals

et al. 2022

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In this study, a comprehensive characterization of iron oxide nanoparticles synthesized by using a simple one-pot thermal decomposition route is presented. In order to obtain monodisperse magnetite nanoparticles with high saturation magnetization, close to the bulk material, the molar ratios between the starting materials (solvents, reducing agents, and surfactants) were varied. Two out of nine conditions investigated in this study resulted in monodisperse iron oxide nanoparticles with high saturation magnetization (90 and 93% of bulk magnetite). The X-ray diffraction analyses along with the inspection of the lattice structure through transmission electron micrographs revealed that the main cause of the reduced magnetization in the other seven samples is likely due to the presence of distortion and microstrain in the particles. Although the thermogravimetric analysis, Raman and Fourier transform infrared spectroscopies confirmed the presence of covalently bonded oleic acid on the surface of all the samples, the particles with higher polydispersity and the lowest surface coating molecules showed the lowest saturation magnetization. Based on the observed results, it could be speculated that the changes in the kinetics of the reactions, induced by varying the molar ratio of the starting chemicals, can lead to the production of the particles with higher polydispersity and/or lattice deformation in their crystal structures. Finally, it was concluded that the experimental conditions for obtaining high-quality iron oxide nanoparticles, particularly the molar ratios and the heating profile, should not be chosen independently; for any specific molar ratio, there may exist a specific heating profile or vice versa. Because this synthetic consideration has rarely been reported in the literature, our results can give insights into the design of iron oxide nanoparticles with high saturation magnetization for different applications.

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Section: Resultsmentioning

confidence: 99%

From Low to High Saturation Magnetization in Magnetite Nanoparticles: The Crucial Role of the Molar Ratios Between the Chemicals

et al. 2022

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“…Both FTIR and TG results indicate that weakly coordinated ligands pass to form stronger coordination as the drying time increases, which is in good agreement with prior studies. 38 …”

Section: Results and Discussionmentioning

confidence: 99%

A Milestone in the Chemical Synthesis of Fe₃O₄ Nanoparticles: Unreported Bulklike Properties Lead to a Remarkable Magnetic Hyperthermia

et al. 2021

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Among iron oxide phases, magnetite (Fe3O4) is often the preferred one for nanotechnological and biomedical applications because of its high saturation magnetization and low toxicity. Although there are several synthetic routes that attempt to reach magnetite nanoparticles (NPs), they are usually referred as “IONPs” (iron oxide NPs) due to the great difficulty in obtaining the monophasic and stoichiometric Fe3O4 phase. Added to this problem is the common increase of size/shape polydispersity when larger NPs (D > 20 nm) are synthesized. An unequivocal correlation between a nanomaterial and its properties can only be achieved by the production of highly homogeneous systems, which, in turn, is only possible by the continuous improvement of synthesis methods. There is no doubt that solving the compositional heterogeneity of IONPs while keeping them monodisperse remains a challenge for synthetic chemistry. Herein, we present a methodical optimization of the iron oleate decomposition method to obtain Fe3O4 single nanocrystals without any trace of secondary phases and with no need of postsynthetic treatment. The average dimension of the NPs, ranging from 20 to 40 nm, has been tailored by adjusting the total volume and the boiling point of the reaction mixture. Mössbauer spectroscopy and DC magnetometry have revealed that the NPs present a perfectly stoichiometric Fe3O4 phase. The high saturation magnetization (93 (2) A·m2/kg at RT) and the extremely sharp Verwey transition (at around 120 K) shown by these NPs have no precedent. Moreover, the synthesis method has been refined to obtain NPs with octahedral morphology and suitable magnetic anisotropy, which significantly improves the magnetic hyperthemia performance. The heating power of properly PEGylated nano-octahedrons has been investigated by AC magnetometry, confirming that the NPs present negligible dipolar interactions, which leads to an outstanding magnetothermal efficiency that does not change when the NPs are dispersed in environments with high viscosity and ionic strength. Additionally, the heat production of the NPs within physiological media has been directly measured by calorimetry under clinically safe conditions, reasserting the excellent adequacy of the system for hyperthermia therapies. To the best of our knowledge, this is the first time that such bulklike magnetite NPs (with minimal size/shape polydispersity, minor agglomeration, and exceptional heating power) are chemically synthesized.

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“…33 Nanocrystal size and size dispersity are highly sensitive to the specific treatment during iron oleate synthesis as a result of the variable binding environment. 17,33,34 Furthermore, remnant sodium and chloride can contaminate growing iron oxide nanocrystals, which may affect their morphology. 35,36 To produce the desired precursors, we utilized an iron salt with a volatile ligand and exchanged that ligand with an excess of oleic acid.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Understanding the Effects of Iron Precursor Ligation and Oxidation State Leads to Improved Synthetic Control for Spinel Iron Oxide Nanocrystals

Plummer

Hutchison

2020

Inorg. Chem.

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Iron oxide nanocrystals have the potential for use in a wide variety of applications if we can finely control and tune the diverse structural attributes that lead to specific, desired properties. At the high temperatures utilized for thermal decomposition based syntheses, commonly used Fe(III) alkylcarboxylate precursors are inadvertently reduced and produce wustite (FeO), which is paramagnetic, as opposed to the desired ferrimagnetic spinel phases of magnetite (Fe 3 O 4 ) and maghemite (γ-Fe 2 O 3 ). To circumvent this issue, we carried out syntheses at lower temperatures (∼230 °C) using an esterification-mediated approach. Under these conditions, formation of the FeO phase can be avoided. However, we found that the precursor oxidation state and ligation had a surprisingly strong influence on the morphologies of the resulting nanocrystals. To investigate the cause of these morphological effects, we carried out analogous nanocrystal syntheses with a series of precursors. The use of Fe(III) oleate precursors yielded highly crystalline, largely twin-free nanocrystals; however, small amounts of acetylacetonate ligation yielded nanocrystals with morphologies characteristic of twin defects. During synthesis at 230 °C, the Fe(III) oleate precursor is partially reduced, providing sufficient quantities of Fe(II) that are needed to grow the Fe 3 O 4 nanocrystals (wherein one-third of the iron atoms are in the Fe(II) state) without twinning. Our investigations suggest that the acetylacetonate ligands prevent reduction of Fe(III) to Fe(II), leading to twinned structures during synthesis. Harnessing this insight, we identified conditions to predictably and continuously grow octahedral, spinel nanocrystals as well as conditions to synthesize highly twinned nanocrystals. These findings also help explain observations in the thermal decomposition synthesis literature which suggest that iron oxide nanocrystals produced from Fe(acac) 3 are less prone to FeO contamination in comparison to those produced from Fe(III) alkylcarboxylates.

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Sub-nanometer scale size-control of iron oxide nanoparticles with drying time of iron oleate

Abstract: The drying time of iron oleate as a single and reliable control parameter for the fine size control (with a sub-nanometer scale step) of monodisperse IONPs in the large-scale thermal decomposition method.

Cited by 20 publications

References 50 publications

From Low to High Saturation Magnetization in Magnetite Nanoparticles: The Crucial Role of the Molar Ratios Between the Chemicals

From Low to High Saturation Magnetization in Magnetite Nanoparticles: The Crucial Role of the Molar Ratios Between the Chemicals

A Milestone in the Chemical Synthesis of Fe₃O₄ Nanoparticles: Unreported Bulklike Properties Lead to a Remarkable Magnetic Hyperthermia

Understanding the Effects of Iron Precursor Ligation and Oxidation State Leads to Improved Synthetic Control for Spinel Iron Oxide Nanocrystals

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Sub-nanometer scale size-control of iron oxide nanoparticles with drying time of iron oleate

Abstract: The drying time of iron oleate as a single and reliable control parameter for the fine size control (with a sub-nanometer scale step) of monodisperse IONPs in the large-scale thermal decomposition method.

Cited by 20 publications

References 50 publications

From Low to High Saturation Magnetization in Magnetite Nanoparticles: The Crucial Role of the Molar Ratios Between the Chemicals

From Low to High Saturation Magnetization in Magnetite Nanoparticles: The Crucial Role of the Molar Ratios Between the Chemicals

A Milestone in the Chemical Synthesis of Fe3O4 Nanoparticles: Unreported Bulklike Properties Lead to a Remarkable Magnetic Hyperthermia

Understanding the Effects of Iron Precursor Ligation and Oxidation State Leads to Improved Synthetic Control for Spinel Iron Oxide Nanocrystals

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A Milestone in the Chemical Synthesis of Fe₃O₄ Nanoparticles: Unreported Bulklike Properties Lead to a Remarkable Magnetic Hyperthermia