Resumo em Inglês:

Emerging and classical pollutants, such as antibiotics, pharmaceuticals, pesticides, dyes and heavy metals derived from human activity, currently pose serious threats to the environment and human health. Despite the grave danger posed by these pollutants, there is still no adequate monitoring of their presence in the environment. The regular determination of these contaminants in the environment can play a crucial role in the protection of human health and the preservation of ecosystems. New analytical techniques allow the reproducible quantification of analytes at very low concentration levels. Molecularly imprinted polymers (MIPs), with selective recognition, have also been combined with quantum dots (QDs) and suggested as valuable materials in the construction of optical sensors. Several strategies have been proposed for the selective detection of these pollutants in recent years. Rather than employing expensive, time-consuming standard analytical methods, fluorescent quantum dots coupled with molecularly imprinted polymers can be used for developing simple, rapid and highly selective analytical methods for the detection of these pollutants. This review presents a brief discussion on the application of tailor-made polymeric materials in tandem with quantum dots for the rational construction of efficient sensors capable of determining the presence of these pollutants in aquatic environments.

Resumo em Inglês:

Criminal minds create new psychoactive substances (NPS) to dribble the Drug Regulatory System. Early Warning Systems (EWA) were instituted worldwide to combat this practice. Brazilian government has started establishing EWA at a national level since August 2021. The role of drug analysis laboratories in EWA is very important and experts working at forensic laboratories are in the main position to detect NPS and any changes in the molecular structures. However, for this practice, it is necessary to use reliable analyses techniques for unequivocal identification. The goal of this work is to use single-crystal X-ray diffraction (XRD) to detect the presence of NPS and elucidate its molecular structure using single crystals from a seized blotter paper. XRD is also useful to prepare reference substances to produce entries to be included in Fourier transformed infrared spectroscopy (FTIR) and mass spectrometry databases, which are some of the most relevant routine techniques in forensic laboratories. This approach was used to study the NPS 25R-NBOH and 25I-NBOMe using XRD, FTIR, Raman, and nuclear magnetic resonance spectroscopies. The results showed that molecular structure methods must be used to elucidate NPS in an unambiguous manner and the potential of XRD use in the forensic area as a reference method.

Resumo em Inglês:

Encapsulation and release of NPK fertilizer by composite films were systematically demonstrated by casting dispersions of chitosan (CS) and sugarcane bagasse (SCB) derivatives (holocellulose (HC), cellulignin (CL), and cellulose (CEL)) fibers under varied CS-to-NPK and CS-to-SCB derivatives mass ratios. SCB derivatives were obtained from sugarcane bagasse as agricultural waste by following the alkali dissolution (4% NaOH, 70 °C for 5 min), sodium chlorite delignification (1.4% NaClO2, pH 3.5, 70 °C, 5 h), or from a combination of both. Nutrientadsorption capacity can be tunable by the chemical composition of SCB derivatives, i.e., fibers with noncellulosics exhibited higher adsorption capacities while the absence of noncellulosics lessened their adsorption capacity. Oven-drying (60 °C, 5 h) of optimal 1:0.5 CS/NPK film-forming solution produced highly uniform films with shape with 0.31 ± 0.02 mm thickness while increasing fiber content in the solution to 25 or 50% prevents films retraction effect. The release of highly water-soluble NPK fertilizer from these composite films was lower with hemicelluloses (52-82%) or lignin (55-92%) contents in SCB fiber than in noncellulosics absence (71-100%), thus could be tuned by varying the chemical composition SCB derivative, followed by a quasi-Fickian diffusion mechanism in water.

Resumo em Inglês:

Baru seeds are commonly found in the Brazilian savanna and present potential to be used by the food industry due to their high content of fat. In this sense, this study aimed to determine the physicochemical properties, and chemical composition of baru seed oil. The thermal and oxidative stability, as well as the interfacial properties of the oil were also evaluated. The free fatty acid, peroxide, moisture, density, viscosity and the refractive index of the oil extracted from baru seeds were 0.08% oleic acid, 6.69 meq O2 kg–1 of oil, 0.03%, 0.92 g cm–3, 32.9 mPa s and 1.47, respectively. Since linoleic acid (L), oleic acid (O), palmitic acid (P) and linolenic acid (Ln) are the main fatty acids present in the oil, the most common predominant triacylglycerols in the oil are POO, POL, OOO, OOL, OLL and LLL. The oil extracted from baru seeds presented good thermal and oxidative stability. Moreover, the oil contains high contents of total phenolics and carotenoids. The reduction of oil-water dynamic interfacial tension was promoted by the presence of small molecules. Therefore, the oil extracted from baru seeds presents promising properties for processing in the food industry.

Resumo em Inglês:

Layered double hydroxides (LDH) with the composition Zn2Cr, intercalated with acetate and chloride ions were synthesized by co-precipitation with increasing pH and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The samples synthesized at optimized pH showed XRD patterns with basal diffraction peaks typical of layered structures, with basal distances of 7.88 and 12.69 Å for intercalated chloride (Zn2Cr/Cl) and acetate (Zn2Cr/Ac), respectively. After optimization experiments, exchange reactions were performed with different anions, using an excess of five times the anions to be intercalated. Zn2Cr/Cl was exchanged with CH3COO-, F-, Br-, I-, SO42- and NO3-, and Zn2Cr/Ac was exchanged with F-, Cl-, Br-, I-, SO42- and NO3-. Not all reactions were effective, indicating that among the evaluated anions, CH3COO- was preferred for exchange, mainly attributed to the pre-expansion with bigger anions, facilitating the exchange with smaller anions.

Resumo em Inglês:

The objective of the present work was to apply self-organizing feature maps (SOFM) and multilayer perceptron (MLP) to evaluate the protective capacity of tert-butylhydroquinone (TBHQ), butylhydroxyanisole (BHA), and butylhydroxytoluene (BHT) antioxidants against the biodiesel oxidation reaction. For this, the antioxidant concentration and the biodiesel compliance parameters were used as continuous input variables and the type of antioxidant as a categorical. The SOFM proved to be an adequate tool for the classification of biodiesel samples containing antioxidants. The performance of the 5 most active networks of the model ranged from 89 to 99% for training, testing, and validation with an error below 1.42 × 10-4. Statistical tests applied to validate the model showed no significant difference between predicted and experimental values. The global sensitivity analysis showed that the relative protection factor (RPF) contributed with 34.89%, the antioxidant with 31.49%, the induction period with 10.69%, the water content with 6.00%, and the others all together with 16.93% in the construction of the regression models by MLP.

Resumo em Inglês:

Sustainable and environmentally friendly methods for nanomaterials synthesis have been emerging recently. The use of extracts of polyphenol-rich plants with high reducing and chelating power is advantageous because the polyphenol can protect the nanomaterial from agglomeration and deactivation. Green nanomaterials have been applied in several areas, including remediation of toxic organic pollutants from contaminated effluents. Herein, we describe the preparation of green iron oxide nanoparticles (IONPs) with extracts of the plant Camellia sinensis as black tea for dye removal application. The as-prepared IONPs were composed of amorphous FeOOH and FeII/III-polyphenol complexes. To obtain crystalline and pure iron-based nanomaterials, the amorphous precursor was annealed at 900 ºC. Samples of black tea from different regions were used to verify the reproducibility of the iron phases formed. The same iron phases were obtained for all black tea samples, α-Fe2O3 (hematite), FePO4, and Fe3PO7, but in different proportions. The materials were applied as heterogeneous-Fenton catalysts for the removal of the dye methyl orange. The amorphous as-prepared IONPs were more active than the respective annealed IONPs due to the proton release from the polyphenol into the reaction medium, setting the pH to around 3, which is the optimum pH for the Fenton system.

Resumo em Inglês:

Tucumã (Astrocaryum aculeatum) pulp presents a large number of secondary metabolites that can mediate the synthesis of metallic nanoparticles through a greener and more sustainable synthetic route than traditional ones. This study investigated the production of silver nanoparticles (AgNPs) mediated by aqueous extracts of tucumã pulp assessing different parameters, such as temperature, concentration of extract, and pH values of the reaction media. The alkaline reaction media produced the most intense and well-defined bands around 400 nm in the electronic spectra, indicating the formation of AgNPs in the three concentrations of tucumã pulp evaluated. The increase in the temperature of the reaction media also enhanced the surface plasmon resonance band of AgNPs but it increased the polydispersivity of produced nanoparticles according to the dynamic light scattering (DLS) and transmission electron microscopy (TEM) data. Zeta potential results indicated moderate stability of the AgNPs (close to -30 mV). Antimicrobial assessment of the colloidal metal particles indicated microbicide activity against the Gram-negative Escherichia coli bacterium.

Resumo em Inglês:

A new approach involving square wave anodic stripping voltammetry was developed to simultaneously determine cadmium and lead and, in the same cell, sequentially copper, in biodiesel after extraction induced by microemulsion breaking. The composition of the water-in-oil microemulsion involved 10.50 mL biodiesel, 4.20 mL n-propanol and 0.30 mL of the 6.0 mol L 1 HNO3 solution. The extraction was carried out by adding 1.10 mL ultrapure water resulting in two well separated phases: an upper organic phase, and a lower aqueous phase containing the analytes. The apparatus comprised a portable potentiostat and a cell with an in situ plated mercury film glassy carbon electrode as working electrode. The limits of detection for Cd, Pb and Cu were 0.33, 0.48 and 0.66 µg L 1, respectively. The accuracy of the method was evaluated by recovery assays of spiked samples and by analyzing a standard reference material.

Resumo em Inglês:

The liquid product of the pyrolysis of biomass is a mixture of an organic phase and other aqueous, being the last one rich in phenol monomers which can be used in industrial chemistry as input for plastic and resin production. This work aimed to develop a method for extracting phenols present in the aqueous fraction obtained from the pyrolysis of guava seeds, using ultrasonic assisted liquid-liquid extraction (UALLE) with ethyl acetate and ionic liquids (ILs) as co-solvents (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide (BMIM.NTF2) and 1-butyl-3-methylimidazolinium hexafluorophosphate (BMIM.PF6)). The percentage IL, ultrasonic bath potency, temperature, and pH were studied. Quantification of twelve phenol monomers was performed using gas chromatography-mass spectrometry (GC-MS) and the total phenol concentration (TPC) was performed using UV-Vis spectrophotometer. The ionic liquid BMIM.NTF2 was more efficient for phenol extraction than BMIM.PF6. The phenolic extractions were influenced by the pH of the aqueous fraction (higher extraction yields at pH ≤ 7), and thus, presented recoveries above 80% for both ionic liquids.

Resumo em Inglês:

Catalysts were synthesized with Ni and bentonite clay, without previous treatment, through wet impregnation with 5, 10 and 20% of Ni (m/m). They were characterized by energy dispersive X-ray fluorescence spectrometry (EDX), X-ray diffraction (XRD), temperature-programmed reduction (TPR), thermogravimetric analysis (TGA), adsorption and desorption of N2 at 77 K, and transmission electron microscopy (TEM). The catalytic activity in relation to the methane conversion reaction was evaluated at 500 ºC for 0.5 h. The addition of 10 and 20% of nickel to the clay led to a disordered bentonite structure, characterized by the disappearance of the 001 reflection on the X-ray diffractograms, with a consequent increase in the interaction between nickel oxide and clay (TPR). All catalysts synthesized showed catalytic activity in relation to the conversion of methane to form ordered carbon. The catalyst with 20% of nickel had the highest activity, with 74% of methane conversion.

Resumo em Inglês:

To expand the variety of density functionalized compounds evaluated against severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2), we decided to prepare new acetylated and disubstituted 3-hydroxy bis-oxindoles and isoindigos coupling compounds using known protocols. The corresponding isatin derivatives were synthesized by ZrCl4/EtOH/reflux or HCl/AcOH/reflux coupling conditions using oxindole and functionalized isatins, furnishing new 3-hydroxy bis-oxindoles, which were dehydrated into new isoindigos. A total of 27 compounds bearing halogen, nitro and/or hydroxy groups on the isatin moiety at the 3-, 5- and 7-positions, were prepared, including 5 new 3-hydroxy bis-oxindoles and 3 new halogenated isoindigos prepared according to adapted procedures described in the literature. This library of nitrogen-isatin derivatives was evaluated against SARS-CoV-2 using a phenotypic screening assay. In this investigation, isatin derivatives 3d, 3e, 3h and 3i showed antiviral activity when tested at a single concentration. Compound 3e showed antiviral activity against SARS-CoV-2 in the concentration-response assay; however, it showed cellular toxicity in Vero cells. The present study identified substituted isatins as a promising new starting point for the development of anti-SARS-CoV-2 agents.