Publications by authors named "Florea Ileana"

We study the influence of electrical biasing on the modification of the chemical composition and electrical performance of perovskite solar cells (PSCs) by coupling electrochemical impedance spectroscopy (EIS) and scanning transmission X-ray microscopy (STXM) techniques. EIS reveals the formation of charge accumulation at the interfaces and changes in the resistive and capacitive properties. STXM study on PSCs after applying a strong electric field for a long biasing time indicates the breakdown of methylammonium (MA) cation, promoting iodide ions to migrate and create defects at the interface.

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Au trisoctahedrons (TOHs) with sharp tips and high-index facets have exceptional properties for diverse applications, such as plasmon-enhanced spectroscopies, catalysis, sensing, and biomedicine. However, the synthesis of Au TOHs remains challenging, and most reported synthetic methods are time-consuming or involve complex steps, hindering the exploration of their potential applications. Herein, we present a facile and fast approach to prepare Au TOHs with high uniformity and good control over the final size and shape, all within less than 10 min of synthesis, for surface-enhanced Raman spectroscopy (SERS) and refractive index sensing.

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2D materials possess great potential to serve as gas-sensing materials due to their large, specific surface areas and strong surface activities. Among this family, transition metal chalcogenide materials exhibit different properties and are promising candidates for a wide range of applications, including sensors, photodetectors, energy conversion, and energy storage. Herein, a high-shear mixing method has been used to produce multilayered MoS nanosheet dispersions.

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Herein, we report on the use of vertically aligned multiwall carbon nanotubes (CNTs) films as support for ZnO/ZnS photocatalytic active nanostructures. The CNTs were synthetized via a hot-filament chemical vapor deposition (HfCVD), using Fe catalyst on top of AlObuffer layer. Controlled point defects in the CNTs outer walls were created by exposure to a low pressure nonthermal water vapors diffusive plasma and acted as seeds for subsequent pulsed-electrodeposition of Zn nanoparticles.

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The growth of transition-metal dichalcogenides (TMDCs) has been performed so far using most established thin-film growth techniques (e.g., vapor phase transport, chemical vapor deposition, molecular beam epitaxy, etc.

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  • Researchers have focused on the unique properties of silicon nanoparticles, particularly their permanent electric dipole moments, primarily in small silicon nanoclusters (SiNCs) around 1-2 nanometers in size.
  • This study investigates whether plasma conditions can create larger silicon clusters (superclusters) with stronger dipole moments using a pulsed plasma method for SiNC production.
  • The findings showed that 1-2 nm SiNCs can form larger superclusters, which have high dipole moments, enabling their orientation and manipulation with external electric fields for advanced nanostructure applications.
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  • * This study focuses on creating robust and reusable SERS microfluidic chips to help first responders identify neurotoxic gases accurately and quickly, emphasizing important features like detection limits, response time, and reusability.
  • * The research includes developing a special 3D structure using mesoporous silica and gold nanoparticles which enhances gas detection performance, specifically evaluating its effectiveness with DMMP, a neurotoxic simulant, under various conditions.
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In an effort to produce alkenes in an energy-saving way, this study presents for the first time a photocatalytic process that allows for the obtention of ethylene with high selectivity from propionic acid (PA) degradation. To this end, TiO nanoparticles (NPs) modified with copper oxides (CuO/TiO) were synthetised via laser pyrolysis. The atmosphere of synthesis (He or Ar) strongly affects the morphology of photocatalysts and therefore their selectivity towards hydrocarbons (CH, CH, CH) and H products.

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Large-scale production of graphene nanosheets (GNSs) has led to the availability of solution-processable GNSs on the commercial scale. The controlled vacuum filtration method is a scalable process for the preparation of wafer-scale films of GNSs, which can be used for gas sensing applications. Here, we demonstrate the use of this deposition method to produce functional gas sensors, using a chemiresistor structure from GNS solution-based techniques.

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Sample preparation on cryo-EM grids can give various results, from very thin ice and homogeneous particle distribution (ideal case) to unwanted behavior such as particles around the "holes" or complexes that do not entirely correspond to the one in solution (real life). We recently run into such a case and finally found out that variations in the 3D reconstructions were systematically correlated with the grid batches that were used. We report the use of several techniques to investigate the grids' characteristics, namely TEM, SEM, Auger spectroscopy and Infrared Interferometry.

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Carbon xerogel nanocomposites with integrated Bi and Fe particles (C–Bi–Fe) represent an interesting model of carbon nanostructures decorated with multifunctional nanoparticles (NPs) with applicability for electrochemical sensors and catalysts. The present study addresses the fundamental aspects of the catalyzed growth of nano-graphites in C–Bi–Fe systems, relevant in charge transport and thermo-chemical processes. The thermal evolution of a C–Bi–Fe xerogel is investigated using different pyrolysis treatments.

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The present study aims to compare the early stages of graphitization of the same DND source for two annealing atmospheres (primary vacuum, argon at atmospheric pressure) in an identical set-up. DND samples are finely characterized by a combination of complementary techniques (FTIR, Raman, XPS, HR-TEM) to highlight the induced modifications for temperature up to 1100 °C. The annealing atmosphere has a significant impact on the graphitization kinetics with a higher fraction of sp-C formed under vacuum compared to argon for the same temperature.

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When Si nanowires (NWs) have diameters below about 10 nm, their band gap increases as their diameter decreases; moreover, it can be direct if the material adopts the metastable diamond hexagonal structure. To prepare such wires, we have developed an original variant of the vapor-liquid-solid process based on the use of a bimetallic Cu-Sn catalyst in a plasma-enhanced chemical vapor deposition reactor, which allows us to prevent droplets from coalescing and favors the growth of a high density of NWs with a narrow diameter distribution. Controlling the deposited thickness of the catalyst materials at the sub-nanometer level allows us to get dense arrays (up to 6 × 10 cm) of very-small-diameter NWs of 6 nm on average (standard deviation of 1.

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Article Synopsis
  • The study explores using hydrogen plasma to reduce fluorine doped tin oxide, creating tin nanodroplets essential for growing silicon nanowires in solar technology.
  • An innovative optical model is introduced to monitor the formation of these droplets on a soda-lime glass substrate, aligning with spectroscopic data during the reduction process.
  • The research emphasizes the importance of real-time monitoring in the fabrication process for developing nanowires and radial junction devices.
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Orientation analyses of macromolecules or artificial particles are vital for both fundamental research and practical bio-applications. An accurate approach is monitoring the polarization spectroscopy of lanthanide-doped nanocrystalline materials. However, nanomaterials are often far from ideal for the colloidal and polarization luminescence properties.

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This scientific data article is related to the research work entitled "Non-Covalent functionalization of Single Walled Carbon Nanotubes with Fe-/Co-porphyrin and Co-phthalocyanine for Field-Effect Transistor Applications" published in "Organic electronics" (10.1016/j.orgel.

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In this work, we report the same trends for the contact potential difference measured by Kelvin probe force microscopy and the effective carrier lifetime on crystalline silicon (c-Si) wafers passivated by AlO layers of different thicknesses and submitted to annealing under various conditions. The changes in contact potential difference values and in the effective carrier lifetimes of the wafers are discussed in view of structural changes of the c-Si/SiO/AlO interface thanks to high resolution transmission electron microscopy. Indeed, we observed the presence of a crystalline silicon oxide interfacial layer in as-deposited (200 °C) AlO, and a phase transformation from crystalline to amorphous silicon oxide when they were annealed in vacuum at 300 °C.

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Silicon-based anode fabrication with nanoscale structuration improves the energy density and life cycle of Li-ion batteries. As-synthesized silicon (Si) nanowires (NWs) or nanoparticles (NPs) directly on the current collector represent a credible alternative to conventional graphite anodes. However, the operating potentials of these electrodes are below the electrochemical stability window of all electrolytes used in commercial Li-ion systems.

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  • Researchers developed single crystalline FeCo nanostars using a straightforward organometallic method, which allowed for direct synthesis without needing a complicated seed-mediated growth process.* -
  • The nanostars are made up of 8 tetrahedrons and showcase high magnetization levels similar to bulk materials, measured at 235 A·m·kg.* -
  • Advanced imaging techniques revealed complex 3D spin configurations influenced by both dipolar and exchange interactions, highlighting how the unique shape of these nanostars can significantly alter their magnetic properties.*
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Single-walled carbon nanotubes (SWCNTs) are promising candidates for gas sensing applications, providing an efficient solution to the device miniaturization challenge and allowing low power consumption. SWCNT gas sensors are mainly based on field-effect transistors (SWCNT-FETs) where the modification of the current flowing through the nanotube is used for gas detection. A major limitation of these SWCNT-FETs lies in the difficulty to measure their transfer curves, since the flowing current typically varies between 10 and 10 A.

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Highly symmetrical gold nanocages can be produced with a controllable number of circular windows of either 2, 3, 4, 6 or 12 via an original fabrication route. The synthetic pathway includes three main stages: the synthesis of silica/polystyrene multipod templates, the regioselective seeded growth of a gold shell on the unmasked part of the silica surface and the development of gold nanocages by dissolving/etching the templates. Electron microscopy and tomography provide evidence of the symmetrical features of the as-obtained nanostructures.

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Multifunctional Bi- and Fe-modified carbon xerogel composites (CXBiFe), with different Fe concentrations, were obtained by a resorcinol-formaldehyde sol-gel method, followed by drying in ambient conditions and pyrolysis treatment. The morphological and structural characterization performed by X-ray diffraction (XRD), Raman spectroscopy, N adsorption/desorption porosimetry, scanning electron microscopy (SEM) and scanning/transmission electron microscopy (STEM) analyses, indicates the formation of carbon-based nanocomposites with integrated Bi and Fe oxide nanoparticles. At higher Fe concentrations, Bi-Fe-O interactions lead to the formation of hybrid nanostructures and off-stoichiometric BiFeO mullite-like structures together with an excess of iron oxide nanoparticles.

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We report on metal-assisted chemical etching of Si for the synthesis of mechanically stable, hybrid crystallographic orientation Si superstructures with high aspect ratio, above 200. This method sustains high etching rates and facilitates reproducible results. The protocol enables the control of the number, angle, and location of the kinks via successive etch-quench sequences.

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Recent advances in structural control during the synthesis of SWCNTs have in common the use of bimetallic nanoparticles as catalysts, despite the fact that their exact role is not fully understood. We therefore analyze the effect of the catalyst's chemical composition on the structure of the resulting SWCNTs by comparing three bimetallic catalysts (FeRu, CoRu and NiRu). A specific synthesis protocol is designed to impede the catalyst nanoparticle coalescence mechanisms and stabilize their diameter distributions throughout the growth.

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Article Synopsis
  • Researchers need nanocrystals with specific shapes for better catalysts, but traditional methods don’t allow for shape control.
  • This study successfully synthesized concave platinum nanocubes with {110} facets and showed how they grow on a Pt(111) support, creating detailed nanostructured surfaces.
  • By carefully selecting the support's crystallographic orientation, scientists can selectively immobilize desired nanostructures from a mixed solution, leading to new possibilities in nanocrystal development.
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