Maria F Casula

University of Pavia, Ticinum, Lombardy, Italy

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Publications (83)221.91 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: We report the detailed structural characterization and magnetic investigation of nanocrystalline zinc ferrite nanoparticles supported on a silica aerogel porous matrix which differ in size (in the range 4-11 nm) and the inversion degree (from 0.4 to 0.2) as compared to bulk zinc ferrite which has a normal spinel structure. The samples were investigated by zero-field-cooling-field-cooling, thermo-remnant DC magnetization measurements, AC magnetization investigation and Mössbauer spectroscopy. The nanocomposites are superparamagnetic at room temperature; the temperature of the superparamagnetic transition in the samples decreases with the particle size and therefore it is mainly determined by the inversion degree rather than by the particle size, which would give an opposite effect on the blocking temperature. The contribution of particle interaction to the magnetic behavior of the nanocomposites decreases significantly in the sample with the largest particle size. The values of the anisotropy constant give evidence that the anisotropy constant decreases upon increasing the particle size of the samples. All these results clearly indicate that, even when dispersed with low concentration in a non-magnetic and highly porous and insulating matrix, the zinc ferrite nanoparticles show a magnetic behavior similar to that displayed when they are unsupported or dispersed in a similar but denser matrix, and with higher loading. The effective anisotropy measured for our samples appears to be systematically higher than that measured for supported zinc ferrite nanoparticles of similar size, indicating that this effect probably occurs as a consequence of the high inversion degree.
    Physical Chemistry Chemical Physics 01/2014; · 3.83 Impact Factor
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    ABSTRACT: We synthesize colloidal CdSe@CdS octapod nanocrystals decorated with Pt domains, resulting in a metal-semiconductor heterostructure. We devise a protocol to control the growth of Pt on the CdS surface, realizing both a selective tipping and a non-selective coverage. Ultrafast optical spectroscopy, particularly femtosecond transient absorption, is employed to correlate the dynamics of optical excitations with the nanocrystal morphology. We find two regimes for capture of photoexcited electrons by Pt domains: a slow capture after energy relaxation in the semiconductor, occurring in tipped nanocrystals and resulting in large spatial separation of charges, and an ultrafast capture of hot electrons occurring in nanocrystals covered in Pt, where charge separation happens faster than energy relaxation and Auger recombination. Besides the relevance for fundamental materials science and control at the nanoscale, our nanocrystals may be employed in solar photocatalysis.
    Nanoscale 01/2014; · 6.23 Impact Factor
  • Journal of Non-Crystalline Solids 01/2014; · 1.60 Impact Factor
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    ABSTRACT: To fully exploit the potential of self-assembly in a single step, we have designed an inte-grated process to get mesoporous graphene nanocomposite films. The synthesis allows in-corporating graphene sheets with a small number of defects into highly ordered and trans-parent mesoporous titania films. The careful design of the porous matrix at the mesoscale ensures the highest diffusivity in the films which exhibit an enhanced photocatalytic effi-ciency while the high order of the mesoporosity is not affected by the insertion of the gra-phene sheets and it is well preserved after controlled thermal treatment. The nanocomposite films can be easily processed by deep X-ray lithography to produce functional arrays.
    ACS Applied Materials & Interfaces 11/2013; · 5.01 Impact Factor
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    ABSTRACT: Magnetic and superparamagnetic colloids represent a versatile platform for the design of functional nanostructures which may act as effective tools for biomedicine, being active in cancer therapy, tissue imaging and magnetic separation. The structural, morphological and hence magnetic features of the magnetic nanoparticles must be tuned for optimal perfomance in a given application. In this work, iron oxide nanocrystals have been prepared as prospective heat mediators in magnetic fluid hyperthermia therapy. A procedure based on the partial oxidation of iron (II) precursors in water based media has been adopted and the synthesis outcome has been investigated by X-Ray diffraction and Transmission electron microscopy. It was found that by adjusting the synthetic parameters (mainly the oxidation rate) magnetic iron oxide nanocrystals with cubic and cuboctahedral shape and average size 50 nm were obtained. The nanocrystals were tested as hyperthermic mediators through Specific Absorption Rate (SAR) measurements. The samples act as heat mediators, being able to increase the temperature from physiological temperature to the temperatures used for magnetic hyperthermia by short exposure to an alternative magnetic field and exhibit a reproducible temperature kinetic behavior.
    Proc SPIE 02/2013;
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    ABSTRACT: We present a systematic experimental comparison of the superparamagnetic relaxation time constants obtained by means of dynamic magnetic measurements and (1)H-NMR relaxometry, on ferrite-based nanosystems with different composition, various core sizes and dispersed in different solvents. The application of a heuristic model for the relaxivity allowed a comparison between the reversal time of magnetization as seen by NMR and the results from the AC susceptibility experiments, and an estimation of fundamental microscopic properties. A good agreement between the NMR and AC results was found when fitting the AC data to a Vogel-Fulcher law. Key parameters obtained from the model have been exploited to evaluate the impact of the contribution from magnetic anisotropy to the relaxivity curves and estimate the minimum approach distance of the bulk solvent.
    Journal of Physics Condensed Matter 01/2013; 25(6):066008. · 2.36 Impact Factor
  • ChemPlusChem. 01/2013; 78(4):364.
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    ABSTRACT: In this work, nanocomposites constituted of FeCo alloy nanoparticles dispersed on a highly porous silica aerogel have been designed as catalysts for low temperature Fischer–Tropsch synthesis. The catalysts were characterized by XRD, TEM, N2 physisorption and SEM analysis. A high catalytic activity with CO conversions up to 95 % has been obtained, with enhanced selectivity for the C2–C4 hydrocarbons. Graphical Abstract
    Catalysis Letters 07/2012; 142:1061. · 2.24 Impact Factor
  • Physical review. B, Condensed matter 05/2012; 85(17).
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    ABSTRACT: We report a broadband 1H-NMR study of the temperature spin dynamics of nearly monodisperse dextran-coated γ-Fe2O3 magnetic nanoparticles. We observed a maximum in T1−1(T) that decreases in amplitude and shifts toward higher temperatures with increasing field. We suggest that this is related to the progressive superparamagnetic spin blocking of the ferrite core. The data can be explained by assuming a single electronic spin-spin correlation time and introducing a field-dependent distribution of anisotropy energy barriers.
    Physical review. B, Condensed matter 05/2012; 85(17).
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    ABSTRACT: In this review an overview about biological applications of magnetic colloidal nanoparticles will be given, which comprises their synthesis, characterization, and in vitro and in vivo applications. The potential future role of magnetic nanoparticles compared to other functional nanoparticles will be discussed by highlighting the possibility of integration with other nanostructures and with existing biotechnology as well as by pointing out the specific properties of magnetic colloids. Current limitations in the fabrication process and issues related with the outcome of the particles in the body will be also pointed out in order to address the remaining challenges for an extended application of magnetic nanoparticles in medicine.
    Chemical Society Reviews 04/2012; 41(11):4306-34. · 24.89 Impact Factor
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    ABSTRACT: Stoichiometric magnetic nanosized ferrites MFe2O4 (M = Mn, Co, Ni) were prepared in form of nearly spherical nanocrystals supported on a highly porous silica aerogel matrix, by a sol-gel procedure. X-ray diffraction and transmission electron microscopy indicate that these materials are made out of non-agglomerated ferrite nanocrystals having size in the 5-10 nm range. Investigation by Mössbauer Spectroscopy was used to gain insights on the superparamagnetic relaxation and on the inversion degree. Magnetic ordering at room temperature varies from superparamagnetic in the NiFe2O4 sample, highly blocked (approximately 70%) in the MnFe2O4 sample and nearly fully blocked in the CoFe2O4 sample. A fitting procedure of the Mössbauer data has been used in order to resolve the spectrum into the tetrahedral and octahedral components; in this way, an inversion degree of 0.68 (very close to bulk values) was obtained for 6 nm silica-supported CoFe2O4 nanocrystals.
    Journal of Nanoscience and Nanotechnology 11/2011; 11(11):10136-41. · 1.15 Impact Factor
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    ABSTRACT: The creation of novel engineered multimodal nanoparticles (NPs) is a key focus in bionanotechnology and can lead to deep understanding of biological processes at the molecular level. Here, we present a multi-component system made of gold-coupled core-shell SPIONs, as a new nanoprobe with signal enhancement in surface Raman spectroscopy, due to its jagged-shaped gold shell coating.
    Chemical Communications 08/2011; 47(37):10404-6. · 6.38 Impact Factor
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    ABSTRACT: Porous organic–inorganic hybrid films with well defined pore shape and dimension have been obtained via a salt-template route. Sodium chloride precipitates during film deposition as templating for cubic shape pores; combining this salt-template route with controlled phase separation, pores of spherical shape in the same film have been also obtained. The dimensions of the nanocubes and nanospheres are in the 20–200 nm range and can be modulated through the film processing conditions. We have systematically investigated the effect of precursor solution aging and surfactant concentration on the porous film structure using infrared spectroscopy, spectroscopic ellipsometry, X-ray diffraction, Raman imaging, atomic force microscopy and transmission electron microscopy. Only a very specific combination of different synthesis parameters, such as surfactant concentration and aging of the precursor solution, allows the formation of the pore templates.
    New Journal of Chemistry 08/2011; 35(8):1624-1629. · 2.97 Impact Factor
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    ABSTRACT: Nanocomposites containing FeCo alloy nanoparticles dispersed in a highly ordered 3D cubic Im3m mesoporous silica (SBA-16) matrix were prepared by a novel, single-step templated-assisted sol-gel technique. Two different approaches were used in the synthesis of nanocomposites; a pure SBA-16 sample was also prepared for comparison. Low-angle X-ray diffraction, transmission electron microscopy and N2 physisorption at 77 K show that after metal loading, calcination at 500 degrees C and reduction in H2 flux at 800 degrees C the nanocomposites retain the cubic mesoporous structure with pore size not very different from the pure matrix. X-ray absorption fine structure (EXAFS) analysis at Fe and Co K-edges demonstrates that the FeCo nanoparticles have the typical bcc structure. The final nanocomposites were tested as catalysts for the production of carbon nanotubes by catalytic chemical vapour deposition and high-resolution TEM shows that good quality multi-walled carbon nanotubes are obtained.
    Journal of Nanoscience and Nanotechnology 08/2011; 11(8):6735-46. · 1.15 Impact Factor
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    ABSTRACT: Mesoporous silica nanoparticles (MSNs) have been proposed as DNA and drug delivery carriers, as well as efficient tools for fluorescent cell tracking. The major limitation is that MSNs enter cells regardless of a target-specific functionalization. Here we show that non functionalized MSNs, synthesized using a PEG surfactant-based interfacial synthesis procedure, do not enter cells, while a highly specific, receptor mediated, cellular internalization of folic acid (FOL) grafted MSNs (MSN-FOL), occurs exclusively in folate receptor (FR) expressing cells. Neither the classical clathrin pathway nor macropinocytosis is involved in the MSN endocytic process, while fluorescent MSNs (MSN-FITC) enter cells through aspecific, caveolae-mediated, endocytosis. Moreover, internalized particles seem to be mostly exocytosed from cells within 96 h. Finally, cisplatin (Cp) loaded MSN-FOL were tested on cancerous FR-positive (HeLa) or normal FR-negative (HEK293) cells. A strong growth arrest was observed only in HeLa cells treated with MSN-FOL-Cp. The results presented here show that our mesoporous nanoparticles do not enter cells unless opportunely functionalized, suggesting that they could represent a promising vehicle for drug targeting applications.
    Nanoscale 07/2011; 3(8):3198-207. · 6.23 Impact Factor
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    ABSTRACT: Porous nanocomposites made out of nickel dispersed on silica or alumina matrices were prepared as prospective catalysts for the nitroxidation of hydrocarbons in the form of aerogel or xerogel by adopting either a supercritical or a conventional gel drying procedure. The structural and textural features of the materials were investigated by X-ray diffraction, transmission electron microscopy and N2 physisorption and combined to the acid/base and reducibility data as deduced by adsorption microcalorimetry and temperature programmed reduction (TPR) profiles. The alumina-based samples are made out of nanocrystalline nickel aluminate and are mesoporous, although the aerogel has larger pore volumes and surface area than the xerogel. On the other hand, in the silica-based samples nickel oxide nanocrystals are dispersed on amorphous silica, the size of the nanocrystals being around 5 nm in the microporous xerogel and 14 nm in the mainly mesoporous aerogel. TPR data point out that the alumina-based samples have similar reducibility, whereas significant differences were observed in the silica-supported composites, the NiO–SiO2 aerogel exhibiting improved reducibility at low temperature. The NO-catalyst interaction was monitored by temperature programmed NO reaction coupled to mass spectrometry and preliminary tests on the use of the NiO–SiO2 xerogel and aerogel nanocomposites for the catalytic nitroxidation of 1-methyl-naphthalene to 1-naphthonitrile were obtained in a fixed-bed continuous-flow reactor. The data indicate that the aerogel exhibits larger selectivity than the corresponding xerogel, pointing out the importance of tuning the sol–gel parameters in the design of porous composite materials for catalytic applications.
    Journal of Sol-Gel Science and Technology 04/2011; 60:324. · 1.66 Impact Factor
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    ABSTRACT: For imaging with different modalities, labels, which provide contrast for all modalities, are required. Colloidal nanoparticles composed out of an inorganic core and a polymer shell offer progress in this direction. Both, the core and the polymer shell, can be synthesized to be fluorescent, magnetic, or radioactive. When different cores are combined with different polymer shells, different types of particles for dual imaging can be obtained, as for example, fluorescent cores with radioactive polymer shells. Properties and perspectives of such nanoparticles for multimodal imaging are discussed.
    Analytical Chemistry 03/2011; 83(8):2877-82. · 5.70 Impact Factor
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    ABSTRACT: Multiwalled carbon nanotube/FeCo nanocomposites were produced by Catalytic Chemical Vapour Deposition using highly porous FeCo-SiO2 aerogels with different loadings and dimensions of FeCo nanoparticles as catalysts. Multiwalled carbon nanotubes with average number of walls depending on the size of the catalyst nanoparticles were obtained. Inside the nanotubes spherical or elliptical FeCo nanoparticles are retained, and the magnetic properties of the resulting nanocomposites were characterized in detail.
    Journal of Nanoscience and Nanotechnology 03/2011; 11(3):2215-25. · 1.15 Impact Factor
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    ABSTRACT: Hybrid organic–inorganic films containing layered organosilicate nanocrystals have been obtained through self-organization from aqueous precursor sols containing 3-glycidoxypropyltrimethoxysilane. Diethoxydiphenylsilane has been added, in different amounts, to the precursor sol containing 3-glycidoxypropyltrimethoxysilane to prepare hybrid films with the ordered nanostructures. The effect of aging time of the precursor sol has been studied preparing different samples from sols aged up to 8days; the formation of crystalline layered films has been observed in the samples obtained from sols of higher aging time. The hybrid films have been characterized by gracing incidence X-ray diffraction, Raman and Fourier transform infrared spectroscopy, transmission electron microscopy and UV–Vis spectroscopy. The change of the surface contact angle as a function of sol aging time and composition has been also measured. The capability of the films to be used in devices through lithographic techniques has been tested by writing the films with direct exposition to deep X-ray lithography and soft lithography with micromolds; patterns of different geometries with a thickness up to 100μm have been obtained. KeywordsSol–gel–Organic–inorganic hybrid–Films–Hybrid crystals–Lithography
    Journal of Sol-Gel Science and Technology 01/2011; 60(3):275-282. · 1.66 Impact Factor

Publication Stats

506 Citations
221.91 Total Impact Points


  • 2013
    • University of Pavia
      • Department of Physics
      Ticinum, Lombardy, Italy
  • 2000–2013
    • Università degli studi di Cagliari
      • • Department of Surgical Science
      • • Department of Chemical and Geological Science
      Cagliari, Sardinia, Italy
  • 2009
    • Philipps-Universität Marburg
      Marburg, Hesse, Germany
  • 2006
    • University of California, Berkeley
      • Department of Chemistry
      Berkeley, MO, United States
  • 2005
    • Universität Ulm
      Ulm, Baden-Württemberg, Germany