New bifunctional aluminum complexes have been prepared with the aim of studying the effect of a counterion on the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2). Neutral ligand 1 was used as a precursor to obtain four novel mesylate, chloride, bromide, and iodide zwitterionic NNO ligands (2–5). The reaction of these ligands with 1 or 2 equiv of AlR3 (R = Me, Et) allowed the synthesis of mono- and bimetallic bifunctional aluminum complexes [AlR2(κ2-mbpzappe)]­X [X = Cl, R = Me (6), Et (7); X = Br, R = Me (8), Et (9); X = I, R = Me (10), Et (11)] and [{AlR2(κ2-mbpzappe)}­(μ-O)­{AlR3}]­X [X = MeSO3, R = Me (12), Et (13); X = Cl, R = Me (14), Et (15); X = Br, R = Me (16), Et (17); X = I, R = Me (18), Et (19)] via alkane elimination. These complexes were studied as catalysts for the synthesis of cyclic carbonates from epoxides and CO2. Iodide complex 11 showed to be the most active catalyst for terminal epoxides, whereas bromide complex 9 was found to be the optimal catalyst when internal epoxides were used, showing the importance of the nucleophile cocatalyst on the catalytic activity.

Accurate-controlled sized graphene quantum dots (GQDs) have been used as an analytical nanoprobe for detecting curcumin as a function of the photoluminescent quenching upon increasing concentrations of the analyte. Regarding the importance of curcumin nanoparticles in nutraceutical food, the analytical method described herein was also proven for the discrimination of curcumin remaining in free solution from that encapsulated into water-soluble nanomicelles of ca. 11 nm. This recognition is based on the displacement of GQD emission when interacting with both curcumin species. Maximum emission wavelength of GQDs suffers a gradual quenching as well as a red-shifting upon increasing concentrations of free curcumin (from 458 to 490 nm, exciting at 356 nm). On the other hand, in the presence of nanocurcumin, GQD photoluminescent response only displays a quenching effect (458/356 nm). The sensitivity of the described method in terms of detection limits was 0.3 and 0.1 μg mL −1 for curcumin and nanocurcumin, respectively. The applicability of the photoluminescent probe for the quantification and discrimination between both curcumin environments was demonstrated in nutraceutical formulations namely functional food capsules and fortified beverages such as ginger tea.

No abstract

Waterborne polyurethane (WBPUR) aerogels using acetone method and freeze-drying procedure have been successfully synthesized. The morphology, chemical structure, and thermal and mechanical properties of obtained aerogels were analysed by means of scanning electron microscopy, Fourier-transform infrared spectroscopy, contact angle, thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis. In addition, the influence of the solids content in the hydrogel (2–15 wt.%), obtained by varying the amount of water added in the suspension, on the density and thermal conductivity was evaluated. Obtained results demonstrated that the properties of aerogels strongly depend on the solids content assayed in the parent solution. As the solids content in the WBPUR aerogels increases, the density and thermal conductivity for materials with 2.5 and 10% solids content follow an upward trend, while their elasticity decreases. Materials with solids content below 2.5% and above 10% have not demonstrated adequate processability due to their high deformity and hardness, respectively. The drying methodology (freeze-drying) can be profitably used to prepare aerogels-like materials in a cost-effective way. Graphical abstract Illustration of the alternative preparation process of WBPUR aerogels and its potential industrial application.

No abstract