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The present study reports a systematic analysis of morphology and hydrogen sorption capacity of mesoporous organic-inorganic silica prepared by varying the silica synthesis parameters. Cationic surfactants of different chain lengths and different proportions of functionalised precursors were introduced in the synthesis mixture. Improved hydrogen storage properties have been obtained, already below 20 bar, reaching a maximum storage capacity around 4.75 wt% at 80 bar. The textural characteristics were analysed by nitrogen sorption and small angle X-ray scattering, and the thermal stability has been characterized by thermogravimetric analysis. The materials show specific surface area between 400 and 700 m2/g and a weakly ordered mesoporosity induced by the short chain surfactant template.

Composite fibrous materials based on (graphene-enriched) nitrogen-doped carbon/transition metal oxides were produced by electrospinning and their physicochemical properties were thoroughly investigated by a combination of characterisation techniques. The electrochemical behaviour of the electrodes prepared with them was evaluated in view of their use in the capacitive deionisation of saline water. The morphology of the materials reminded of usnea florida lichens, wheat ears, sea sponges and noodles and depended on the transition metal (Mn, Fe, Ti or Zn). The morphology and the relative amount (14.1–22.2 wt%) of the surface nitrogen and carbon-bonded oxygen functional species, beneficial to wettability and involving pseudocapacitive processes, had strong impact on the specific capacitance (43.7–67.4 F g−1, at 5 m V s−1 scan rate), whereas also the specific micropore volume (0.4–5.6 mm3 g−1) affected the effective areal capacitance of the electrodes (1.2–6.0 F m−2, at 5 mV s−1). Ion storage in the composite materials occurred via a mixed capacitive/pseudocapacitive process. Hence, increasing the content of the oxide (from 24.6 to 56.7 wt%), thanks to the fast-reversible redox reactions at or near surface it involves, partly compensated for the growing hindrance to diffusion encountered by the ions (hampered electrostatic adsorption) as the scan rate increased from 5 to 100 mV s−1.

The target for European decarburization encourages the use of renewable energy sources and H2 is considered the link in the global energy system transformation. So, research studies are numerous, but only few facilities can test materials and components for H2 storage. This work offers a brief review of H2 storage methods and presents the preliminary results obtained in a new facility. Slow strain rate and fatigue life tests were performed in H2 at 80 MPa on specimens and a tank of AISI 4145, respectively. Besides, the storage capacity at 30 MPa of a solid-state system, they were evaluated on kg scale by adsorption test. The results have shown the H2 influence on mechanical properties of the steel. The adsorption test showed a gain of 26% at 12 MPa in H2 storage with respect to the empty condition. All samples have been characterized by complementary techniques in order to connect the H2 effect with material properties.

The methane adsorption properties of activated carbon samples from pinecones using chemical activation with different KOH/precursor ratio were estimated at room temperature (≅298 K) and pressure up to 35 bar using a volumetric Sievert-type apparatus. A complete and detailed characterization of the synthesized activated carbon samples was obtained using nitrogen adsorption/desorption measurements at liquid nitrogen temperature (77 K), for the textural properties analysis, by scanning electron microscopy and X-ray diffraction for topography and long-range order estimation, and by wavelenght-dispersive spectrometry for chemical composition, respectively. All the adsorption data were analyzed by the Toth isotherm model. The probed activated carbon samples show both higher methane storage values for pressures up to 35 bar (the maximum value reached is 15 wt%) and totally reversible methane uptake up to many cycles without any treatment in between indication of very stable properties. The experimental work repo...

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.

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 of the fibres. It allows fully profiting of the more favourable pore size distribution in the graphene-enriched fibres, endowed with higher conductivity and capacitance, for the obtainment of unprecedented electro-sorption capacities via an extremely simple synthesis process, with no need of activation treatments.

Pure and titanium- or silicon-doped iron oxide fibres are synthesised by electro-spinning over conductive fluorine doped tin oxide (FTO)/glass substrates, and the effect of the type of dopant on the morphology of the fibres and the crystalline phase of the oxide is investigated by means of several complementary characterisation techniques. Results show that in the absence of dopant, highly porous fibres, consisting of interconnected polycrystalline hematite grains, are obtained. Doping with titanium does not influence the crystalline phase of the oxide, but the better packed structure of the fibres causes them to detach from the support. Silicon-doping results in a different phase of the host oxide (maghemite) and good adhesion of the fibres to the FTO/glass support. Very preliminary tests to evaluate the photo-electrochemical activity of the samples demonstrate that the photocurrent measured with Si-doped maghemite fibres is 53% higher with respect to that obtained with pure hematite fibres, as an effect of the nearly threefold increase in the donor concentration brought about by doping. This, in turn, improves the charge transfer at the interface, leading to a higher charge injection from the electrode to the electrolyte and, thus, to a greater photo-oxidation efficiency.

Pure and Al- and/or Ca-added ZnO fibers are synthesized by electro-spinning. Their morphological, structural and optical properties are investigated by means of several complementary characterization techniques, focusing attention on optical properties and fiber surface roughness, which are of relevance in many applications. The comparative analysis of the results obtained demonstrates that all the fibers consist of rounded polycrystalline oxide nanoparticles interconnected to each other, with the (dopant-dependent) nanoparticle size controlling their surface roughness. Non-stoichiometry affects all the samples and strongly influences their photoluminescence properties. Calcium segregates in a secondary phase forming calcite. On the contrary, aluminum well disperses within zincite as an isolated impurity, with Al 3+ ions substituting Zn 2+ ions in the ZnO lattice. Its content controls the relative exciton-to-defect emission band intensity, as well as the frequency of the main Zn O absorption peak.

Poly(e-caprolactone) (PCL) is a cheap and sustainable polymer with long-term degradation (3–4 years) and low temperature transition ( T m = ∼60 °C). We report on the investigation of PCL as a valid green candidate for Carbon Capture and Utilization (CCU). Studies were carried out by two complementary tools: a Sievert-type volumetric apparatus, to thoroughly analyse the CO 2 adsorption/desorption process inside the polymer, and Nuclear Magnetic Resonance (NMR) spectroscopy for a deeper study of the molecular dynamics and confinement effects through 13 C – pulsed field gradient (PFG) method (self-diffusion measurements), relaxation times (T 1 ) and spectral analysis. The morphology of the solid-state PCL was also investigated by Scanning Electron Microscopy (SEM). The effects of both the physical state and the adsorption process conditions on the PCL's CO 2 sorption capabilities were investigated as well as those concerning the cyclic life and the regeneration process. We find that two kind of adsorption sites are present in PCL matrix. Furthermore, PCL show a remarkable and complete thermoreversibility of the CO 2 adsorption process, a key condition in view of possible applications in this field.

Carbon-based nanostructures are considered promising materials for gas storage thanks to robust structure, tunable porosity, lightweight, high thermal/chemical stability and easy production. This study reports the development of activated carbon fibers prepared from commercial Kevlar® through an innovative pyrolysis method, consisting of carbonization in inert ambient and subsequent physical activation in oxidizing atmosphere, using a unique apparatus. Varying three key parameters, time (range 60- 240 min), temperature (range 1023- 1123 K) and gas-flow (0.3/0.9/1.2 Nl/min of CO2), the correlation between the activation procedure and the resulting samples structure was evaluated. The best results in terms of microporosity and gas adsorption properties have been obtained by reducing the activation times of the material. Furthermore, the purpose has been to optimize the characteristics in terms of Specific Surface Area, Total Pore Volume and optimal Pore Size Distribution. The method made it possible to develop an adsorbent material with a high fraction of micropores up to 94 % of the total pore volume, straddling the supermicroporosity (0.7- 2 nm) and ultramicroporosity (

In this work, low-cost ceramic clay ultra-filtration membranes have been fabricated with a low sintering temperature, using natural aluminosilicate nanotubes (Halloysite) for the separation of macromolecular proteins. Tubular supports for membranes were prepared from quartz sand and calcite (natural materials) using the extrusion method. The effect of calcination temperatures on the structure of the membrane supports was studied in order to obtain the appropriate average pore size (APS) and porosity. Using the slip casting technique, two layers were deposited on the supports. The titania (TiO2) intermediate layer and the Halloysite top-layer were sintered at 1050 and 580 °C, respectively. The membranes were characterized in terms of mechanical properties, porosity; pores size distribution, water permeability and scanning electron microscopy. Finally, capability for proteins separation (proteins used include: bovine serum albumin, egg albumin and casein), is evaluated.

H2 adsorption properties of ordered mesoporous silica prepared with different ratios of functionalized precursors have been studied. Silica particles were synthesized by sol-gel method, with tetradecyltrimethyl ammonium bromide (C14) or dodecyl trimethyl ammonium bromide (C12) as structure directing agents, and tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES), by varying the molar ratio of the two precursors. The porosity and microstructure of the materials in function of the MTES/TEOS ratio were evaluated by using nitrogen adsorption and X-ray diffraction and showed that the samples contained amorphous and ordered porous domains. Stable porous structure able to hold H2 molecule and give them back when required has been obtained. The higher hydrogen adsorption capacities measured at 77 K were obtained for the samples synthesized with reduced amount of MTES, followed by the samples with no MTES, with both C12 and C14 directing agents. Increased amount of MTES precursor led to lowering of the adsorption capacity. The increase of the adsorption capacity already below 20 bar, observed for all samples, could be an advantage for practical application since a lower pressure is preferable. The study revealed the influence of the synthesis parameters to the hydrogen sorption performance and serves as guidance for applications as hydrogen adsorptive materials.

A light emitting structure consisting of three coupled microcavities has been realized and studied. All three cavities contain a luminescent organic thin film of tetrakis(4-methoxyphenyl)porphyrin and they are coupled by means of two same LiF/ZnS Distributed Bragg Reflector. The entire structure is enclosed between a bottom and a top Bragg mirror with different layer number. Reflectivity spectra collected at different growing steps allow us to demonstrate the effective strong coupling between the three bare cavity modes. The reflectivity spectrum of the whole structure shows the presence of three well defined cavity dips. At normal incidence, the device emits three, well separated, peaks each one corresponding to a delocalized optical mode of the coupled system, while at higher angles the peaks result blue shift. The experimental reflectivity spectra are in good agreement with a theoretical model based on the transfer matrix method. The model is applicable to any device, therefore, once the materials to employ as emitters are established, the cavity can be designed in order to amplify just the modes that correspond to the peak wavelengths of the emission spectrum and/or to change completely the spectral shape.

Carbon/germanium dioxide (C/GeO 2 ) paper-like self-supporting membranes to be used as binder- and collector-free anodes in flexible Li-ion batteries (LIBs) are synthesised via electrospinning (ES) followed by stabilisation and carbonisation heat treatments. Carbonisation is operated at relatively low temperature (550 °C) in order to keep high nitrogen concentration in the carbonaceous fibre network, which is claimed to be beneficial for Li-ion storage. Regardless of the germanium load in the spinnable solution (2.50–4.25 wt%), α-quartz GeO 2 nanoparticles (NPs) encapsulated in highly N-doped (10–16 at%) C fibres are produced. The size of the oxide NPs and the fibre diameter increase with increasing germanium load. Based on the results of the compositional analysis, the specific capacities of the composite fibres are expected to range between 590 and 780 mAh/g. Preliminary results of half-cell tests substantially confirm the expectations, with Coulombic efficiencies of 92–96% at the second charge/discharge cycle.

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).

A new type of porous ceramic supports for membranes has been designed. The new supports have been fabricated from polycrystalline quartz sand and calcite raw materials. In this work, two configurations of support (tubular and flat) have been produced using extrusion method. The open porosity, the pore size distribution, the average pore size (APS), the strength and the permeability of sintered supports have been found to depend mainly on the weight ratio of calcite (CaCO3) additive. The results showed that with the addition of 15–35 wt.% of calcite and sintering temperature of about 1375 °C for 1 h the best characteristics of sintered supports could be obtained. The developed tubular ceramic supports with the APS 6.3–12 μm, open porosity 42–55%, the water permeability (16–68 m3/h m2 bar) and flexural strength 8–18 MPa hopefully offer many perspectives for a wide use in membranes technology.

Titania/carbon nanotubes/platinum (TiO 2 -CNTs/Pt) nanohybrids, prepared by the micro-emulsion method followed by wet impregnation for Pt loading, were synthesized and investigated as active materials for H 2 O 2 oxidation. Steps of preparation method employed were optimized in order to improve the sensing performance of TiO 2 -CNTs/Pt nanocomposite towards the H 2 O 2 oxidation. By changing the order in which CNTs are added to the solution, hetero-structures with different grain size and crystalline phase of the metal oxide were synthesised. Adding CNTs to the micro-emulsion solution favoured the aggregation between oxide nanoparticles over the interaction with CNTs, leading to the formation of larger anatase titania agglomerates. Instead, smaller-sized rutile particles formed by adding CNTs before the onset of precipitation. The order of CNT addition to the solution was found to influence also Pt particle size, with the smaller metal particles observed on the sample prepared by the latter procedure. The nanocomposite consisting of uniformly distributed TiO 2 particles on the surface of CNTs and smaller Pt nanoparticles showed the best performance sensing towards H 2 O 2 . An amperometric H 2 O 2 sensor was fabricated by modifying the working electrode surface of a planar screen printed carbon electrode (SPCE) device. The sensor showed excellent sensitivity (120 μA mM −1 cm −1 ) and linearity in a large range (from 70 μM to 6 mM), and a low detection limit

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.

A new and very simple approach to the synthesis of oxide nanopowders enriched with very high contents of carbon nanotubes (CNTs) is proposed. The procedure consists of three steps: 1) generation of nanofibres over mats of CNTs via the electro-spinning technique; 2) thermo-mechanical treatment of the so-prepared composite to improve interfacial interaction between as-spun fibres and carbonaceous support; 3) calcination in air to obtain the desired oxide from its precursor. Its ease and efficacy are here demonstrated in the case of titania, but the proposed procedure can be extensively used for any other oxide, provided that it can be prepared by ES technique. In this preliminary study, a fixed titanium concentration (0.9wt%) in the solution to be spun is considered, and the influence of titania precursor (titanium butoxide or titanium isopropoxide) and type of polymer (polyvinilpyrrolidone or polyvinilacetate) on morphology and crystalline phase of the oxide nanoparticles is investigated. Viscosity of the precursor/polymer solution is found to chiefly control not only morphology of the oxide, but indirectly also its crystalline phase. CNT load of the hybrids ranges between 38 and 88 wt%.

In this paper, we study both experimentally and theoretically the photoluminescence PL properties of a monolithic organic based optical device constituted by two coupled MCs. The PL spectra from this coupled structure display two narrow peaks despite only one cavity b contains an active layer weakly coupled to the cavity mode. The presence of two peaks of comparable height in the emission spectrum originates from the coupling of the two cavities. These emission peaks arise from the photonic analog of cavity polaritons. Cavity polaritons result from quantum wells QW excitons strongly coupled to cavity photons. Polariton PL arises after the incoherent pumping of one subsystem QW excitons, detecting quanta from the other one escaping cavity photons. Analogously, in the present device, we can detect light PLa from the passive top cavity a while pumping the bottom cavity b by exciting the incoherent PL of the embedded active organic layer. However in contrast to the cavity polaritons, we can also pump and probe the same subsystem PLbthe bottom cavity with the embedded organic layer. By this way it is possible to achieve a more complete characterization of the strong coupling between two subsystems and a more complete test of the theoretical models. The study of the incoherent emission properties of cavity embedded quantum systems is also useful for understanding the emission properties of electroluminescent devices. In

Strong coupled organic-inorganic microcavities device has been realized and studied. One of the two cavities contains an organic thin film of tetrakis(4-methoxyphenyl)porphyrin, whereas the other microcavity is a dielectric structure coupled to the organic one by means of a LiF/ZnS Bragg mirror. Reflectivity spectra show the presence of two well defined cavity dips. We observe an energy splitting of the two cavity-modes. Despite only one cavity contains the active layer, the photoluminescence spectra display two peaks at the same energy of the reflectivity dips. These observations indicate the strong coupling of the two cavities. The comparison of the diagonalized effective Hamiltonian with the observed resonances further confirms the strong coupling.

A light emitting structure consisting of two coupled microcavities has been realized and studied. One of the two cavities contains a luminescent organic thin film of tetrakis (4-methoxyphenyl)porphyrin, whereas the other microcavity is a dielectric structure coupled to the organic one by means of a LiF/ZnS Bragg mirror. Reflectivity spectra show the presence of two well defined cavity dips. We observe an energy splitting of the two cavity modes. Despite the fact that only one cavity contains the active layer, the photoluminescence spectra display two peaks with comparable intensities at the same energy of the reflectivity dips. These observations indicate the strong coupling of the two cavities. The comparison of the diagonalized effective Hamiltonian with the observed resonances further confirms the strong coupling. (C) 2009 American Institute of Physics.

We study the emission properties of a high quality monolithic microcavity with an embedded ultrathin organic tetrakis(4-methoxyphenyl)porphyrin layer. Spectral and angle-resolved photoluminescence measurements show a well defined polarized doublet at detection angles larger than 15 degrees. The splitting energy ranges up to 70 meV. The usual employed mechanism, based on the mismatch between the center of the mirror stop band and the wavelength of the microcavity, accounts only for a small fraction of the observed splitting. A transfer matrix model taking into account the optical anisotropy of the organic layer, has been employed to reproduce the observed experimental results. The anisotropy of the organic layer, confirmed by optical absorption spectroscopy, origins from a local molecular order as inferred by atomic force microscopy measurements.

We demonstrate a giant polarization splitting of the emission of a high quality monolithic microcavity with an embedded ultrathin organic tetrakis(4-methoxyphenyl)porphyrin layer. The usual employed mechanism, based on the mismatch between the center of the mirror stopband and the wavelength of the microcavity, accounts only for a small fraction of the observed splitting. Optical and atomic force microscopy measurements allowed us to attribute it to local crystalline molecular order. This opens the way for the design and optimization of highly polarized compact optical sources.