Resumo em Inglês:

Recently, graphene and modified graphene as one of the most suitable and the most important carbon nanomaterials have been introduced for drug delivery. In this paper, we have studied the binding characteristics of the EDC-NHS cross-linking process of graphene-phenyl-NH2 and 5-aminolevulinic acid (ALA) drug in both gas and solvent phases by density functional theory calculations. For describing binding properties and reaction nature between graphene-ghenyl-NH2 and ALA drug, quantum molecular descriptors, topological analysis, natural bond orbital analysis, analysis of the bond order, the density of states, and analysis bond length was investigated in solvent and gas phases. Due to the results, the complex of the graphene-phenyl-NH2 @ALA turns to absorb more electrons in water solvent than gas phase. Furthermore, the binding of graphene-phenyl-NH2 and ALA is mainly based on covalent interactions, and bond order of graphene-phenyl-NH2 @ALA complex is one in solvent and gas phases. The praphene-phenyl- NH2 @ALA complex has displayed a meaningful improvement of electronic and structural properties. Therefore, it represented that praphene-phenyl-NH2 being combined with the ALA drug is appropriate for use in drug delivery.

Resumo em Inglês:

The ternary amorphous CuSeP2 was designed and prepared as the anode material of potassium ion battery for the first time, and its electrochemical performance was also investigated. After ball-milling with commercial graphene powder, it is used as the anode material for potassium ion battery with reversible specific capacity up to 300 mAh g-1, and the corresponding initial coulombic efficiency is close to 60%. What’s more, the specific capacity remains above 150 mAh g-1 after 100 cycles at 200 mA g-1. When increasing the current density to 1000 mA g-1, the CuSeP2/graphene composites still has a potassium storage specific capacity of 100 mAh g-1. Our results show that the potassium storage mechanism of the ternary CuSeP2 anode material is a typical conversion reaction and the introduction of Cu can not only buffer the volume expansion during the subsequent electrochemical reaction, but also effectively enhance the electrochemical reversibility of potassium ion.

Resumo em Inglês:

Sanitary landfill leachate (SLL) is a mixture of highly toxic and recalcitrant pollutants that threatens the water quality of the Yucatán Peninsula karst aquifer, one of the most extensive aquifers on the planet. To reduce the adverse environmental impacts of this wastewater, a triple-stage Fenton process (FP) was applied in an old SLL. Removal efficiencies were evaluated in terms of physicochemical variables, metal(oid)s concentrations, mass spectrometric identification of organic compounds and Daphnia magna acute toxicity test. The triple-stage FP achieved an 88% chemical oxygen demand (COD) removal, representing an improvement of 13% compared to FP performed in a single stage. Further, metal(oid)s such as aluminum, arsenic, chromium, nickel and zinc as well as organic compounds were substantially reduced. With respect to acute toxicity, the treatment produced a 64% reduction. Thus, this treatment system seems to be an effective option to reduce the dangerous level of SLL.

Resumo em Inglês:

Sodium chloride is used in the cheese salting process as it promotes sensory changes and food preservation. However, in excess can cause hypertension problems, and for this reason, it has been partially replaced by potassium chloride. In the present work, Prato cheese was subjected to joint diffusion of NaCl and KCl by immersion in static and stirred brine. The salt concentration values on the cheese surface were determined as a function of time. They were tabulated and presented to the self-organizing map (SOM)-type neural networks and the multilayer perceptron (MLP) for analysis and modeling of the film formed on the surface of the cheese during static and dynamic salting. The SOM network showed that the behavior of the diffusive process, on the surface of the cheese, depends on the analyzed position and that the points in which occupy similar positions, concerning the distance from the edge, have similar behavior. Regression models for NaCl and KCl were significant at the 5% level and can be used for predictive purposes.

Resumo em Inglês:

This work reports a multivariate calibration partial least square regression (PLS) model to quantify the liquid-phase concentrations of 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ), bicarbonate, PZ monocarbamate, and PZ dicarbamate during the absorption/desorption process by Fourier Transform Mid-Infrared spectroscopy (mid-FTIR). The model could predict 33 different concentrations ranging from 0 to 40 wt.% AMP, 0 to 15 wt.% PZ, and 0 to 12 wt.% total CO2 with relative errors lower than 10%, and 87% of the variance of all samples have been represented (R2), except for PZ dicarbamate. A comparison of a single PLS2 model was made with multiple PLS1 models, one for each chemical species present in the liquid phase. The latter had better predictions and made it possible to differentiate CO2 from its chemical forms, allowing a better understanding of the CO2 capture processes.

Resumo em Português:

In this study, the corrosion mechanism of an Al-Cu-Li alloy manufactured by two different treatment routes (T3 and T851) was evaluated by immersion and electrochemical tests in solutions containing chloride ions (Cl-). For both alloys, the formation of cavities on the surface was associated with micrometer-sized intermetallics (IM’s), however, in addition to this attack, the alloy submitted to T851 treatment also presented an attack called severe localized corrosion (SLC), caused by the preferential attack to the nanometric T1 (Al2CuLi) phase. The electrochemical concepts involved in these two types of attacks were discussed. During the IM’s corrosive process, whereas the O2 reduction occurred over the IM’s, the Al dissolution is favored around the particle, forming trenching and cavities (with 2 and 6 μm of depth). On the other hand, the mechanism associated with the SLC is related to the formation of a differential aeration cell followed by the evolution of H2, with greater depth of attack penetration (8 and 35 μm). Additionally, by the use of the Scanning Vibrating Electrode Technique (SVET), it was concluded that the higher anodic currents observed for the T851 temper were related to the relation between the anodic area (Aa) and the cathodic area (Ac).

Resumo em Português:

In recent years, there has been an increasing interest in the development of antimicrobial materials for different applications, especially in the biomedical field. In this context, chitosan is one of the most employed materials due to its highly attractive properties, such as biocompatibility, biodegradability, non-toxicity, and antimicrobial activity against gram-negative and gram-positive bacteria and fungi. In this review, we discuss the different methods used to obtain chitosan and point out how they affect the structural and chemical properties of this material, followed by a detailed discussion on how these properties influence its antimicrobial activities. Additionally, we summarize the most accepted antimicrobial mechanisms of action for chitosans. Specifically, we aim to provide a comprehensive overview on the last findings and progress reported in the literature on the factors that influence the antimicrobial activity of chitosan, e.g., polymeric average molecular weight (MW¯), average degree of acetylation (DA¯), water-soluble derivatization and sample degree of purity. The data available in the literature indicate that in addition to the structural properties, the effectiveness of such antimicrobial activity of chitosan is also dependent on the target microorganisms. This review will help researchers to better understand the mechanism of action of chitosan against microorganisms based on its structural characteristics.

Resumo em Português:

Environmental pollution from plastics and microplastics is currently one of the most relevant issues of the scientific community and cosmetic industry. In particular, microplastics are referred to as small pieces of plastic less than five millimeters (<5mm) and do not dissolve in water, can be harmful to the ocean and aquatic life. Microplastics can be designated as i) primary - particles that are intentionally developed as micro sized plastic particles used in cosmetic formulations like microbeads, and ii) secondary microplastics - stem from all kinds of plastic material debris result of decomposition caused by UV radiation, mechanical stress (ocean waves) and wind action. This article gives an overview about plastics/microplastics, that are mainly used in personal care products and cosmetic. Moreover, we attempt to demonstrated some of the major problems that microplastics based materials can cause in the aquatic life leading to a human health concern. In this context, the interaction between microplastic-contaminants and possible effects in the environment or organisms was explore based on the literature analysis.

Resumo em Inglês:

Transformations involving structurally complex molecules, natural products and representative molecules are extremely important to obtain key reaction intermediates, in addition to accessing molecules with bioactive properties. The development of cyanation methodologies in those molecules becomes important, because nitriles are versatile and important building blocks in organic synthesis. They can be converted into other organic functions, including amines, alcohols, α-amino acids and various carbonyl compounds and can therefore become relevant synthetic intermediates. Recent studies show new and intriguing asymmetric cyanation protocols or reagents as those that use electrophilic cyanide source, metal- and oxidant-free or avoid the use of toxic cyanide reagents. Photoredox catalysis emerges as a relevant approach from the point of view of green and sustainable chemistry; usually provides access to the versatile skeleton of α-aminonitriles that among their various modes of reactivity and provide access to reactive iminium ion. Thus, this perspective aims to highlight these impressive advances as well as to show their main advantages and applications.

Resumo em Inglês:

The lyophilized strawberry anthocyanins were extracted using a supercritical extraction (SE) process. The effect of pulsed electric fields (PEF) as pretreatment and the influence of the addition of ethanol as a cosolvent on the percentage of extraction yield (EY) and the total anthocyanin concentration (TAC) were analyzed. The effect of PEF was evaluated at 0.5 and 1.0 kV/cm, while the effect of the cosolvent was studied in mixtures of supercritical carbon dioxide - ethanol (SCCO2 + ethanol) at 1.6 and 3.3% by weight. The best results (% EY = 0.506, TAC = 0.428 g /100 g of lyophilized strawberry) were obtained with a PEF pretreatment of 1.0 kV cm-1, 3.3%wt. ethanol at 200 bar and 333.15 K. The experimental results of solubility were suitably adjusted with the Kumar and Johnston model. The maximum solubility (0.114 g/100 g of solvent mixture) was obtained at 300 bar and 313.15 K.

Resumo em Inglês:

In this work an unmanned aerial vehicle (UAV) was adapted to be used as an environmental tool to collect water samples of sea, estuary, and mangrove for further analysis by gas chromatography with a mass detector (GC-MS). The sampling automated system was based on a microcontroller, a solenoid valve, and a peristaltic mini-pump that was coupled to a quadcopter UAV. The apparatus was properly calibrated to acquire 100 mL of environmental water at 4.6 min. After, the concentration of BTEX (benzene, toluene, ethylbenzene, and o, m, p-xylenes) was analyzed in laboratory using GC-MS and the BTEX concentration ranged from 0.3 to 5.0 µg L-1 with a recovery from 83.9 to 118% with a relative standard deviation lower than 7.0%. Tests of cross-contamination were performed by simultaneous sampling and laboratory blank was carried out and no contamination was found for BTEX analysis. Based on the results, the adapted UAV presented a very useful ability to collect samples in difficult access areas such as mangroves, points between rocks, corals reefs, without health risk and without impacting the fragile ecosystem being an interesting tool for environmental purposes.

Resumo em Inglês:

Excessive degeneracy in the ground state of the π-electron energy levels of anthracene was removed using the Hückel method by correcting the Coulomb integral of the four central carbon atoms. A further correction to the resonance integral was proposed based on the ring-current model, which describes the π-ring current flow along the molecule’s perimeter, by introducing a new parameter for the bridge carbon atoms expressed as a fraction of the resonance energy. The solution to the Hamiltonian was obtained based on the symmetry group theory, which provides the advantage of solving the determinant matrix or secular equations in a particular irreducible representation with a relatively small matrix dimension. The results were further analyzed to determine the bond order and bond length. The values of the harmonic oscillator model of aromaticity, GEO, and EN indices of aromaticity and their ratio for the central and outer rings of benzene were used to evaluate the validity of the correction. Applying the same method to phenanthrene as a topological analog of anthracene allows for an interesting comparison of the stabilities of the two molecules.

Resumo em Inglês:

There is a trend of development of analytical methodologies and technologies that allow in situ analysis, producing accurate information in real time, at low cost, using homemade experiments and devices to increase interest in scientific knowledge with a constructive approach in an interdisciplinary perspective in Chemistry Education. In this context, a photometric-chemometric method of analysis was developed to measure the pH of solutions using easily accessible and low-cost material based on the use of natural pigments found in red cabbage (Brassica oleracea L.). Calibrations and determinations were performed by RGB measurements of pigment coloration in solution at different pH values using the free app Photometrix, converted to HSV, YCbCr and YUV color spaces and processed by Partial Least Squares regression (PLS). The best PLS model found was HSV with mean central scale obtained pH measurements with RMSEP 0.98, R2 0.97 and bias close to zero. In addition, experimental data were statistically validated. Analyzes of predicted pH from three independents experiments revealed high recoveries (95-103%) and low relative standard deviations. Thus, the PhotoMetrix app was viable for colorimetric pH determinations using the low-cost photometric pH meter sensor and a smartphone, improving accessibility and applicability in Chemistry Education.

Resumo em Português:

The new coronavirus, called Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), was discovered in late December 2019 after cases were reported in the city of Wuhan, China. In January 2020, the World Health Organization (WHO) officially declared the Coronavirus Disease 2019 (COVID-19) as a pandemic, which has an official record of around 500 million cases and more than 6.0 million deaths in worldwide. An important factor in controlling the pandemic is the development of more effective and efficient diagnostic tests. In this context, this review has as its main proposal to discuss the effective differences between the possible diagnostic tests, the implications of molecular and serological methods available on the market and the analytical and clinical parameters involved in the development and application of these methods.