Saveria Santangelo - Academia.edu (original) (raw)
Papers by Saveria Santangelo
Applied Sciences, 2021
Fe2O3 and Fe2O3:Ge nanofibers (NFs) were prepared via electrospinning and thoroughly characterize... more Fe2O3 and Fe2O3:Ge nanofibers (NFs) were prepared via electrospinning and thoroughly characterized via several techniques in order to investigate the effects produced by germanium incorporation in the nanostructure and crystalline phase of the oxide. The results indicate that reference Fe2O3 NFs consist of interconnected hematite grains, whereas in Fe2O3:Ge NFs, constituted by finer and elongated nanostructures developing mainly along their axis, an amorphous component coexists with the dominant α-Fe2O3 and γ-Fe2O3 phases. Ge4+ ions, mostly dispersed as dopant impurities, are accommodated in the tetrahedral sites of the maghemite lattice and probably in the defective hematite surface sites. When tested as anode active material for sodium ion batteries, Fe2O3:Ge NFs show good specific capacity (320 mAh g−1 at 50 mA g−1) and excellent rate capability (still delivering 140 mAh g−1 at 2 A g−1). This behavior derives from the synergistic combination of the nanostructured morphology, the ...
Applied Sciences, 2021
Synthetic dyes, dispersed in water, have harmful effects on human health and the environment. In ... more Synthetic dyes, dispersed in water, have harmful effects on human health and the environment. In this work, Ti and/or Zn oxide nanofibers (NFs) with engineered architecture and surface were produced via electrospinning followed by calcination. Calcination and subsequent cooling were operated at fast rates to generate porous NFs with capture centers to reduce the recombination rate of the photogenerated charges. After morphological and microstructural characterisation, the NFs were comparatively evaluated as photocatalysts for the removal of methylene blue from water under UV irradiation. The higher band gap and lower crystallinity were responsible for the lower photocatalytic activity of the ternary oxides (ZnTiO3 and Zn2TiO4) towards the degradation of the dye. The optimal loads of the highly performing binary oxides were determined. By using 0.66 mg mL−1 wurtzite ZnO for the discoloration of an aqueous solution with a dye concentration of 15 µM, a higher rate constant (7.94 × 10−2...
Nanomaterials, 2020
The effect of the type of dopant (titanium and manganese) and of the reduced graphene oxide conte... more The effect of the type of dopant (titanium and manganese) and of the reduced graphene oxide content (rGO, 30 or 50 wt %) of the α-Fe2O3@rGO nanocomposites on their microstructural properties and electrochemical performance was investigated. Nanostructured composites were synthesized by a simple one-step solvothermal method and evaluated as anode materials for sodium ion batteries. The doping does not influence the crystalline phase and morphology of the iron oxide nanoparticles, but remarkably increases stability and Coulombic efficiency with respect to the anode based on the composite α-Fe2O3@rGO. For fixed rGO content, Ti-doping improves the rate capability at lower rates, whereas Mn-doping enhances the electrode stability at higher rates, retaining a specific capacity of 56 mAhg−1 at a rate of 2C. Nanocomposites with higher rGO content exhibit better electrochemical performance.
Desalination, 2020
Electrosorptive desalination is a very simple and appealing approach to satisfy the increasing de... more Electrosorptive desalination is a very simple and appealing approach to satisfy the increasing demand for drinking water. The large-scale application of this technology calls for the development of easy-to-produce, cheap and highly performing electrode materials and for the identification and tailoring of their most influential properties, as well. Here, biosynthesised bacterial cellulose is used as a carbon precursor for the production of three-dimensional nanostructures endowed with hierarchically porous architecture and different density and type of intrinsic and hetero-atom induced lattice defects. The produced materials exhibit unprecedented desalination capacities for carbon-based electrodes. At an initial concentration of 585 mg L −1 (10 mmol L −1), they are able to remove from 55 to 79 mg g −1 of salt; as the initial concentration rises to 11.7 g L −1 (200 mmol L −1), their salt adsorption capacity reaches values ranging between 1.03 and 1.35 g g −1. The results of the thorough material characterisation by complementary techniques evidence that the relative amount of oxygenated surface functional species enhancing the electrode wettability play a crucial role at lower NaCl concentrations, whereas the availability of active non-sp 2 defect sites for adsorption is mainly influential at higher salt concentrations.
Desalination, 2018
Electro-spun carbon fibres doped with very high nitrogen concentrations (19−21 wt%) are obtained ... more Electro-spun carbon fibres doped with very high nitrogen concentrations (19−21 wt%) are obtained operating carbonisation at low temperature (500°C). The as-synthesised fibres are evaluated as electrode materials for the electrochemical desalination of water. The effect of the enrichment of the nitrogen doped carbon fibres with thermally reduced graphene oxide is also investigated. The fibrous electrodes are able to remove amazing amounts of NaCl (17.0−27.6 mg/g) from a salty solution with an initial concentration of 585 mg/L. The nitrogen doping, which dramatically improves the wettability, plays a crucial role in determining the outstanding electro-sorption capacities
Solid State Ionics, 2017
Cobalt oxide fibres are synthesised via electro-spinning followed by calcination in air at 600°C.... more Cobalt oxide fibres are synthesised via electro-spinning followed by calcination in air at 600°C. Texture, morphology and surface composition of the fibres, as well as phase of the oxide formed are investigated by means of a combination of characterisation techniques. The electrochemical performance of the electro-spun Co 3 O 4 fibres as anode material in Na-ion rechargeable batteries is evaluated, and the conversion reaction mechanism is investigated by carrying out ex-situ analyses on the cycled electrodes. The formation of the CoO after the first sodiation/desodiation cycle accounts for the cathodic specific capacity lowering from 983 down to 580 mAh g − 1. The high aspect ratio morphology of the fibres is responsible for the high value of initial cathodic specific capacity and the slow capacity fading (after 30 cycles, a cathodic capacity of 407 mAh g − 1 is retained).
Crystalline hematite/polycrystalline nickel oxide (α-Fe2O3/NiO) core/shell nanofibers are prepare... more Crystalline hematite/polycrystalline nickel oxide (α-Fe2O3/NiO) core/shell nanofibers are prepared by electrospinning and calcination, followed by a varying number (100–1150) of atomic layer deposition cycles of NiO. The deposition of the conformal NiO layer leads to the passivation of the surface states and the appearance of a photoluminescence band in the micro-Raman spectra excited by 532 nm laser. As a continuous NiO layer is formed, a peak, possibly arising from a two-magnon mode, appears at 1585 cm−1. The detection of the peak, which is not observed in the spectra excited by a 633 nm laser, is assisted by the surface plasmon at around 510 nm introduced by the polycrystalline NiO layer, due to the electron doping induced by coordination-defects at its edge-rich surface.
The European Physical Journal Plus
Abstract.The two most significant categories of physical and chemical pollutants in sediments (ra... more Abstract.The two most significant categories of physical and chemical pollutants in sediments (radionuclides and metals) were investigated in this article, in order to evaluate pollution levels in marine sediments from eight different selected sites of the Calabria region, south of Italy. In particular samples were analyzed to determine natural and anthropic radioactivity and metal concentrations, in order to assess any possible radiological hazard, the level of contamination and the possible anthropogenic impact in the investigated area. Activity concentrations of 226Ra, 232Th, 40K and 137Cs were measured by High Purity Germanium (HPGe) gamma spectrometry. The obtained results show that, for radium (in secular equilibrium with uranium), the specific activity ranges from ($ 14 \pm 1$14±1) Bq/kg dry weight (d.w.) to ($ 54 \pm 9$54±9) Bq/kg d.w.; for thorium, from ($ 12 \pm 1$12±1) Bq/kg d.w. to ($ 83 \pm 8$83±8) Bq/kg d.w.; for potassium, from ($ 470 \pm 20$470±20) Bq/kg d.w. to ($ 1000 \pm 70$1000±70) Bq/kg d.w. and for cesium it is lower than the minimum detectable activity value. The absorbed gamma dose rate in air (D), the annual effective dose equivalent (AEDE) outdoor and the external hazard index ($ H_{\rm ex}$H ex ) were calculated to evaluate any possible radiological risk, mainly due to the use of marine sediments for the beach nourishment. The results show low levels of radioactivity, thus discarding any significant radiological risk. Some metals (As, Cd, Crtot, Hg, Ni, Pb, Cu, Zn, Mn and Fe), that could be released into the environment by both natural and anthropogenic sources, were investigated through inductively coupled plasma mass spectrometry (ICP-MS) measurements and compared with the limits set by the Italian Legislation, to assess any possible contamination. Experimental results show that they are much lower than the contamination threshold value, thus excluding their presence as pollutants. The degree of sediment contaminations were quantified using enrichment factor (EF) and geoaccumulation index ( Igeo) for some potential hazardous elements. Results show that EF and Igeo values of As, Pb and Mn were the greatest among the studied metals. Data of this preliminary study could be helpful in the future to obtain background levels in marine sediments of the investigated region and to develop environmental regulatory frameworks.
Electrochimica Acta
Abstract The development of sodium ion batteries as alternative technology to the lithium ion dep... more Abstract The development of sodium ion batteries as alternative technology to the lithium ion depends on the design of electrode based on cheap and high abundant elements. Iron oxides are potentially good candidates as negative electrode thanks to their high specific capacity, but they suffer from poor electronic transport properties and large volume change during sodiation/de-sodiation cycles. Stable performance in hematite or magnetite based electrodes requires the use of Fe/C composites made by expensive carbon precursors such as graphene oxides or carbon nanotubes. However, the limits of iron (III) oxide can also be tackled using a different approach by combining the advantages of the nanostructuring and the doping with an aliovalent element. In this work, we present for the first time the use of Si-doped Fe2O3 nanofibres obtained by an easy scalable process based on the electrospinning method. The silicon doping does not just improve the transport properties but induces also changes in the structure and morphology. The electrochemical results show that the Si-doped Fe2O3 fibres deliver an anodic capacity of 350 mAh·g−1 at the average potential of 1.5 V vs. Na+/Na after 70 cycles, a result never achieved for iron oxide based electrode standard formulation.
Materials Chemistry and Physics, 2016
Abstract The electrochemical behavior of different platinum-decorated nanocarbons (Pt@C) towards ... more Abstract The electrochemical behavior of different platinum-decorated nanocarbons (Pt@C) towards the oxidation of hydrogen peroxide (H2O2) was investigated. Three different types of nanocarbons were considered: i) carbon black, ii) dahlia-like carbon nanohorns and iii) carbon nanotubes, which included both commercial (single-wall and multi-wall) and laboratory prepared (multi-wall) samples. Shape and size distribution of the platinum nanoparticles and morphology of the nanocarbons were analyzed by transmission electron microscopy. Their nanostructure was investigated by micro-Raman spectroscopy, while elemental composition of the samples and chemical bonding states were studied by X-ray photoelectron spectroscopy. Electrochemical behavior towards H2O2 oxidation was evaluated by means of cyclic voltammetry modifying the working screen-printed carbon electrode surface with the prepared Pt@C nanocomposites. Data obtained suggest that the size and dispersion of the Pt nanoparticles play a key role in increasing the sensitivity towards H2O2 detection. Thanks to the presence of smaller and more dispersed platinum particles and of a greater amount of platinum hydroxide, acting as intermediary in the H2O2 oxidation process, Pt@dahlia-like carbon nanohorns result to be the most promising platform for the development of H2O2 electrochemical sensors.
Il Nuovo Cimento D, 1993
An additive process using the three-level resist scheme for X-ray mask fabrication by electron be... more An additive process using the three-level resist scheme for X-ray mask fabrication by electron beam lithography is analysed by Monte Carlo simulation of electron scattering. The resist exposure is calculated for specific e-beam test patterns aimed at 0.2 ?m resolution. The time evolution of the developed resist profiles is simulated by using a string model for dissolution. Relevant process variables such as e-beam energy (25 to 50 keV) and resist thickness are investigated. Simulation results demonstrate that 50keV is altogether a preferred condition, compared to 25 keV, leading however to different pattern transfer techniques, according to resist thickness. The process modelling is compared with previously reported experimental results. Good qualitative agreement is found, indicating that modelling can be used as an effective aid in the quantitative evaluation of the process.
Microelectronic Engineering, 1995
In this paper, Buckingham's theorem on physically similar systems is applied for the first ti... more In this paper, Buckingham's theorem on physically similar systems is applied for the first time to the derivation of interpolation curves of numerical data. A simplified dependence of the curves on a limited number of effective dimensionless parameters is found by a novel approach. In particular, the method is applied to Monte Carlo modelling and the calculation is considered of the backscattering coefficient @h from a general substrate in the elastic regime. A single dimensionless backscattering parameter is introduced and a simple scaling law is determined, indicating how the configuration of the many variables involved can eventually change without affecting the result. The validity of the law is demonstrated in the 5 to 100 keV energy range, with substrate thicknesses ranging from 10 to 21000A@?and for all the substrates of the periodic table.
European Transactions on Telecommunications, 1990
A single-layer resist process for X-ray master mask fabrication by electron beam lithography is t... more A single-layer resist process for X-ray master mask fabrication by electron beam lithography is theoretically and experimentally investigated. In the mask fabrication process boron nitride membranes are utilized and final absorber structures are obtained by Au electroplating after e-beam patterning at different primary beam energies, on a single PMMA layer of 10000 A. The e-beam energies experimentally utilized are 20 and 30 keV. Detailed Monte Carlo analysis of the rnultilayer structure is carried out at 10, 20, 30 and 40 keV, the corresponding proximity function calculated and compared to experiment. It is found that an important source of backscattering is constituted by the thin metal layer as plating base, while the ultimate limit for resolution seems to be determined by forward scattering. Finally, it is demonstrated that by proper selection of the e-beam energy it is possible to obtain high contrast absorbers down to 0.3 pm lines and spaces.
Communications Chemistry
Niobium pentoxides are promising acid catalysts for the conversion of biomass into fuels and chem... more Niobium pentoxides are promising acid catalysts for the conversion of biomass into fuels and chemicals. Developing new synthesis routes is essential for designing niobium pentoxide catalysts with improved activity for specific practical processes. Here we show a synthesis approach in acetophenone, which produces nanostructured niobium pentoxides with varying structure and acidity that act as efficient acid catalysts. The oxides have orthorhombic structures with different extents of distortions and coordinatively unsaturated metal atoms. A strong dependence is observed between the type and strength of the acid sites and specific structural motifs. Ultrasmall niobium pentoxide nanoparticles, which have strong Brønsted acidity, as well as Lewis acidity, give product yields of 96% (3 h, 140 °C, 100% conversion), 85% (3 h, 140 °C, 86% conversion), and 100% (3 h, 110 °C, 100% conversion) in the reactions of furfuryl alcohol, 5-(hydroxymethyl)furfural, and α-angelica lactone with ethanol, ...
Advanced Functional Materials
Physical Chemistry Chemical Physics
The chemical groups present at the surface of graphite have been thought of for a long time as th... more The chemical groups present at the surface of graphite have been thought of for a long time as the main responsible for the catalytic activity in the oxygen reduction. Recently,...
International Journal of Hydrogen Energy
Nanomaterials (Basel, Switzerland), Jan 22, 2018
This work highlights the importance of the hydrophilicity of a catalyst's active sites on an ... more This work highlights the importance of the hydrophilicity of a catalyst's active sites on an oxygen reduction reaction (ORR) through an electrochemical and physico-chemical study on catalysts based on nitrogen-modified carbon doped with different metals (Fe, Cu, and a mixture of them). BET, X-ray Powder Diffraction (XRPD), micro-Raman, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and hydrophilicity measurements were performed. All synthesized catalysts are characterized not only by a porous structure, with the porosity distribution centered in the mesoporosity range, but also by the presence of carbon nanostructures. In iron-doped materials, these nanostructures are bamboo-like structures typical of nitrogen carbon nanotubes, which are better organized, in a larger amount, and longer than those in the copper-doped material. Electrochemical ORR results highlight that the presence of iron and nitrogen...
Materials Research Bulletin
Applied Sciences, 2021
Fe2O3 and Fe2O3:Ge nanofibers (NFs) were prepared via electrospinning and thoroughly characterize... more Fe2O3 and Fe2O3:Ge nanofibers (NFs) were prepared via electrospinning and thoroughly characterized via several techniques in order to investigate the effects produced by germanium incorporation in the nanostructure and crystalline phase of the oxide. The results indicate that reference Fe2O3 NFs consist of interconnected hematite grains, whereas in Fe2O3:Ge NFs, constituted by finer and elongated nanostructures developing mainly along their axis, an amorphous component coexists with the dominant α-Fe2O3 and γ-Fe2O3 phases. Ge4+ ions, mostly dispersed as dopant impurities, are accommodated in the tetrahedral sites of the maghemite lattice and probably in the defective hematite surface sites. When tested as anode active material for sodium ion batteries, Fe2O3:Ge NFs show good specific capacity (320 mAh g−1 at 50 mA g−1) and excellent rate capability (still delivering 140 mAh g−1 at 2 A g−1). This behavior derives from the synergistic combination of the nanostructured morphology, the ...
Applied Sciences, 2021
Synthetic dyes, dispersed in water, have harmful effects on human health and the environment. In ... more Synthetic dyes, dispersed in water, have harmful effects on human health and the environment. In this work, Ti and/or Zn oxide nanofibers (NFs) with engineered architecture and surface were produced via electrospinning followed by calcination. Calcination and subsequent cooling were operated at fast rates to generate porous NFs with capture centers to reduce the recombination rate of the photogenerated charges. After morphological and microstructural characterisation, the NFs were comparatively evaluated as photocatalysts for the removal of methylene blue from water under UV irradiation. The higher band gap and lower crystallinity were responsible for the lower photocatalytic activity of the ternary oxides (ZnTiO3 and Zn2TiO4) towards the degradation of the dye. The optimal loads of the highly performing binary oxides were determined. By using 0.66 mg mL−1 wurtzite ZnO for the discoloration of an aqueous solution with a dye concentration of 15 µM, a higher rate constant (7.94 × 10−2...
Nanomaterials, 2020
The effect of the type of dopant (titanium and manganese) and of the reduced graphene oxide conte... more The effect of the type of dopant (titanium and manganese) and of the reduced graphene oxide content (rGO, 30 or 50 wt %) of the α-Fe2O3@rGO nanocomposites on their microstructural properties and electrochemical performance was investigated. Nanostructured composites were synthesized by a simple one-step solvothermal method and evaluated as anode materials for sodium ion batteries. The doping does not influence the crystalline phase and morphology of the iron oxide nanoparticles, but remarkably increases stability and Coulombic efficiency with respect to the anode based on the composite α-Fe2O3@rGO. For fixed rGO content, Ti-doping improves the rate capability at lower rates, whereas Mn-doping enhances the electrode stability at higher rates, retaining a specific capacity of 56 mAhg−1 at a rate of 2C. Nanocomposites with higher rGO content exhibit better electrochemical performance.
Desalination, 2020
Electrosorptive desalination is a very simple and appealing approach to satisfy the increasing de... more Electrosorptive desalination is a very simple and appealing approach to satisfy the increasing demand for drinking water. The large-scale application of this technology calls for the development of easy-to-produce, cheap and highly performing electrode materials and for the identification and tailoring of their most influential properties, as well. Here, biosynthesised bacterial cellulose is used as a carbon precursor for the production of three-dimensional nanostructures endowed with hierarchically porous architecture and different density and type of intrinsic and hetero-atom induced lattice defects. The produced materials exhibit unprecedented desalination capacities for carbon-based electrodes. At an initial concentration of 585 mg L −1 (10 mmol L −1), they are able to remove from 55 to 79 mg g −1 of salt; as the initial concentration rises to 11.7 g L −1 (200 mmol L −1), their salt adsorption capacity reaches values ranging between 1.03 and 1.35 g g −1. The results of the thorough material characterisation by complementary techniques evidence that the relative amount of oxygenated surface functional species enhancing the electrode wettability play a crucial role at lower NaCl concentrations, whereas the availability of active non-sp 2 defect sites for adsorption is mainly influential at higher salt concentrations.
Desalination, 2018
Electro-spun carbon fibres doped with very high nitrogen concentrations (19−21 wt%) are obtained ... more Electro-spun carbon fibres doped with very high nitrogen concentrations (19−21 wt%) are obtained operating carbonisation at low temperature (500°C). The as-synthesised fibres are evaluated as electrode materials for the electrochemical desalination of water. The effect of the enrichment of the nitrogen doped carbon fibres with thermally reduced graphene oxide is also investigated. The fibrous electrodes are able to remove amazing amounts of NaCl (17.0−27.6 mg/g) from a salty solution with an initial concentration of 585 mg/L. The nitrogen doping, which dramatically improves the wettability, plays a crucial role in determining the outstanding electro-sorption capacities
Solid State Ionics, 2017
Cobalt oxide fibres are synthesised via electro-spinning followed by calcination in air at 600°C.... more Cobalt oxide fibres are synthesised via electro-spinning followed by calcination in air at 600°C. Texture, morphology and surface composition of the fibres, as well as phase of the oxide formed are investigated by means of a combination of characterisation techniques. The electrochemical performance of the electro-spun Co 3 O 4 fibres as anode material in Na-ion rechargeable batteries is evaluated, and the conversion reaction mechanism is investigated by carrying out ex-situ analyses on the cycled electrodes. The formation of the CoO after the first sodiation/desodiation cycle accounts for the cathodic specific capacity lowering from 983 down to 580 mAh g − 1. The high aspect ratio morphology of the fibres is responsible for the high value of initial cathodic specific capacity and the slow capacity fading (after 30 cycles, a cathodic capacity of 407 mAh g − 1 is retained).
Crystalline hematite/polycrystalline nickel oxide (α-Fe2O3/NiO) core/shell nanofibers are prepare... more Crystalline hematite/polycrystalline nickel oxide (α-Fe2O3/NiO) core/shell nanofibers are prepared by electrospinning and calcination, followed by a varying number (100–1150) of atomic layer deposition cycles of NiO. The deposition of the conformal NiO layer leads to the passivation of the surface states and the appearance of a photoluminescence band in the micro-Raman spectra excited by 532 nm laser. As a continuous NiO layer is formed, a peak, possibly arising from a two-magnon mode, appears at 1585 cm−1. The detection of the peak, which is not observed in the spectra excited by a 633 nm laser, is assisted by the surface plasmon at around 510 nm introduced by the polycrystalline NiO layer, due to the electron doping induced by coordination-defects at its edge-rich surface.
The European Physical Journal Plus
Abstract.The two most significant categories of physical and chemical pollutants in sediments (ra... more Abstract.The two most significant categories of physical and chemical pollutants in sediments (radionuclides and metals) were investigated in this article, in order to evaluate pollution levels in marine sediments from eight different selected sites of the Calabria region, south of Italy. In particular samples were analyzed to determine natural and anthropic radioactivity and metal concentrations, in order to assess any possible radiological hazard, the level of contamination and the possible anthropogenic impact in the investigated area. Activity concentrations of 226Ra, 232Th, 40K and 137Cs were measured by High Purity Germanium (HPGe) gamma spectrometry. The obtained results show that, for radium (in secular equilibrium with uranium), the specific activity ranges from ($ 14 \pm 1$14±1) Bq/kg dry weight (d.w.) to ($ 54 \pm 9$54±9) Bq/kg d.w.; for thorium, from ($ 12 \pm 1$12±1) Bq/kg d.w. to ($ 83 \pm 8$83±8) Bq/kg d.w.; for potassium, from ($ 470 \pm 20$470±20) Bq/kg d.w. to ($ 1000 \pm 70$1000±70) Bq/kg d.w. and for cesium it is lower than the minimum detectable activity value. The absorbed gamma dose rate in air (D), the annual effective dose equivalent (AEDE) outdoor and the external hazard index ($ H_{\rm ex}$H ex ) were calculated to evaluate any possible radiological risk, mainly due to the use of marine sediments for the beach nourishment. The results show low levels of radioactivity, thus discarding any significant radiological risk. Some metals (As, Cd, Crtot, Hg, Ni, Pb, Cu, Zn, Mn and Fe), that could be released into the environment by both natural and anthropogenic sources, were investigated through inductively coupled plasma mass spectrometry (ICP-MS) measurements and compared with the limits set by the Italian Legislation, to assess any possible contamination. Experimental results show that they are much lower than the contamination threshold value, thus excluding their presence as pollutants. The degree of sediment contaminations were quantified using enrichment factor (EF) and geoaccumulation index ( Igeo) for some potential hazardous elements. Results show that EF and Igeo values of As, Pb and Mn were the greatest among the studied metals. Data of this preliminary study could be helpful in the future to obtain background levels in marine sediments of the investigated region and to develop environmental regulatory frameworks.
Electrochimica Acta
Abstract The development of sodium ion batteries as alternative technology to the lithium ion dep... more Abstract The development of sodium ion batteries as alternative technology to the lithium ion depends on the design of electrode based on cheap and high abundant elements. Iron oxides are potentially good candidates as negative electrode thanks to their high specific capacity, but they suffer from poor electronic transport properties and large volume change during sodiation/de-sodiation cycles. Stable performance in hematite or magnetite based electrodes requires the use of Fe/C composites made by expensive carbon precursors such as graphene oxides or carbon nanotubes. However, the limits of iron (III) oxide can also be tackled using a different approach by combining the advantages of the nanostructuring and the doping with an aliovalent element. In this work, we present for the first time the use of Si-doped Fe2O3 nanofibres obtained by an easy scalable process based on the electrospinning method. The silicon doping does not just improve the transport properties but induces also changes in the structure and morphology. The electrochemical results show that the Si-doped Fe2O3 fibres deliver an anodic capacity of 350 mAh·g−1 at the average potential of 1.5 V vs. Na+/Na after 70 cycles, a result never achieved for iron oxide based electrode standard formulation.
Materials Chemistry and Physics, 2016
Abstract The electrochemical behavior of different platinum-decorated nanocarbons (Pt@C) towards ... more Abstract The electrochemical behavior of different platinum-decorated nanocarbons (Pt@C) towards the oxidation of hydrogen peroxide (H2O2) was investigated. Three different types of nanocarbons were considered: i) carbon black, ii) dahlia-like carbon nanohorns and iii) carbon nanotubes, which included both commercial (single-wall and multi-wall) and laboratory prepared (multi-wall) samples. Shape and size distribution of the platinum nanoparticles and morphology of the nanocarbons were analyzed by transmission electron microscopy. Their nanostructure was investigated by micro-Raman spectroscopy, while elemental composition of the samples and chemical bonding states were studied by X-ray photoelectron spectroscopy. Electrochemical behavior towards H2O2 oxidation was evaluated by means of cyclic voltammetry modifying the working screen-printed carbon electrode surface with the prepared Pt@C nanocomposites. Data obtained suggest that the size and dispersion of the Pt nanoparticles play a key role in increasing the sensitivity towards H2O2 detection. Thanks to the presence of smaller and more dispersed platinum particles and of a greater amount of platinum hydroxide, acting as intermediary in the H2O2 oxidation process, Pt@dahlia-like carbon nanohorns result to be the most promising platform for the development of H2O2 electrochemical sensors.
Il Nuovo Cimento D, 1993
An additive process using the three-level resist scheme for X-ray mask fabrication by electron be... more An additive process using the three-level resist scheme for X-ray mask fabrication by electron beam lithography is analysed by Monte Carlo simulation of electron scattering. The resist exposure is calculated for specific e-beam test patterns aimed at 0.2 ?m resolution. The time evolution of the developed resist profiles is simulated by using a string model for dissolution. Relevant process variables such as e-beam energy (25 to 50 keV) and resist thickness are investigated. Simulation results demonstrate that 50keV is altogether a preferred condition, compared to 25 keV, leading however to different pattern transfer techniques, according to resist thickness. The process modelling is compared with previously reported experimental results. Good qualitative agreement is found, indicating that modelling can be used as an effective aid in the quantitative evaluation of the process.
Microelectronic Engineering, 1995
In this paper, Buckingham's theorem on physically similar systems is applied for the first ti... more In this paper, Buckingham's theorem on physically similar systems is applied for the first time to the derivation of interpolation curves of numerical data. A simplified dependence of the curves on a limited number of effective dimensionless parameters is found by a novel approach. In particular, the method is applied to Monte Carlo modelling and the calculation is considered of the backscattering coefficient @h from a general substrate in the elastic regime. A single dimensionless backscattering parameter is introduced and a simple scaling law is determined, indicating how the configuration of the many variables involved can eventually change without affecting the result. The validity of the law is demonstrated in the 5 to 100 keV energy range, with substrate thicknesses ranging from 10 to 21000A@?and for all the substrates of the periodic table.
European Transactions on Telecommunications, 1990
A single-layer resist process for X-ray master mask fabrication by electron beam lithography is t... more A single-layer resist process for X-ray master mask fabrication by electron beam lithography is theoretically and experimentally investigated. In the mask fabrication process boron nitride membranes are utilized and final absorber structures are obtained by Au electroplating after e-beam patterning at different primary beam energies, on a single PMMA layer of 10000 A. The e-beam energies experimentally utilized are 20 and 30 keV. Detailed Monte Carlo analysis of the rnultilayer structure is carried out at 10, 20, 30 and 40 keV, the corresponding proximity function calculated and compared to experiment. It is found that an important source of backscattering is constituted by the thin metal layer as plating base, while the ultimate limit for resolution seems to be determined by forward scattering. Finally, it is demonstrated that by proper selection of the e-beam energy it is possible to obtain high contrast absorbers down to 0.3 pm lines and spaces.
Communications Chemistry
Niobium pentoxides are promising acid catalysts for the conversion of biomass into fuels and chem... more Niobium pentoxides are promising acid catalysts for the conversion of biomass into fuels and chemicals. Developing new synthesis routes is essential for designing niobium pentoxide catalysts with improved activity for specific practical processes. Here we show a synthesis approach in acetophenone, which produces nanostructured niobium pentoxides with varying structure and acidity that act as efficient acid catalysts. The oxides have orthorhombic structures with different extents of distortions and coordinatively unsaturated metal atoms. A strong dependence is observed between the type and strength of the acid sites and specific structural motifs. Ultrasmall niobium pentoxide nanoparticles, which have strong Brønsted acidity, as well as Lewis acidity, give product yields of 96% (3 h, 140 °C, 100% conversion), 85% (3 h, 140 °C, 86% conversion), and 100% (3 h, 110 °C, 100% conversion) in the reactions of furfuryl alcohol, 5-(hydroxymethyl)furfural, and α-angelica lactone with ethanol, ...
Advanced Functional Materials
Physical Chemistry Chemical Physics
The chemical groups present at the surface of graphite have been thought of for a long time as th... more The chemical groups present at the surface of graphite have been thought of for a long time as the main responsible for the catalytic activity in the oxygen reduction. Recently,...
International Journal of Hydrogen Energy
Nanomaterials (Basel, Switzerland), Jan 22, 2018
This work highlights the importance of the hydrophilicity of a catalyst's active sites on an ... more This work highlights the importance of the hydrophilicity of a catalyst's active sites on an oxygen reduction reaction (ORR) through an electrochemical and physico-chemical study on catalysts based on nitrogen-modified carbon doped with different metals (Fe, Cu, and a mixture of them). BET, X-ray Powder Diffraction (XRPD), micro-Raman, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and hydrophilicity measurements were performed. All synthesized catalysts are characterized not only by a porous structure, with the porosity distribution centered in the mesoporosity range, but also by the presence of carbon nanostructures. In iron-doped materials, these nanostructures are bamboo-like structures typical of nitrogen carbon nanotubes, which are better organized, in a larger amount, and longer than those in the copper-doped material. Electrochemical ORR results highlight that the presence of iron and nitrogen...
Materials Research Bulletin