Classification and application of metal-based nanoantioxidants in medicine and healthcare

• Nguyen Nhat Nam,
• Nguyen Khoi Song Tran,
• Tan Tai Nguyen,
• Nguyen Ngoc Trai,
• Nguyen Phuong Thuy,
• Hoang Dang Khoa Do,
• Nhu Hoa Thi Tran and
• Kieu The Loan Trinh

Beilstein J. Nanotechnol. 2024, 15, 396–415, doi:10.3762/bjnano.15.36

• -line ferrihydrite, 2-line ferrihydrite, goethite, akageneite, feroxyhyte, hematite, magnetite, maghemite, schwertmannite, and lepidocrocite were compared regarding CAT activity [34]. The highest CAT activity was shown by 2-line ferrihydrite, followed by 6-line ferrihydrite and feroxyhyte. Iron-based

• ]. Similarly, gallic acid was covalently grafted on magnetite with an average size of 5 and 8 nm. The functionalization of ultrasmall magnetite with gallic acid increased free radical scavenging two- to fourfold compared to free magnetite [60]. Centurion et al. investigated the assembly of natural polyphenolic

Vinorelbine-loaded multifunctional magnetic nanoparticles as anticancer drug delivery systems: synthesis, characterization, and in vitro release study

• Zeynep Özcan and
• Afife Binnaz Hazar Yoruç

Beilstein J. Nanotechnol. 2024, 15, 256–269, doi:10.3762/bjnano.15.24

• ]. The crystal structure of Fe3O4 nanoparticles can be tailored to allow for precise control, and these nanostructures find utility in various production processes. Magnetite nanoparticles exhibit superparamagnetic behavior due to the negligible energy barrier in the hysteresis of the particles

• average size of 18 nm. The Fe3O4 NPs consist of 99.9% magnetite and have a cubic reverse spinel structure. Magnetite exhibits a spinel crystal structure resulting in a face-centered cubic arrangement in which oxygen atoms are positioned opposite the other constituent atoms. The Fe3O4 NP (311) reflection

• °, 56.08°, 62.7°, and 73.92°. These peaks can be assigned to the corresponding crystallographic planes of magnetite Fe3O4: (220), (311), (400), (422), (511), (440), and (533), respectively. Fe3O4 NPs exhibit a peak consistent with the data obtained for the reference ICDD no. 19-629 [43]. The FTIR spectra

Ferromagnetic resonance spectra of linear magnetosome chains

• Elizaveta M. Gubanova and
• Nikolai A. Usov

Beilstein J. Nanotechnol. 2024, 15, 157–167, doi:10.3762/bjnano.15.15

• that of random clusters of interacting spherical magnetite nanoparticles. The shape of FMR spectra of both assemblies is shown to differ appreciably even at sufficiently large values of filling density of random clusters. Keywords: chains of magnetosomes; ferromagnetic resonance spectra; magnetite

• nanoparticles; numerical simulation; Introduction Magnetotactic bacteria are living organisms that grow within themselves magnetite nanoparticles called magnetosomes [1][2][3][4]. In contrast to chemically synthesized magnetite nanoparticles [5][6], magnetosomes have a perfect crystal structure, a narrow size

• distribution, and a high saturation magnetization close to that of bulk magnetite. In particular, magnetotactic bacteria M. gryphiswaldense produce linear chains of quasi-spherical magnetite nanoparticles with sizes ranging from 30 to 50 nm [1][2][7][8][9]. However, there are also magnetotactic bacteria that

Green SPIONs as a novel highly selective treatment for leishmaniasis: an in vitro study against Leishmania amazonensis intracellular amastigotes

• Brunno R. F. Verçoza,
• Robson R. Bernardo,
• Luiz Augusto S. de Oliveira and
• Juliany C. F. Rodrigues

Beilstein J. Nanotechnol. 2023, 14, 893–903, doi:10.3762/bjnano.14.73

• using coconut water [9]. In this article, the ability of macrophages to uptake these SPIONs was evaluated, together with some physical and chemical characterizations. The synthesized green SPIONs are around 4 nm in diameter, are composed of pure nonstoichiometric magnetite, exhibit superparamagnetic

Two-step single-reactor synthesis of oleic acid- or undecylenic acid-stabilized magnetic nanoparticles by thermal decomposition

• Mykhailo Nahorniak,
• Pamela Pasetto,
• Jean-Marc Greneche,
• Volodymyr Samaryk,
• Sandy Auguste,
• Anthony Rousseau,
• Nataliya Nosova and
• Serhii Varvarenko

Beilstein J. Nanotechnol. 2023, 14, 11–22, doi:10.3762/bjnano.14.2

• of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic Institut des Molécules et Matériaux du Mans (IMMM), UMR 6283 CNRS − Le Mans Université, Avenue Olivier Messiaen, 72085 Le Mans Cedex, France 10.3762/bjnano.14.2 Abstract Different iron oxides (i.e., magnetite, maghemite, goethite

• single reactor using Fe(III) acetylacetonate as the initial precursor for the synthesis of Fe(III) oleate or Fe(III) undecylate followed by their thermolysis in situ. We proposed a new approach, according to which the essential magnetite precursor (a complex salt of higher acids – Fe(III) alkanoates) is

• particle mass. The result is a significantly different resistance to oxidation of the nanoparticle inorganic cores. The core of the particles synthesized using oleic acid is composed of more than 90% of maghemite. When undecylenic acid is used for the synthesis, the core is composed of 75% of magnetite

Non-stoichiometric magnetite as catalyst for the photocatalytic degradation of phenol and 2,6-dibromo-4-methylphenol – a new approach in water treatment

• Joanna Kisała,
• Anna Tomaszewska and
• Przemysław Kolek

Beilstein J. Nanotechnol. 2022, 13, 1531–1540, doi:10.3762/bjnano.13.126

• the organic compounds are discussed, as well as their influence on the degradation reaction rates. The degradation efficiency in photocatalytic processes was higher for DBMP (98%) than for phenol (approximately 50%). This proves the high efficiency of magnetite in the photocatalytic degradation of

• halogenated aromatic pollutants. The particularly high degradation efficiency regarding halogen-containing DBMP molecules and the yield of bromide ions indicate that DBMP degradation follows a mixed reduction–oxidation mechanism. DBMP molecules interact with the magnetite surface, enabling them to react with

• the available electrons, and, as a result, bromide ions can be released. The results confirm that magnetite is an effective photocatalyst in the degradation of halogenated aromatic pollutants. Keywords: magnetite; ozonolysis; persistent organic pollutants; photocatalysis; water treatment

A new method for obtaining the magnetic shape anisotropy directly from electron tomography images

• Cristian Radu,
• Ioana D. Vlaicu and
• Andrei C. Kuncser

Beilstein J. Nanotechnol. 2022, 13, 590–598, doi:10.3762/bjnano.13.51

• developed in order to increase the reliability of the correlations between morphology and magnetism. Using the Magn3t software, the magnetic shape anisotropy magnitude and direction of magnetite nanoparticles has been extracted for the first time directly from transmission electron tomography. Keywords

• : electron tomography; magnetite; Python; shape anisotropy; Introduction For any nanoparticle (NP) system, among the most important pieces of physical information for scientists is information related to the morphology (size, shape, and organization) of its constituents. In nanoscale systems, this

• -house designed software for image analysis (Magn3t) together with a brief description of a newly designed image filtering utility. Further, a validity check of the software on fully resolved (simulated) input data is shown. The efficiency of the software is finally shown on a real-life, magnetite

Photothermal ablation of murine melanomas by Fe₃O₄ nanoparticle clusters

• Xue Wang,
• Lili Xuan and
• Ying Pan

Beilstein J. Nanotechnol. 2022, 13, 255–264, doi:10.3762/bjnano.13.20

• needed to elicit sufficient hyperthermia by NIR irradiation, lingering magnetite may impose potential systemic toxicity. Thus, Fe3O4 single nanoparticles must be modified to reduce the dosage while keeping their therapeutic efficacy. In our earlier report, we synthesized Fe3O4 nanoparticle-containing

Theranostic potential of self-luminescent branched polyethyleneimine-coated superparamagnetic iron oxide nanoparticles

• Rouhollah Khodadust,
• Ozlem Unal and
• Havva Yagci Acar

Beilstein J. Nanotechnol. 2022, 13, 82–95, doi:10.3762/bjnano.13.6

• sensitivity the results obtained from TEM are usually more reliable [52]. The XRD pattern of SPION@bPEI synthesized in situ indicates a crystalline magnetite structure composed of both magnetite (Fe3O4) and maghemite (Fe2O3), including nanoparticles (Figure 1c). Considering only XRD patterns it would be

• difficult to distinguish the percentage of magnetite and maghemite in magnetic nanoparticles. However, electron paramagnetic resonance (EPR) spectroscopy analysis can be applied to overcome this problem. According to EPR spectroscopy results, SPION@bPEI nanoparticles synthesized in situ were composed of 23

• % magnetite and 77% of maghemite SPIONs [35]. Here, the cytotoxicity of SPION@bPEI, its potential for therapeutic gene delivery, and label-free optical imaging were investigated. For this purpose, PIC which is a synthetic dsRNA was electrostatically loaded into SPION@bPEI at different N/P ratios (1.4/1, 2.8/1

Heating ability of elongated magnetic nanoparticles

• Elizaveta M. Gubanova,
• Nikolai A. Usov and
• Vladimir A. Oleinikov

Beilstein J. Nanotechnol. 2021, 12, 1404–1412, doi:10.3762/bjnano.12.104

• .12.104 Abstract Low-frequency hysteresis loops and specific absorption rate (SAR) of various assemblies of elongated spheroidal magnetite nanoparticles have been calculated for a range of particle semiaxis ratios a/b = 1.0–3.0. The SAR of a dilute randomly oriented assembly of magnetite nanoparticles in

• -dipole interaction on the SAR of a dilute assembly of oriented clusters of elongated magnetite nanoparticles has also been investigated depending on the volume fraction of nanoparticles in a cluster. It has been found that the SAR of the assembly of oriented clusters decreases by approximately an order

• perfect crystal structure and narrow size distribution, which makes them potential agents for magnetic hyperthermia [27][42]. In this work, by using the stochastic Landau–Lifshitz equation [43][44][45][46], we calculate low-frequency hysteresis loops and SAR of assemblies of elongated spheroidal magnetite

Biocompatibility and cytotoxicity in vitro of surface-functionalized drug-loaded spinel ferrite nanoparticles

• Sadaf Mushtaq,
• Khuram Shahzad,
• Tariq Saeed,
• Anwar Ul-Hamid,
• Bilal Haider Abbasi,
• Nafees Ahmad,
• Waqas Khalid,
• Muhammad Atif,
• Zulqurnain Ali and
• Rashda Abbasi

Beilstein J. Nanotechnol. 2021, 12, 1339–1364, doi:10.3762/bjnano.12.99

• -assisted control of the behavior of MNPs makes them suitable candidates for targeted drug delivery, hyperthermia, biosensors, magnetic resonance imaging (MRI), and magnetic separation [9][10]. Magnetite (Fe3O4) nanoparticles (NPs), belonging to the spinel ferrite class, are the most extensively studied

• , magnetite NPs have some serious limitations, such as chemical reactivity, rapid oxidation, particle agglomeration, and high surface energy which may affect their biocompatibility and performance [11]. Moreover, they have low magnetization at a smaller size and the presence of iron has been associated with

A review of defect engineering, ion implantation, and nanofabrication using the helium ion microscope

• Frances I. Allen

Beilstein J. Nanotechnol. 2021, 12, 633–664, doi:10.3762/bjnano.12.52

• ], tungsten [83][84][85], an Fe–Zr alloy [86], a Y2O3/Fe bilayer [87], and nanocluster films of magnetite and core–shell iron–magnetite nanoparticles [88]. In these studies, various implantation effects have been investigated, including the tendency for grain boundaries and interfaces to act as sinks for

Differences in surface chemistry of iron oxide nanoparticles result in different routes of internalization

• Barbora Svitkova,
• Vlasta Zavisova,
• Veronika Nemethova,
• Martina Koneracka,
• Miroslava Kretova,
• Filip Razga,
• Monika Ursinyova and
• Alena Gabelova

Beilstein J. Nanotechnol. 2021, 12, 270–281, doi:10.3762/bjnano.12.22

• , determines the toxicity of NPs, and affects geometry and size of NPs, which play a crucial role in cellular uptake [38][39]. Despite nearly identical magnetite core size, hydrodynamic size, and zeta potential of the MNPs in the stock solution, the hydrodynamic size of PEG-SO-MNPs in culture medium was almost

• of new nanotechnology-based pharmaceuticals and their targeting to specific intracellular locations. Experimental Magnetic iron oxide nanoparticles (MNPs) Synthesis, coating, and physicochemical characteristics of the spherical magnetic iron oxide nanoparticles with magnetite (Fe3O4) core and

• different hydrophilic shells have been published before [37]. Two types of MNPs were used in this study: BSA-SO-MNPs (weight ratio of BSA/magnetite = 2) and PEG-SO-MNPs (weight ratio of PEG/magnetite = 0.25). Additionally, RITC-BSA-SO-MNPs (RITC/BSA, ratio 4:1) were used in some experiments. The basic

Antimicrobial metal-based nanoparticles: a review on their synthesis, types and antimicrobial action

• Matías Guerrero Correa,
• Fernanda B. Martínez,
• Cristian Patiño Vidal,
• Camilo Streitt,
• Juan Escrig and
• Carol Lopez de Dicastillo

Beilstein J. Nanotechnol. 2020, 11, 1450–1469, doi:10.3762/bjnano.11.129

• modification, intrinsic properties and the type of targeted microorganism [18]. A special category of metallic NPs is superparamagnetic iron-oxide nanoparticles (SPIONs) (e.g., magnetite (Fe3O4) and maghemite (γ-Fe2O3) NPs) whose antimicrobial activity increases upon the application of an external magnetic

• most known and studied SPIONs. Magnetite (Fe3O4) and maghemite (γ-Fe2O3) are two crystalline phases of iron oxide that present superparamagnetic properties at the nanoscale (<20 nm). This superparamagnetism is generated due to the reduced size of these nanoparticles which allow for a higher surface-to

Transient coating of γ-Fe₂O₃ nanoparticles with glutamate for its delivery to and removal from brain nerve terminals

• Konstantin Paliienko,
• Artem Pastukhov,
• Michal Babič,
• Daniel Horák,
• Olga Vasylchenko and
• Tatiana Borisova

Beilstein J. Nanotechnol. 2020, 11, 1381–1393, doi:10.3762/bjnano.11.122

• moderate stirring. The forming black suspension was left to maturate for 45 min still under stirring and nitrogen flushing. The black precipitate of magnetite (Fe3O4) was then repeatedly washed with Milli-Q water with the help of magnetic separation (approx. 10×) until spontaneous deflocculation was

• achieved. In the next step, the magnetite colloid was stabilized with 0.1 M sodium citrate solution under sonication. The formation of maghemite was completed by oxidation of the magnetite colloid with 5% sodium hypochlorite solution and a subsequent sonication for 5 min. The final washing of the maghemite

Magnetic-field-assisted synthesis of anisotropic iron oxide particles: Effect of pH

• Andrey V. Shibaev,
• Petr V. Shvets,
• Darya E. Kessel,
• Roman A. Kamyshinsky,
• Anton S. Orekhov,
• Sergey S. Abramchuk,
• Alexei R. Khokhlov and
• Olga E. Philippova

Beilstein J. Nanotechnol. 2020, 11, 1230–1241, doi:10.3762/bjnano.11.107

• University, Albert-Einstein-Allee 11, 89069 Ulm, Germany 10.3762/bjnano.11.107 Abstract The synthesis of magnetite (Fe3O4) nanorods using reverse co-precipitation of Fe3+ and Fe2+ ions in the presence of a static magnetic field is reported in this work. The phase composition and crystal structure of the

• the dipole–dipole interaction between their building blocks (small hexagonal faceted magnetite nanocrystals), which are formed during the first step of the reaction. The study suggests a facile, green and controllable method for synthesizing anisotropic magnetic nanoparticles in the absence of

• stabilizers, which is important for further modification of their surfaces and/or incorporation of the nanoparticles into different media. Keywords: anisotropic nanoparticles; magnetic nanoparticles; magnetite; nanorods; transmission electron microscopy; Introduction The research field dedicated to the

Influence of the magnetic nanoparticle coating on the magnetic relaxation time

• Mihaela Osaci and
• Matteo Cacciola

Beilstein J. Nanotechnol. 2020, 11, 1207–1216, doi:10.3762/bjnano.11.105

• generating heat. This heat increases the tumour cell temperature which leads to cell death [1][2][3][4]. Iron-oxide magnetic nanoparticles, in particular magnetite (Fe3O4) and maghemite (γ-Fe2O3), have been intensely studied in the context of magnetic hyperthermia applications. These nanoparticles can be

• oleic acid coating method used on pristine nanoparticles [14]. Homogeneous, polymer-coated spherical magnetite nanoparticles with superparamagnetic properties have been successfully synthesised. The polymer coating provides extra stability to the magnetic nanoparticles in aqueous media [15]. To increase

• , we considered the case in which a colloid is electrostatically stabilised. The system is composed of water-dispersed spherical magnetite nanoparticles whose sizes follow a lognormal distribution. The Hamaker constant for magnetite in water is given as a reference value [20]. The system parameter

Photothermally active nanoparticles as a promising tool for eliminating bacteria and biofilms

• Mykola Borzenkov,
• Piersandro Pallavicini,
• Angelo Taglietti,
• Laura D’Alfonso,
• Maddalena Collini and
• Giuseppe Chirico

Beilstein J. Nanotechnol. 2020, 11, 1134–1146, doi:10.3762/bjnano.11.98

• irradiated gold nanocrosses attached to the bacteria was effective in eliminating and preventing bacterial regrowth. By combining the magnetic and optical properties of Fe3O4 and gold nanoparticles, respectively, multifunctional nanohybrids based on Fe3O4@Au (i.e., magnetite nanoparticles decorated with gold

Applications of superparamagnetic iron oxide nanoparticles in drug and therapeutic delivery, and biotechnological advancements

• Maria Suciu,
• Corina M. Ionescu,
• Alexandra Ciorita,
• Septimiu C. Tripon,
• Dragos Nica,
• Hani Al-Salami and
• Lucian Barbu-Tudoran

Beilstein J. Nanotechnol. 2020, 11, 1092–1109, doi:10.3762/bjnano.11.94

• of iron oxides in the form of magnetite (Fe3O4) or maghemite (Fe2O3) and are easy to produce through a few well-documented synthesis methods yielding different forms and structures (e.g., round, cubic, hexagonal, clusters, core–shell with gold, silica, polymers, or surfactants). A lot of research is

• many species including humans. There are reports of natural magnetite and ferritin formation in the brain and in tumors [50]. When degraded in the body (but only up to certain concentrations/doses), SPIONs are turned into nontoxic iron ions, and are stored in the liver [38]. If the concentration is too

• magnetite (Fe3O4), maghemite (γ-Fe2O3) or hematite (α-Fe2O3) [60]. There are various geometric forms of SPIONs, which depend on the synthesis. The most extensively studied form are spherical SPIONs, followed by cubic, hexagonal, rod-like, octagonal, nanoworm, and octopod (star-shaped) SPIONs [61][62]. Non

Key for crossing the BBB with nanoparticles: the rational design

• Sonia M. Lombardo,
• Marc Schneider,
• Akif E. Türeli and
• Nazende Günday Türeli

Beilstein J. Nanotechnol. 2020, 11, 866–883, doi:10.3762/bjnano.11.72

• ) are based on magnetite (Fe3O4) or maghemite (γ-Fe2O3) molecules encapsulated in polysaccharides, synthetic polymers or monomer coatings and have a size range from 1 to 100 nm [21][182]. SPIONs possess interesting magnetic properties and some formulations have already been approved as MRI contrast

Multilayer capsules made of weak polyelectrolytes: a review on the preparation, functionalization and applications in drug delivery

• Varsha Sharma and
• Anandhakumar Sundaramurthy

Beilstein J. Nanotechnol. 2020, 11, 508–532, doi:10.3762/bjnano.11.41

• changing the integrity or permeability. Magnetic NPs have shown greater cytotoxicity in comparison with microcapsules containing an equivalent amount of magnetite [79]. The first and foremost way of incorporating NPs into the shell is either by the adsorption of NPs over the sacrificial template or using

Use of data processing for rapid detection of the prostate-specific antigen biomarker using immunomagnetic sandwich-type sensors

• Camila A. Proença,
• Tayane A. Freitas,
• Thaísa A. Baldo,
• Elsa M. Materón,
• Flávio M. Shimizu,
• Gabriella R. Ferreira,
• Frederico L. F. Soares,
• Ronaldo C. Faria and
• Osvaldo N. Oliveira Jr.

Beilstein J. Nanotechnol. 2019, 10, 2171–2181, doi:10.3762/bjnano.10.210

• -linked immunosorbent assay. The approaches for immunoassays and data processing are generic, and therefore the strategies described here may provide a simple platform for clinical diagnosis of cancers and other types of diseases. Keywords: cancer biomarkers; magnetite nanoparticles; microfluidic devices

• ], including magnetic nanoparticles (MNPs) that can be exploited for their catalytic properties [10] and magnetic separation in pre-concentrating the analyte [11][12][13][14][15][16]. The most common magnetic nanoparticles used for this purpose are magnetite (Fe3O4) nanoparticles, which have a stronger

Magnetic properties of biofunctionalized iron oxide nanoparticles as magnetic resonance imaging contrast agents

• Natalia E. Gervits,
• Andrey A. Gippius,
• Alexey V. Tkachev,
• Evgeniy I. Demikhov,
• Sergey S. Starchikov,
• Igor S. Lyubutin,
• Alexander L. Vasiliev,
• Vladimir P. Chekhonin,
• Maxim A. Abakumov,
• Alevtina S. Semkina and
• Alexander G. Mazhuga

Beilstein J. Nanotechnol. 2019, 10, 1964–1972, doi:10.3762/bjnano.10.193

• nanoparticles located inside and outside of each capsule [11] and integration of the nanoparticles in the matrix of HSA threads, as will be discussed in this paper. The problem of distinguishing between magnetite Fe3O4 and maghemite γ-Fe2O3, both of which usually appear as synthesis products of iron oxide

• of the structure due to the presence of both magnetite Fe3O4 and maghemite γ-Fe2O3. Another method to distinguish between Fe2+ and Fe3+ and their positions in the crystal structure is Mössbauer spectroscopy. However, the use of ionizing radiation and radioactive sources in this method limits the

• possibility of its transfer to production. Raman spectroscopy can also be used to discriminate nanoscale magnetite and maghemite. However, this method gives only qualitative information about the iron oxide structure and does not allow the number of Fe2+ and Fe3+ atoms or their positions to be determined

The effect of magneto-crystalline anisotropy on the properties of hard and soft magnetic ferrite nanoparticles

• Hajar Jalili,
• Bagher Aslibeiki,
• Ali Ghotbi Varzaneh and
• Volodymyr A. Chernenko

Beilstein J. Nanotechnol. 2019, 10, 1348–1359, doi:10.3762/bjnano.10.133

• substituting iron ions in the magnetite structure. This indicates an increase of the interplane distances (d) in the spinel structure. Similar results have been reported for NixCo1−xFe2O4 NPs by Caetano and co-workers [15]. According to Bragg’s law, λ = 2d·sin θ, (λ is the wavelength of X-ray wavelength, here

• , tend to occupy both the B-sites and the smaller A-sites (see Figure 6). This mixed occupancy in cobalt-substituted magnetite nanoparticles has been confirmed by Mössbauer spectroscopy [30]. Therefore, it is expected that when cobalt ions substitute iron ions at the A-sites, an increasing Me–O bond

On the relaxation time of interacting superparamagnetic nanoparticles and implications for magnetic fluid hyperthermia

• Andrei Kuncser,
• Nicusor Iacob and
• Victor E. Kuncser

Beilstein J. Nanotechnol. 2019, 10, 1280–1289, doi:10.3762/bjnano.10.127

• -free nanoparticles, the Brownian relaxation mechanism becomes dominant over the Néel mechanism only for nanoparticles larger than a critical radius (e.g., 8 nm in the case of magnetite nanoparticles) [21]. In such conditions, the heat transfer mechanism might also be completed by a hysteretic loss (the

• magnetite nanoparticle based ferrofluids of different volume fractions were independently derived by alternative techniques [26][33]. Detailed experimental and methodological aspects involving a very diluted ferrofluid as reference are described in [26]. The adiabatic-like curve obtained in the case of a

• concentrated ferrofluid (φ = 0.094) consisting of quasi-ellipsoidal magnetite nanoparticles of average magnetic volume of 4.3 × 10−25 m3 dispersed in transformer oil, with a spontaneous magnetization Ms = 4.5 × 105 A m−2, as determined by DC low temperature magnetometry and an effective anisotropy energy