Papers by maria benelmekki
Sensor Letters, 2013
Composites consisting on poly(vinylidene fluoride), PVDF, and nano-size NiZnFe 2 O 4 ferrites hav... more Composites consisting on poly(vinylidene fluoride), PVDF, and nano-size NiZnFe 2 O 4 ferrites have been prepared by solution casting. The addition of NiZnFe 2 O 4 nucleates the polar-phase of PVDF, leading to magnetoelectric composites suitable for sensor and actuator applications. The amount of-phase increases with increasing amount of nanoparticles up to filler concentrations of ∼ 5 %wt. For this concentration almost 90% of the crystalline phase of the polymer is in the electroactive-phase. The nucleation occurs due to epitaxial crystallization at the nanoparticle surface, leading to variations in the crystallization kinetics and to the stabilization of the-phase.
MRS Proceedings, 2011
Multiferroics and magnetoelectric materials show interesting scientific challenges and technnolog... more Multiferroics and magnetoelectric materials show interesting scientific challenges and technnologial applications in sensors, acuators and data storage. In view of the fact that only a small number of materials show this kind of properties, exhaustive research activity is being pursued towards the development of new composite materials. Multiferroic nanocomposites films composed of piezoelectric poly(vinylidene fluoride) (PVDF) and magnetostrictive nanosize CoFe 2 O 4 , NiFe 2 O 4 or NiZnFe 2 O 4 ferrites were prepared by a solution method. Those ferrite nanoparticles have the ability to nucleate the electroactive β-phase of the polymer, providing in this way an easy route for the preparation of magnetoelectric particulate composites. The fact that the different nanoparticles promotes different amount of β-phase nucleation for different concentrations of nanoparticles indicates that filler size is not the most important parameter determining phase nucleation but the filler-matrix surface interaction. Further, when the polymer-ferrite surface interaction is modified through surfactation, the electroactive phase is not nucleated.
IOP Publishing eBooks, May 1, 2021
IOP Publishing eBooks, May 1, 2021
IOP Publishing eBooks, May 1, 2021
Journal of medical physics and applied sciences, 2020
Applied Surface Science, 2020
We report a simple and scalable two-step method for the simultaneous synthesis and functionalizat... more We report a simple and scalable two-step method for the simultaneous synthesis and functionalization of hexagonal boron nitride (hBN) nanosheets and nanoscrolls. The first step is conventional chemical exfoliation under alkaline conditions to weaken the interlayer interactions, and the second step is exposure to low-frequency ultrasonic irradiation to obtain partially oxidized nanosheets and nanoscrolls. The successful formation of both nanosheets and nanoscrolls is confirmed using electron microscopy. The effective incorporation of O atoms into the structure of hBN nanosheets and nanoscrolls was confirmed through i) the changes in the optical bandgaps deduced from UV-vis absorption, and ii) the decrease in B atoms bonded to three N atoms and the increase in the BN x O y component observed using high-resolution X-ray photoelectron spectroscopy. This incorporation is likely due to the in-situ reaction with H 2 O during ultrasonic irradiation and 2 the reactivity of B sites with OH groups. Raman spectroscopy was used to analyze the evolution of the active phonon modes upon further exposure to irradiation, and confirmed a phase transition from sp 2 bonding to a mixture of sp 2-sp 3 bonding at the occurrence of the shape trasformation from nanosheets to nanoscrolls. This phase transition is attributed to the asymmetric vibrations and bending deformations of hBN nanosheets upon scrolling to form stable nanoscrolls.
Molecules
The term “nanosheets” has been coined recently to describe supported and free-standing “ultrathin... more The term “nanosheets” has been coined recently to describe supported and free-standing “ultrathin film” materials, with thicknesses ranging from a single atomic layer to a few tens of nanometers. Owing to their physicochemical properties and their large surface area with abundant accessible active sites, nanosheets (NSHs) of inorganic materials such as Au, amorphous carbon, graphene, and boron nitride (BN) are considered ideal building blocks or scaffolds for a wide range of applications encompassing electronic and optical devices, membranes, drug delivery systems, and multimodal contrast agents, among others. A wide variety of synthetic methods are employed for the manufacturing of these NSHs, and they can be categorized into (1) top-down approaches involving exfoliation of layered materials, or (2) bottom-up approaches where crystal growth of nanocomposites takes place in a liquid or gas phase. Of note, polymer template liquid exfoliation (PTLE) methods are the most suitable as th...
Materials Today Chemistry, Mar 1, 2021
Abstract Controlling the morphology and composition of one-dimensional (1D) and two-dimensional (... more Abstract Controlling the morphology and composition of one-dimensional (1D) and two-dimensional (2D) assemblies of matter is essential to design and create nanostructures with exceptional material properties, for applications ranging from nanoelectronics to nanomedicine. Within this latter, a great interest is placed on assembling magnetoplasmonic nanostructures to enable multimodal biosensing and bioimaging for early diagnosis and prognosis of diseases. To date, the synthesis of such complex nanostructures is mostly relying on wet chemistry and templates. Herein, we employed a templateless physical method to generate FeAg-based anisotropic nanostructures, using a modified cluster source. Under tuned experimental conditions, we demonstrated the successful magnetic-assisted assembly of Fe nanoclusters (Fe NCs), to form stable and permanent branched Fe nanorods (Fe NRs), core@shell Fe@Ag-NRs, Fe nanosheets (Fe NSs), and Fe/Ag-NSs. This assembly is driven by the need to reduce their magnetic interaction energy on one hand and their overall surface energy on the other hand. When NCs and NRs are magnetically brought into intimate contact, they undergo a coalescence process, through the interfacial diffusion of the surface atoms, resulting in the formation of 1D and 2D nanostructures. For Fe@Ag NRs, the advantage conferred by the Ag shell is to protect Fe NRs from oxidation and prevent them from aggregation at the same time. The observed contrast reversal in Scanning Electron Microscopy (SEM) images of Fe NRs and Fe NSs is discussed.
Nanostructures that contain both magnetic and optically active components have emerged as attract... more Nanostructures that contain both magnetic and optically active components have emerged as attractive candidates for advanced biomedical applications, such as multimodal bioimaging, targeted drug delivery and magnetic hyperthermia. In particular, carbon nanomaterials, such as graphene, graphite nanosheets, and nanoscrolls have been attracting considerable interest due to their high surface area, light weight, superior electronic function, thermal conductivity, and robust physical stability. Distinct from carbon nanotubes (CNTs), carbon nanoscrolls (CNS) are open tubular carbon structures with tuneable interlayer gaps between thin films and their radius, endowing higher molecular accessible surface areas than nanosheets and nanotubes, and thus making them robust in harsh environments, such as heat, humidity, and aggregation. Because CNS architectures comprise interlayer corridors, which are created by wrapping a C-nanofilm into a helical structure, the scroll topology allows their pro...
The effects of different sputtering deposition processes and post-treatment parameters on the ele... more The effects of different sputtering deposition processes and post-treatment parameters on the electrical, optical, structural and morphological properties of Gaand Al-doped ZnO thin films are reported, bearing in mind tentative applications for electrodes in photovoltaic and thermoelectric applications. Highly transparent and electrically-conductive films were deposited on glass and silicon surfaces by d.c. pulsed magnetron sputtering in an argon atmosphere. From X-ray diffraction experiments it was found that all films have a hexagonal wurtzite structure with the [001] preferred crystallographic direction, being the morphology of the films (obtained from scanning electron microscope analysis) sensitive to the process parameters. All ZnO:Ga films presented an average transmittance above 80 % in the visible region, and the lowest electrical resistivity of ~10 -4 Ω·cm was achieved for the sample submitted to the lowest bias voltage (-40 V), which corresponds to a carrier concentration...
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Papers by maria benelmekki