Repositório Institucional da Universidade de Aveiro
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Ionic liquid-based three phase partitioning (ILTPP) systems: Ionic liquid recovery and recycling
No full textIonic liquid-based three phase partitioning (ILTPP) is a promising technique to recover lactoferrin, a high-added value whey protein, because it combines the advantages associated with the use of ionic liquids and the feasibility of the product recovery characteristic of three phase partitioning. The recyclability of the ionic liquid is essential for the feasibility and development of ILTPP technique, due to the high cost and environmental impact associated with the discharge of this type of compounds. For this purpose, the thermodynamic characterization of the systems of interest for ILTPP, which are based on the use of 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BmimTfO) and sodium dihydrogenophosphate (NaH2PO4), is here performed to determine the composition of the liquid phases in equilibrium and the distribution coefficient between them. In addition, the fraction of ionic liquid that cannot be reused in the ILTPP process has been assessed, concluding that the recyclability of this compound is highly dependent on the protein concentration in the feed stream. At high protein concentrations (2 g L-1) and moderate ILTPP efficiencies (around 80%) it is possible to recycle more than 99% of the ionic liquid, which improves both the economic and environmental performance of the ILTPP process. (C) 2014 Elsevier BM. All rights reserved
A convenient noninjection one-pot synthesis of Cds nanoparticles and their studies
No full textWater-dispersible CdS quantum dots (QDs) were synthesized in a simple one-pot noninjection route. The X-ray diffraction (XRD) pattern of the nanoparticles shows the cubic structure with particle size of the order 5-7 nm which was in good agreement with the transmission electron microscopic (TEM) studies. Selected area electron diffraction (SAED) recognized the cubic structure of CdS. The energy dispersive X- ray spectroscopy (EDAX) analysis confirms the presence of Cd and S elements in the samples. The optical properties are characterized by Ultraviolet-Visible (UV-Vis) absorption and Photoluminescence (PL) spectra. The synthesis parameters of this simple and rapid approach, including the reaction temperature and time, the pH of the reaction solution and the molar ratio of the 3-mercaptopropionic acid (MPA) stabilizer to Cd2+, have considerable influence on the particle size and photoluminescence of the CdS quantum dots. The 3-mercaptopropionic acid (MPA) stabilized CdS QDs can be used in solar cells, light emitting diodes, biological imaging etc © 2013 VBRI press
Modeling Self-Assembly of Silica/Surfactant Mesostructures in the Templated Synthesis of Nanoporous Solids
No full textA novel coarse-grained (CG) model to study the self-assembly of silica/surfactant mesostructures during the synthesis of periodic mesoporous silica is reported. Molecular dynamics simulations of hexadecyltrimethylammonium bromide (also called cetyltrimethy-lammonium bromide, or CTAB) surfactants in water and in aqueous silicate solutions have been performed to understand micelle formation, micelle growth, and their size evolution during the synthesis of surfactant-templated mesoporous materials. Direct comparison of density profiles obtained for preassembled micelles employing an all-atom description, AA, with those calculated with the CG model has been carried out for checking the validity of the latter model. Good agreement between AA and CG approaches was found, demonstrating the potential of the CG approximation for modeling these highly complex systems. The micelle formation and micelle fusion/fission processes were analyzed after performing long CG simulations for surfactant and ionized silica-surfactant aqueous solutions. We observed the formation of rodlike micelles in the case of silica-surfactant solutions, while spherical micelles were stable under the same conditions for the CTAB+H2O system. This demonstrates that the interaction of anionic silicates with cationic surfactants promotes a sphere-to-rod transition in surfactant solutions, a key step in the synthesis of nanoporous silica materials
Solution and solid-state spectroscopic characterization of chloro dimethylsulfoxide polythioether ruthenium(II) complexes, complemented with DFT calculations in the gas phase
No full textSeveral ruthenium(II)-chloro-dimethylsulfoxide complexes with formulae [RuCl2(DMSO)(k(3)-L-1)] or [RuCl(DMSO)(k(4)-L-2)](+), where L-1=[9]aneS(3) (2) or ttbt (5) and L-2=[12]aneS(4) (3), [14]aneS(4) (4) or [14]aneN(4) (6), have been synthesized from cis,fac-[RuCl2(S-DMSO)(3)(O-DMSO)] (1) and the respective macrocycle. They were spectroscopically characterized by FT-IR, FT-Raman, NMR, and UV/Vis. Particular attention was given to fac-[RuCl2(DMSO)(k(3)-ttbt)] (5), the first octahedral complex of ttbt, which was also studied by DFT calculations. The behavior of the complexes in coordinating solvents water, acetonitrile, and dimethylsulfoxide was studied to understand their reactivity and predict the resulting ions formed in solution. The role of the counter ion (Cl(-)vs. ) was also evaluated. The results indicate that the chosen macrocycle, the counter-ion, and the solvent have a direct impact on the chemical species formed in solution
Biochemical and populational responses of an aquatic bioindicator species, Daphnia longispina, to a commercial formulation of a herbicide (Primextra (R) Gold TZ) and its active ingredient (S-metolachlor)
No full textThe growing demand of human populations for food supplies has led to an increase in the use of synthetic products, mainly pesticides, which induce adverse effects not only to target organisms, but also to nontarget biota of agroecosystems. Aquatic ecosystems in the proximity of agricultural areas are particularly vulnerable to pesticides, which cause underperformance or extinction of non-target sensitive species. Once in the aquatic system, these chemicals can affect biological processes at multiple levels (molecular, individual, populational), causing ecosystem imbalance across multiple scales. In this study, the effect of a commercial formulation of a herbicide (Primextra (R) Gold TZ) and its main active ingredient (a.i., S-metolachlor) was studied on a freshwater cladoceran species (Daphnia longispina), at different levels of biological organization and temporal scales. S-metolachlor is used in many herbicide formulations applied in corn/maize cultures, which is a relevant culture worldwide. As a first step, the acute and chronic effects of both commercial formulation and a.i. were quantified, and both formulations negatively affected the cladoceran's survival and reproductive parameters (age at first reproduction, number of offspring and number of broods), as well as the population's rate of increase. Whilst acute effects were comparable, the commercial formulation was slightly more toxic (EC50 was two-times lower) than the a.i. in chronic exposures, being prejudicial to D. longispina populations above 4.0 mg/L of S-metolachlor. In a second experimental step, we focused on the potential multi-generational impacts of the exposure to the a.i. alone on biochemical (lipid biomarkers, namely fatty acids) and populational responses, because of the relevance of S-metolachlor as a biosynthesis inhibitor in many herbicidal formulations. The herbicide caused a significant decrease in Daphnia fecundity (in the size of the 1st clutch), but no concomitant alterations were found in fatty acid profiles of mothers or offspring. More important, this experiment showed that S-metolachlor did not cause effects in the subsequent generation, thus suggesting that biotic communities may recover after exposure to the xenobiotic. (C) 2015 Elsevier Ltd. All rights reserved
Cyclen derivatives with two trans-methylnitrophenolic pendant arms: a structural study of their copper(II) and zinc(II) complexes
No full textTwo new cyclen derivatives, H(2)do2nph and H(2)cb-do2nph, containing two trans-2-methyl-4-nitrophenol pendant arms and the latter including also an ethylene cross-bridge, were prepared in good yields using the bisaminal synthetic route. The two ligands were studied comparatively regarding their metal complexation behaviour. The copper(II) and zinc(II) complexes of H(2)do2nph and H(2)cb-do2nph were studied in dimethylsulfoxide-water (9 : 1 v/v) solution by a range of spectroscopic techniques. Copper(II) complexes were also studied in solid state by X-ray single crystal diffraction. These studies showed that the copper(II) and zinc(II) complexes of H(2)do2nph exhibited a distorted square pyramidal coordination environment with the four nitrogen atoms of the cyclen ring defining the basal plane, and that one of the nitrophenolate arms did not coordinate to the metal, independently of its protonation state. On the other hand, depending on the protonation state of one of the nitrophenolic arms, the cross-bridged derivative forms copper(II) complexes with distorted square pyramidal or octahedral geometries with one or two arms coordinated to the metal centre, respectively. In the complex with distorted octahedral geometry, the two phenolic oxygen atoms are coordinated to the metal centre in a cis-fashion. Acid-assisted dissociation assays in 1 mol dm(-3) HCl DMSO-H2O (9 : 1 v/v) solution at 298.2 K allowed one to determine the half-life of both copper(II) complexes, which is lower for the derivative without a cross-bridge as expected, while for the other one it is quite high and in line with similar cross-bridged cyclen derivatives from the literature
Synthesis and electrochemical study of a hybrid structure based on PDMS-TEOS and titania nanotubes for biomedical applications
No full textMetallic implants and devices are widely used in the orthopedic and orthodontic clinical areas. However, several problems regarding their adhesion with the living tissues and inflammatory responses due to the release of metallic ions to the medium have been reported. The modification of the metallic surfaces and the use of biocompatible protective coatings are two approaches to solve such issues. In this study, in order to improve the adhesion properties and to increase the corrosion resistance of metallic Ti substrates we have obtained a hybrid structure based on TiO2 nanotubular arrays and PDMS-TEOS films. TiO2 nanotubes have been prepared with two different diameters by means of electrochemical anodization. PDMS-TEOS films have been prepared by the sol-gel method. The morphological and the elemental analysis of the structures have been investigated by scanning electron microscopy and energy dispersive spectroscopy (EDS). Electrochemical impedance spectroscopy (EIS) and polarization curves have been performed during immersion of the samples in Kokubo's simulated body fluid (SBF) at 37 degrees C to study the effect of structure layers and tube diameter on the protective properties. The obtained results show that the modification of the surface structure of TiO2 and the application of PDMS-TEOS film is a promising strategy for the development of implant materials
Unravelling the distinct crystallinity and thermal properties of suberin compounds from Quercus suber and Betula pendula outer barks
No full textThe main purpose of this study was to investigate the potential of suberin (a naturally occurring aromatic-aliphatic polyester ubiquitous to the vegetable realm) as a renewable source of chemicals and, in particular, to assess their physical properties. A comparison between cork and birch suberin fragments obtained by conventional depolymerisation processes (hydrolysis or methanolysis) is provided, focusing essentially on their thermal and crystallinity properties. It was found that suberin fragments obtained by the hydrolysis depolymerisation of birch had a high degree of crystallinity, as indicated by their thermal analysis and corroborated by the corresponding XRD diffractions, as opposed to hydrolysis-depolymerised cork suberin counterparts, which were essentially amorphous. (C) 2016 Elsevier B.V. All rights reserved
Concentration Dependence of the Infrared Photoluminescence of Pr3+ in Fluoroindate Glasses
No full textInfrared photoluminescence properties are investigated for Pr3+ containing fluoroindate glasses with formula (mol% compositions) (99-x)[ 40InF(3)-20SrF(2)-20BaF(2)-20ZnF(2)]:xPrF(3) (x= 0.1, 0.2, 0.5, 1.0 and 2.0 mol%). Different mechanisms of population and quenching for Pr3+ D-1(2) and (1)G(4) levels are shown from photoluminescence (PL), photoluminescence excitation (PLE) and decay time values. Cross relaxation processes are put in evidence in different ways for the population of excited levels as a function of the Pr3+ concentration, depending on the excitation wavelength. Different dependences on Pr3+ concentrations are observed for D-1(2) and (1)G(4) levels
Valorisation of industrial iron oxide waste to produce magnetic barium hexaferrite
No full textBarium M-type hexagonal ferrite (BaM, BaFe12O19) is an immensely important magnetic material, which we have successfully made from the simple valorisation of Fe-rich industrial waste from steel wire drawing, with addition of BaCO3 and heating in air to 1000 degrees C. The optimum ratio of Fe. Ba (producing 86 wt% BaM) was found to be 11: 1 (non-stoichiometric), and secondary phases of alpha-Fe2O3 (non-magnetic) and ZnFe2O4 (poorly antiferromagnetic) were always present. This material consisted of small submicron platelets. A hard magnetic ferrite was produced with Ms=48.6 A m(2) kg(-1) and H-c=211.5 kA m(-1). The highest density was achieved by sintering samples with Fe: Ba ratios of 11: 1 and 12: 1 at 1200 degrees C /2 hr, with an increase in grain size up to 2 mm. The sintered 11: 1 had electrical conductivity comparable to that of commercial sintered BaM. Such materials are suitable for industrial applications as hard magnets, and EM shielding in architectural and construction materials