Nanosized Iron Oxide Particles Entrapped in Pseudo-Single Crystals of γ-Cyclodextrin

Bonacchi, Daniele; Caneschi, Andréa; Dorignac, D.; Falqui, Andrea; Gatteschi, Dante; Rovai, Donella; Sangregorio, Claudio; Sessoli, Roberta

doi:10.1021/cm034948e

Cited by 57 publications

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References 29 publications

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“…Few publications report on the synthesis of maghemite NPs with a diameter below 3 nm: thermolysis of organometallic precursors, [36,38] laser pyrolysis, [9] and precipitation can lead to a particle size down to 1.8 nm, as shown by Bonnachi et al [12] Herein, we show that the iron precursor, Fe[NA C H T U N G T R E N N U N G (SiMe 3 ) 2 ] 2 , leads to very small maghemite particles directly at room temperature, and that whatever the synthetic conditions, the NPs possess the same size. We can therefore easily study the influence of the alkyl chain length of the amine surrounding the NPs on their magnetic properties.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, for the smallest systems, contradictory results have been obtained, and the magnetic properties of particles less than 3 nm in diameter still are an open question. [8,12,13] All these characteristics widely depend on the synthetic method.…”

Section: Introductionmentioning

confidence: 99%

“…[10,12,45] The values of the M S range from 11 to 23.6 emu g À1 starting from sample 6 to sample 1. As a general tendency, one can observe that the samples prepared in toluene and in the presence of a ligand possessing a shorter alkyl chain (OA) display the higher M S values, thus leading to the following evolution:…”

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confidence: 99%

“…Finally, an estimate of the effective anisotropy gives a value of 1.6 10 6 erg cm À3 for the sample synthesized in THF and stabilized by HDA (i.e., sample 6), in agreement with values reported in the literature for small maghemite NPs. [12,13,45,47] To go further into the analysis of the magnetic properties of these systems and especially to characterize the role of the magnetic interactions, we investigated the dynamical magnetic properties by means of alternating current susceptibility (c ac ; see Supporting Information, Figure S2) for frequencies in the range of 0.01 to 10 3 Hz and using Mçssbauer measurements. In the case of Mçssbauer spectroscopy, the blocking temperature corresponds to the temperature at which the ferrimagnetic contribution is half of the low-temperature signal.…”

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confidence: 99%

“…In some studies, a magnetic disordered state is observed with a spin-glass behavior. [9,12,13,25] For that purpose, we measured the ZFC and FC magnetizations between 2 and 300 K under a magnetic field of 5 T, as well as the hysteresis loops after ZFC and FC under 5 T. Figure 7 displays these measurements for sample 1. A small deviation between the ZFC and FC curves is observed at low temperature, which corresponds to a small T B of 3-4 K. Also, a small exchange field of 180 Oe is evidenced after the FC process.…”

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confidence: 99%

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An Organometallic Approach for Very Small Maghemite Nanoparticles: Synthesis, Characterization, and Magnetic Properties

et al. 2008

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Maghemite (gamma-Fe(2)O(3)) nanoparticles stabilized by long-alkyl-chain amines are synthesized by using an organometallic approach. This method consists of the hydrolysis and oxidation of an organometallic precursor, Fe[N(SiMe(3))(2)](2), in the presence of amine ligands as stabilizing agent in an organic solvent, namely tetrahydrofuran or toluene. Whatever the experimental conditions, particles with a diameter of 2.8 nm are obtained. The use of high-resolution transmission electron microscopy and wide-angle X-ray scattering, together with Mössbauer spectroscopy and SQuId magnetometry, allows a complete characterization of these particles. Herein, we show that their structure is composed of a well-ordered core surrounded by a more disordered shell. The size of the latter varies from 0.65 to 0.50 nm depending on the experimental conditions and is of prime importance for the understanding of the magnetic properties. We demonstrate that the shorter the alkyl chain length of the amine 1) the better the crystallinity of the particle's core and 2) the stronger the interparticle interactions.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Organometallic Approach for Very Small Maghemite Nanoparticles: Synthesis, Characterization, and Magnetic Properties

et al. 2008

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Microfluidic Synthesis of Iron Oxide and Oxyhydroxide Nanoparticles

Abou‐Hassan¹,

Sandre²,

Cabuil³

2010

Microfluidic Devices in Nanotechnology

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Metal–Organic Frameworks from Edible Natural Products

et al. 2010

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Metal-organic frameworks (MOFs) represent [1] an extensive class of porous crystals in which organic struts link metalcontaining clusters. The success in controlling the functionality and structure of MOFs has led to numerous applications, [2] most notably gas adsorption, [3] storage of clean gas fuels, [4] catalysis, [5] separations, [6] and drug delivery. [7] However, the vast majority of MOFs described to date are composed of organic struts derived from non-renewable petrochemical feedstocks and transition metals. The challenge in preparing MOFs from natural products lies in the inherent asymmetry of the building units, which are not amenable to crystallization in the form of highly porous frameworks. Herein, we report a strategy to overcome this problem using g-cyclodextrin (g-CD), a symmetrical cyclic oligosaccharide that is mass-produced enzymatically from starch [8] and comprised of eight asymmetric a-1,4-linked dglucopyranosyl residues. These g-CD building units are then linked by potassium ions, in aqueous media at ambient temperature and pressure, to form a body-centered cubic structure, termed CD-MOF-1, which has the empirical formula [(C 48 H 80 O 40 )(KOH) 2 ] n . CD-MOFs can be prepared entirely from edible ingredients: combining food-grade g-CD with salt substitute (KCl) or potassium benzoate (food additive E212) in bottled water and Everclear grain spirit (EtOH) yields porous frameworks which constitute edible MOFs.While there have been a few reports of MOFs assembled from amino acids, [9] nucleobases, [7a, 10] peptides, [11] magnesium formates, [12] and metal glutarates, [13] examples of these materials are not common despite the rapidly growing desire to fabricate MOFs from naturally available building blocks. We suspect that the key to our success in assembling CD-MOFs lies in the symmetric arrangement (C 8 ) within the g-CD torus of eight asymmetric (C 1 ) a-1,4-linked d-glucopyranosyl residues and the ready availability of g-CD as a chiral molecular building block (Figure 1). CD-MOF-1 was prepared by combining 1.0 equiv of g-CD with 8.0 equiv of KOH in aqueous solution, followed by vapor diffusion of MeOH into the solution during 2-7 days, resulting in colorless, cubic, single crystals, suitable for X-ray crystallography, in approximately 70 % yield. Other CD-MOFs were readily obtained using salts of Na + , Rb + , and Cs + , giving rise to an extensive new family of porous materials. A complete list of metal salts employed to form CD-MOFs and the full synthesis of CDMOFs are provided in Section S2 of the Supporting Information.The X-ray crystal structure of CD-MOF-1 [14] reveals that eight-coordinate K + ions not only assist in the assembly of (g-CD) 6 cubes (Figure 2 a,b), wherein six g-CD units occupy the faces of a cube, but they also serve to link these cubes together in a three-dimensional array which extends throughout the crystal (Figure 2 c). The (g-CD) 6 repeating motifs adopt a body-centered cubic packing arrangement wherein each symmetrically equivalent K + ion links two co...

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Nanosized Iron Oxide Particles Entrapped in Pseudo-Single Crystals of γ-Cyclodextrin

Cited by 57 publications

References 29 publications

An Organometallic Approach for Very Small Maghemite Nanoparticles: Synthesis, Characterization, and Magnetic Properties

An Organometallic Approach for Very Small Maghemite Nanoparticles: Synthesis, Characterization, and Magnetic Properties

Microfluidic Synthesis of Iron Oxide and Oxyhydroxide Nanoparticles

Metal–Organic Frameworks from Edible Natural Products

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