Free and partially encapsulated manganese ferrite nanoparticles in multiwall carbon nanotubes

• Saja Al-Khabouri,
• Salim Al-Harthi,
• Toru Maekawa,
• Mohamed E. Elzain,
• Ashraf Al-Hinai,
• Ahmed D. Al-Rawas,
• Abbsher M. Gismelseed,
• Ali A. Yousif and
• Myo Tay Zar Myint

Beilstein J. Nanotechnol. 2020, 11, 1891–1904, doi:10.3762/bjnano.11.170

• free MnFe2O4 nanoparticles, two different subspectra associated with tetrahedral (A) and octahedral (B) sublattices, with close but different hyperfine fields, were used in addition to a superparamagnetic doublet (Figure 1f). Isomer shift values reflect the presence of high-spin Fe3+ ions [14], whereas

• on a relatively small superparamagnetic doublet due to the presence of very small crystallites [20]. The values of hyperfine fields are smaller than those obtained for bulk MnFe2O4 [21]. The reduction in the hyperfine field values follows the change in degree of inversion of the nanoparticles, in

• and superparamagnetic behavior (Figure 3a). The saturation magnetization at room temperature, with an observed value of 52 emu/g, is lower than the reported bulk value of 80 emu/g [20]. This saturation magnetization value is reported for particles with 11 nm in size [27], which is approximately the

Design of V-shaped cantilevers for enhanced multifrequency AFM measurements

• Mehrnoosh Damircheli and
• Babak Eslami

Beilstein J. Nanotechnol. 2020, 11, 1525–1541, doi:10.3762/bjnano.11.135

• systems (MEMS), superparamagnetic particle embedded microprobe (SPEM) sensors, or lab-on chips devices [5][6][7][8]. Microcantilevers are also an important component of atomic force microscopes (AFM). Due to their importance in AFM, there have been many studies on modeling the cantilevers to represent the

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

• agents. Although the most studied nanoparticles with antimicrobial properties are metallic or metal-oxide nanoparticles, other types of nanoparticles, such as superparamagnetic iron-oxide nanoparticles and silica-releasing systems also exhibit antimicrobial properties. Finally, since the quantification

• 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

• antimicrobial studies revealed good antimicrobial activity against E. coli, S. flexneri, and S. aureus cells [123]. Superparamagnetic iron-oxide nanoparticles Superparamagnetic iron oxide nanoparticles are a special class of metal-oxide NPs with magnetic properties and excellent biocompatibility. Their shape

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

• neurological disorders. Excessive ambient glutamate concentration is a characteristic feature of, among others, stroke, brain trauma, epilepsy, and seizure development. Superparamagnetic γ-Fe2O3 nanoparticles are very promising in targeted drug delivery, cancer therapy, diagnostics, and hyperthermia treatment

• due to their magnetism and chemical stability [9][10][11][12][13]. Among a variety of other nanoparticles, superparamagnetic iron oxide nanoparticles are used for magnetic resonance imaging in cancer theranostics and magnetic hyperthermia [9][10][11][14]. Controlled magnetic fields can lead to induced

• their instability in biological media where the nanoparticles may lose their biological coating [19]. The organic/inorganic agents form a shell (1–5 nm thick) around superparamagnetic iron oxide nanoparticles interacting with their surface functional groups [14]. Sousa et al. studied the chemisorption

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

• Abstract Colloidal systems consisting of monodomain superparamagnetic nanoparticles have been used in biomedical applications, such as the hyperthermia treatment for cancer. In this type of colloid, called a nanofluid, the nanoparticles tend to agglomeration. It has been shown experimentally that the

• relaxation time; nanoparticle coating; numerical simulation; stochastic Langevin dynamics method; superparamagnetic nanoparticles; Introduction One of the most important biomedical applications of colloidal magnetic nanoparticle systems is magnetic hyperthermia applied as an alternative for cancer treatment

• that influence the characteristics of the final material [7]. Uncoated superparamagnetic nanoparticles are difficult to synthesise since they are not stable in colloidal suspensions. Therefore, it is challenging to use these nanoparticles in magnetic hyperthermia therapy [8]. By exposing these

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

• .11.94 Abstract Superparamagnetic iron oxide nanoparticles (SPIONs) have unique properties with regard to biological and medical applications. SPIONs have been used in clinical settings although their safety of use remains unclear due to the great differences in their structure and in intra- and inter

• therapeutic efficacy, and safety studies. Keywords: drug delivery; drug targeting; endocytosis; medical; nanoparticles; superparamagnetic iron oxide nanoparticles (SPIONs); toxicity; Introduction Nanoencapsulation technologies have been researched over the past several decades and have been widely

• magnetic resonance imaging (MRI) (for more on this topic consult [11][12][13][14]). Among the abovementioned nanoscience products, iron oxide nanoparticles, especially superparamagnetic iron oxide nanoparticles (SPIONs) hold a lot of promise in many domains, not only regarding biology [15]. SPIONs consist

Uniform Fe₃O₄/Gd₂O₃-DHCA nanocubes for dual-mode magnetic resonance imaging

• Miao Qin,
• Yueyou Peng,
• Mengjie Xu,
• Hui Yan,
• Yizhu Cheng,
• Xiumei Zhang,
• Di Huang,
• Weiyi Chen and
• Yanfeng Meng

Beilstein J. Nanotechnol. 2020, 11, 1000–1009, doi:10.3762/bjnano.11.84

• measurement system (PPMS) operating at 300 K and the Fe3O4 nanocubes were used as control. Figure 2j shows that both Fe3O4 and FGDA nanocubes were superparamagnetic and the magnetic saturation was reached at 0.2132 and 0.7612 emu·g−1, respectively. Even though both values were low (probably due to the small

Wet-spinning of magneto-responsive helical chitosan microfibers

• Dorothea Brüggemann,
• Johanna Michel,
• Naiana Suter,
• Matheus Grande de Aguiar and
• Michael Maas

Beilstein J. Nanotechnol. 2020, 11, 991–999, doi:10.3762/bjnano.11.83

• [39]. Since the magnetic particles used in this work were approximately 100 nm in diameter, the wet-spun chitosan fibers obtained were clearly ferromagnetic rather than superparamagnetic [40]. This observation was confirmed by the magnetic hysteresis curves which showed a maximum remanent

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

• nanoparticles (AuNPs); blood–brain barrier (BBB); drug delivery; liposomes; nanomedicine; polymeric nanoparticles; solid lipid nanoparticles; superparamagnetic iron oxide nanoparticles (SPIONs); Introduction Neurological disorders and brain diseases are real burdens for modern societies and healthcare systems

• (e.g., human serum albumin) [28], gold nanoparticles [29] and superparamagnetic iron oxide nanoparticles [30]. This review aims to summarize (i) the different pathways to cross the BBB, (ii) the strategies that can be employed to increase nanoparticle BBB permeation without disrupting the BBB, as well

• brain delivery. Interestingly, in a study by Peira et al., SLNs have been successfully loaded with superparamagnetic iron oxide and were able to cross the BBB [163]. Thus, SLNs could be potentially used as carriers for CNS MRI contrast agents. Nanostructured lipid carriers: Although most of the reported

Luminescent gold nanoclusters for bioimaging applications

• Nonappa

Beilstein J. Nanotechnol. 2020, 11, 533–546, doi:10.3762/bjnano.11.42

• –nanocluster agglomerates as luminescent nanocarriers for imaging and combination therapy [89][90]. Core–shell nanoparticles consisting of oleic acid-capped superparamagnetic iron oxide nanoparticles (IONPs, d = 6.7 ± 1.2 nm) were used (Figure 5A). The IONPs were subsequently coated with a gold shell using the

• endocytosis. The superparamagnetic nature of the PML-MF allowed for the magnetic targeting of the nanocarriers. Further, the ability of BSA to encapsulate drug molecules was explored to load doxorubicin (DPML-MF) in the nanocarriers. The release kinetics of doxorubicin studied at pH 7.4 and 4.4 were found to

• potential for photothermal therapy. While PML-MF alone was not toxic to healthy HEK cell lines, the treatment with DPML-MF showed a similar antiproliferative effect on healthy cell lines as that of cancerous cells. Therefore, the selective killing of cancer cells was not achieved. The superparamagnetic

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

Dynamics of superparamagnetic nanoparticles in viscous liquids in rotating magnetic fields

• Nikolai A. Usov,
• Ruslan A. Rytov and
• Vasiliy A. Bautin

Beilstein J. Nanotechnol. 2019, 10, 2294–2303, doi:10.3762/bjnano.10.221

• director are distinguished depending on frequency and amplitude of the rotating magnetic field. The specific absorption rate of a dilute assembly of superparamagnetic nanoparticles in rotating magnetic field is calculated by solving the Landau–Lifshitz stochastic equation for the unit magnetization vector

• ]. Unfortunately, the specific absorption rate (SAR) measured in RMFs [41][43] for assemblies of particles distributed in a viscous liquid turned out to be very small, of the order of a few watts per gram of magnetic material. At the same time, the SAR of an assembly of superparamagnetic nanoparticles in AMF under

• geometric and magnetic parameters of the nanoparticles, as well as the amplitudes and frequencies at which the SAR of the superparamagnetic nanoparticle assembly in RMFs will be large enough to be used in magnetic hyperthermia. In this work, detailed numerical calculations of the SAR in RMFs for a dilute

Targeted therapeutic effect against the breast cancer cell line MCF-7 with a CuFe₂O₄/silica/cisplatin nanocomposite formulation

• B. Rabindran Jermy,
• Vijaya Ravinayagam,
• Widyan A. Alamoudi,
• Dana Almohazey,
• Hatim Dafalla,
• Lina Hussain Allehaibi,
• Abdulhadi Baykal,
• Muhammet S. Toprak and
• Thirunavukkarasu Somanathan

Beilstein J. Nanotechnol. 2019, 10, 2217–2228, doi:10.3762/bjnano.10.214

• (magnetic resonance imaging), tissue repair, and thermal ablation have been gaining considerable attention in recent years. In particular, the use of superparamagnetic iron oxide nanoparticles (SPIONs) is now advantageous as they are FDA-approved for clinical use [2]. Magnetic Fe3O4-based mesoporous silica

• inverse spinels occupying the A site, while Cu2+ prefers the B site. SQUID-vibrating sample magnetometry (VSM) analysis showed the formation of superparamagnetic behavior, while a temperature dependence study using field cooling and zero field cooling analysis (ZFC/FC) showed spin-glass-like surface

• presence of small-sized nanoclusters at the walls of hexagonal-shaped MCM-41 tends to form superparamagnetic interactions among Fe3+ species, while large nanoclusters contribute to ferromagnetic properties [17]. In our study, paramagnetic behavior with narrow hysteresis demonstrates the formation of small

Nitrogen-vacancy centers in diamond for nanoscale magnetic resonance imaging applications

• Alberto Boretti,
• Lorenzo Rosa,
• Jonathan Blackledge and
• Stefania Castelletto

Beilstein J. Nanotechnol. 2019, 10, 2128–2151, doi:10.3762/bjnano.10.207

• microscale magnetic field gradients produced in the cells and tissues. Macrophage was labeled with 200 nm superparamagnetic IONPs and was internalized. Three-dimensional magnetic field images of the cells were achieved by using NV vector magnetometry. ODMR signals of the four NV orientations in bulk diamond

• shown that in the NV-SPION system, the NV spin relaxation time is reduced, while the T2 coherence dephasing time stays the same. By configuring the applied AC magnetic fields, the NV electron spin Rabi oscillation rate decreased, due to a resultant superparamagnetic nanoparticle magnetization at the NV

Microbubbles decorated with dendronized magnetic nanoparticles for biomedical imaging: effective stabilization via fluorous interactions

• Da Shi,
• Justine Wallyn,
• Dinh-Vu Nguyen,
• Francis Perton,
• Delphine Felder-Flesch,
• Sylvie Bégin-Colin,
• Mounir Maaloum and
• Marie Pierre Krafft

Beilstein J. Nanotechnol. 2019, 10, 2103–2115, doi:10.3762/bjnano.10.205

• MBs that incorporate IONPs are often made of polymers. For example, ultrasmall superparamagnetic iron oxide nanoparticles were embedded in the wall of poly(butyl cyanoacrylate)-based MBs, allowing the blood‒brain barrier penetration to be monitored [23]. Soft-shell colloids called lipospheres have

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

• of coating on the particle size and their magnetic properties is also raised. It has been shown that different types of coatings shift the magnetic blocking temperature [10][13][14]. In our present study, we observe a superparamagnetic transition of coated and uncoated samples in the temperature

• range from 10 to 300 K by means of Mössbauer spectroscopy, which allows one to estimate the ratio of the magnetic and superparamagnetic phases at different temperatures. Results and Discussion The XRD patterns of the nanoparticles are shown in Figure 1. All peaks can be indexed according to a cubic

• found that smaller (<11 nm in diameter) nanoparticles preferably adopt a maghemite phase. The Mössbauer spectra of uncoated and HSA-coated MNPs at higher temperatures are shown in Figure 8. A typical superparamagnetic behavior was observed in the spectra of both samples. However, the transition to the

Engineered superparamagnetic iron oxide nanoparticles (SPIONs) for dual-modality imaging of intracranial glioblastoma via EGFRvIII targeting

• Xianping Liu,
• Chengjuan Du,
• Haichun Li,
• Ting Jiang,
• Zimiao Luo,
• Zhiqing Pang,
• Daoying Geng and
• Jun Zhang

Beilstein J. Nanotechnol. 2019, 10, 1860–1872, doi:10.3762/bjnano.10.181

• Education, 826 Zhangheng Road, Shanghai 201203, China 10.3762/bjnano.10.181 Abstract In this work, a peptide-modified, biodegradable, nontoxic, brain-tumor-targeting nanoprobe based on superparamagnetic iron oxide nanoparticles (SPIONs) (which have been commonly used as T2-weighted magnetic resonance (MR

• imaging (MRI); molecular imaging; superparamagnetic iron oxide nanoparticles (SPIONs); nanomedicine; tumor resection; Introduction Tumor resection is one of the most promising clinical treatments of glioblastoma, which is commonly associated with high mortality and inevitable tumor recurrence. To achieve

• , gadolinium (Gd)-based agents (often Gd-diethylenetriaminepentaacetic acid (DTPA)) and superparamagnetic iron oxide nanoparticles (SPIONs) are the paramagnetic materials generally used as contrast agents to impact the relaxation time T1 or T2, thus generating bright or dark images via MR imaging. Gd-DTPA, as

Energy distribution in an ensemble of nanoparticles and its consequences

• Dieter Vollath

Beilstein J. Nanotechnol. 2019, 10, 1452–1457, doi:10.3762/bjnano.10.143

• scattered on a sheet of silicon oxide. Additionally, these particles were separated by an oleic acid coating of 2 nm. Woods et al. [5] determined the magnetic noise power as a function of temperature during the superparamagnetic transition. For this example, the experimental data obtained from 5 nm

• , it was also applied to calculate particle size distributions from experimental data of phase transformations. As examples, the superparamagnetic transition of cobalt particles and the transition of lead particles from normal conductance to superconductivity were applied. Within the precision of the

• of two normal distributions, taking care of the larger particles. The result of the latter approximation is displayed as green line. Size distribution of cobalt particles, determined from the transition to superparamagnetic state [5]. Two assumptions were made for the particle size distribution: (1

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

• superparamagnetic regime in the presence of interparticle dipolar interactions is considered. The direct implications of such interactions for magnetic fluid hyperthermia therapy through susceptibility loss mechanisms give rise to an indirect method for their study via specific absorption rate measurements

• nanoparticles. For noninteracting MNPs in the dynamic magnetic regime (superparamagnetic regime), it has been shown by Rosensweig in 2002 [21] that only a susceptibility loss mechanism has to be considered (P* ≈ χ’’ where χ’’ is the out of phase component of the magnetic susceptibility). Furthermore, earlier

• superparamagnetic nanoparticles on the specific absorption rate of ferrofluids, through susceptibility loss mechanisms, are discussed. Various models supporting the influence of interparticle interactions on the relaxation time are reviewed, leading to the conclusion that they are controversial, not versatile

Tailoring the magnetic properties of cobalt ferrite nanoparticles using the polyol process

• Malek Bibani,
• Romain Breitwieser,
• Alex Aubert,
• Vincent Loyau,
• Silvana Mercone,
• Souad Ammar and
• Fayna Mammeri

Beilstein J. Nanotechnol. 2019, 10, 1166–1176, doi:10.3762/bjnano.10.116

• while the sub-stoichiometric NPs (particularly for x ≈ 0.7) are expected to be less magnetostrictive but to present a higher magnetocrystalline anisotropy constant, as previously observed in bulk cobalt ferrites. To control the size of the NPs, in order to overcome the superparamagnetic limit, as well

• stoichiometric NPs of different sizes, between 5 and 7 nm, in diethylene glycol, starting from iron and cobalt acetates, and using a seed-mediated growth approach [23]. They obtained monodisperse and stable particles, superparamagnetic at room temperature (RT), with, once again, high saturation magnetization

• is that of ferrite particles in their single magnetic domain state. As it is summarized in Table 2, quite all the samples showed very high TB values (>300 K). The only superparamagnetic nanoparticles at room temperature are the stoichiometric particles synthesized in TriEG for 6 h (Co-1-TriEG-6). In

Photoactive nanoarchitectures based on clays incorporating TiO₂ and ZnO nanoparticles

• Eduardo Ruiz-Hitzky,
• Pilar Aranda,
• Marwa Akkari,
• Nithima Khaorapapong and
• Makoto Ogawa

Beilstein J. Nanotechnol. 2019, 10, 1140–1156, doi:10.3762/bjnano.10.114

• ][132]. The incorporation of various types of NPs using neat clay and applying a two-step synthesis has been reported. A recent example of this refers to the incorporation of ZnO nanoparticles to a Fe3O4-sepiolite nanoarchitecture previously prepared by in situ formation of superparamagnetic iron-oxide

Scavenging of reactive oxygen species by phenolic compound-modified maghemite nanoparticles

• Małgorzata Świętek,
• Yi-Chin Lu,
• Rafał Konefał,
• Liliana P. Ferreira,
• M. Margarida Cruz,
• Yunn-Hwa Ma and
• Daniel Horák

Beilstein J. Nanotechnol. 2019, 10, 1073–1088, doi:10.3762/bjnano.10.108

• analysis. Magnetic measurements indicated that the polymer coating does not affect the superparamagnetic character of the iron oxide core. However, magnetic saturation decreased with increasing thickness of the polymer coating. The antioxidant properties of the nanoparticles were analyzed using a 2,2

• conjugation via esterification or amidation, and free-radical grafting [16]. The aim of this work was to design and fabricate superparamagnetic iron oxide nanoparticles with antioxidant properties. Positively charged γ-Fe2O3 nanoparticles were synthesized through co-precipitation, and their surface was

• magnetism of nanoparticles is the particle size. γ-Fe2O3 nanoparticles with sizes below the single-domain critical diameter are superparamagnetic, whereas larger particles are ferrimagnetic [26][27]. Superparamagnetism is an important feature of magnetic nanoparticles intended for biomedical applications

Influence of dielectric layer thickness and roughness on topographic effects in magnetic force microscopy

• Alexander Krivcov,
• Jasmin Ehrler,
• Marc Fuhrmann,
• Tanja Junkers and
• Hildegard Möbius

Beilstein J. Nanotechnol. 2019, 10, 1056–1064, doi:10.3762/bjnano.10.106

• overlapped by additional forces acting on the tip such as electrostatic forces. In this work the possibility to reduce capacitive coupling effects between tip and substrate is discussed in relation to the thickness of a dielectric layer introduced in the system. Single superparamagnetic iron oxide

• coupling can be tuned and minimized for thick layers. Using the theory of capacitive coupling and the magnetic point dipole–dipole model we could theoretically explain and experimentally prove the phase signal for single superparamagnetic nanoparticles as a function of the layer thickness of the dielectric

• roughness of dielectric films with increasing film thickness. Keywords: capacitive coupling; electrostatic effects; magnetic force microscopy; nanoparticles; superparamagnetic iron oxide nanoparticle (SPION); Introduction MFM has become an important tool for studying magnetic properties of surface

Magnetic field-assisted assembly of iron oxide mesocrystals: a matter of nanoparticle shape and magnetic anisotropy

• Julian J. Brunner,
• Marina Krumova,
• Helmut Cölfen and
• Elena V. Sturm (née Rosseeva)

Beilstein J. Nanotechnol. 2019, 10, 894–900, doi:10.3762/bjnano.10.90

• Julian J. Brunner Marina Krumova Helmut Colfen Elena V. Sturm (nee Rosseeva) University of Konstanz, Konstanz, Germany 10.3762/bjnano.10.90 Abstract This letter describes the formation and detailed characterization of iron oxide mesocrystals produced by the directed assembly of superparamagnetic

• superparamagnetic nanoparticles and how a magnetic field can be used to design anisotropic mesocrystals with different structures. Keywords: directed assembly; magnetite; mesocrystal; nanoparticle; transmission electron microscopy; Findings In materials science, nanoparticles and their assemblies belong to the

• with sizes less than 30 nm become superparamagnetic [11][12][13]. Hence, assemblies consisting of superparamagnetic magnetite nanocrystals are still superparamagnetic although their sizes can be tens or hundreds of micrometres [14][15]. This can be useful to obtain increased magnetization while

Co-doped MnFe₂O₄ nanoparticles: magnetic anisotropy and interparticle interactions

• Bagher Aslibeiki,
• Parviz Kameli,
• Hadi Salamati,
• Giorgio Concas,
• Maria Salvador Fernandez,
• Alessandro Talone,
• Giuseppe Muscas and
• Davide Peddis

Beilstein J. Nanotechnol. 2019, 10, 856–865, doi:10.3762/bjnano.10.86

• , where they spontaneously reverse their direction in a superparamagnetic (SPM) regime, in analogy to atomic paramagnetism [10]. On the other hand, in concentrated ensembles of NPs, interparticle interactions can arise from long-range magnetostatic forces or local exchange coupling among particles [13][14

• confirmed the presence of magnetic interactions between nanoparticles as reported in the literature for similar systems [34][35][36]. For interacting superparamagnetic particles, the phenomenological Vogel–Fulcher law gives a better description, introducing the value T0 as the temperature at which a

• were investigated by 57Fe Mössbauer spectroscopy at room temperature to estimate the superparamagnetic fraction of the sample at a given temperature. Figure 4 shows the spectra with the fit of the total signal and the subcomponents due to the ferromagnetic ordered (six lines) and superparamagnetic non