Synthesis and electrochemical investigation of <Emphasis Type="Italic">beta</Emphasis>-substituted thiophene-based donor–acceptor copolymers with 3,4-ethylenedioxythiophene (EDOT)

The present work reports the synthesis of four electron-acceptor beta-substituted thiophenes that were studied as monomers for electrochemical polymerization with 3,4-ethylenedioxythiophene (EDOT), an electron-donating monomer, aiming the combination of electron-acceptor and donor monomer thiophene to a simpler and convenient build up of novel donor–acceptor copolymeric materials via electrochemical polymerization. Four novel copolymers poly(EDOT-co-3-thiophene phenylacetate), (PEDOT-co-PPhTAc-2a), poly(EDOT-co-3-thiophene(4-nitrophenyl)acetate) (PEDOT-co-PPhTAc-2b), poly(EDOT-co-3-thiophenephenylcarboxylate) (PEDOT-co-PPhTCb), and poly(EDOT-co-3-(phenoxymethyl)thiophene) (PEDOT-co-PPhOMT) were electrochemically polymerized. The monomers were characterized by spectrometric techniques (FTIR, ¹H NMR, and ¹³C NMR), and the copolymers were identified by electrochemical analyses and FT-IR. Although the corresponding homopolymers could not be obtained, in the presence of EDOT, the copolymers were formed in a quasi-reversible electrochemical kinetics. The infrared spectra of the copolymers as well the electrochemical profile corroborates their obtaining. The mass variation during the electrosynthesis was analyzed using a quartz crystal microbalance. The film’s morphologies were investigated by SEM. Interestingly, the combination of electron-rich monomer thiophene (EDOT) and these electron-deficient carboxy-substituted thiophenes might be a convenient building block couple to increase the performance control of physic-chemical properties of mixed polythiophenes with innovative applications and they also showed a possible applicability as charge storage device.     

Chitosan-modified TiO<Subscript>2</Subscript> as photocatalyst for ethanol reforming under visible light

This work reports the reforming of bio-ethanol on chitosan–TiO₂ hybrid photocatalysts at ambient temperature. The influence of chitosan composition on the photocatalytic performance of chitosan–TiO₂ hybrid was studied. The hybrids were characterized by CHN elemental analysis, nitrogen adsorption–desorption isotherms, thermogravimetric analysis, diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the preparation variables used for the incorporation of chitosan on TiO₂ promoted changes in the morphology, superficial area, crystal size and porosity of the photocatalyst, affecting the band gap of this semiconductor and consequently the reactivity of the chitosan–TiO₂ hybrids. The catalysts were evaluated for hydrogen production from ethanol under visible light. It was demonstrated that the calcination temperature of 623 K and a chitosan content of 20% were the most appropriate preparation conditions and the resulting product displays a pore size of 1.9 nm, crystal size of 11.3 nm, BET area of 178 m² g^?1 and band gap of 2.92 eV. The calcination temperature of 623 K and incorporation of 20% of chitosan obtained the same results in the conversion rate of hydrogen in comparison to the pure TiO₂ P25.     

Iodine(III)-promoted ring contraction of 1,2-dihydronaphthalenes: a diastereoselective total synthesis of (+/-)-indatraline

[reaction: see text] A new approach for the synthesis of (+/-)-indatraline, which is a 3-phenyl-1-indanamine that displays several biological activities, is described. The strategy features as the key step a diastereoselective ring contraction of a 1,2-dihydronaphthalene promoted by PhI(OTs)OH, to construct the indan ring system. The oxidative rearrangement of other 1,2-dihydronaphthalenes was also investigated, generalizing this method to obtain indans.     

Cellulases and Hemicellulases from Endophytic <Emphasis Type="Italic">Acremonium</Emphasis> Species and Its Application on Sugarcane Bagasse Hydrolysis

The aim of this work was to have cellulase activity and hemicellulase activity screenings of endophyte Acremonium species (Acremonium zeae EA0802 and Acremonium sp. EA0810). Both fungi were cultivated in submerged culture (SC) containing l-arabinose, d-xylose, oat spelt xylan, sugarcane bagasse, or corn straw as carbon source. In solid-state fermentation, it was tested as carbon source sugarcane bagasse or corn straw. The highest FPase, endoglucanase, and xylanase activities were produced by Acremonium sp. EA0810 cultivated in SC containing sugarcane bagasse as a carbon source. The highest β-glucosidase activity was produced by Acremonium sp. EA0810 cultivated in SC using d-xylose as carbon source. A. zeae EA0802 has highest α-arabinofuranosidase and α-galactosidase activities in SC using xylan as a carbon source. FPase, endoglucanase, β-glucosidase, and xylanase from Acremonium sp. EA0810 has optimum pH and temperatures of 6.0, 55 °C; 5.0, 70 °C; 4.5, 60 °C; and 6.5, 50 °C, respectively. α-Arabinofuranosidase and α-galactosidase from A. zeae EA0802 has optimum pH and temperatures of 5.0, 60 °C and 4.5, 45 °C, respectively. It was analyzed the application of Acremonium sp. EA0810 to hydrolyze sugarcane bagasse, and it was achieved 63% of conversion into reducing sugar and 42% of conversion into glucose.     

Enhanced catalytic activity of Fe phthalocyanines linked to Au(111) via conjugated self-assembled monolayers of aromatic thiols for O2 reduction

We have obtained and characterized self assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (FePc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/FePc was examined for the reduction of O₂ in aqueous media (pH = 4) and compared with that of bare gold and of gold coated directly with FePc molecules. Scanning tunneling microscopy (STM) studies confirm the functionalization of the 4-ATP by FePc. The electrocatalytic studies carried out with Au/FePc, Au/4-ATP/FePc and Au/MDPP/FePc electrodes show that the O₂ reduction takes place by a 4-electron transfer to give water in contrast to a 2-electron-transfer process observed on the bare gold. The activity of the electrodes increases as follows: Au < Au/FePc < Au/4-ATP/FePc < Au/MDPP/FePc.     

Sustainable nanocomposite films based on bacterial cellulose and pullulan

Bionanocomposites with improved properties based on two microbial polysaccharides, pullulan and bacterial cellulose, were prepared and characterized. The novel materials were obtained through a simple green approach by casting water-based suspensions of pullulan and bacterial cellulose and characterized by TGA, RDX, tensile assays, SEM and AFM. The effect of the addition of glycerol, as a plasticizer, on the properties of the materials was also evaluated. All bionanocomposites showed considerable improvement in thermal stability and mechanical properties, compared to the unfilled pullulan films, evidenced by the significant increase in the degradation temperature (up to 40 °C) and on both Young’s modulus and tensile strength (increments of up to 100 and 50%, for films without glycerol and up to 8,000 and 7,000% for those plasticized with glycerol). Moreover, these bionanocomposite films are highly translucent and could be labelled as sustainable materials since they were prepared entirely from renewable resources and could find applications in areas as organic electronics, dry food packaging and in the biomedical field.     

Vibrational properties of polyatomic molecules by quantum chemical methods

Force constants and dipole moment derivatives have been computed for the molecules CH₃ X(X=F, Cl, Br, I) using MO wavefunctions with pseudo-potentials for the interaction between the inner shell and valence electrons. The values obtained at the SCF approximation level from a set of gaussian valence orbitals contracted in double-zeta form and enriched with polarization functions compare well with experimental assignments of force and interaction constants, as well as integrated intensities from infrared data. The transferability of atomic force fields and polar tensors (second derivatives of total energies and first derivatives of dipole moments with respect to atomic displacements in cartesian coordinates) is discussed.     

ESR in a gapped Anderson model

We applied the numerical renormalization group method to study the electron spin resonance (ESR) of a single-impurity Anderson model with a gap $\Delta$ in the conduction electron density of states, centered at the Fermi level. We analyzed the relaxation rate $1/T_1$ of a magnetic probe located at a position $\overrightarrow{R}$ around the Anderson impurity. It presents different behaviors for the symmetric and the asymmetric case. For the symmetric case and any $\Delta >0$, $1/T_1$ goes to a constant for $T?{\Gamma }_{\text{k}}$ (Kondo resonance). $1/T_1$ decreases monotonically to zero only for $\Delta =0$. For the asymmetric case, there is a $\Delta$ under which $1/T_1$ decreases monotonically to zero as $T\to 0$, and above which $1/T_1$ saturates, as occurs in the symmetric case for $\Delta >0$. This behavior indicates a quantum phase transition from the quenched to the unquenched magnetic moment in the ground state of the Anderson ion.     

High-pressure phase equilibrium data for systems with carbon dioxide, α-humulene and trans-caryophyllene

The aim of this work is to report phase equilibrium data for the binary systems (CO₂ + α-humulene) and (CO₂ + trans-caryophyllene), and for the ternary system (CO₂ + α-humulene + trans-caryophyllene). Results from literature show that α-humulene and trans-caryophyllene are the main compounds responsible for the anti-inflammatory and anti-allergic characteristics attributed to the medicinal plant Cordia verbenacea D.C., hence giving importance to the phase behaviour investigation performed in this work. Phase equilibrium experiments were performed in a high-pressure, variable-volume view cell over the temperature range of T = (303 to 343) K and pressures up to 20 MPa. (Liquid + liquid) and (vapour + liquid + liquid) equilibrium were observed at T = 303 K, while (vapour + liquid) phase transitions were verified to occur from T = (313 to 343) K, for all systems studied. Thermodynamic modelling was performed using the Peng–Robinson equation of state and the classical quadratic mixing rules, with a satisfactory agreement between experimental and calculated values.     

Fast LC–MS Electrospray Ionization for the Quantification of Digoxin in Human Plasma and Its Application to Bioequivalence Studies

A fast, sensitive and specific liquid chromatography-mass spectrometry method has been developed for quantification of digoxin in human plasma. The method was optimized to bioequivalence studies aiming higher sensitivity and selectivity than previously published methods, in addition to shorter run time allowing high-throughput sample analyses from volunteers. Chromatographic separation was achieved by an RP-18e column hyphenated to an API 5000 mass spectrometer system set at negative electrospray ionization and operating in the MRM mode. Calibration curve was linear over a wide range of concentration (50.0–6000.0 pg mL⁻¹), with the lower limit of quantification at 50.0 pg mL⁻¹ and without interfering peaks at the retention time of digoxin (2.09 min). Dexamethasone was used as internal standard and samples were cleaned up by liquid-liquid extraction obtaining a mean recovery of 73.8%. Validation results confirmed inter-batch accuracy (−8.66 to 5.78%), precision (4.1–10.6%) and stability, in accordance with the U.S. Food and Drug Administration and the Brazilian National Health Surveillance Agency guidelines. The developed analytical method could be successfully applied to a single oral dose (0.25 mg), one-way, randomized, two-sequence, crossover bioequivalence study validating, up to date, the fastest analysis and the most sensitive and specific method already published for digoxin quantification.