Publications by authors named "Raluca F Negrea"

Titanium dioxide nanobelts were prepared via the alkali-hydrothermal method for application in chemical gas sensing. The formation process of TiO-(B) nanobelts and their sensing properties were investigated in detail. FE-SEM was used to study the surface of the obtained structures.

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Zirconia- and hafnia-based thin films have attracted tremendous attention in the past decade because of their unexpected ferroelectric behavior at the nanoscale, which enables the downscaling of ferroelectric devices. The present work reports an unprecedented ferroelectric rhombohedral phase of ZrO that can be achieved in thin films grown directly on (111)-Nb:SrTiO substrates by ion-beam sputtering. Structural and ferroelectric characterizations reveal (111)-oriented ZrO films under epitaxial compressive strain exhibiting switchable ferroelectric polarization of about 20.

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Article Synopsis
  • The study outlines the creation of core-double shell nanofibers made from nylon, zinc oxide (ZnO), and polypyrrole using three main methods: electrospinning, sol-gel synthesis, and electrodeposition.
  • It describes how nylon nanofibers were initially produced, then coated with a ZnO film to enhance material properties, before adding a polypyrrole layer through electrochemical deposition.
  • Characterization techniques like X-ray diffraction and spectroscopy confirmed the successful layering and unique properties of the nanofibers, revealing their potential for diverse applications due to their flexibility and transparency.
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The work describes the development of a flexible, hydrogel embedded pH-sensor that can be integrated in inexpensive wearable and non-invasive devices at epidermal level for electrochemical quantification of H ions in sweat. Such a device can be useful for swift, real time diagnosis and for monitoring specific conditions. The sensors' working electrodes are flexible poly(methyl methacrylate) electrospun fibers coated with a thin gold layer and electrochemically functionalized with nanostructured palladium/palladium oxide.

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Controlling the semiconductor-to-metal transition temperature in epitaxial VO thin films remains an unresolved question both at the fundamental as well as the application level. Within the scope of this work, the effects of growth temperature on the structure, chemical composition, interface coherency and electrical characteristics of rutile VO epitaxial thin films grown on TiO substrates are investigated. It is hereby deduced that the transition temperature is lower than the bulk value of 340 K.

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Hierarchical flowers-like zinc oxide structures have been successfully obtained by a simple and fast ultrasound-assisted method performed in a ordinary ultrasonic bath using an ammonia solution and zinc acetate, in the absence of any surfactant or template. The composition, structure, crystallinity, morphology and optical properties of the materials obtained at different ultrasound irradiation times were characterized by infrared, UV-Vis and photoluminescence spectroscopy, X-ray diffraction, scanning and transmission electron microscopy investigations. It was proved that the ultrasound irradiation time manipulates both the defect content (implicit the photoluminescent properties) and morphology of the ZnO materials: shorter irradiation times leads to the synthesis of high-defected ZnO structures of flower morphology with triangular-shaped petals, while higher irradiation times favours the formation of low-defected ZnO structures with tipped rod-like petals.

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Here we report the extraordinary thermal stability of Mg rich bimetallic nanoparticles (NPs), which is important for hydrogen storage technology. The enhanced NP stability is accomplished because of two critical improvements: (i) no void development within NPs (nanoscale Kirkendall effect) during their formation and (ii) suppressed Mg evaporation and NP hollowing during Mg hydrogenation at elevated temperature. The mechanism leading to the improved thermal stability of Mg-based bimetallic NPs is shown to be due to MgH2 hydride formation before evaporation can take place.

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