Synthesis, photophysical and electrochemical properties of π-conjugated pyrene based down-shifting molecules with fluorinated aryl groups

ABSTRACT: Pyrene molecule, with excellent photophysical properties (strong absorption cross section, excellent emission properties and a long-excited state lifetime), excellent thermal and photochemical stability, has been widely used as a building block for the synthesis of pyrene-based fluorophores for optoelectronic applications. In this work, we report the synthesis of two series of pyrene-pi-A compounds, series I (3-6) and II (10-13), in which nitro, cyano, cyanoacrylonitrile and cyanoacrylic acid as electron acceptor groups are connected to the pyrene core via aryl or fluoroaryl pi-conjugating bridges. The incorporation of fluorine atom on the pi-extension bridge cause a slightly red-shift at emission wavelength (lambda em) in solution and polymethylmethacrylate (PMMA) films and in-crease the Stokes shift due to greater stabilization of molecular orbitals in the excited state, especially for series I. Solvatochromic measurements and theoretical computational studies suggest a higher intramolecular charge transfer in the excited state for series II when compared to series I due to their stronger electron acceptor moieties. All pyrene derivatives are stable and exhibited initial mass loss at temperature above 200 degrees C. The good photophysical and thermal properties of the synthesized pyrene derivatives, associated with high molar ab-sorption coefficients in the UV spectrum and good fluorescence emission in the range of 430-480 nm (series I) and 505-567 nm (series II) in PMMA films, make them possible candidates for organic light-emitting diode (OLED) and luminescent down-shifting (LDS) layers for stable perovskite solar cells, respectively.info:eu-repo/semantics/publishedVersio

Photocatalytic hydrogen production using noble and transition metals surface modified titania [Resumo]

ABSTRACT: A large number of photocatalytic materials have been studied for water splitting since the seminal work of Fujishima and Honda1, showing great potential for solar energy conversion, including H2 production. The irradiation of a suspension of semiconductor oxides, as is the case of TiO2, presents attracting features but also stringent requirements regarding materials properties, including the tailoring of the electronic structure. Furthermore, efficient charge transport is necessary, as well as effective charge separation and prevention of electron-hole pair recombination, before the redox reactions can proceed2,3. In this work, the catalytic activity under UV excitation of TiO2-Au photocatalyst for H2 production was undertaken using glycerol and ethanol as sacrificial agents. Furthermore, substitution of Au by transition metal Cu was attempted with good results. Comparison is made with results obtained using TiO2-rGO-Pt catalyst under analogous loading conditions.N/

Enhancing Pt electrocatalytic activity by surface functionalization of carbon support with aromatic sulphonic groups

Preliminary results are presented for Pt deposited on 4-aminobenzenesulphonic acid-functionalized carbon, Pt/C_ABSA. Vulcan XC-72R was functionalized with the objective of influencing the dispersion of catalyst nanoparticles and to decrease the resistance of three phase boundaries, by introducing sulphonic groups. Electrochemical characterization of the supported catalyst was done in a 0.5 M sulphuric acid solution with added chloride and also using methanol demonstrating well defined features and stable voltammograms after 30 cycles, with apparent higher currents when compared with commercial catalyst. The structure sensitive adsorption of anions on platinum is confirmed by the blocking effect of chloride ions in the hydrogen adsorption-desorption region as well as by the consequent dissolution of platinum, evident in both anodic and cathodic features of the voltammograms regarding surface oxide formation and reduction. The partial reversibility of the effect of chloride ions is discussed. Research is in progress in order to accomplish a comprenhensive characterization of the synthesized catalyst and to ascertain the effect of the sulphonic groups

Generation of hydrogen from chemical hydrides under pressure up to 70 Bar

Hydrogen production by sodium borohydride through hydrolysis in alkaline solutions has been extensively studied as a production/storage option. The potential application of this option is dependent on an easily controllable catalysed hydrolysis reaction at significant rates to comply with fuel cell feeding but also on the increase of the gravimetric density being of paramount importance, the design and implementation of compact and efficient reactors and the reaction characterization under pressure. In this work, hydrogen generation by the catalyzed hydrolysis of sodium borohydride was studied under pressure up to 70 bar with excellent result

Challenges arising from the use of TiO2/rGO/Pt photocatalysts to produce hydrogen from crude glycerol compared to synthetic glycerol

ABSTRACT: Photoreforming has emerged as a novel technology expected to obtain chemical energy through solar energy transformation. In this way, sustainable valorization of glycerol, a biodiesel by-product, to clean fuels is a promising alternative to help meet the world's growing energy demand. In this work, TiO2/rGO(x)/Pt(y) photocatalysts have been developed for hydrogen production from synthetic and crude glycerol solutions. The effect of several key operating parameters (including vol% of glycerol, pH, catalyst loading, wt% of GO, wt% of Pt, temperature, and light source) on hydrogen production rate has been studied. The results indicated different optimal operating parameters depending on glycerol origin, achieving up to 70.8 and 12.7 mmol h(-1) g(-1) of hydrogen using synthetic glycerol and crude glycerol, respectively. Additionally, GO nanosheets and Pt nanoparticles strongly influenced the hydrogen production rate but not the overall reaction mechanism. Impurities contented in crude glycerol are key factors in developing realistic hydrogen production processes.info:eu-repo/semantics/publishedVersio

Evaluation of the growth-inhibitory effect of trifluralin analogues on in vitro cultured Babesia bovis parasites

Bovine babesiosis, caused by Babesia bovis, is a global tick borne hemoprotozoan parasite disease characterized by fever, anemia, weight losses and ultimately death. Several babesicidal drugs that have been in use in cattle for years have proven to be only partially effective and the development of alternative chemotherapeutics that are highly specific and have low toxicity against babesiosis is needed. Trifluralin derivatives specifically bind alpha-tubulin in plants and protozoa parasites causing growth inhibition. A set of 12 trifluralin analogues (TFLA) has previously been shown to be inhibitory for the growth of Leishmania species. The conservation of several key amino acids involved in the trifluralin binding site of alpha-tubulin among Leishmania sp. and B. bovis provides rationale for testing these compounds also as babesiacides. The previously tested Leishmania inhibitory, TFLA 1-12 minus TFLA 5, in addition to three novel TFLA (termed TFLA 13-15), were tested against in vitro cultured B. bovis parasites. While all of the TFLA tested in the study showed inhibition of B. bovis growth in vitro TFLA 7, TFLA 10 and TFLA 13, were the most effective inhibitors with estimated IC50 (μM) at 72h of 8.5±0.3; 9.2±0.2; 8.9±0.7, respectively for the biologically attenuated cloned B. bovis Mo7 strain, and 13.6±1.5; 18.7±1.6; 10.6±1.9, respectively for the virulent B. bovis T3Bo strain. The differences found between the two strains were not statistically significant. Importantly, these drugs displayed low levels of toxicity for the host erythrocytes and bovine renal arterial endothelial cells at the doses tested. The demonstrated ability of trifluralin analogues to inhibit in vitro growth of B. bovis parasites combined with their low toxicity for host cells suggests that these compounds may be further developed as novel alternatives for the treatment of bovine babesiosis.publishersversionpublishe

Photocatalytic hydrogen production using ethanol as sacrificial agent from gas and liquid phases on reduced graphene oxide-TiO2- Pt nanocomposites

ABSTRACT: Various strategies such as heterostructuring, crystal/textural modifications and band gap engineering, have been applied to the improvement of the photocatalytic activity of Titania for hydrogen production from water splitting. In this work deposited Pt on TiO2 is used as electron trap to suppress charge recombination. To reinforce this effect, composites with graphene oxide (GO) have been prepared, exhibiting promising photocatalytic performance for both hydrogen generation and the degradation of ethanol added as hole scavenger. Photocatalytic reactions were conducted in gas and liquid phases.N/

Traumatic brain injury patients: does frontal brain lesion influence basic emotion recognition?

Adequate emotion recognition is relevant to individuals’ interpersonal communication. Patients with frontal traumatic brain injury (TBI) exhibit a lower response to facial emotional stimuli, influencing social interactions. In this sense, the main goal of the current study was to assess the ability of TBI patients in recognizing basic emotions. Photographs of facial expressions of five basic emotions (happiness, sadness, fear, anger, and surprise) were presented to 32 TBI patients and 41 healthy controls. Emotion recognition was measured by accuracy and reaction time. Overall performance of the TBI group was poorer than control group for emotion recognition, both in terms of accuracy and reaction time. It is suggested that TBI patients show impairment on emotion recognition, and this relation seems to be moderated by the lesion localization. Keywords: emotion recognition, basic emotions, TBI patients

Novos nanocompósitos de óxido de titânio para a produção de hidrogénio solar

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMO: Neste trabalho foram sintetizados uma série de novos compósitos de TiO2-rGO e TiO2-g-C3N4, como base para o desenvolvimento de fotocatalisadores ativos na produção de hidrogénio solar a partir de soluções aquosas de etanol. Os compósitos foram dopados com metais nobres e de transição (Pt, Au e Cu), tendo sido estes fotodepositados a partir dos respetivos sais. Para 6 h de irradiação UV, o volume de gás produzido com os catalisadores TiO2-Pt1.5% e TiO2-Au1.5% é semelhante, embora com perfis de velocidade diferentes, que mostram 2 declives no caso da Pt. A substituição da Pt por Cu deu resultados promissores em termos de gás produzido, ainda que nas presentes condições experimentais não foi significativamente alterado pela presença de rGO ou g-C3N4. A irradiação contínua até 24 h evidenciou velocidades constantes para os fotocatalisadores TiO2-Cu contrariamente ao TiO2-rGO3%-Pt3.8% cuja produção de gás parou pelas 12 h, devido a envenenamento pelos produtos de oxidação do etanol. A substituição de Pt por Cu revela-se também vantajosa considerando as questões associadas à escassez e custo da Pt.ABSTRACT: In this work, a new series of composite materials based on TiO2-rGO e TiO2-g-C3N4 were synthesized in the search for active photocatalysts for solar hydrogen production in aqueous ethanol containing solutions. The composites were doped with noble and transition metals (Pt, Au e Cu), which were photodeposited from solutions of their respective salts. Using UV irradiation up to 6 h, photocatalyst TiO2-Pt1.5% and TiO2-Au1.5%, produced similar amounts of gas but their production rate profiles were different, with a 2 slope profile in the case of Pt. The substitution of Pt by Cu gave promising results in terms of volume of gas produced, which in the present experimental conditions was not significantly influenced by the presence of rGO or g-C3N4. Continuous irradiation up to 24 h evidenced constant hydrogen production rates for TiO2-Cu photocatalysts over the whole testing period, contrary to TiO2-Pt composites that stopped producing hydrogen after 12 h, due to active site poisoning by ethanol oxidation products. Pt substitution by Cu is also advantageous in tackling the associated Pt scarcity and cost issues.info:eu-repo/semantics/publishedVersio