We report the observation of non-metallic electrical conduction, resistive switching, and a negative temperature coefficient of resistance in nanostructured gold films above the electrical percolation and in strong-coupling regime, from... more
We report the observation of non-metallic electrical conduction, resistive switching, and a negative temperature coefficient of resistance in nanostructured gold films above the electrical percolation and in strong-coupling regime, from room down to cryogenic temperatures (24 K). Nanostructured continuous gold films are assembled by supersonic cluster beam deposition of Au aggregates formed in the gas phase. The structure of the cluster-assembled films is characterized by an extremely high density of randomly oriented crystalline nanodomains, separated by grain boundaries and with a large number of lattice defects. Our data indicates that space charge limited conduction and Coulomb blockade are at the origin of the anomalous electrical behavior. The high density of extended defects and grain boundaries causes the localization of conduction electrons over the entire investigated temperature range.
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Networks of nanoscale objects are the subject of increasing interest as resistive switching systems for the fabrication of neuromorphic computing architectures. Nanostructured films of bare gold clusters produced in gas phase with... more
Networks of nanoscale objects are the subject of increasing interest as resistive switching systems for the fabrication of neuromorphic computing architectures. Nanostructured films of bare gold clusters produced in gas phase with thickness well beyond the electrical percolation threshold, show a non-ohmic electrical behavior and resistive switching, resulting in groups of current spikes with irregular temporal organization. Here we report the systematic characterization of the temporal correlations between single spikes and spiking rate power spectrum of nanostructured Au two-terminal devices consisting of a cluster-assembled film deposited between two planar electrodes. By varying the nanostructured film thickness we fabricated two different classes of devices with high and low initial resistance respectively. We show that the switching dynamics can be described by a power law distribution in low resistance devices whereas a bi-exponential behavior is observed in the high resistan...
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Superparamagnetic magnetite nanoparticles are coated with a tunable number of free surface –SH, enabling them to decorate gold nanostars.
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Monolayers of gold nanostars with two NIR LSPRs can be irradiated on one, or the other or both LSPRs, obtaining additive photothermal response.
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This work focuses on the mechanical behaviour of nanoporous Au samples alternately exposed to ozone and carbon dioxide. Nanoporous Au was fabricated by freely corroding the Ag70Au30 parent alloys prepared by mechanical alloying in the... more
This work focuses on the mechanical behaviour of nanoporous Au samples alternately exposed to ozone and carbon dioxide. Nanoporous Au was fabricated by freely corroding the Ag70Au30 parent alloys prepared by mechanical alloying in the form of powder and subsequently compacted by cold pressing. Dealloying was performed in acidic solution, and conditions were suitably adjusted to obtain fine nanoporous Au structures with ligaments about 15 nm thick. Nanoporous Au samples with increasingly thicker ligaments, up to about 40 nm, were fabricated by annealing the pristine nanoporous Au structure for different time intervals at 473 K. For all of the samples, the cyclic variation of gaseous atmosphere results in a macroscopic strain variation due to the occurrence of surface oxidation and reduction processes. We show that the reiterated cyclic exposure to the different gases also induces the progressive hardening of nanoporous Au, which can be ascribed to irreversible strain contributions. F...
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SEM and SEM-EDS characterization Fig. S1 (A) shows four different low-magnification secondary electron (SE) SEM images of the external surface of a PSi_8%_A sample and the corresponding EDS elemental maps of Si (blue), O (red) and Er... more
SEM and SEM-EDS characterization Fig. S1 (A) shows four different low-magnification secondary electron (SE) SEM images of the external surface of a PSi_8%_A sample and the corresponding EDS elemental maps of Si (blue), O (red) and Er (green) being respectively reported below. The external surface of the PSi layer shows a quite homogenous morphology. As expected, a lower silicon amount is mapped in correspondence of the PSi semicircular layer if compared to the area out of it, where the silicon is still in its pristine, bulk form. Besides, again in correspondence of the semicircular PSi layer, the homogenous presence of both oxygen and erbium is revealed, the former being due to the silicon oxidation related to the fabrication of the PSi layer, the latter as a consequence of the ED. Fig. S1 (B) display a high magnification SE-SEM cross sectional image of Er-doped PSi layer: the measured thickness of the porous layer is about 1.3 µm, and in order to understand how the doping Erbium in...
Vascular oxidative stress is considered a worsening factor in the progression of Alzheimer’s disease (AD). Increased reactive oxygen species (ROS) levels promote the accumulation of amyloid-β peptide (Aβ), one of the main hallmarks of AD.... more
Vascular oxidative stress is considered a worsening factor in the progression of Alzheimer’s disease (AD). Increased reactive oxygen species (ROS) levels promote the accumulation of amyloid-β peptide (Aβ), one of the main hallmarks of AD. In turn, Aβ is a potent inducer of oxidative stress. In early stages of AD, the concomitant action of oxidative stress and Aβ on brain capillary endothelial cells was observed to compromise the blood–brain barrier functionality. In this context, antioxidant compounds might provide therapeutic benefits. To this aim, we investigated the antioxidant activity of cerium oxide nanoparticles (CNP) in human cerebral microvascular endothelial cells (hCMEC/D3) exposed to Aβ oligomers. Treatment with CNP (13.9 ± 0.7 nm in diameter) restored basal ROS levels in hCMEC/D3 cells, both after acute or prolonged exposure to Aβ. Moreover, we found that the extent of CNP uptake by hCMEC/D3 was +43% higher in the presence of Aβ. Scanning electron microscopy and western...
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Er clustering plays a major role in hindering sufficient optical gain in Er-doped Si materials. For porous Si, the long-standing failure to govern the clustering has been attributed to insufficient knowledge of the several, concomitant... more
Er clustering plays a major role in hindering sufficient optical gain in Er-doped Si materials. For porous Si, the long-standing failure to govern the clustering has been attributed to insufficient knowledge of the several, concomitant and complex processes occurring during the electrochemical Er-doping. We propose here an alternative road to solve the issue: instead of looking for an equilibrium between Er content and light emission using 1-2% Er, we propose to significantly increase the electrochemical doping level to reach the filling the porous silicon pores with luminescent Er-rich material. To better understand the intricate and superposing phenomena of this process, we exploit an original approach based on needle electron tomography, EXAFS and photoluminescence. Needle electron tomography surprisingly shows a heterogeneous distribution of Er content in the silicon thin pores that until now couldn't be revealed by the sole use of scanning electron microscopy compositional ...
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The structure of DNA was determined in 1953 by x-ray fiber diffraction. Several attempts have been made to obtain a direct image of DNA with alternative techniques. The direct image is intended to allow a quantitative evaluation of all... more
The structure of DNA was determined in 1953 by x-ray fiber diffraction. Several attempts have been made to obtain a direct image of DNA with alternative techniques. The direct image is intended to allow a quantitative evaluation of all relevant characteristic lengths present in a molecule. A direct image of DNA, which is different from diffraction in the reciprocal space, is difficult to obtain for two main reasons: the intrinsic very low contrast of the elements that form the molecule and the difficulty of preparing the sample while preserving its pristine shape and size. We show that through a preparation procedure compatible with the DNA physiological conditions, a direct image of a single suspended DNA molecule can be obtained. In the image, all relevant lengths of A-form DNA are measurable. A high-resolution transmission electron microscope that operates at 80 keV with an ultimate resolution of 1.5 Å was used for this experiment. Direct imaging of a single molecule can be used ...
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The physical and chemical properties shown by nanoporous metals, related to their unique structure, make them very promising for application in several fields. Recently, vapor-phase dealloying has been reported as a method for the... more
The physical and chemical properties shown by nanoporous metals, related to their unique structure, make them very promising for application in several fields. Recently, vapor-phase dealloying has been reported as a method for the preparation of several non-noble nanoporous metals, alternatively to dealloying in aqueous solutions. Using this approach, we have successfully fabricated nanoporous Al starting from an Al20Zn80 nanocomposite obtained by ball milling. The nanocomposite was annealed at 550 °C under high-vacuum conditions, and the difference in the vapor pressures allowed the selective removal of Zn by vapor-phase dealloying. The morphology of the resulting nanoporous material was analyzed by Scanning Electron Microscopy showing pores from few to thousands of nm; moreover, the nanoporous 3D structure was observed through Serial Block Face-Scanning Electron Microscopy. A specific surface area as high as 73 m2 g−1 was estimated by N2 physisorption measurements. In addition, a ...
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Energy Filtered Transmission Electron Microscopy (EFTEM) is an analytical tool that has been successfully and widely employed in the last two decades for obtaining fast elemental maps in TEM mode. Several studies and efforts have been... more
Energy Filtered Transmission Electron Microscopy (EFTEM) is an analytical tool that has been successfully and widely employed in the last two decades for obtaining fast elemental maps in TEM mode. Several studies and efforts have been addressed to investigate limitations and advantages of such technique, as well as to improve the spatial resolution of compositional maps. Usually, EFTEM maps undergo post-acquisition treatments by changing brightness and contrast levels, either via dedicated software or via human elaboration, in order to maximize their signal to noise ratio and render them as visible as possible. However, elemental maps forming a single set of EFTEM images are usually subjected to independent map-by-map image treatment. This post-acquisition step becomes crucial when analyzing materials that change composition over time as a consequence of an external stimulus, because the map-by-map approach doesn’t take into account how the chemical features of the imaged materials ...
The work explores the reactions between Cu2−xSe premade nanoparticles and a Pt(ii) precursor, and confirms the formation of ternary CuPtSe phases with flexible stoichiometry and photocatalytic activity towards the hydrogen evolution... more
The work explores the reactions between Cu2−xSe premade nanoparticles and a Pt(ii) precursor, and confirms the formation of ternary CuPtSe phases with flexible stoichiometry and photocatalytic activity towards the hydrogen evolution reaction.
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CuFe2O4 is an example of ferrites whose physico-chemical properties can vary greatly at the nanoscale. Here, sol-gel techniques are used to produce CuFe2O4-SiO2 nanocomposites where copper ferrite nanocrystals are grown within a porous... more
CuFe2O4 is an example of ferrites whose physico-chemical properties can vary greatly at the nanoscale. Here, sol-gel techniques are used to produce CuFe2O4-SiO2 nanocomposites where copper ferrite nanocrystals are grown within a porous dielectric silica matrix. Nanocomposites in the form of both xerogels and aerogels with variable loadings of copper ferrite (5 wt%, 10 wt% and 15 wt%) were synthesized. Transmission electron microscopy and X-ray diffraction investigations showed the occurrence of CuFe2O4 nanoparticles with average crystal size ranging from a few nanometers up to around 9 nm, homogeneously distributed within the porous silica matrix, after thermal treatment of the samples at 900 °C. Evidence of some impurities of CuO and -Fe2O3 was found in the aerogel samples with 10 wt% and 15 wt% loading. DC magnetometry was used to investigate the magnetic properties of these nanocomposites, as a function of the loading of copper ferrite and of the porosity characteristics. All the...
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Silver nanoparticles were produced with AgF as the starting Ag(I) salt, with pectin as the reductant and protecting agent. While the obtained nanoparticles (pAgNP-F) have the same dimensional and physicochemical properties as those... more
Silver nanoparticles were produced with AgF as the starting Ag(I) salt, with pectin as the reductant and protecting agent. While the obtained nanoparticles (pAgNP-F) have the same dimensional and physicochemical properties as those already described by us and obtained from AgNO3 and pectin (pAgNP-N), the silver nanoparticles from AgF display an increased antibacterial activity against E. coli PHL628 and Staphylococcus epidermidis RP62A (S. epidermidis RP62A), both as planktonic strains and as their biofilms with respect to pAgNP-N. In particular, a comparison of the antimicrobial and antibiofilm action of pAgNP-F has been carried out with pAgNP-N, pAgNP-N and added NaF, pure AgNO3, pure AgF, AgNO3 and added NaF and pure NaNO3 and NaF salts. By also measuring the concentration of the Ag+ cation released by pAgNP-F and pAgNP-N, we were able to unravel the separate contributions of each potential antibacterial agent, observing an evident synergy between p-AgNP and the F− anion: the F− ...
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Theranostics based on two-photon excitation of therapeutics in the NIR region is an emerging and powerful tool in cancer therapy since this radiation deeply penetrates healthy biological tissues and produces selective cell death.... more
Theranostics based on two-photon excitation of therapeutics in the NIR region is an emerging and powerful tool in cancer therapy since this radiation deeply penetrates healthy biological tissues and produces selective cell death. Aggregates of gold nanoparticles coated with glutathione corona functionalized with the dansyl chromophore (a-DG-AuNPs) were synthesized and found efficient nanodevice for applications in photothermal therapy (PTT). Actually the nanoparticle aggregation enhances the quenching of radiative excitation and the consequent conversion into heat. The a-DG-AuNPs are readily internalized in Hep G2 where the chromophore acts as both antenna and transducer of the NIR radiation under two-photons excitation, determining efficient cell ablation via photothermal effect.
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The capability of synthesizing specific nanoparticles (NPs) by varying their shape, size and composition in a controlled fashion represents a typical set of engineering tools that tune the NPs magnetic response via their anisotropy. In... more
The capability of synthesizing specific nanoparticles (NPs) by varying their shape, size and composition in a controlled fashion represents a typical set of engineering tools that tune the NPs magnetic response via their anisotropy. In particular, variations in NP composition mainly affect the magnetocrystalline anisotropy component, while the different magnetic responses of NPs with isotropic (i.e., spherical) or elongated shapes are mainly caused by changes in their shape anisotropy. In this context, we propose a novel route to obtain monodispersed, partially hollow magnetite nanorods (NRs) by colloidal synthesis, in order to exploit their shape anisotropy to increase the related coercivity; we then modify their composition via a cation exchange (CE) approach. The combination of a synthetic and post-synthetic approach on NRs gave rise to dramatic variations in their magnetic features, with the pores causing an initial magnetic hardening that was further enhanced by the post-synthe...
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Even though sub-micron and nano-sized iron particles generally display single or polycrystalline structures, a growing interest has also been dedicated to the class of amorphous ones, whose absence of a crystal structure is capable of... more
Even though sub-micron and nano-sized iron particles generally display single or polycrystalline structures, a growing interest has also been dedicated to the class of amorphous ones, whose absence of a crystal structure is capable of modifying their physical properties. Among the several routes so far described to prepare amorphous iron particles, we report here about the crystallization of those prepared by chemical reduction of Fe3+ ions using NaBH4, with sizes ranging between 80 and 200 nm and showing a high stability against oxidation. Their crystallization was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and in situ heating transmission electron microscopy (TEM). The latter technique was performed by the combined use of electron diffraction of a selected sample area, and bright and dark field TEM imaging, and allowed determining that the crystallization turns the starting amorphous particles into polycrystalline α-Fe ones. Also, under the h...
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Ceria nanocubes have been doped with increasing amounts of lanthanum to enhance their redox ability.
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Magnetic nanocomposites formed by metal oxide nanoparticles and organic polymers can be produced from a polymer-metal ion complex material by a soft thermal treatment. With only slight variations in the preparation procedure it is... more
Magnetic nanocomposites formed by metal oxide nanoparticles and organic polymers can be produced from a polymer-metal ion complex material by a soft thermal treatment. With only slight variations in the preparation procedure it is possible to obtain: 1) different iron oxide phases, e.g., hematite (antiferromagnetic), goethite and akaganeite (both canted antiferromagnets), and maghemite (ferrimagnetic); 2) nanocomposites with a different particle size, in a range from 2 nm to 20 nm; and 3) different particle density. In this contribution the preparation and properties of maghemite nanoparticles in polyvinyl pyridine composites are reported.
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The occupational exposure to airborne fine and ultrafine particles (UFPs) and noise in aircraft personnel employed in airport taxiway was investigated. Stationary samplings and multiple personal sampling sites and job tasks were... more
The occupational exposure to airborne fine and ultrafine particles (UFPs) and noise in aircraft personnel employed in airport taxiway was investigated. Stationary samplings and multiple personal sampling sites and job tasks were considered. Size distribution, particle number concentrations, lung dose surface area were measured by personal particle counters and by means of an electric low pressure impactor (ELPI+TM). Morphological and chemical characterization of UFPs were performed by transmission and scanning electron microscopy, the latter together with energy dispersive X-Ray spectroscopy based spatially resolved compositional mapping. A-weighted noise exposure level A-weighted noise exposure level normalized to an 8 h working day and Peak Sound C-weighted Pressure Level was calculated for single worker and for homogeneous exposure groups. Our study provides evidence on the impact of aviation-related emissions on occupational exposure to ultrafine particles and noise exposure of ...
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Herein we report a novel, easy, fast and reliable microwave-assisted synthesis procedure for the preparation of colloidal zinc oxide nanocrystals (ZnO NCs) optimized for biological applications. ZnO NCs are also prepared by a conventional... more
Herein we report a novel, easy, fast and reliable microwave-assisted synthesis procedure for the preparation of colloidal zinc oxide nanocrystals (ZnO NCs) optimized for biological applications. ZnO NCs are also prepared by a conventional solvo-thermal approach and the properties of the two families of NCs are compared and discussed. All of the NCs are fully characterized in terms of morphological analysis, crystalline structure, chemical composition and optical properties, both as pristine nanomaterials or after amino-propyl group functionalization. Compared to the conventional approach, the novel microwave-derived ZnO NCs demonstrate outstanding colloidal stability in ethanol and water with long shelf-life. Furthermore, together with their more uniform size, shape and chemical surface properties, this long-term colloidal stability also contributes to the highly reproducible data in terms of biocompatibility. Actually, a significantly different biological behavior of the microwave-...
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Correction for 'Dependence of the Ce(iii)/Ce(iv) ratio on intracellular localization in ceria nanoparticles internalized by human cells' by Daniela Ferraro, et al., Nanoscale, 2017, 9, 1527-1538.
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The synthesis of large pentatwinned five-branched gold nanostars (GNS) has been modified so to obtain overall dimensions shrunk to 60% and a lower branches aspect ratio, leading to a dramatic blue shift of their two near-infrared (NIR)... more
The synthesis of large pentatwinned five-branched gold nanostars (GNS) has been modified so to obtain overall dimensions shrunk to 60% and a lower branches aspect ratio, leading to a dramatic blue shift of their two near-infrared (NIR) localized surface plasmon resonances (LSPR) absorptions but still maintaining one LSPR in the biotransparent NIR range. The interactions of polyethylene glycol (PEG) coated large and shrunk GNS with SH-SY5Y cells revealed that the large ones (DCI - diameter of the circumference in which GNS can be inscribed=76nm) are internalized more efficiently than the shrunk ones (DCI=46nm), correlating with a decreased cells surviving fraction.
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A method for water-soluble Mn doped iron oxide clusters and their magnetic properties.
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Energy Filtered Transmission Electron Microscopy (EFTEM) is an analytical tool that has been successfully and widely employed in the last two decades for obtaining fast elemental maps in TEM mode. Several studies and efforts have been... more
Energy Filtered Transmission Electron Microscopy (EFTEM) is an analytical tool that has been successfully and widely employed in the last two decades for obtaining fast elemental maps in TEM mode. Several studies and efforts have been addressed to investigate limitations and advantages of such technique, as well as to improve the spatial resolution of compositional maps. Usually, EFTEM maps undergo post-acquisition treatments by changing brightness and contrast levels, either via dedicated software or via human elaboration, in order to maximize their signal-to-noise ratio and render them as visible as possible. However, elemental maps forming a single set of EFTEM images are usually subjected to independent map-by-map image treatment. This post-acquisition step becomes crucial when analyzing materials that change composition over time as a consequence of an external stimulus, because the map-by-map approach doesn't take into account how the chemical features of the imaged materi...
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... a reduced flow was then continued for additional 2 h. The resulting powder, the orange g-ferric oxide hydrate [g–FeO(OH)], was ... refinements were carried out using the PC version of the GSAS (Generalized Structure Analysis System)... more
... a reduced flow was then continued for additional 2 h. The resulting powder, the orange g-ferric oxide hydrate [g–FeO(OH)], was ... refinements were carried out using the PC version of the GSAS (Generalized Structure Analysis System) program.25 A pseudo-Voigt function26 was ...
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Mesoporous nanocomposite materials have been fabricated through integration of evaporation-induced self-assembly and deep X-ray lithography. Micropatterned films made using a mesoporous ordered silica matrix which contains silver... more
Mesoporous nanocomposite materials have been fabricated through integration of evaporation-induced self-assembly and deep X-ray lithography. Micropatterned films made using a mesoporous ordered silica matrix which contains silver nanoparticles have been obtained. The exposure of the mesoporous films to high energy X-rays, which are generated by a synchrotron source, produces several effects: the removal of the surfactant, the densification of the silica backbone and the formation of silver nanoparticles. This integrated process produces a nanocomposite material which has a 2D-hexagonal organized porosity and silver nanoparticles with a sharp size distribution around 5 nm. The patterned nanostructured films have been tested as a lab-on-chip device for intrinsic surface enhanced Raman scattering detection using a solution containing rhodamine 6G in ethanol and measuring Raman response as a function of laser power.
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The factors that determine the local magnetic properties of FeCo/SiO2 nanocomposite powders and films have been analysed by electron energy-loss spectroscopy (EELS) and transmission electron microscopy (TEM). Attention has been given to... more
The factors that determine the local magnetic properties of FeCo/SiO2 nanocomposite powders and films have been analysed by electron energy-loss spectroscopy (EELS) and transmission electron microscopy (TEM). Attention has been given to the chemical composition, the local electronic structure and the atomic arrangement. The results show that the nanoparticles from sol-gel prepared powders are generally Fe-rich, whereas they are Co-rich in sol-gel prepared films. In addition, a subnanometre oxide layer at the surface of the FeCo nanoparticles has been clearly observed in the powder sample. It is found that the magnetic moment should be partly governed by alloying effects. Numerical values of the near-surface magnetic moment have been obtained using the ab-initio layer-KKR method. These values should be helpful in understanding the layer-by-layer changes of the white line ratio close to the surface of the nanoparticles.
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Stable iron nanoparticles have been synthesised by the decomposition of {Fe(N[Si(CH3)3]2)2}2 under dihydrogen pressure. Those conditions lead to a system of monodisperse and metallic nanoparticles which diameter is less than 2 nm and... more
Stable iron nanoparticles have been synthesised by the decomposition of {Fe(N[Si(CH3)3]2)2}2 under dihydrogen pressure. Those conditions lead to a system of monodisperse and metallic nanoparticles which diameter is less than 2 nm and stabilized by HN[Si(CH3)3]2. The magnetization is found to be MS=1.92muB/at., i.e., 10% lower than the bulk value. The Mössbauer spectrum is fitted by two contributions of metallic