198 research outputs found
Role of Fe in the oxidation of methanol electrocatalyzed by Ni based layered double hydroxides: X-ray spectroscopic and electrochemical studies
No full textNi/Al and Ni/Fe layered double hydroxides (LDHs) were electrosynthesized on Pt electrodes to be used as catalysts for the development of methanol fuel cells. The electrochemical characterization and the electrocatalytic activity of the two LDHs towards methanol electro-oxidation in alkaline conditions were investigated. Furthermore, the role of Fe on the electronic and structural properties of the LDHs was investigated performing X-ray Absorption Spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). By the means of these techniques the materials were studied just electrosynthesized and after potentiostatic oxidation. The percentage of Ni active sites in the Ni/Fe LDH was higher than that of Ni/Al LDH, leading to a more efficient catalytic effect towards methanol oxidation in terms of current recorded at any potential value. Furthermore, methanol oxidation occurred at a lower potential for the same current density in the case of Ni/Fe LDH. The electrocatalytic performance displayed by the Ni/Fe LDH suggested the occurrence of a synergic effect between Ni and Fe sites, even if Fe is not directly involved in the redox process, and this evidence was confirmed by XAS and XPS experiment
Physical Activation of Waste-Derived Materials for Biogas Cleaning
No full textBiogas produced from biomass is carbon neutral. In fact, the carbon feedstock of biomass is converted into gas phase. Biogas use in high efficient energy systems, such as Solid Oxide Fuel Cells is a viable choice. One of the most important drawbacks for such systems is related to the interaction between trace compounds and anode section. Gas cleaning through physical removal mechanisms is the simplest and cheapest method adopted in the literature. Coupled with this solution, the recovery of waste materials is an efficient application of the circular economy approach. In this work, a physical activation process was investigated experimentally for waste-derived materials at a temperature of 700 °C. The removal of H2S was considered as the most abundant trace compound. Activated biochar showed an adsorption capacity comparable to commercial sorbents, while the performance of ashes are still too poor. An important parameter to be considered is the biogas humidity content that enters in competition with trace compounds that must be removed
Electrospun matrices for sustained drug release made by a PCL-chitosan blend shell and a PVA core
No full textCore-shell electrospinning is a versatile technique for tissue engineering applications due to the possibility of
uploading drugs in the core layer. The drug is protected by the shell layer that also allows its release by diffusion.
The aim of the present work is the development of a drug release system for the release of doxorubicin, a
chemotherapeutic agent commonly used for osteosarcoma treatment. In core–shell fibres, polycaprolactone
(PCL) is often proposed for the shell layer as it is bioresorbable and biocompatible, but it is hydrophobic and
lacks adhesive sites for cellular attachment. In this work, a PCL-chitosan blend was used for the shell layer to
increase PCL hydrophilicity and to provide cell-recognition sites to support cell adhesion. Polyvinyl alcohol
(PVA) has been used for the core layer and doxorubicin was introduced with a concentration of 100 μg/mL. Core-
shell fibres of dimension of 300–500 nm were successfully obtained and doxorubicin was released in a sustained
way up to 28 days
High surface area zincosilicates as efficient catalysts for the synthesis of ethyl lactate: an in-depth structural investigation
No full textNovel Zn-MCM-41 mesoporous materials with particle diameters ranging from 20 to 120 nm were successfully prepared following a straightforward synthesis route. The structural and textural properties of the solids were characterized by N2-physisorption, X-ray diffraction, 29Si MAS-NMR, TEM and EDX. These results allow evidencing the presence of an ordered mesoporous structure with a very high specific surface area. The insertion of zinc as single site species within the silica framework was investigated using XPS via the Auger parameter in a Wagner plot representation. This is the first time that an in-depth investigation of these types of solids using XPS techniques was performed. The presence of Brønsted and Lewis acidity was elucidated by following in the IR the interaction with ammonia and carbon monoxide. The materials were tested for the conversion of dihydroxyacetone into ethyl lactate with good results both in terms of yield and selectivity and the catalytic activity resulted in excellent agreement with IR and XPS analysis
Mimicking the inorganic component of bone through mesoporous hydroxyapatite and mesoporous bioactive glasses
No full textThis work represents the initial phase of the ERC Boost Project whose aim is the fabrication of a smart scaffold that mimics the natural bone chemistry, structure and topography for the treatment of osteoporotic fractures. Since human bone is composed of an organic matrix (mainly type I collagen) and an inorganic phase made up by nanometric crystals of hydroxyapatite, the starting material chosen for the project is a composite material made by collagen, mesoporous hydroxyapatite (MHA) and/or mesoporous bioactive glasses (MBG). Mesoporous materials have exceptional textural properties (high surface area, high pore volume and ordered mesoporosity) that lead to an improved reactivity in body fluids, making them particularly suitable for bone tissue regeneration
Mesoporous hydroxyapatite and mesoporous bioactive glasses, a new strategy to mimic the inorganic component of bone
No full textHuman bone is a composite material composed of an organic matrix (mainly collagen) and an inorganic phase made up by nanometric crystals of hydroxyapatite. The aim of the present work is to fabricate a smart scaffold that mimics the natural bone chemistry, structure and topography for the treatment of osteoporotic fracture. The starting material chosen for this purpose is a composite matrix made of collagen, mesoporous hydroxyapatite (MHA) and/or mesoporous bioactive glasses (MBG). Mesoporous materials have exceptional textural characteristics (high surface area, high pore volume and highly ordered mesoporosity) that lead to an improved reactivity in body fluids, making these materials particularly suitable for bone tissue regeneration.
MBG has been synthesised through an aerosol-assisted spray-drying process in mild acidic aqueous environment, obtaining spherical microparticles with highly controlled shape and dimensions. They belong to the system 85%SiO2/15%CaO (mol %) and have been doped with therapeutic ions to further increase their regenerative potential. In particular Sr has been chosen for its osteogenic and bone antiresorptive properties (Sr_MBG_SD) whereas copper for its antibacterial and angiogenetic behaviour (Cu_MBG_SD).
MHA will be prepared through a modified co-precipitation method, using an elevated concentration of templating agent based on the work of Zhao and Ma. The aim is to obtain a rod-like shape with dimensions similar to bone hydroxyapatite.
These two materials have been characterized through FESEM coupled with EDXS and through adsorption and desorption of nitrogen to evaluate their mesoporous structure. In particular, bioactivity and ion release tests have been carried out on MBGs to investigate their behaviour in a physiologic-like fluid. MHA has been analysed with XRD to investigate its crystalline structure and the size of nanocrystals
Bi-functionalization of silica spheres with sulfonic and carboxylic groups via a co-condensation route
No full textIron oxide inside SBA-15 modified with amino groups as reusable adsorbent for highly efficient removal of glyphosate from water
No full textIron oxide clusters were incorporated into amino-functionalized SBA-15 in order to obtain a magnetically recoverable adsorbent. The physical-chemical properties of the material were characterized by FE-SEM, STEM, XRD, TGA, XPS, FT-IR and acid-base titration analysis. Iron oxide nanoparticles were uniformly dispersed into the pore of mesoporous silica and that the adsorbent is characterized high specific surface area (177 m2/g) and accessible porosity. The sorbent was successfully tested for the removal of glyphosate in real water matrices. Despite the significant content of inorganic ions, a quantitative removal of the contaminant was found. The complete regeneration of the sorbent after the adsorption process through diluted NaOH solution was also proved
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