Resumo em Inglês:

Metal-organic frameworks (MOFs) based on Calcium-terephthalate(Ca-MOFs) were synthesized by the sonochemical method and applied to remove methylene blue (MB) from an aqueous solution via adsorption. The samples were prepared and characterized by X-ray Powder Diffraction (PXRD), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Thermal Analysis (TGA-DTA), and Scanning Electron Microscopy (SEM). The studied of the effect of the synthesis temperature on the crystallization of MOFs indicated two different crystal structures were identified, Ca(BDC) and Ca(BDC)(H2O)3. Observed that samples with a higher proportion of the Ca(BDC) phase showed greater dye adsorption capacity. The experimental data fit the pseudo-second-order kinetic model. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms, and the isotherm constants were also determined. The adsorption equilibrium data preferably fit the Freundlich model. The samples were applied to methylene blue adsorption at pH 5.6, with maximum adsorption of 60.241 μmol.g-1 and high reuse efficiency, reaching 97% of the initial adsorption capacity in the second reuse cycle.

Resumo em Inglês:

Beer is commonly produced with four inputs: water, malt, hops, yeast and, in some cases, brewing adjuncts. Industrial and artisanal processes essentially follow the same steps and may undergo minor changes due to the style of beer. Despite this, many consumers attribute higher quality to craft beer compared to industrial ones. In this study, we applied the analytical techniques of infrared (IR), hydrogen nuclear magnetic resonance (1H NMR) and mass spectrometry (ESI(±)FT-ICR MS) to discriminate craft beers from industrial ones (brands common to the Brazilian market). In addition, Partial Least Squares (PLS) and Support Vector Machine (SVR) regression were used to estimate some beer properties (pH, total acidity (meq·L-1, color (EBC), bitterness (IBU), alcohol content (%v/v) and density (g·mL-1)). The use of the IR allowed the identification of vibrations attributed to chemical compounds common to beverages, such as water (3320 and 1640 cm-1), carbohydrates (1500 cm-1) and ethanol (1050-1040 and 875-865 cm-1). 1H NMR showed good applicability in identifying classes of organic compounds in the beverage, where signs attributed to alcohols, organic acids, carbohydrates and amino acids were observed. The ESI(+)FT-ICR MS allowed the identification of chemical compounds present in beverages, allowing the construction of a fingerprint of the beers. In addition, the application of chemometric tools enabled the prediction of physicochemical properties, presenting promising results in the prediction of alcohol content (RMSEC 0.2430 and RMSEP 0.3929) and bitterness (RMSEC 1.3022 and RMSEP 1.6008), and also in the classification regarding the manufacturing process (craft and industrial beer).

Resumo em Inglês:

Honey is a substance that contains a variety of macro and micro minerals present in the range between 0.02-1.03%. The main objective of this study was to determine the concentration of elements inorganic in 15 honey samples collected in various regions of Maranhão (Northeast Brazil), using highly sensitive analytical techniques, such as inductively coupled plasma optical emission spectrometry (ICP-OES), in addition to applying multivariate statistical tools, such as Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) in the treatment of data. The method presented detection limits between 0.4 to 2.8 mg kg-1. Fifteen samples and 19 metals were analyzed, and two of these samples had high levels of lead, exceeding the limits allowed by Brazilian legislation. Thus, it can be concluded that the presence of potentially toxic metals in honey is an indication that the production areas may be contaminated by different external sources. The chemometric analysis of the data by PCA and HCA allowed to classify honey in two main groups: honey produced in urban areas and honey produced in rural areas with PCA explaining 73% of the data variance with the sum of the first 3 components.

Resumo em Inglês:

An alternative route to synthesis of metal-organic frameworks containing Eu(III) ion was proposed via solvothermal process in aqueous medium. The compounds of the minimal formulae [Ln2(NDC)3(H2O)4] were synthesized starting from the mixture of the 2,6-naphthalenedicarboxylic acid with europium(III) oxide. So far, this type of metalorganic framework based on the lanthanide ion synthetic route has not been investigated before as the main metal sources are nitrate and chloride salts. The structural characterizations were performed by FTIR spectroscopy, thermal analysis TG-DSC, and X-ray diffraction. The results of IR and TG were consistent with the structural determination results and complemented by X-ray diffraction patterns. SEM images also corroborate the morphologies found in recent research on this material. The materials obtained shown high-intensity luminescence, for the Eu-NDC compound, which corroborates with an energy transfer efficient of the ligand to Eu(III) ion.

Resumo em Inglês:

This study assessed the effects of volume concentration (0.3%, 0.6%, 1.2%, and 12% v/v) and type of polymer flocculant (acrylamide, chitosan, and purified and non-purified acrylamide grafted chitosan) on the flocculation mechanism of kaolinite-rich mining tailings samples. We measured the flocculated samples’ transmittance using UV-VIS spectrometry to check for particles in the supernatant medium in order to verify the flocculation efficiency. It was observed that flocculation directly depends on the pH of the medium, the isoelectric point of the kaolinite, and the polymer chains’ molecular mass. The concentration of H+ and OH- ions is responsible for producing charges of different electrical nature on the particles present in the suspension, thereby affecting the flocculation process. In the acrylamide samples, the aggregation of particles occurs by electrostatic interaction; and in the other samples by bridging, suggesting that the chains’ molecular mass interferes in the coagulation and flocculation mechanisms. Moreover, the results of absorbance measurements and flocs’ apparent density highlight that the grafting of acrylamide on the chitosan chain may improve the kaolin waste flocculation. For flocculant concentrations of up to 1.2% (v/v), the absorbances were mostly below 1.0, indicating removal of suspended materials.

Resumo em Inglês:

The study of the spectrum of light has increased its range of action in the field of chemistry, with the help of several advanced equipment and innovative techniques that have become a strong ally of analytical chemistry. However, the simplicity of obtaining results integrated with mobile devices appears as an interesting path to be taken in the field of chemical analysis. This work addresses the dissemination of an application called REDGIM for smartphones on the Android platform capable of working with multivariate image analysis using chemometric methods through the luminous intensities of photos and R (red), G (green) and B (blue) channels. In order to show the potential of REDGIM, we propose two applications using the partial least squares (PLS) regression method: 1) quantification of free chlorine in tap water; and 2) quantification of cannabinol, (CBN, a type of cannabinoid) in marijuana and hashish samples. The free chlorine concentration obtained for two investigated samples was 0.73 and 0.74 mg L-1 and 0.74 and 0.76 mg L-1 by the spectrophotometer and by the application (container: cuvette), respectively. For the quantification of CBN in marijuana and hashish samples, the mean concentration ranged from 6.137 to 8.823 mg mL-1. The results obtained by the application are compatible with results from traditional techniques, such as UV-Vis spectrophotometry, for example. Therefore, REDGIM was proved to be a simple and accessible technological tool for the scientific community, being viable for chemical tests of a multivariate nature.

Resumo em Inglês:

Theranostic can be used to define therapeutic and imaging agents in a system. It is consisting of four components: signal emitter, therapeutic agent, targeting ligand and carrier. Naphthoimidazole and naphthoxazole are extended aromatic systems, and can participate in theranostic systems (TS) acting as a therapeutic agent and/or a signal emitter considering of their broad spectrum of biological activities and their optical properties of fluorescence emission. This systematic review investigated the applicability of the naphthoimidazole and naphthoxazole nuclei as constituents of TS and shows the synthesis methodologies described in the articles selected. Among the scientific articles suitable for the criteria of the systematic review, more than 35% described the evaluation of biological activities, mainly the naphthoimidazole derivatives, and approximately 18% explored the fluorescence emission of naphthoxazole derivatives and their applicability in biological systems. Among the selected articles 53% and 44% show synthetic routes for the preparation of naphthoxazoles and naphthoimidazoles, respectively. It was observed that both nuclei can be synthesized from various reagents, such as naphthoquinones, naphthols, naphthoic acids, aminonaphthoquinones and cyanophthalides. The results of this study suggests that naphthoimidazole and naphthoxazole derivatives are promising for application as components of TS, and there are various synthetic possibilities for obtaining these heterocycles.

Resumo em Inglês:

The bone formation process is an example of how both time and nature acted harmonically to pave the path for life as we know. The unique association between calcium phosphate (CaP) and collagen in a single building block, gave rise to one of the most remarkable biomaterials that we know. Our aim in this revision is to provide a brief glance at the different organization levels of the bone tissue, by describing the main their main features. We start with a brief discussion regarding the thermodynamic conditions for mineral formation and how living organisms surpass them. Then we present collagen, the major organic component of bone, in the light of its hierarchical organization as well as its association to CaP crystals. The mechanisms that control both mineral formation and the association with the organic phase are further presented, in which cells and other components of the extracellular matrix, such as matrix vesicles and noncollagenous proteins, become agents of bone construction. Finally, we underline the difficulty of studying the complex process of bone mineralization and present liposomes, proteoliposomes, and Langmuir monolayers as biomimetic approaches to this end.

Resumo em Inglês:

Titanium (Ti)-layered materials have interesting characteristics for photocatalytic applications, such as the high specific surface area and ease of intercalation of species in the interlamellar region, which are extremely favorable for the surface processes. In this sense, this review addresses the data available in the literature related to the preparation, structure and main photocatalytic applications of Ti-layered materials. The main synthesis methodologies of these materials were addressed: the hydrothermal, which is mainly used to obtain powders (containing TiO2 or titanates) and the anodization process that is commonly used to obtain films composed mainly of TiO2 nanotubes. Prominent photocatalytic applications for semiconductors were also addressed, focusing on the use of pure or associated Ti-layered materials for the photodegradation of emerging pollutants, photoreduction of CO2 or metals, hydrogen production and the inactivation of microorganisms. It was possible to observe that, despite these being extremely promising materials and with outstanding efficiency in some processes, such materials can still be considered little explored and deserve greater attention from researchers in the area.

Resumo em Inglês:

In this work, a discussed and step-wise tutorial for LC-MS and GC-MS data processing using the open-access software MZMine2 is presented and discussed. The rationale behind each step was demonstrated to enable the readers to go through their own data and process it accordingly. The main lesson to be learned is that each parameter must be chosen in light of the raw data and no guidelines should suggest a predetermined value. Still, it is worth mentioning that ideal values for each parameter do not exist, and that the user might end up investing too much time futilely optimizing values. Our suggestion is to process your data in light of the raw data (and the study design) following the preview figure result and the resulting feature list generated in each processing step, interpret your data, and go back to process it again to tune the detection of important features.

Resumo em Inglês:

Mango peel, a by-product obtained from the industrialization of this fruit, is a promising and inexpensive source of phenolic compounds. In the present study, both the drying of the mango peel and the extraction of phenolic compounds were optimized using the response surface methodology. In this sense, temperature and charge/area ratio were selected as depend variables to drying process. Instead, for the ultrasonic assisted extraction (UAE) the temperature, ethanol-water concentration and time were optimized. For both processes, the total phenolic content (TPC) and mangiferin concentrations were the response variables. The TPC and the xanthone concentration were determined by the Folin-Ciocalteu method and HPLC-ESI-IT-MSn, respectively. The optimal conditions for the dehydration process were 54 °C and 2.3 kg m-2, reaching a TPC of 21.7 ± 1.6 mg GAE g-1 dw and a concentration of mangiferin of 1.94 ± 0.22 mg g-1 dw. Regarding to UAE, the optimum conditions were 51 °C, 50% ethanol and 71 min. Under these conditions, the TPC was 19.5 ± 0.8 mg GAE g-1 dw and the mangiferin concentration corresponded to 1.50 ± 0.13 mg g-1 dw. Additionally, 38 compounds were identified in the extract obtained under optimal conditions.

Resumo em Inglês:

Students undertaking courses in the field of sciences and engineering need to learn practical skills and conceptual knowledge, and the experimental classes are the best moment for this. In this paper, we propose a practical experiment to aid nanotechnology learning by synthesizing gold nanoparticles (AuNPs) and their application as a colorimetric sensor of sulfathiazole. AuNPs were prepared using sodium citrate as a reducing and capping agent. The existence of the synthesized AuNPs was detected using the Tyndall effect while their optical properties were investigated by molecular absorption spectrophotometry. The gold nanoparticles exhibit spherical-like shape morphology and an average size of 13.6 nm, determined by transmission electron microscopy. The AuNPs were applied as a colorimetric sensor for the detection of sulfathiazole in mixed water/ethanol solution by simple visual inspection and using molecular absorption spectrophotometry. Due to the simplicity of the experimental steps, this activity is well-suited for a hands-on introduction of nanoparticles synthesis and its application as a molecular sensor. In addition, the experiment encompasses knowledge from different fields being suitable for interdisciplinary classes.

Resumo em Inglês:

This paper contemplates the scientific contributions of the seven winners, from the creation of the Nobel Prize to the year 2020. The laureates are Marie Curie, Irène Joliot-Curie, Dorothy Crowfoot Hodgkin, Ada Yonath, Frances Hamilton Arnold, Emmanuelle Marie Charpentier, and Jennifer Anne Doudna. In 112th editions of the Nobel Prize in Chemistry, there were 186 awards, where only seven winners were women, an amount less than 4% of the total, which makes clear the low female representation. Marie was the pioneer, being the first woman to win, alone, a Nobel Prize in Chemistry. She was the only woman to win two Nobel Prizes, and the only person awarded in two distinct scientific areas: Chemistry and Physics. Only Marie and Dorothy received the award alone, Irène, Ada and Frances shared the award with men, and Emmanuelle and Jennifer became the first pair of women to share a Nobel Prize in Chemistry. There is an evident under-representation of women in the Nobel Prize in Chemistry, but this should not be a reason not to remember and celebrate the trajectory of these brilliant scientists, who must be present in training courses in scientific areas, as well as in Basic Education schools.