A green approach to the edge functionalization of graphene layers with a bio-based 2-pyrone

Increasing awareness and concerns about climate change have spotlighted the need for a sustainable development. Green chemistry, defined as “the design of chemical products and processes to reduce or eliminate the use and generation of hazardous substances”, pursues the aim to transform hydrolyzed biomass, mainly composed by carbohydrates, into suitable building blocks. In this context, 2-pyrones build up a class of C-6 unsaturated lactone from lignocellulosic feedstock and intriguing building blocks for the preparation of key intermediates in synthetic organic, medicinal and polymeric chemistry. In this work, a green and efficient pathway for the preparation of a 2-pyrone starting from mucic acid is presented. Furthermore, a 2-pyrone derivative, ethyl 3-hydroxy-2-oxo-2H-pyran-6-carboxylate (Pyr-COOEt ), was used for selectively decorating the edge of a nano-sized graphite with high surface area (HSAG), without altering the graphitic bulk structure. The preparation of adducts between HSAG and Pyr-COOEt was performed through a sustainable method, with the help of either thermal or mechanical energy, reaching high functionalization yield (up to 90%). Few layers of graphene were easily obtained by means of a mild sonication of a water dispersion of the HSAG/Pyr-COOEt adducts

Edge functionalization of graphene layers with a 2-pyrone

Conversion of hydrolyzed biomass, mainly composed by carbohydrates, into suitable building blocks is one of the major purposes of Green Chemistry, defined as ‘‘the design of chemical products and processes to reduce or eliminate the use and generation of hazardous substances”. 2-pyrones are a class of unsaturated heterocyclic C-6 sugar derivatives, prevalent in many natural products and, due to their versatile chemical reactivity, intriguing building blocks in organic and polymer chemistry. In this work, a green and efficient procedure for the preparation of 2-pyrone is presented, starting from galactaric acid, also known as mucic acid, easily obtained from galactose or galacturonic acid. A 2-pyrone derivative, 5-hydroxy-6-oxo-6H-pyran-2-carboxylic acid ethyl ester (Pyr-COOEt) was used for the functionalization of nano-sized graphite with high surface area (HSAG). Adducts of Pyr-COOEt with HSAG were prepared by means of a simple and sustainable method, with the help of either thermal or mechanical energy. Functionalization yield was in all cases larger than 90%. After the functionalization reaction, the bulk structure of HSAG remained substantially unaltered, thanks to the edge functionalization. Few layers graphene were easily obtained by means of a mild sonication of a water dispersion of the HSAG/Pyr-COOEt adducts

A Janus Molecule for Screen-Printable Conductive Carbon Ink for Composites with Superior Stretchability

Inspired by decades of research in the compatibilization of fillers into elastomeric composites for high-performance materials, a novel polyurethane-based stretchable carbon ink is created by taking advantage of a Janus molecule, 2-(2,5-dimethyl-1H-pyrrol-1-yl)propane-1,3-diol (serinol pyrrole, SP). SP is used to functionalize the carbon and comonomer in the polymer phase. The use of SPs in both the organic and inorganic phases results in an improved interaction between the two phases. When printed, the functionalized material has a factor 1.5 lower resistance-strain dependence when compared to its unfunctionalized analogue. This behavior is superior to commercially available carbon inks. To demonstrate the suitability of ink in an industrial application, an all-printed, elastomer-based force sensor is fabricated. This “pyrrole methodology” is scalable and broadly applicable, laying the foundation for the realization of printed functionalities with improved electromechanical performance.</p

Functionalization of graphene related materials with biosourced C-3 and C-6 building blocks. From synthesis to applications

The functionalization of sp2 carbon allotropes is one of the hot research topics in advanced research on materials. Nowadays, carbon nanotubes and graphene related materials are extensively studied due to their exceptional mechanical and electrical properties. They are capable of substantially improving the properties of polymeric materials. Their functionalization is a crucial step, for allowing an even dispersion in the matrix. In this research, the functionalization of graphene related materials was performed with biosourced C-3 and C-6 molecules. They were glycerol and galactaric acid derivatives: pyrrole compounds (PyC) and 2-pyrones. The reactions for their synthesis and for the carbon allotrope functionalization were green and characterized by high atom efficiency, with a yield up to 96%. Indeed, the reactions were carried out in the absence of solvents and catalysts and adducts were obtained by simply mixing, with the help of either thermal or mechanical energy. The developed functionalization methods were successful for: carbon black, carbon nanotubes, few layers graphene. The bulk structure of the carbon substrate was left substantially unaltered: functionalization occurred in peripheral positions, at the edges of the graphene layers. Functional groups of defined chemical structure were covalently bound to the carbon material and stable adducts, up to very high temperature, were formed. Reliable hypotheses for the functionalization mechanisms were elaborated. In Figure 1b the supposed domino reaction based on the pyrrole compound, with the Diels Alder cycloaddition as the last step is represented. Such functionalization technique was developed as a pervasive technology, which allowed to pursue a variety of applications: (i) decoration with metals to obtain catalysts for the selective deuteration of pharmaceutical molecules as well as antibacterial ingredients (ii) rubber compounds for dynamic-mechanical applications (tires) (iii) conductive inks

Pyrrole Compounds from the Two-Step One-Pot Conversion of 2,5-Dimethylfuran for Elastomer Composites with Low Dissipation of Energy

A one-pot, two-step process was developed for the preparation of pyrrole compounds from 2,5-dimethylfuran. The first step was the acid-catalyzed ring-opening reaction of 2,5-dimethylfuran (DF), leading to the formation of 2,5-hexanedione (HD). A stoichiometric amount of water and a sub-stoichiometric amount of sulfuric acid were used by heating at 50 °C for 24 h. Chemically pure HD was isolated, with a quantitative yield (up to 95%), as revealed by 1H-NMR, 13C-NMR, and GC-MS analyses. In the second step, HD was used as the starting material for the synthesis of pyrrole compounds via the Paal–Knorr reaction. Various primary amines were used in stoichiometric amounts. 1H-NMR, 13C-NMR, ESI-Mass, and GC-Mass analyses confirmed that pyrrole compounds were prepared with very good/excellent yields (80–95%), with water as the only co-product. A further purification step was not necessary. The process was characterized by a very high carbon efficiency, up to 80%, and an E-factor down to 0.128, whereas the typical E-factor for fine chemicals is between 5 and 50. Water, a co-product of the second step, can trigger the first step and therefore make the whole process circular. Thus, this synthetic pathway appears to be in line with the requirements of a sustainable chemical process. A pyrrole compound bearing an SH group (SHP) was used for the functionalization of a furnace carbon black (CB). The functionalized CB (CB/SHP) was utilized in place of silica, resulting in a 15% mass reduction of reinforcing filler, in an elastomeric composite based on poly(styrene-co-butadiene) from solution anionic polymerization and poly(1,4-cis-isoprene) from Hevea Brasiliensis. Compared to the silica-based composite, a reduction in the Payne effect of about 25% and an increase in the dynamic rigidity (E’ at 70 °C) of about 25% were obtained with CB/SHP

Characterization and In Vivo Antiangiogenic Activity Evaluation of Morin-Based Cyclodextrin Inclusion Complexes

Morin (MRN) is a natural compound with antiangiogenic, antioxidant, anti-inflammatory, and anticancer activity. However, it shows a very low water solubility (28 μg/mL) that reduces its oral absorption, making bioavailability low and unpredictable. To improve MRN solubility and positively affect its biological activity, particularly its antiangiogenic activity, in this work, we prepared the inclusion complexes of MNR with sulfobutylether-β-cyclodextrin (SBE-β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD). The inclusion complexes obtained by the freeze-drying method were extensively characterized in solution (phase-solubility studies, UV–Vis titration, and NMR spectroscopy) and in the solid state (TGA, DSC, and WAXD analysis). The complexation significantly increased the water solubility by about 100 times for MRN/HP-β-CD and 115 times for MRN/SBE-β-CD. Furthermore, quantitative dissolution of the complexes was observed within 60 min, whilst 1% of the free drug dissolved in the same experimental time. 1H NMR and UV–Vis titration studies demonstrated both CDs well include the benzoyl moiety of the drug. Additionally, SBE-β-CD could interact with the cinnamoyl moiety of MRN too. The complexes are stable in solution, showing a high value of association constant, that is, 3380 M−1 for MRN/HP-β-CD and 2870 M−1 for MRN/SBE-β-CD. In vivo biological studies on chick embryo chorioallantoic membrane (CAM) and zebrafish embryo models demonstrated the high biocompatibility of the inclusion complexes and the effective increase in antiangiogenic activity of complexed MRN with respect to the free drug

Rutin/Sulfobutylether-β-Cyclodextrin as a Promising Therapeutic Formulation for Ocular Infection

Ocular pathologies present significant challenges to achieving effective therapeutic results due to various anatomical and physiological barriers. Natural products such as flavonoids, alone or in association with allopathic drugs, present many therapeutic actions including anticancer, anti-inflammatory, and antibacterial action. However, their clinical employment is challenging for scientists due to their low water solubility. In this study, we designed a liquid formulation based on rutin/sulfobutylether-β-cyclodextrin (RTN/SBE-β-CD) inclusion complex for treating ocular infections. The correct stoichiometry and the accurate binding constant were determined by employing SupraFit software (2.5.120) in the UV-vis titration experiment. A deep physical–chemical characterization of the RTN/SBE-β-CD inclusion complex was also performed; it confirmed the predominant formation of a stable complex (Kc, 9660 M−1) in a 1:1 molar ratio, with high water solubility that was 20 times (2.5 mg/mL) higher than the free molecule (0.125 mg/mL), permitting the dissolution of the solid complex within 30 min. NMR studies revealed the involvement of the bicyclic flavonoid moiety in the complexation, which was also confirmed by molecular modeling studies. In vitro, the antibacterial and antibiofilm activity of the formulation was assayed against Staphylococcus aureus and Pseudomonas aeruginosa strains. The results demonstrated a significant activity of the formulation than that of the free molecules