Resumo em Inglês:

Carbon-supported platinum-iridium nanowire-shape electrocatalysts containing 20% of metallic loading were synthesized by chemical reduction method using formic acid as a reducing agent and tested towards the oxidation of ethanol in acidic medium. The developed electrocatalysts were synthesized with the following compositions: Pt0.9Ir0.1/C, Pt0.8Ir0.2/C, Pt0.7Ir0.3/C, Pt0.6Ir0.4/C and Pt0.5Ir0.5/C using for comparison the commercial Pt/C Alfa Aesar catalyst. Physico-chemical characterization was performed using X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray fluorescence (XRF, for chemical composition) techniques. All the nanowires present a face-centered cubic crystalline structure of the platinum with modifications in the lattice parameter due to the inclusion of iridium. The XRF analyzes show that the theoretical compositions of the synthesized catalysts are very close to the experimental nominal values. TEM analyses showed the formation of nanowires by the synthesis method used. The electrochemical results on the oxidation of ethanol show that the addition of a second metal to the platinum in the composition of the nanowires increases the catalytic activity of the electrode. The nanowire catalysts with low Ir content (Pt0.9Ir0.1/C, Pt0.8Ir0.2/C, Pt0.7Ir0.3/C) present the best outcomes under the analyzed conditions and are promising for application as anodes in direct ethanol fuel cells.

Resumo em Inglês:

This work describes the superficial modification of Ti/TiO2 nanotubes by copper oxide electrochemical deposition, in different temperatures (25 and 65 ºC), and its application on the photoelectrocatalytic conversion of CO2 and biogas in products of energy interest. The different temperatures deposition resulted in the formation of different geometric forms on the surface of Ti/TiO2 nanotubes and in different photoelectrocatalytic activities. The photoelectrocatalytic conversion in 0.1 mol L-1 Na2SO4 with application of -0.1 V and UV irradiation resulted in the formation of acetone and methanol from CO2 and acetone and ethanol from biogas, being that the acetone production was higher for the semiconductor synthesized at 65 ºC, while the methanol and ethanol production was higher for the semiconductor at 25 ºC. The different characteristics observed, as well as the preferential formation of different products of photoelectrocatalytic reactions for semiconductors synthesized with different electrochemical deposition temperatures are discussed.

Resumo em Inglês:

We evaluated the biomass of twenty Amazonian fungal isolates as a potential source of mycelium-bound lipases with hydrolytic, synthetic or enantioselective activity for biocatalysis application. We compared the hydrolytic activity of three biomass treatments (delipidated, non-delipidated and cultivated in medium without inducer). Delipidated biomass showed better results in the hydrolysis of p-nitrophenyl palmitate compared to the other two treatments for fifteen isolates. Delipidated biomass of six Aspergillus strains and UEA_115 strain showed a high synthesis activity of ethyl palmitate by transesterification in organic medium. Results were confirmed by spectrophotometry (410 nm) and gas chromatography. In this reaction, the isolate DPUA_1539 A. flavo-furcatis reached a maximum value of 668.5 ± 23.5 mU g-1. Enantioselective activity assays indicated that biomass-bound lipases from UEA_115 isolate (E = 3.58; ees = 7 ± 0) and in particular from the DPUA_1539 A. flavo-furcatis isolate (E = 24.15; ees = 91 ± 1) have the ability to discriminate enantiomers of the drug ibuprofen by ester synthesis, preferably with (R)-enantiomer. These results encourage further investigations of these fungi as potential lipase suppliers for biocatalytic processes such as biodiesel production and enantiopure drugs.

Resumo em Inglês:

It has been recurring adulterations in fuels (such as gasoline, ethanol and diesel), being necessary the exploration of the use of more modern analytical techniques capable of controlling the quality of these fuels, since some regulated tests may be inefficient to detect the adulteration. Among them, it is highlighted proton nuclear magnetic resonance (1H NMR) spectroscopy, and portable near infrared spectroscopy (microNIR). In this work, it was studied the conformities of 115 samples of seized fuels (76 of gasoline, 23 of ethanol, and 16 of diesel) by means of standardized techniques with parameters established by the ANP. Results obtained were compared to photometer, MicroNIR and 1H NMR analyzes. The analyzes carried out by ANP showed four nonconforming samples (one of gasoline and three of ethanol). By the photometric technique, only 14 gasoline samples had ethanol content permitted by legislation (i.e ≈ 27 %v/v). By 1H NMR analysis, it was possible to verify nonconformities by presence of aromatics and olefins compounds in the gasoline and diesel samples as well as of methanol in fuel ethanol samples. It is also worth noting the efficiency of MicroNIR when combined with unsupervised chemometric methods to indicate nonconformities presented by 1H NMR and photometry techniques.

Resumo em Inglês:

In recent years, the increase in the generation of waste (e.g., bones and skin) from the processing of fish-based food related to the increase in fish consumption and the accumulation of synthetic polymers in the environment are causing major environmental concerns. Hydroxyapatite (HA) extracted from the bones and collagen from the skin of fish processing residues can be combined with synthetic polymers to maximize the use of waste material derived from fish while simultaneously reducing the use of synthetic polymers. Hence, in this study, collagen and HA were extracted from the carcasses of Lophiosilurus alexandri, and the obtained materials were reused to prepare low-density polyethylene (LDPE) blends and composites. The integrity of the triple helix structure of collagen was confirmed by FTIR and DSC showing that there was no collagen denaturation during its extraction and sample processing. The results indicated that the material produced by the incorporation of collagen into LDPE compatibilized with polyethylene-graft-maleic anhydride exhibits good mechanical and surface properties for use as a support material for ornamental articles, among other applications.

Resumo em Inglês:

Parabens are widely used as preservatives in the last decades. Others preservatives such as 2-phenoxyethanol, which in addition to his good antimicrobial activity, has low allergenic potential as well others properties of interest to the cosmetic industry. In this work was developed a method for determination of methylparaben (MP), propylparaben (PP) and 2-phenoxyethanol (FE) in cosmetic products by HPLC-DAD using QuEChERS as sample preparation. For application in cosmetic samples, the original QuEChERS method was modified and optimized by evaluate of different solvents for extraction and sorbents for clean up step. Increases at recoveries of analytes were obtained employing acetone as solvent and PSA for clean up step, showed recoveries between 83.7% and 88.6% for all analytes. The method was validated according to ANVISA (linear range: 0.1 to 2.5 µg mL-1 for MP and PP, and 1.5 to 6.0 µg mL-1 for FE). Precision was evaluated by repeatability and intermediate precision with coefficients of variation (%) lower than 10% in all concentrations analysed, and accuracy was evaluated, with values ranging from 93.77% to 108.13%. The QuEChERS-HPLC-DAD method was tested in real samples (moisturizing cream and lotion, cleansing gel), where the concentration values were found below the maximum limit established by ANVISA.

Resumo em Inglês:

Phytochemical study of aerial parts from Sinningia mauroana Chautems (Gesneriaceae) yielded 17 known compounds: sitosterol, stigmasterol, betulinic acid, oleanolic acid, hederagenin, maslinic acid, ursolic acid, pomolic acid, soranjidiol, methyl 4-hydroxyphenylacetate, 6-hydroxy-7-methoxy-α-dunnione, 7-hydroxy-6-methoxy-α-dunnione, jacaranone, calceolarioside A, conandroside, luteolin, and luteolin-7-O-glucoside. Complete NMR data of 6-hydroxy-7-methoxy-α-dunnione and 7-hydroxy-6-methoxy-α-dunnione were obtained in two different solvents. Hexane, ethyl acetate and ethanol extracts were screened for antimicrobial, antioxidant and cytotoxic activities. The antimicrobial activity was assayed against Staphylococcus aureus, S. epidermidis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, C. parapsilosis, C. dubliniensis, and C. glabrata, using the microdillution method. All extracts were inactive (MIC > 100 µg mL-1). The antioxidant activity was evaluated with the ORAC method; the ethyl acetate and ethanol extracts were active (TE relative > 800 µg g-1). The cytotoxic activity was tested against PC-3 (prostate) and SKMEL-103 (melanoma) human tumor cell lines, and 3T3 fibroblast cell line, using the MTT assay. The hexane extract showed strong activity against PC-3 and SKMEL-103 human tumor cell lines (IC50 < 0.25 and 3.07 µg mL-1, respectively), and a lower activity towards 3T3 fibroblasts (IC50 = 6.84 µg mL-1). The other extracts were inactive (IC50 > 50 µg mL-1).

Resumo em Inglês:

We report on the study of the spectroscopic properties in Ytterbium-Terbium (Yb3+-Tb3+) co-doped calcium lithium borate (CaLiBO) glasses, with the study’s focus being on the upconversion process. Intensity parameters Ωλ for CaLiBO:Tb3+ are determined by the Judd-Ofelt method to be Ω2 = 15.5 × 10-20 cm2, Ω4 = 1.90 × 10-20 cm2 and Ω6 = 3.69 × 10-20 cm2. We have also obtained electric-dipole (and magnetic-dipole) radiative transition probabilities, branching ratios, and lifetime for the Tb3+:5D4 and 5D3 levels. In addition, an evaluation of the upconversion processes by luminescence and time-resolved spectroscopy were carried out. The upconversion rise and decay times, energy transfer probability from Yb3+ to Tb3+ ions, and the efficiency of the processes that depopulate the Tb3+:5D4 level after resonantly pumping the Yb3+:2F5/2 level were estimated. Our results showed that a cooperative energy transfer (CET) from two Yb3+ ions to one Tb3+ ion is the origin of the Tb3+ upconversion luminescence in the visible region. While, CET followed of the cross relaxation or/and excited state absorption is responsible for the upconversion luminescence in the ultraviolet region.

Resumo em Inglês:

The compounds nitrosyl cis-[Ru(bpy)(phen)TU(NO)](PF6)3 (compound 1) and cis-[Ru(bpy)(phen)(4-N-Imd)(NO)](PF6)3 (compound 2) (bpy = 2,2’-bipyridine, phen = 1,10’-phenanthroline, TU = thiourea and 4-N-Imd = 4-nitroimidazole) were synthesized and characterized by UV-visible, infrared spectroscopies and electrochemical techniques. In the study of the reactivity it was possible to verify the nitric oxide labilization by square wave voltammetry and a photochemical upon blue light irradiation. This feature is very important for a potential application in phototherapy. Additionally, the antibacterial activity of the nitrosyl complexes was tested against gram-negative bacteria Pseudomonas aeruginosa. Thus, it has been observed that the complexes are capable of inhibiting the growth of such microorganisms.

Resumo em Inglês:

The aim of this study was to determine the chemical variability of Allamanda cathartica flowers collected in different localities of Santa Catarina State, Brazil. Extractive solutions (25 samples) were analyzed by HPLC-DAD for the qualitative and quantitative profiles of the iridoid plumieride, the flavonoid rutin as well as total flavonoid content expressed in rutin. The chemical variability was evaluated by Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA). The samples demonstrated similar chromatographic profiles. In PCA analysis, Araquari samples AC01, AC08 and AC25 did not group with other samples obtained from other locations. In the HCA analysis, it was possible to observe hierarchially similar groups, generating 5 clusters. Group 5 (samples AC01, AC08 and AC25) presented lower similarity compared to the other groups. This dissimilarity can be explained by the amount of metabolites from each collection. Regarding the content of markers, it was observed a variation between 27 to 230 mg/g, 2.7 to 9.5 mg/g and 7.14 to 17.8 mg/g for plumieride, rutin, and total flavonoids, respectively. The samples from Araquari (AC01, AC08, AC25) presented the highest concentrations of chemical markers. Therefore, for reproducibility and standardization of A. cathartica flower extracts, it is important to determine the location and the plant cultivation conditions.

Resumo em Inglês:

The Mundaú-Manguaba lagoon estuary complex is the most important ecosystem in the state of Alagoas, and a source of sustenance for a large number of the state’s inhabitants. However, degradation by anthropic sources has been causing impacts on this ecosystem. Understanding the characteristics of the natural organic material of the waters of the mundaú-manguaba lagoon complex is extremely important to understand the interaction dynamics of the contaminants in these lagoons. Thus, the objective of this work was to extract and characterize aquatic humic substances from the Mundau-Manguaba lagoon complex and to evaluate the interaction of this organic material with mercury ions. The profile of the aquatic humic substances of the respective lagoons evidenced the greater influence of aliphatic groups in their structures. The interactions of aquatic humic substances and mercury ions are directly related to the oxygen groups in their structures, corroborated by Principal Component Analysis. Thus, understanding the water and organic matter characteristics present in the Mundaú-Manguaba estuarine lagoon complex is fundamental for establishing strategies, seeking the preservation of this ecosystem and remediation of environmental contamination.

Resumo em Inglês:

Limitations of conventional treatment and dosage forms prompted the investigation of novel approaches that combine efficacy, selectivity and fewer adverse effects. These are the main promises of nanomedicine, generally defined as the application of nanotechnology to the biomedical field. Despite the considerable advances over the years and the large number of publications resulting from the growth of nanomedicine, there are still many hurdles and unknown factors limiting its successful translation from promise to reality. These factors range from the lack of standardization in the terminology and regulations, to the lack of understanding of interactions between nanocarriers and the biological system, and their influence on drug pharmacodynamics. In this manuscript, we aim at presenting and discussing concepts and terminologies used in the nanomedicine field and examining the main types of nanocarriers and their effects to modulate biological barriers and aid drug transport, bioavailability and targeting.

Resumo em Inglês:

Besides increasing shelf life of fluid milk, milk powder has physical and functional properties that allow it to be used as ingredient. The rehydration process is complex and happens in four steps: wettability, sinkability, dispersibility and solubility. Works have been conducted aiming at the development of an easier, more convenient and reproducible method to evaluate the dissolution properties of dairy powders. Therefore, the aim of this work was to evaluate dispersibility and solubility through particle size distribution in order to establish a new rehydration index for whole milk powder. The particle size distribution and morphological characteristics of seven samples of milk powder (from A to G) were analyzed. Samples F and C differed from the others which formed a similar group. Principal component analysis divided the samples into three different groups, allowing the indication of an efficient rehydration index to determine the powders dispersability.

Resumo em Inglês:

This experimental activity proposes the use of lily (Lilium sp.), agapanthus (Agapanthus sp.) and hydrangea (Hydrangea sp.) extracts to investigate the colorimetric profile of each extract between pH 1-14. Water, ethanol and ethanol/HCl 1% (w/w) were used as extractive solvents. Among the flowers tested, the extracts of orange lily and burnt yellow lily were the ones that presented the greatest color variation with the solution pH change. In addition, the total content of anthocyanins in relation to cyanidin-3-glycosidic was determined and in ascending order we have: yellow lily (LAM: 0,07 ± 0,03) < agapanthus white (AGB: 0,21 ± 0,03) < agapanthus violet (AGV: 1,72 ± 0,13) < blue hydrangea (HAZ: 1,83 ± 0,47) < orange lily (LAL: 2,87 ± 0,52) < burnt yellow lily (LAQ: 9,55 ± 0,46). For this determination methanol/HCl 1% (w/w) was used as the solvent. Using UV-Vis spectroscopy, it is suggested that the behaviors are due to the presence of cyanidin in AGB, AGV, LAL and LAQ, delphinidin in HAZ and apigeninidine in LAM. This activity can be applied in courses that have Chemistry in their curricular matrix and in General Chemistry subjects when the acid-base theme is approached.

Resumo em Inglês:

The aim of this research was to verify student performance, participation and frequency when they study in a student-centered learning environment. Data collection included the application of questionnaires and semi-structured interviews. Data analysis combined quantitative and qualitative approaches. In the results on frequency and participation, 32% of the students had a high number of absences and more than 25% indicated participation less than or equal to 5 (in a 1-10 scale). This is an expressive data, since the low engagement, due to absence in classes, or low participation, in a course aligned with Vygotsky’s assumptions, compromises the construction of knowledge. In these environments, it is not enough that the students try to solve the proposed questions by themselves: the adopted strategy presupposes the social interaction as a differential for learning promotion. Regarding performance, 37% of them were disapproved. To understand the reasons of such unsatisfactory performance, semi-structured interviews were conducted. The analysis of these data revealed that the overload of credits had a great impact on participation and frequency in biochemistry classes. This data indicates the need for integrated curricular organization, without which, even innovative disciplines, with student-centered methods, have discrete possibilities of success.

Resumo em Inglês:

Making experimental measurements, whether we are at peace in the face of such a reality or not, invariably involves experimental uncertainty. Unfortunately, presenting uncertainty alongside the results is not as widespread as it should be. The author attempts here to simplify, improve understanding, and appeal to a healthy living with uncertainty. One of the main tools scientists should know that there is available is the uncertainty propagation equation, which can be applied to all equations involving experimental results.