Publications

DOI: https://doi.org/10.1016/j.mtchem.2024.102046
Over the last decade, cryogels have proven to be effective catalytic supports in various hybrid systems for the conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-NP). A critical determinant influencing the conversion of nitroaromatic compounds in the presence of sodium borohydride is the solution pH as suggested from Grzeschik's model. This study aims to investigate the catalytic mechanism and the role of pH in reactions mediated by hybrid catalysts. In particular, polymeric cryogels with different acid/base properties were prepared and used as supports for the in-situ preparation of Au and Pd nanocatalysts. Notably, catalytic tests showed the significant influence of the polymeric support's acidity on 4-NP reduction, with poly(acrylic acid)-based catalysts emerging as the most effective systems. To further probe the reaction mechanism, a series of catalytic tests were carried out, and the results demonstrated the effect of pH on the reaction process, allowing to propose a novel mechanism based on an extension of Grzeschik's model. Moreover, data emphasized the pivotal role of the polymer in the catalytic mechanism, showcasing its capacity to tune catalytic activity by altering the acid/base properties of the matrix substrates.

DOI: https://doi.org/10.1002/pc.28439
In this work, polylactide (PLA) was loaded with wood flour (WF) or hazelnut shells (HSs) (10% and 20% of fillers). The matrix and biocomposites were fully characterized from a mechanical and rheological point of view to test their processability and mechanical performance. Compost burial degradation test (30 days), with or without a prior photo-oxidation step, assessed their biodegradability after an outdoor application, and was monitored by weight loss (WL). The viscosity of the biocomposites was lower than that of the matrix and this unusual result can be attributed to a limited adhesion between the PLA and fillers. Both fillers increased the elastic modulus but decreased the tensile strength and elongation at break. As for the weathering, the degradation of PLA was mostly due to hydrolytic chain scission due to the presence of humidity. Resistance of PLA to UV irradiation improved in presence of both the two fillers. Their lignocellulosic nature was responsible for this behavior. Both fillers induced a high resistance and lower degradation in compost: WL percentages of virgin PLA was about 26%, biocomposites with 20% of WF or HS showed WL of about 10% and 14%, respectively. Photo-oxidation (36 h with condensation cycle) increased the compost degradation rate of both biocomposites and WL of PLA with 20% of WF or HS were about 15% and 21%, respectively, after 30 days.

DOI:  https://doi.org/10.3390/gels10030163
The investigation of the mechanical, thermal, and adsorption properties of hydroxyethyl methacrylate (HEMA) cryogels as a function of a reactant ratio is herein reported to better address materials for specific applications. To this aim, cryogels have been synthesized using different monomer/crosslinker (N,N'-methylene-bisacrylamide?MBAA) ratios. The study of SEM images made it possible to identify the trend in the material’s macroporosity. As would be expected, the average measured pore width decreased as the amount of MBAA increased while the number of pores grew. Swelling capacity ranges from 8.7 gW/g_gel (grams of water per gram of gel) to 9.3 gW/g_gel. These values are strictly connected with the pore’s size and distribution, revealing that the water uptake for the most crosslinked sample is inferior to other samples. The equilibrium-adsorption capacity (Qe) towards the methylene violet (MV) was also assessed, revealing no remarkable differences after 24 h of a batch test. As expected, thermogravimetric analysis (TGA) also showed no significant changes in stability that ranged from a maximum weight loss temperature (T Max) of 420 °C to 425 °C, which increased as a function of crosslinker content. Conversely, compression strength measurements showed a notable difference of about 50% in modulus (Ec), moving from the higher to the lower HEMA/MBAA ratio. These new comparative results indicate how slight variations in the reactant’s ratio can steadily improve the mechanical properties of the HEMA cryogel without affecting its adsorption efficiency. This can be helpful in the design of materials for water and energy purposes. Since swelling properties are needed in the case of biomedical applications, the HEMA/MBAA ratio should be tuned versus high values.

DOI: https://doi.org/10.3390/polym16040460
Polyimides are a polymer class that has been extensively investigated as a membrane material for gas separation owing to its interesting permselective properties in a wide range of operation temperatures and pressures. In order to improve their properties, the addition of different filler types is currently studied. p-tert-Butylcalix[n]arene macrocycles (PTBCs) with different cavity sizes (PTBC4, PTBC6, PTBC8) were used as fillers in a commercial thermoplastic polyimide, with a concentration in the range 1-9 wt%, to develop nanocomposite membranes for gas separation. The selected macrocycles are attractive organic compounds owing to their porous structure and affinity with organic polymers. The nanocomposite membranes were prepared in the form of films in which the polymeric matrix is a continuous phase incorporating the dispersed additives. The preparation was carried out according to a pre-mixing approach in a mutual solvent, and the solution casting was followed by a controlled solvent evaporation. The films were characterized by investigating their miscibility, morphology, thermal and spectral properties. The gas transport through these films was examined as a function of the temperature and also time. The results evidenced that the incorporation of the chosen nanoporous fillers can be exploited to enhance molecular transport, offering additional pathways and promoting rearrangements of the polymeric chains.

DOI: https://doi.org/10.1016/j.heliyon.2024.e24469
PLA/PBAT bioplastic is a commercial biodegradable plastic employed for packaging and several food and agriculture applications. In this regard, properties such as the antioxidant ability to extend food shelf life and light resistance, are of great interest in the production of packaging and mulching films, respectively. These features are obtained by developing blends with pure chemicals and/or natural products as additives. In the present work blend formulations of PLA/PBAT with a walnut shell extract rich in antioxidants were developed and evaluated for their properties in comparison with classic PLA/PBAT. Specifically, natural additives, and most importantly the production process were purposely selected to i) be green and cost-effective; ii) confer antioxidant properties; and iii) improve material performance To this aim, a walnut shell extract (EWS) with high antioxidant activity was obtained thanks to a novel green and cost-effective microwave-assisted extraction (MAE) procedure. A response surface methodology was utilized to explore how the total phenolic content (TPC) and antioxidant activity are influenced by varying aqueous ethanol concentration, extraction time, and microwave power. The highest predicted TPC and antioxidant activity were achieved when employing the ideal conditions for Microwave-Assisted Extraction (MAE): using a mixture of 30 % ethanol in water, an irradiation time of 120 s, and a microwave power of 670 W. The optimized EWS was characterized by HPLC-MS determining qualitative and quantitative data with the identification of flavonoids, fatty acids, and anacardic acids among the main components, responsible for antioxidant activity. The resulting EWS powder was melt-mixed at 140C° and 20 RPM with the bio-based PLA/PBAT bioplastic at two different concentrations (0.5 and 1.5 w/w) by forming film specimens. All EWS-based bioplastic films showed increased antioxidant features determined by the DPPH bleaching test, TEAC, and ORAC assays. The films keep the antioxidant capacity even after 7 days of UV-accelerated aging. Remarkably, adding 1.5 % EWS boosted the bioplastic UV light resistance, reducing the abatement of molecular masses by more than 60 % without affecting mechanical properties.

DOI: https://doi.org/10.1021/acsami.3c13470
Light-powered micro- and nanomotors based on photocatalytic semiconductors convert light into mechanical energy, allowing self-propulsion and various functions. Despite recent progress, the ongoing quest to enhance their speed remains crucial, as it holds the potential for further accelerating mass transfer-limited chemical reactions and physical processes. This study focuses on multilayered MXene-derived metal-TiO₂ micromotors with different metal materials to investigate the impact of electronic properties of the metal-semiconductor junction, such as energy band bending and built-in electric field, on self-propulsion. By asymmetrically depositing Au or Ag layers on thermally annealed Ti₃C₂T_x MXene microparticles using sputtering, Janus structures are formed with Schottky junctions at the metal?semiconductor interface. Under UV light irradiation, Au-TiO₂ micromotors show higher self-propulsion velocities due to the stronger built-in electric field, enabling efficient photogenerated charge carrier separation within the semiconductor and higher hole accumulation beneath the Au layer. On the contrary, in 0.1 wt % H₂O₂, Ag-TiO₂ micromotors reach higher velocities both in the presence and absence of UV light irradiation, owing to the superior catalytic properties of Ag in H₂O₂ decomposition. Due to the widespread use of plastics and polymers, and the consequent occurrence of nano/microplastics and polymeric waste in water, Au-TiO₂ micromotors were applied in water remediation to break down polyethylene glycol (PEG) chains, which were used as a model for polymeric pollutants in water. These findings reveal the interplay between electronic properties and catalytic activity in metal-semiconductor junctions, offering insights into the future design of powerful light-driven micro- and nanomotors with promising implications for water treatment and photocatalysis applications.

DOI: https://doi.org/10.3389/fchem.2023.1350994
Chemistry stands as the cornerstone for life’s sustenance and progress on our planet, offering solutions to humanity’s challenges throughout history. In the modern era, Chemistry is an integral part of daily life, influencing science and technology. While its foundations lie in natural elements, synthetic chemistry advancements have excelled in cost, manufacturing ease, scalability, and consistency. Yet, concerns about health and environmental effects urge a reevaluation of the exploitation and applications of natural sources. Since 2000, global concerns like climate change and resource depletion have fueled extensive exploration for alternative solutions to using natural resources, especially amid environmental disasters, pandemics, and geopolitical struggles. One of the major approaches being considered to meet and overcome these challenges is by maximizing the use of natural resources and minimizing the generation of waste (Tseng et al., 2020). In this context, the concept of circular economy, where the waste and coproducts generated by one process are considered as inputs for another one and converted into value added products through clean and green approaches, is being aggressively pursued and adopted (Velenturf and Purnell, 2021).

Based on current statistics, the global agriculture market is expected to cross US$ 5 trillion by 2028. Consequently, the generation of byproducts and coproducts during agricultural production and processing is also set to increase steeply (Kircher, 2019; Díaz-Bonilla, 2023). Stems, leaves and husks generated during agricultural production and several byproducts, including proteins and carbohydrates, supplied as coproducts during agricultural processing are available in large quantities at low cost. These byproducts and coproducts have the essential constituents to be converted into monomers, polymers, compounds and further into any desired substance through specific chemical transformations, ranging from carbonyl reductions to carboxyl decarboxylations, hydroxyl oxidations, glycosylation, and transglycosylation (Li et al., 2014; Donner et al., 2021). For instance, corn-based biorefineries utilizing starch, corn husks, corn cobs, distillers dried grains and other coproducts have generated biofuels (ethanol, methane), biopolymers (polylactide), amino acids, animal feed and enzymes. Similarly, sugarcane based biorefineries have excelled in the production of biofuels, paper, fertilizers, animal feed, chemicals such as acetic acid, cosmetics and perfumes (Gerrior et al., 2022). Not only regular food crops but also non-food products such as poultry feathers have been considered for production of composite, plastics, biofuels, etc. Based on these approaches, it is evident that there is unlimited scope for extending the biorefinery and circular economy concepts to almost all agricultural byproducts and coproducts.

To achieve successful utilization and exploitation of renewable resources, the development of innovative and efficient conversion processes is essential. The purpose of the present Research Topic, "Chemistry and The Circular Economy", aligns with this goal. It displays the continuous progress and the potential of chemistry in addressing global challenges by bringing together research articles that explore advancements in energy storage, hydrogen production, polymer synthesis, and biochar utilization.

In the realm of energy storage, researchers have dedicated over 2 decades to refining biomass through rapid pyrolysis technology. However, challenges emerge as the primary product, biomass pyrolysis oil, grapples with low energy density and poor thermal stability. The intrigue deepens as exploration leads towards catalytic reforming as a transformative avenue, offering a potential solution for the subsequent utilization of bio-oil in hydrogen production. In a captivating mini review, Zhang focuses on the innovative technique of CO₂ adsorption-enhanced catalytic reforming, presenting itself as a beacon of hope for efficient and sustainable hydrogen generation. The review briefly introduces recent progress in biomass catalytic reforming hydrogen production technology, covering mechanisms, catalyst selection, new processes, and technology developments. It also addresses current challenges in this field, providing potential ideas and directions for future development.

Shifting the focus to the captivating world of bio-derived polymers, the synthesis of poly-γ-glutamic acid (γ-PGA) comes into play. This water-soluble marvel holds promise as a game-changer in various applications. Its potential spans from the realms of drug delivery and cosmetics to bioremediation and wastewater treatment, weaving a tale of sustainability and versatility. Parati et al. explores the synthesis of γ-PGA from scalable macroalgal biomass assessing the influence of pre-treatment type, macroalgal species, and collection time on brown seaweed cultivated under controlled conditions in Scotland. Laminaria digitata, Saccharina latissima, and Alaria esculenta, three brown seaweed species native to the United Kingdom, are analyzed for their variation in carbon, antioxidant, protein, and ash content. The research evaluated the effect of different algal species on the yields and chemical composition of γ-PGA produced by Bacillus subtilis natto, also investigating the variations during the specific cultivation period.

Li et al. present a review delving into the promising realm of biochar, an environmentally friendly material drawing attention for its potential use as a potassium ion anode in batteries. The manuscript explores the transformative possibilities of biochar through modifications, particularly highlighting atomic doping to enhance electrochemical performance. This type of materials exhibits not only efficient energy conduction but also increased potassium storage capacity. The review covers the application of atomically doped biomass carbon materials (BCMs) and recent advancements in pure BCMs, emphasizing considerations for simpler production, reduced costs, and environmental protection. Key challenges in developing BCMs, such as irreversible potassium buildup and electrolyte breakdown, are discussed and potential solutions have also been proposed. Supporting the circular economy model, a beacon of hope for combating the environmental impact of poly(ethylene terephthalate) (PET), a commonly produced and consumed polymer, comes from (Gabrielli et al.). Their proposed approach involves a microwave-assisted recycling process, focused on aminolysis of PET waste to create polyurethane acrylate (PUA) derived coatings. The process utilizes substituted ß-hydroxy amines for chemical depolymerization of PET waste, employing a sodium acetate catalyst. The first step achieves efficient depolymerization of PET within a short time, resulting in the formation of terephthalimide diols. This environmentally friendly method enables the synthesis of a diverse range of diol monomers with customizable organic structures suitable for PUA UV-curable coatings. In this tapestry of research, each article of the present Research Topic not only unravels scientific complexities but also paints a vivid picture of innovation, sustainability, and the transformative power of human ingenuity in the pursuit of a brighter, greener future.

DOI: https://doi.org/10.3390/polym15132809
Currently, the epoxy resin market is expressing concerns about epoxy resins’ non-recyclability, which can hinder their widespread use. Moreover, epoxy monomers are synthesized via petroleum-based raw materials, which also limits their use. So, it is crucial to find more environmentally friendly alternative solution for their formulation. Within this context, the aim of this paper is to exploit a Cradle-to-Cradle approach, which consists of remodeling and reshaping the productive cycle of consumer products to make sure that they can be infinitely reused rather than just being recycled with a downgrading of their properties or uses, according to the principle of the complete circular economy. Indeed, after starting with a fully-recyclable bio-based epoxy formulation and assessing its recyclability as having a process yield of 99%, we obtained a recycled polymer that could be reused, mixing with the same bio-based epoxy formulation with percentages varying from 15 wt% to 27 wt%. The formulation obtained was thoroughly characterized by a dynamic-mechanical analysis, differential scanning calorimetry, and flexural tests. This approach had two advantages: (1) it represented a sustainable disposal route for the epoxy resin, with nearly all the epoxy resin recovered, and (2) the obtained recycled polymer could be used as a green component of the primary bio-based epoxy matrix. In the end, by using replicated general factorial designs (as statistical tools) combined with a proper optimization process, after carrying out a complete thermo-mechanical characterization of the developed epoxy formulations, the right percentage of recycled polymer content was selected with the aim of identifying the most performing epoxy matrix formulation in terms of its thermo-mechanical properties.

DOI: https://doi.org/10.1002/mas.21869
Biodegradable polymers have been getting more and more attention because of their contribution to the plastic pollution environmental issues and to move towards a circular economy. Nevertheless, biodegradable materials still exhibit various disadvantages restraining a widespread use in the market. Therefore, additional research efforts are required to improve their performance. Mass spectrometry (MS) affords a relevant contribution to optimize biodegradable polymer synthesis, to confirm macromolecular structures, to examine along the time the progress of degradation processes and highlight advantages and drawbacks in the extensive applications. This review aims to provide an overview of the MS investigations carried out to support the synthesis of biodegradable polymers, with helpful information on undesirable products or polymerization mechanism, to understand deterioration pathways by the structure of degradation products and to follow drug release and pharmacokinetic. Additionally, it summarizes MS studies addressed on environmental and health issues related to the extensive use of plastic materials, that is, potential migration of additives or microplastics identification and quantification. The paper is focused on the most significant studies relating to synthetic and microbial biodegradable polymers published in the last 15 years, not including agro-polymers such as proteins and polysaccharides.

DOI: https://doi.org/10.1172/jci.insight.166470
Sialidosis is an ultra-rare multisystemic lysosomal disease caused by mutations in the neuraminidase 1 (NEU1) gene. The severe type II form of the disease manifests with a prenatal/infantile or juvenile onset, bone abnormalities, severe neuropathology, and visceromegaly. A subset of these patients present with nephrosialidosis, characterized by abrupt onset of fulminant glomerular nephropathy. We studied the pathophysiological mechanism of the disease in 2 NEU1-deficient mouse models, a constitutive Neu1-knockout, Neu1^ΔEx3, and a conditional phagocyte-specific knockout, Neu1^Cx3cr1ΔEx3. Mice of both strains exhibited terminal urinary retention and severe kidney damage with elevated urinary albumin levels, loss of nephrons, renal fibrosis, presence of storage vacuoles, and dysmorphic mitochondria in the intraglomerular and tubular cells. Glycoprotein sialylation in glomeruli, proximal distal tubules, and distal tubules was drastically increased, including that of an endocytic reabsorption receptor megalin. The pool of megalin bearing O-linked glycans with terminal galactose residues, essential for protein targeting and activity, was reduced to below detection levels. Megalin levels were severely reduced, and the protein was directed to lysosomes instead of the apical membrane. Together, our results demonstrated that desialylation by NEU1 plays a crucial role in processing and cellular trafficking of megalin and that NEU1 deficiency in sialidosis impairs megalin-mediated protein reabsorption.