Catalytic Transformation of Nitroarenes to Amines over Ba(1-x)SrxTiO3 (0 < x < 1) Perovskites in Water.

This work is focused on the application of lanthanide-free perovskite Ba1-xSrxTiO3 (0 < x < 1) in valorization of toxic pollutants as 4-nitrophenol (4-NPh). The series of perovskites were fabricated by facile, one-step solid-state preparation method and characterized via various techniques: elemental analysis (Inductively Coupled Plasma Optical Emission Spectrometry, ICP-OES), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and dielectric properties (impedance spectroscopy, IS). The methods confirmed the assumed composition, structure and high purity of the materials. The results showed that substitution of Ba2+ by Sr2+ in the perovskite crystal lattice influenced the dielectric properties of samples and the size of the grains. The absorption and catalytic properties of Ba(1-x)SrxTiO3 (0 < x < 1) series were evaluated in reduction of 4-NPh in water using NaBH4 as reducing agent. No adsorption of 4-NPh was found for all the materials during 180 min of contact (experiment without reducing agent), and the best catalytic performance was found for the Ba(1-x)SrxTiO3 (x = 0.3) sample. The catalytic transformation of 4-NPh to 4-APh follows a pseudo-first-order model, and the catalysts can be easily regenerated via mild annealing (300 °C).

Hybrid Zn-ß-Aminoporphyrin-Carbon Nanotubes: Pyrrolidine and Direct Covalent Linkage Recognition, and Multiple-Photo Response.

To unveil and shape the molecular connectivity in (metallo)porphyrin-carbon nanotube hybrids are of main relevance for the multiple medicinal, photoelectronic, catalytic, and photocatalytic applications of these materials. Multi-walled carbon nanotubes (MWCNTs) were modified through 1,3-dipolar cycloaddition reactions with azomethine ylides generated in situ and carrying pentafluorophenyl groups, followed by immobilization of the ß-amino-tetraphenylporphyrinate Zn(II). The functionalities were confirmed via XPS and FTIR, whereas Raman spectroscopy showed disruptions on the graphitic carbon nanotube surface upon both steps. The functionalization extension, measured via TGA mass loss and corroborated via XPS, was 0.2 mmol·g-1. Photophysical studies attest to the presence of the different porphyrin-carbon nanotube connectivity in the nanohybrid. Significantly different emission spectra and fluorescence anisotropy of 0.15-0.3 were observed upon variation of excitation wavelength. Vis-NIR absorption and flash photolysis experiments showed energy/charge transfer in the photoactivated nanohybrid. Moreover, evidence was found for direct reaction of amino groups with a carbon nanotube surface in the presence of molecular dipoles such as the zwitterionic sarcosine amino acid.

Venous Thrombosis and Thrombocyte Activity in Zebrafish Models of Quantitative and Qualitative Fibrinogen Disorders.

Venous thrombosis occurs in patients with quantitative and qualitative fibrinogen disorders. Injury-induced thrombosis in zebrafish larvae has been used to model human coagulopathies. We aimed to determine whether zebrafish models of afibrinogenemia and dysfibrinogenemia have different thrombotic phenotypes. Laser injuries were used to induce venous thrombosis and the time-to-occlusion (TTO) and the binding and aggregation of fluorescent Tg(itga2b:EGFP) thrombocytes measured. The fga-/- larvae failed to support occlusive venous thrombosis and showed reduced thrombocyte binding and aggregation at injury sites. The fga+/- larvae were largely unaffected. When genome editing zebrafish to produce fibrinogen Aα R28C, equivalent to the human Aα R35C dysfibrinogenemia mutation, we detected in-frame skipping of exon 2 in the fga mRNA, thereby encoding AαΔ19-56. This mutation is similar to Fibrinogen Montpellier II which causes hypodysfibrinogenemia. Aα+/Δ19-56 fish had prolonged TTO and reduced thrombocyte activity, a dominant effect of the mutation. Finally, we used transgenic expression of fga R28C cDNA in fga knock-down or fga-/- mutants to model thrombosis in dysfibrinogenemia. Aα R28C expression had similar effects on TTO and thrombocyte activity as Aα+/Δ19-56. We conclude that thrombosis assays in larval zebrafish can distinguish between quantitative and qualitative fibrinogen disorder models and may assist in anticipating a thrombotic phenotype of novel fibrinogen mutations.

Associations between binge eating, depressive symptoms and anxiety and weight regain after Roux-en-Y gastric bypass surgery.

BACKGROUND: Weight regain (WR) after bariatric surgery (BS) is frequent. OBJECTIVE: The aim of this study was to evaluate whether the occurrence of psychiatric disorders would be associated with short- and long-term WR after BS. METHODS: Ninety-six patients (77.6% female, age 40.2 ± 10.1 years, BMI of 50 ± 8.2 kg/m2) from the Obesity and Bariatric Surgery Outpatient Clinic of the Universidade Federal São Paulo completed the Questionnaire on Eating and Weight Patterns-Revised, the Beck Depression Inventory and an anxiety inventory to assess the occurrence of binge eating, depressive symptoms (DS) and anxious symptoms (AS) before and after short-term and long-term BS. RESULTS: Twenty-four months after BS, the prevalence of binge eating, depression and anxiety decreased from 100 to 13%, 100 to 15% and 43 to 4%, respectively. The mean WR of 35.2 ± 17.3% of weight loss occurred in nine patients after 24 months and was associated with binge eating (p = 0.002) but not with DS or AS. At long-term follow-up (12 ± 1.5 years), 67% had a mean WR of 50.3 ± 24.9%. The prevalence of binge eating, DS and AS were 48%, 46% and 63%, respectively, in this group, and significant associations were observed between WR and binge eating (p = 0.001), DS (p = 0.029) and AS (p = 0.001). Furthermore, the number of psychiatric disorders was inversely associated with the percentage of weight loss (p < 0.05) and positively associated with WR (p < 0.05). CONCLUSION: Weight regain was associated with the occurrence of binge eating in the short and long term after BS, whereas the occurrence of depressive and anxious symptoms was associated with WR only in the long term. LEVEL III: Evidence obtained from well-designed cohort or case-control analytic studies.

Vine-Canes Valorisation: Ultrasound-Assisted Extraction from Lab to Pilot Scale.

Wine production generates large amounts of vine-canes, a devalued by-product that could be used for the recovery of bioactive compounds. In this work, two vine-canes varieties, namely Touriga Nacional (TN) and Tinta Roriz (TR), were submitted to different ultrasound-assisted extraction (UAE) conditions. The highest phenolic and flavonoid content was observed for TR extract obtained at lab-scale without an ice bath and pilot-scale after 60 min of extraction (32.6 ± 2.1 and 26.0 ± 1.5 mg gallic acid equivalent/g dry weight (dw) and 9.5 ± 0.6 and 8.3 ± 0.8 mg epicatechin equivalents/g dw, respectively). Further, all extracts demonstrated a high antioxidant activity to scavenge DPPH free radicals with the best value reached by TR at the lab-scale without an ice bath after 30 min and pilot-scale extraction after 60 min (34.2 ± 2.4 and 33.4 ± 2.1 mg trolox equivalents/g dw, respectively). Extracts phenolic composition were also evaluated by HPLC, demonstrating that resveratrol, myricetin and catechin were the main compounds. According to our knowledge, this is the first time that a pilot scale of UAE of phenolic compounds from vine-canes was performed. This paper represents an important step to the use of UAE as an industrial process to recover bioactive compounds.

Binge eating disorder is not predictive of alcohol abuse disorders in long-term follow-up period after Roux-en-Y gastric bypass surgery.

INTRODUCTION: Some studies have shown an increase in alcohol use disorders (AUD) after Roux-en-Y gastric bypass surgery (RYGB), but its relationship with binge eating disorder (BED) has not been fully explored. The purpose of this study was to determine the prevalence of AUD and BED after RYGB and also to evaluate if BED is predictive of late postoperative occurrence of AUD or BED. METHODS: Patients (n = 46) submitted to RYGB, in a tertiary outpatient weight management service at a Federal University of Sao Paulo, Brazil, were tested for BED and AUD using the Questionnaire on Eating and Weight Patterns-Revised (QEWP-R) and AUDIT, respectively. BED was tested before surgery, while both disorders were evaluated with a follow-up period of 12 ± 1.6 years after RYGB. RESULTS: No patients reported AUD before RYBP. After a mean period of 12 years from surgery, ten patients (21.7%) were diagnosed with AUD. Before surgery, BED was present in 24 patients (52.2%) and it was detected in seven out of these 24 patients (29.2%) after RYGB. Thirteen new cases of BED (28.2%) were detected after surgery; total of 20 patients (43.5%) with BED. No association was found between pre- and postsurgery BED (p = 0.148). After RYGB, four out of 24 patients (16.6%) with presurgery BED developed AUD, and no association was found between presurgery BED and postsurgery AUD (p = 0.384). Seven out of ten patients (70%) with AUD after RYGB also developed BED, but no statistical significance was found between these two disorders (p = 0.061). CONCLUSION: The presence of BED before RYGB did not predict AUD and BED after RYGB. Nevertheless, factors involved in a possible association between BED and AUD after surgery remain to be determined. LEVEL OF EVIDENCE: Level III, cohort study.

Polyoxotungstate@Carbon Nanocomposites As Oxygen Reduction Reaction (ORR) Electrocatalysts.

The oxygen reduction reaction (ORR) has a crucial function as the cathode reaction in energy-converting systems, such as fuel cells (FCs), which contributes to a sustainable energy supply. However, the current use of precious Pt-based electrocatalysts (ECs) is a major drawback for the economic viability of fuel cells. Hence, it is urgent to develop cost-effective and efficient electrocatalysts (ECs) without noble metals to substitute the Pt-based ECs. Herein, we report the preparation and application as ORR electrocatalysts of four new nanocomposites based on sandwich-type phosphotungstate (TBA)7H3[Co4(H2O)2(PW9O34)2] (TBA-Co4(PW9)2) immobilized onto different carbon nanomaterials [single-walled carbon nanotubes (SWCNT), graphene flakes (GF), carbon nanotubes doped with nitrogen (N-CNT), and nitrogen-doped few layer graphene (N-FLG)]. In alkaline medium, the four nanocomposites studied presented comparable onset potentials (0.77-0.90 V vs RHE), which are similar to that observed for Pt/C (0.91 V vs RHE). Higher diffusion-limiting current densities ( jL,0.26V,1600 rpm = -168.3 mA cm-2 mg-1) were obtained for Co4(PW9)2@N-CNT, as compared to Pt/C electrode -130.0 mA cm-2 mg-1) and the other ECs (-45.0, -50.7, and -87.5 mA cm-2 mg-1 for Co4(PW9)2@SWCNT, Co4(PW9)2@GF, and Co4(PW9)2@N-FLG, respectively). All the Co4(PW9)2@CM ECs showed selectivity toward direct O2 reduction to water with the exception of Co4(PW9)2@GF where a mixture of the 2- and 4-electron mechanisms is observed. Furthermore, low Tafel slopes were obtained for all the nanocomposites (68-96 mV dec-1). Co4(PW9)2@CM ECs also showed excellent tolerance to methanol with no significant changes in current density, in contrast to Pt/C (decrease of ≈59% after methanol addition) and good long-term electrochemical stability with current retentions between 75 and 84%.

Multicolour Electrochromic Film Based on a TiO2@poly[Ni(salen)] Nanocomposite with Excellent Electrochemical Stability.

We report the electrochromic properties of a polymeric nanocomposite prepared by potentiodynamic deposition of transition-metal complex [Ni(3-Mesalen)], designated as [1], in the presence of TiO2 nanoparticles (NPs) with an average size of 9.7 ± 1.1 nm. Entrapment of TiO2 NPs in the poly[1] matrix was confirmed by several techniques. The nanocomposite TiO2@poly[1] films showed similar electrochemical responses to the original (nanoparticle-free) poly[1] films, but with higher electroactive surface coverages (Γ), showing the advantage of the nanocomposite preparation. The results indicated that the electronic structure of poly[1] was retained in the nanocomposite; nonetheless, a lower ε value was obtained for the charge-transfer band of the former, revealing superior stability of the nanocomposite for ligand high oxidation states. The TiO2@poly[1] nanocomposite showed interesting color changes, from yellow (reduced state) to green and russet (oxidized states), with enhanced electrochemical stability, demonstrated by a charge loss of only 7.3% over ca. 10 000 redox cycles surpassing the original polymer film stability: the loss of electroactivity is a factor of ca. 2 less than for pristine poly[1]. Furthermore, an enhancement of 16.7% in the optical modulation (ΔOD = 0.48) was also observed for the nanocomposite, confirming the benefit of TiO2 incorporation into the EC properties of the original polymer film.

Driving Forces in the Sharpless Epoxidation Reaction: A Coupled AIMD/QTAIM Study.

In order to better understand the epoxide-formation step of the Sharpless epoxidation process, a set of 263 oxygen-transfer reactions reflecting the complexity of the Sharpless epoxidation process were studied using density functional theory (DFT) and Bader's quantum theory of atoms in molecules (QTAIM). The diversity within these reactions reflects the different ligands in the coordination sphere of vanadium and also different substrates (alkene and an allylic alcohol both free and in the form of an alcoxo ligand). The transition states for 76 of these reactions were also characterized using DFT and QTAIM, allowing for an estimation of the impact of the different ligands and substrates on the activation barriers. A smaller subset of the latter was further subjected to an ab initio molecular dynamics (AIMD) simulation coupled to QTAIM analysis. The results show that the type of active catalyst plays an important role in the thermodinamic outcome of these reactions, with vanadium(V) tert-butylhydroperoxide adducts being responsible for the most exoenergetic reactions. On the other hand, the different ligands tested play only a limited role in modulating the thermodynamics and kinetics of these reactions. Moreover, no evidence was found to support a thermodynamic or kinetic preference for the epoxidation of an allylic alcohol over that of an unfunctionalized alkene. However, the results suggest that the reaction path is strongly influenced by the orientation of the substrate upon approximation to the active catalyst, confirming the well-known regioselectivity of the Sharpless epoxidation process.

Roots of Acetate-Vanadium Linkage Isomerism: A QTAIM Study.

The possibility of linkage isomerism in a number of vanadium(IV) and vanadium(V) complexes with acetate was surveyed using Density Functional Theory (DFT) and Bader's Quantum Theory of Atoms in Molecules (QTAIM). The results show that vanadium-acetate linkages may be classified as bidentate symmetrical, bidentate asymmetrical, or monodentate, the latter being observed in about 40% of the cases. These latter ones correspond to situations where the two oxygen atoms of the acetate moiety are not equivalent. They are associated with an energy penalty of about 263 kJ·mol(-1), as determined by the distribution of the scaled kinetic energy of the atomic basins forming the acetate ligand. In the presence of bidentate symmetrical vanadium-acetate linkages, the inner valence-shell charge concentrations on the vanadium atom deviate from the traditional VSEPR-derived arrangement, with an energy penalty of about 780 kJ·mol(-1). A compromise situation is partially accomplished in the case of bidentate asymmetrical linkages, which allow a Gillespiean-like arrangement of the inner valence-shell charge concentrations. In this case, one of these local charge concentrations lies close to a V-OAcO bond, which slightly disrupts the equivalence between the two oxygen atoms in the acetate ligand.

Progress in the Raman spectra analysis of covalently functionalized multiwalled carbon nanotubes: unraveling disorder in graphitic materials.

Raman spectroscopy is highly sensitive to the morphology and electronic structures of graphitic materials, but a convenient interpretation model has been lacking for multiwalled carbon nanotubes (MWCNTs), in particular for the discrimination of spectral changes induced by covalent functionalization. The present work describes a systematic investigation of the Raman analysis of covalently functionalized MWCNTs by diazonium chemistry and oxidation methodologies, with typically different mechanisms and reaction sites. A multi-peak deconvolution system and spectral band assignment were proposed based on the chemical and structural modifications identified by X-ray photoelectron spectroscopy, thermogravimetry, X-ray diffraction, specific surface areas and the comparative analysis of the first and second order regions of the Raman spectra. Diazonium functionalization takes place mainly in the π-system of the external sidewall, while oxidation occurs on defects and leads to structure burning. This allowed us to distinguish between spectral features related to aromaticity disruptions within the sidewalls and spectral features related to changes within the inner tubes. The model was validated extending the studies to the functionalization of MWCNTs by the Bingel reaction.

Iron(III) Fluorinated Porphyrins: Greener Chemistry from Synthesis to Oxidative Catalysis Reactions.

Iron(III) fluorinated porphyrins play a central role in the biomimetics of heme enzymes and enable cleaner routes to the oxidation of organic compounds. The present work reports significant improvements in the eco-compatibility of the synthesis of 5,10,15,20-tetrakis-pentafluorophenylporphyrin (H2TPFPP) and the corresponding iron complex [Fe(TPFPP)Cl], and the use of [Fe(TPFPP)Cl] as an oxidation catalyst in green conditions. The preparations of H2TPFPP and [Fe(TPFPP)Cl] typically use toxic solvents and can be made significantly greener and simpler using microwave heating and optimization of the reaction conditions. In the optimized procedure it was possible to eliminate nitrobenzene from the porphyrin synthesis and replace DMF by acetonitrile in the metalation reaction, concomitant with a significant reduction of reaction time and simplification of the purification procedure. The Fe(III)porphyrin is then tested as catalyst in the selective oxidation of aromatics at room temperature using a green oxidant (hydrogen peroxide) and green solvent (ethanol). Efficient epoxidation of indene and selective oxidation of 3,5-dimethylphenol and naphthalene to the corresponding quinones is observed.

Multielectrocatalysis by layer-by-layer films based on pararosaniline and vanadium-substituted phosphomolybdate.

Hybrid multilayer films based on the two molecular species pararosaniline (PR) and Keggin-type polyoxometalate K5[PMo11VO40)] (PMo11V) were prepared on different substrates using the electrostatic layer-by-layer (LbL) self-assembly method. The film buildup, monitored by electronic spectroscopy, showed a regular stepwise growth, and X-ray photoelectron spectroscopy data confirmed the presence of both molecular components within the LbL films. Scanning electron microscopy images revealed a completely covered surface with a nonuniform distribution of film components, and atomic force microscopy images confirmed a rough surface. The film electrochemical responses and permeability were studied by cyclic voltammetry. Films revealed three Mo-based redox processes (Mo(VI) → Mo(V)) and one V-based redox process (V(V) → V(IV)) in the potential range between 0.8 and -0.4 V vs Ag/AgCl. Studies with the redox probes [Fe(CN)6](3-/4-) and [Ru(NH3)6](3+/2+) showed that the films maintain the permeability even after six bilayers. Furthermore, the {PR/PMo11V}n multilayer films exhibit excellent Mo-based electrocatalytic activity toward reduction of iodate and V-based electrocatalytic activity toward ascorbic acid oxidation, thus acting as a versatile multielectrocatalyst.

Biomimetic one-pot route to acridine epoxides.

The first direct epoxidation of acridine on the edge positions is reported. The reaction proceeds under mild conditions using a biomimetic catalytic system based on a Mn(III) porphyrin. The successive oxyfunctionalization to mono-, di-, and tetraepoxy derivatives is accomplished using hydrogen peroxide as a green oxidant at room temperature. Computed optimized geometries showed only slight shifts to the base planarity upon dearomatization by epoxidation, which is an important feature for DNA intercalation and bioactivity. NMR studies and comparison with theoretical values allowed the assignment of the stereochemistry of the anti- and syn-diepoxy and -tetraepoxy derivatives as well as compounds resulting from epoxide ring opening, exemplified by epoxydiol. The diepoxide is formed in an anti:syn ratio of ∼4, and the attack by nucleophiles, exemplified by ethylaniline, occurs selectively and with full conversion, using a microwave process with acetonitrile reflux for 10 min. Finally, studies of the electrostatic potential allowed the mechanisms of the formation of 4-hydroxyacridine and the regioselective reaction of diepoxyacridine with nucleophiles to be rationalized.

Principal component analysis of Mn(salen) catalysts.

The theoretical study of Mn(salen) catalysts has been traditionally performed under the assumption that Mn(acacen') (acacen' = 3,3'-(ethane-1,2-diylbis(azanylylidene))bis(prop-1-en-olate)) is an appropriate surrogate for the larger Mn(salen) complexes. In this work, the geometry and the electronic structure of several Mn(salen) and Mn(acacen') model complexes were studied using Density Functional Theory (DFT) at diverse levels of approximation, with the aim of understanding the effects of truncation, metal oxidation, axial coordination, substitution on the aromatic rings of the salen ligand and chirality of the diimine bridge, as well as the choice of the density functional and basis set. To achieve this goal, geometric and structural data, obtained from these calculations, were subjected to Principal Component Analysis (PCA) and PCA with orthogonal rotation of the components (rPCA). The results show the choice of basis set to be of paramount importance, accounting for up to 30% of the variance in the data, while the differences between salen and acacen' complexes account for about 9% of the variance in the data, and are mostly related to the conformation of the salen/acacen' ligand around the metal centre. Variations in the spin state and oxidation state of the metal centre also account for large fractions of the total variance (up to 10% and 9%, respectively). Other effects, such as the nature of the diimine bridge or the presence of an alkyl substituent in the 3,3 and 5,5 positions of the aldehyde moiety, were found to be less important in terms of explaining the variance within the data set. A matrix of discriminants was compiled using the loadings of the principal and rotated components that best performed in the classification of the entries in the data. The scores obtained from its application to the data set were used as independent variables for devising linear models of different properties, with satisfactory prediction capabilities.

Effects of axial coordination on immobilized Mn(salen) catalysts.

The consequences of anchoring Mn(salen) catalysts onto a supporting material using one of the vacant positions of the metal center are tackled by studying several Mn(salen) complexes with different axial ligands attached. This is accomplished using Density Functional Theory at the X3LYP/Triple-ζ level of theory and the Atom In Molecules formalism. The results suggest that both Mn(salen) complexes and their oxo derivatives should lie in a triplet ground state. Also, the choice of the axial ligand bears a moderate effect on the energy involved in the oxidation of the former to oxo-Mn(salen) complexes, as well as in the stability of such complexes toward ligand removal by HCl. AIM analysis further suggests that the salen ligand acts as a "charge reservoir" for the metal center, with strong correlations being obtained between the charge of salen and the electron population donated by the axial ligand to the metal center. Moreover, the results suggest that the Mn atom in Mn(salen) complexes holds different hybridization of its valence orbitals depending on the type of axial ligand present in the system.

In vitro evaluation of Portuguese propolis and floral sources for antiprotozoal, antibacterial and antifungal activity.

Propolis is a beehive product with a very complex chemical composition, used since ancient times in several therapeutic treatments. As a contribution to the improvement of drugs against several tropical diseases caused by protozoa, we screened Portuguese propolis and its potential floral sources Populus x Canadensis and Cistus ladanifer against Plasmodium falciparum, Leishmania infantum, Trypanosoma brucei and Trypanosoma cruzi. The toxicity against MRC-5 fibroblast cells was evaluated to assess selectivity. The in vitro assays were performed following the recommendations of WHO Special Programme for Research and Training in Tropical Diseases (TDR) and revealed moderate activity, with the propolis extracts presenting the relatively highest inhibitory effect against T. brucei. Additionally, the antimicrobial activity against Staphylococcus aureus, Candida albicans, Trichophyton rubrum and Aspergillus fumigatus was also verified with the better results observed against T. rubrum. The quality of the extracts was controlled by evaluating the phenolic content and antioxidant activity. The observed biological activity variations are associated with the variable chemical composition of the propolis and the potential floral sources under study.

Ternary (molybdenum disulfide/graphene)/carbon nanotube nanocomposites assembled via a facile colloidal electrostatic path as electrocatalysts for the oxygen reduction reaction: Composition and nitrogen-doping play a key role in their performance.

Nanocomposites have garnered attention for their potential as catalysts in electrochemical reactions vital for technologies like fuel cells, water splitting, and metal-air batteries. This work focuses on developing three-dimensional (3D) nanocomposites through aqueous phase exfoliation, non-covalent functionalization of building blocks with surfactants and polymers, and electrostatic interactions in solution leading to the nanocomposites assembly and organization. By combining molybdenum disulfide (MoS2) layers with graphene nanoplatelets (GnPs) to form a binary 2D composite (MoS2/GnP), and subsequently incorporating multiwalled carbon nanotubes (MWNTs) to create ternary 3D composites, we explore their potential as catalysts for the oxygen reduction reaction (ORR) critical in fuel cells. Characterization techniques such as X-ray photoelectron spectroscopy, scanning electron microscopy, and X-ray diffraction elucidate material composition and structure. Our electrochemical studies reveal insights into the kinetics of the reactions and structure-activity relationships. Both the (MoS2/GnP)-to-MWNT mass ratio and nitrogen-doping of GnPs (N-GnPs) play a key role on the electrocatalytic ORR performance. Notably, the (MoS2/N-GnP)/MWNT material, with a 3:1 mass ratio, exhibits the most effective ORR activity. All catalysts demonstrate good long-term stability and methanol crossover tolerance. This facile fabrication method and observed trends offer avenues for optimizing composite electrocatalysts further.

Phenolic profiling of Portuguese propolis by LC-MS spectrometry: uncommon propolis rich in flavonoid glycosides.

INTRODUCTION: Propolis is a chemically complex resinous substance collected by honeybees (Apis mellifera) from tree buds, comprising plant exudates, secreted substances from bee metabolism, pollen and waxes. Its chemical composition depends strongly on the plant sources available around the beehive, which have a direct impact in the quality and bioactivity of the propolis. Being as Portugal is a country of botanical diversity, the phenolic characterisation of propolis from the different regions is a priority. OBJECTIVE: Extensive characterisation of the phenolic composition of Portuguese propolis from different continental regions and islands. METHOD: Forty propolis ethanolic extracts were analysed extensively by liquid chromatography with diode-array detection coupled to electrospray ionisation tandem mass spectrometry (LC-DAD-ESI-MS(n) ). RESULTS: Seventy-six polyphenols were detected in the samples and two groups of propolis were established: the common temperate propolis, which contained the typical poplar phenolic compounds such as flavonoids and their methylated/esterified forms, phenylpropanoid acids and their esters, and an uncommon propolis type with an unusual composition in quercetin and kaempferol glycosides - some of them never described in propolis. CONCLUSION: The method allowed the establishment of the phenolic profile of Portuguese propolis from different geographical locations, and the possibility to use some phenolic compounds, such as kaempferol-dimethylether, as geographical markers. Data suggest that other botanical species in addition to poplar trees can be important sources of resins for Portuguese propolis.

Graphene-Type Materials for the Dispersive Solid-Phase Extraction Step in the QuEChERS Method for the Extraction of Brominated Flame Retardants from Capsicum Cultivars.

A new application of graphene-type materials as an alternative cleanup sorbent in a quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure combined with GC-ECD/GC-MS/GC-MS/MS detection was successfully used for the simultaneous analysis of 12 brominated flame retardants in Capsicum cultivar samples. The chemical, structural, and morphological properties of the graphene-type materials were evaluated. The materials exhibited good adsorption capability of matrix interferents without compromising the extraction efficiency of target analytes when compared with other cleanups using commercial sorbents. Under optimal conditions, excellent recoveries were obtained, ranging from 90 to 108% with relative standard deviations of <14%. The developed method showed good linearity with a correlation coefficient above 0.9927, and the limits of quantification were in the range of 0.35-0.82 µg/kg. The developed QuEChERS procedure using reduced graphite oxide (rGO) combined with GC/MS was successfully applied in 20 samples, and the pentabromotoluene residues were quantified in two samples.