Search

In this work, we obtained supramolecular gels in deep eutectic solvents (DES) from polysaccharides like chitosan and chitosan : cellulose composites. We thoroughly characterized our gels by determining the minimum gelation concentration, as well as their porosity and swelling. We also investigated their mechanical properties by rheology, and morphology by scanning electron measurements. These properties were mainly influenced by the number of hydrogen bond sites on the hydrogen bond donor, (HBD), while FTIR-ATR investigation suggested that, upon gelation, cholinium cations interpose between polysaccharide chains affecting interchain hydrogen bonding. Our gels also exhibited self-healing and load bearing ability and proved injectable. Subsequently, we evaluated antioxidant ability of the gels by the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay. We found that gelation of the DES reduces their radical scavenging ability, so we doped the gels with natural antioxidants like trans-ferulic acid (TA) and α-tocopherol (VE), finding that their high scavenging ability is fully preserved in the gel matrix. We then prepared films from one of the gels and evaluated their stability to sunlight and exposure to water, finding that the TA-doped film was the most resistant to UV-light, and retained its radical scavenging ability even after being exposed to significant amounts of water.

Despite natural fibers gaining significant attention in recent decades, their limited performance and poor durability under humid environments cannot allow them to fully replace their synthetic counterparts as reinforcement for structural composites. In such a context, this paper aims to investigate how exposure to a humid/dry cycle affects the mechanical response of epoxy laminates reinforced with flax and glass fibers. In particular, the main goal is to assess the performance evolution of a glass–flax hybridized stacking sequence in comparison with the full glass and flax fiber reinforced composites. To this end, the investigated composites were first exposed to salt-fog for 15 or 30 days and then to dry conditions (i.e., 50% R.H. and 23 °C) for up to 21 days. The presence of glass fibers in the stacking sequence significantly stabilizes the mechanical performance of composites during the humid/dry cycle. Indeed, hybridization of inner flax laminae with outer glass ones, acting as a protective shield, hinders the composite degradation due to the humid phase also promoting performance recovery during the dry phase. Hence, this work showed that a tailored hybridization of natural fibers with glass fibers represents a suitable approach to extend the service-life of natural fiber reinforced composites exposed to discontinuous humid conditions, thus allowing their employment in practical indoor and outdoor applications. Finally, a simplified theoretical pseudo-second-order model that aimed to forecast the performance recovery shown by composites was proposed and experimentally validated, highlighting good agreement with the experimental data.

This review article discusses the environmental and economic effects of recycling, as well as sustainable thermoplastic polymer recycling technologies. Several researchers have utilized recycled thermoplastics as matrices in the production of a variety of natural and synthetic-based composites, which is also the focus of this study. All of the industries (food and packaging, construction and building, transportation, and indoor usage) where recycled thermoplastics have a large market share (food and packaging, construction and building, transportation, and indoor usage) are covered in this review. The desirable properties of thermoplastic polymers, such as corrosion resistance, low density, and user-friendliness, have caused plastic production to surpass aluminum and other metals in use over the past 60 years. Furthermore, recycling is one of the most important measures available to mitigate these effects and is one of the most dynamic segments of the plastics industry at present. Increased landfilling and incineration of plastics have a negative impact on the ecosystem, and the continued increase in the production of virgin fossil plastic also has a negative impact on the environment. Consequently, this continuous production could lead to the depletion of fossil fuel resources, an increase in environmental emissions during processing, and eventual incineration. Increasing numbers of nations are adopting the circular economy concept in an effort to avoid all of these problems. This concept emphasizes the reuse of products and resources, as well as the recycling of materials according to the waste hierarchy, rather than their cremation or disposal in the environment.

Nowadays, the world requires more sustainable and eco-friendly materials to replace or limit the usage of synthetic materials. Moreover, several researchers focused their attention on the use of agricultural sources as reinforcement for biocomposites since they are abundant, cost-effective and environmentally favorable sources. In such a context, purpose of the present paper is the evaluation of lemongrass plant (Cymbopogon flexuosus) as possible source of natural reinforcement for biocomposites. To this aim, natural fibers were obtained from the leaf and the stem of lemongrass and their main properties were compared for the first time. To this scope, mechanical and thermal characterizations, chemical investigation, Fourier-transform infrared spectroscopy, X-Ray diffraction and scanning electron microscope analysis were carried out. The experimental campaign showed that, despite having similar chemical composition (i.e., cellulose, hemicellulose and lignin contents equal to 44–45%, 28–29% and 17%, respectively), leaf fibers possess higher mechanical properties (i.e., + 55% and + 76% in the tensile strength and modulus, respectively) than stem ones. This result can be ascribed to different factors such as larger amount of absorbed water (i.e., + 4%) and ash content (+ 2%) shown by stem fibers in addition to a more compact structure evidenced by leaf fibers which also present higher density (i.e., 1.139 g/cm3 versus 1.019 g/cm3).

In this work, we describe the preparation and characterization of supramolecular ionic liquid gels based on binary mixtures of biopolymers, comprising chitosan, chitin, cellulose and lignin. The gels were obtained in ionic liquids differing in the cation or the anion, with no need for a cross-linking agent or acid treatment. The materials obtained were characterized for the minimum gelation concentration, porosity, swelling and rheological properties, finding a prominent influence of the nature of the ionic liquid anion. Then, we investigated the ability of the gels to scavenge free radicals, finding that the gels exhibit a higher antioxidant ability than their individual components. Moreover, our gels showed a bactericidal activity toward Gram-positive and Gram-negative bacterial strains like Streptomyces coelicolor and Escherichia coli, respectively. The kinetics of bacterial cell viability showed that the gel based on a chitosan : chitin mixture in the IL [bmim][Cl] was the fastest acting against E. coli, with a practically total killing of bacterial cells within 30 min. Once again, a major influence of the ionic liquid anion was detected. Finally, we found an inverse relationship between the antioxidant and antimicrobial activities of our gels.

Air pollution is one of the major global problems causing around 7 million dead per year. In fact, a connection between infectious disease transmission, including COVID-19, and air pollution has been proved: COVID-19 consequences on human health are found to be more severe in areas characterized by high levels of particulate matter (PM). Therefore, after the COVID-19 pandemic, the production of air filtration devices with high filtration efficiency has gained more and more attention. Herein, a review of the post-COVID-19 pandemic progress in nanofibrous polymeric membranes for air filtration is provided. First, a brief discussion on the different types of filtration mechanism and the key parameters of air filtration is proposed. The materials recently used for the production of nanofibrous filter membranes are presented, distinguishing between non-biodegradable polymeric materials and biodegradable ones. Subsequently, production technique proposed for the fabrication of nanofibrous membranes, i.e., electrospinning and solution blow spinning, are presented aiming to analyze and compare filtration efficiency, pressure drop, reusability and durability of the different polymeric system processed with different techniques. Finally, present challenges and future perspectives of nanofibrous polymeric membranes for air filtration are discussed with a particular emphasis on strategies to produce greener and more performant devices.

Magnetic oxide nanoparticles (NPs) are probably the most common nanomaterials in everyday biomedicine, and have been in use since the 1990’s. They are usually magnetic iron oxide NPs, made of magnetite (Fe3O4) or maghemite (γ-Fe2O3), or a mixture of the two. Both of these have the spinel structure, and other spinel ferrites such as ZnFe2O4, CoFe2O4 and NiFe2O4 are also used. For applications in magnetic hyperthermia these NPs must be below the magnetic domain size, making them superparamagnetic, which means that their magnetisation can be “switched on” by the application of an external magnetic field. Magnetic hyperthermia treatment is a form of thermotherapy which is used to kill tumour cells with thermal energy (heat) in a very localised manner, by causing magnetic oxide NPs to heat up near tumour cells. Under an applied AC magnetic field the magnetic spin of the NPs switches rapidly in direction, transforming the magnetic energy into thermal energy. Temperatures of 41-46 °C are sufficient, this localised heating elevating the temperature of tumour cells, inhibiting growth, killing them, or inducing tumour cell apoptosis. Magnetic NPs were first used in tumour thermotherapy in 1996, and since then there has been a great deal of research in this field. The treatment can be applied alone, or used in combination with other therapies such as surgery, radiotherapy and chemotherapy, and it has shown excellent synergistic effects in combination with anticancer drugs (chemotherapeutics).

We report the first ever robocast (additive manufacturing/3D printing) sintered ceria scaffolds, and explore their use for the production of renewable fuels via solar thermochemical fuel production using concentrated solar energy.

3D printability of green composites is currently experiencing a boost in importance and interest, envisaging a way to valorise agricultural waste, in order to obtain affordable fillers for the preparation of biodegradable polymer-based composites with reduced cost and environmental impact, without undermining processability and mechanical performance. In this work, an innovative green composite was prepared by combining a starch-based biodegradable polymer (Mater-Bi®, MB) and a filler obtained from the lignocellulosic waste coming from Solanum lycopersicum (i.e., tomato plant) harvesting. Different processing parameters and different filler amounts were investigated, and the obtained samples were subjected to rheological, morphological, and mechanical characterizations. Regarding the adopted filler amounts, processability was found to be good, with adequate dispersion of the filler in the matrix. Mechanical performance was satisfactory, and it was found that this is significantly affected by specific process parameters such as the raster angle. The mechanical properties were compared to those predictable from the Halpin–Tsai model, finding that the prepared systems exceed the expected values.

Elastic strains in metallic catalysts induce enhanced selectivity for carbon dioxide reduction (CO

The increase in concrete structures’ durability is a milestone to improve the sustainability of buildings and infrastructures. In order to ensure a prolonged service life, it is necessary to detect the deterioration of materials by means of monitoring systems aimed at evaluating not only the penetration of aggressive substances into concrete but also the corrosion of carbon-steel reinforcement. Therefore, proper data collection makes it possible to plan suitable restoration works which can be carried out with traditional or innovative techniques and materials. This work focuses on building heritage and it highlights the most recent findings for the conservation and restoration of reinforced concrete structures and masonry buildings.

The present work aims to evaluate how an innovative and eco-friendly anodizing process with tartaric-sulfuric acid (TSA) bath and a pore widening in an aqueous solution of NaOH 0.1M can improve the durability in marine environment of co-cured adhesive joints between an aluminum alloy (AA 5083) and fiber (i.e., glass or basalt)-reinforced composite substrates. The aging was carried out by exposing samples to salt-fog spray conditions (5wt.% NaCl) for 30, 60 and 90days in a climate chamber, in accordance with ASTM B117. In order to get further insights on the aging behaviour of bonded joints, neat matrix was also exposed to the same environment for 60days. Quasi-static mechanical tests and morphological analysis through SEM microscope coupled with EDX analyser were carried out to deeper understand how the fracture surfaces change during aging and how this affected the mechanical performances of joints.

Nanostructured TiO2 is one of the best materials for photocatalysis, thanks to its high surface area and surface reactivity, but its large energy bandgap (3.2 eV) hinders the use of the entire solar spectrum. Here, it is proposed that defect-engineered nanostructured TiO2 photocatalysts are obtained by hydrogenation strategy to extend its light absorption up to the near-infrared region. It is demonstrated that hydrogenated or colored TiO2 hollow spheres (THS) composed of hierarchically assembled nanoparticles result in much broader exploitation of the solar spectrum (up to 1200 nm) and the engineered surface enhances the photogeneration of charges for photocatalytic processes. In turn, when applied for photodegradation of a targeted drug (Ciprofloxacin) this results in 82% degradation after 6 h under simulated sunlight. Valence band analysis by photoelectron spectroscopy revealed the presence of oxygen vacancies, whose surface density increases with the hydrogenation rate. Thus, a tight correlation between degree of hydrogenation and photocatalytic activity is directly established. Further insight comes from electron paramagnetic resonance, which evidences bulk Ti3+ centers only in hydrogenated THS. The results are anticipated to disclose a new path toward highly efficient photocatalytic titania in a series of applications targeting water remediation and solar fuel production. Validerad;2023;Nivå 2;2023-07-04 (hanlid);Funder: Convenzione operativa per collaborazione scientifica tra CNR ISM e Dipartimento di Scienze Molecolari e Nanosistemi Università Cà Foscari Venezia (709, 14/04/2021); EUROFEL-ROADMAP ESFRI

TiO2 thin films are known to promote photodegradation of dyes and pollutants in water solution via heterogeneous photocatalysis. This ability is guided by the photoexcitation through photons having energies above the band gap. To improve photocatalytic activity, nanostructures with high surface area can be applied, which can ease molecular adsorption/desorption mechanisms, enhance electronic transfer properties and lower excitation energy. For this purpose, square cross-section TiO2 vertically aligned nanorod (TNR) array configuration has been chosen as a semiconductor substrate. On top of it, a thin layer of sub-stoichiometric TiO2−x has been deposited, aiming at inducing a vacancy doped homojunction between two different oxygen rich/deficient TiO2 layers, possibly leading to lower band gap and enhanced photochemical activity. In principle, promotion of electron and holes separation and suppression of charge recombination could occur. Vertically aligned TNRs have been deposited through a hydrothermal growth in acidic conditions on a pre-seeded glass conducting substrate, optimizing the seeding process through spin coating. Sub-stoichiometric TiO2−x layer (50 nm nominal thickness) has been deposited on top of TNRs via radiofrequency magnetron sputtering at three different stoichiometries, tuning the oxygen partial pressure in sputtering argon atmosphere at 10 %, 15 % and 20 %, respectively. Photocatalytic activity has been investigated in the photodegradation of an aqueous solution of methylene blue, both under UV and simulated solar light irradiation at room temperature and atmospheric pressure, resulting in the degradation of methylene blue target molecule up to 99 % under UV and 85 % under simulated solar irradiation after 6 h. These promising achievements unlock new environmental applications for enhanced dye degradation industrial processes. Validerad;2023;Nivå 2;2023-04-17 (hanlid);Funder: ÅFORSK Foundation; Ca’ Foscari Universityof Venice (SPIN2019); Ministerio de Ciencia eInnovaci ́on of Spain (ID2021-126235OB-C32, ED2021-130756B-C31; FEDER funds

Metal borides/borates have been considered promising as oxygen evolution reaction catalysts; however, to date, there is a dearth of evidence of long-term stability at practical current densities. Here we report a phase composition modulation approach to fabricate effective borides/borates-based catalysts. We find that metal borides in-situ formed metal borates are responsible for their high activity. This knowledge prompts us to synthesize NiFe-Boride, and to use it as a templating precursor to form an active NiFe-Borate catalyst. This boride-derived oxide catalyzes oxygen evolution with an overpotential of 167 mV at 10 mA/cm2 in 1 M KOH electrolyte and requires a record-low overpotential of 460 mV to maintain water splitting performance for over 400 h at current density of 1 A/cm2. We couple the catalyst with CO reduction in an alkaline membrane electrode assembly electrolyser, reporting stable C2H4 electrosynthesis at current density 200 mA/cm2 for over 80 h., Metal borides/borates are promising candidates to become high-performance alkaline oxygen evolution reaction catalysts. This study reports an in-situ phase composition modulation approach to fabricate boride/borate-based catalysts.

Wearable sensors for sweat biomarkers can provide facile analyte capability and monitoring for several diseases. In this work, a green wearable sensor for sweat absorption and chloride sensing is presented. In order to produce a sustainable device, polylactic acid (PLA) was used for both the substrate and the sweat absorption pad fabrication. The sensor material for chloride detection consisted of silver-based reference, working, and counter electrodes obtained from upcycled compact discs. The PLA substrates were prepared by thermal bonding of PLA sheets obtained via a flat die extruder, prototyped in single functional layers via CO2 laser cutting, and bonded via hot-press. The effect of cold plasma treatment on the transparency and bonding strength of PLA sheets was investigated. The PLA membrane, to act as a sweat absorption pad, was directly deposited onto the membrane holder layer by means of an electrolyte-assisted electrospinning technique. The membrane adhesion capacity was investigated by indentation tests in both dry and wet modes. The integrated device made of PLA and silver-based electrodes was used to quantify chloride ions. The calibration tests revealed that the proposed sensor platform could quantify chloride ions in a sensitive and reproducible way. The chloride ions were also quantified in a real sweat sample collected from a healthy volunteer. Therefore, we demonstrated the feasibility of a green and integrated sweat sensor that can be applied directly on human skin to quantify chloride ions.

Decarbonization of plastics is based on two main pillars: bio-based polymers and recycling. Mechanical recycling of biodegradable polymers could improve the social, economic and environmental impact of the use of these materials. In this regard, the aim of this study was to investigate whether concentrations of the same recycled biopolymer could significantly affect the rheological and mechanical properties of biodegradable monopolymer blends. Monopolymer blends are blends made of the same polymers, virgin and recycled. A sample of commercially available biodegradable blend was reprocessed in a single-screw extruder until two extrusion cycles were completed. These samples were exposed to grinding and melt reprocessed with 75% and 90% of the same virgin polymer. The blends were characterized by tensile tests and rheological tests. The results obtained showed that while multiple extrusions affected the mechanical and rheological properties of the polymer, the concentration of the reprocessed material present in the blends only very slightly affected the properties of the virgin material. In addition, the experimentally observed trends were accurately predicted by the additive model adopted.

In this thesis various plasmonic materials, such as hyperbolic metamaterial nanohole arrays and Au-coated free standing nanoassembly supporting nanopores, are investigated with the aim to perform optical sensing of DNA molecules with Surface-Enhanced Raman Spectroscopy in flow-through configuration., PhD Thesis