Due to the high energy demand and search for clean, efficient and safe energy, new materials have been tested and improved for direct use in lithium-ion batteries (LIBs). Tungsten oxide (WO3) and graphene oxide (GO) are two materials that, separately, have good applicability in LIBs and, therefore, it becomes interesting to obtain and study the WO3/GO composite, to study the electrochemical stability in LIBs. Using the hydrothermal method, different crystalline structures were obtained for WO3, through variation in pH and, citric acid, and oxalic acid as chelating agents. For the synthesis of GO, the modified Hummer’s method was used. X-ray diffraction analyzes confirmed the presence of two distinct crystalline phases for WO3, the hexagonal phase (h-WO3) at pH 1.5 and 2.0 and the monoclinic phase (m-WO3) at pH 1 ,0. XDR also confirmed the formation of GO, due to the presence of the diffraction peak at 2θ = 10.49°. The FTIR spectra and RAMAN spectra showed the presence of groups related to the materials of interest. Thermogravimetric analyzes showed the mass losses for the samples before and after combining the materials. Cyclic voltammetry tests showed that the WO3/CA/GO composites, synthesized at pHs 1.0 and 1.5, and the WO3/OA/GO composite, synthesized at pH 1.5, exhibited the best electrochemical performances, being promising candidates for use in Li+ ion batteries.

The Nucleophilic Fluorination reactions have gained notoriety over the years, this the due to great applications that Organic Fluorine Chemistry presents. Among these, we can mention positron emission tomografy, better known as (oncological PET), where F-18-FDG, a glucose analogue that has the ability to map benign and maglignant cells, is injected into the patient´s blood. In pharmacology, in 2014, it was estimated that there are more than 200 fluorinated drugs on the marked and, currently, new fluorinated drugs continue to emerge, at 15 to 20% per year, as they have several advantegeous biological properties derived from the insertion of fluorine element. However, for nucleophilic fluorination reactions , toxic reagents are still used and often have low solubility in organic solvents, in addition to the competition between SN2 e E2. However, to resolve these issues regarding solubility and seletivity, crown ethers are used together with alcoohols that will assist in the solubilization stage and activation of the SN2 reaction. In this work proposal, we wish to investigate the use of primary bromides for fluorination , using a phase transfer catalyst such crown ethers together with a bulkyl alcohol or fluorinated alcohol , to obtain primary fluorides selectively and with good yields. The result using 3 mmol of TBOHF6 stands out, where 80% conversion of the fluorinated product was achieved, demonstrating that the use of TBOHF6 is more favorable than BDMB.

The Carbon Dots (CDs) are zero-dimensional fluorescent nanomaterials that have physical, chemical and optical characteristics that make these materials potential for application in various areas, such as biomedical, environmental and energy conversion. Recent studies seek to understand the luminescence mechanism of these materials and the influence of property parameters on the properties of these materials, to make the properties more predictable and result in Carbon Dots with interesting properties. In the present work, the synthesis of Carbon Dots was carried out using the precursor of 1,3,6 - Trinitropyrene, previously synthesized through the nitration of pyrene, the synthesis of CDs was carried out using the solvothermal method, varying two synthesis parameters, the first parameter was the synthetic time, varying in 2 h, 6 h and 12 h of occurrence for each synthesis and the second parameter was the synthesis solvent. Toluene, N, N dimethylformamide and a mixture between N, N dimethylformamide and water in a 2:1 ratio, variations of these settings resulted in 9 samples. Structural and optical characterization of the CDs obtained was carried out. The CDs were dispersed in different solvents and it was found that there was a solvatochromic effect in the samples with deviations in the emission wavelengths with the variation in the polarity of the solvents in which the CDs were dispersed. They were tested on solar cells, but these did not yield significant results, possibly due to CD not being well adsorbed to TiO2 after sensitization, which can be attributed to the absence of good functional groups to anchor CD to TiO2. The Carbon Dots presented quantum yields ranging from 18.8% to 58.9%, emissions at different wavelengths were observed in the CDs both with the variation of the synthesis solvent and with the variation of the solvent used to disperse the Carbon Dots after syntheses. The effect of synthetic time was mainly observed in the XRD patterns of the samples, indicating that the different synthetic times lead to important changes in the nanoparticle core. It was confirmed that the choice of synthetic and post-synthetic configurations are of great relevance for adjusting the properties of Carbon Dots.

Asymmetric catalysis is an interesting way to obtain enantiomerically pure compounds or with high enantiomeric purity. Asymmetric catalysis techniques have been modernized and expanded in the last 20 years. Modern synthetic methodologies seek to reconcile agility, low cost and minimal environmental impacts. Asymmetric catalysis is divided into three main areas: organocatalysis, biocatalysis and metallic catalysis. This work focused on the synthesis of chromenes (benzopyrans) through organocatalysis and biocatalysis of the oxa-Michael-aldol reaction of nitrostyrene or cinnamaldehyde with salicylaldehyde. Chromenes are heterocycles with a basic nucleus consisting of a pyran ring fused to a benzene ring (bicyclic). They are important molecules for several industrial branches, but mainly the pharmaceutical one. Chiral drugs occupy a prominent place in the industry due to their ability to selectively interact with enzymes or with a stereospecific biological receptor (chiral macromolecules), thus provoking a biological response. Through organocatalysis, using thiazolidines (3a and 3b) and L-proline derivative (4) under different conditions, it was attempted to synthesize compounds 1a and 1b, with enantiomeric excess. The results showed that for the conditions and compounds tested, it is not possible to synthesize molecules with enantiomeric excess. With the use of enzymes (biocatalysis), CAL-B and α-amylase, attempts were made to synthesize compounds 1a and 1b, 2a and 2b with enantiomeric excess, once again without success. Both in the organocatalysis and in the biocatalysis of the chromene derivatives that were tried to synthesize, the enantiomeric excess was unsuccessful, this may be related to non-activation of the nucleophile and electrophile or lack of induced orientation of the olefin during the transition step.

Experiments reported in the literature involving phenol alkylation under conditions of phase transfer catalysis support the formation of the R4N+PhO-(PhOH) complex in the organic phase. This complex may be directly involved in the transition state. In thepresent theoretical study, the phase transfer catalyzed alkylation of phenol was investigated using M06-2X/def2-TZVPP//X3LYP/def2/SVP level of calculation and including the solvent effect using the SMD model combined with reliable experimental data from free energy of solvation of ionic species in aqueous solution. The analysis was done for tetraethylammonium, tetrapropylammonium and tetrabutylammonium phase transfer catalysts. In the case of the tetrabutylammonium ion, the calculations predicted reaction kinetics compatible with the experimental data. Furthermore, the Bu4N+PhO-(PhOH) complex is calculated to be the active species in catalysis. For the tetraethylammonium and tetrapropylammonium cations, the R4N+PhO-and R4N+PhO-(PhOH) complexes are not able to explain the catalysis, suggesting that another more complex aggregate may be involved in the process. Aiming at the development of new catalysts for this reaction, we studied the modified crown ether catalysts (DBEC4OH), a variation of the Jadhav catalyst (BAC5CAt) and the Takemoto catalyst. In general, these catalysts were not very promising for this reaction, but the BAC5CAt catalyst that produces a free energy barrier equal to 21.50 kcal/mol in MIBK stands out, being a good candidate to promote selectivity for O-alkylation especially in nonpolar solvents. The classical alkylation reaction of benzene with isopropyl chloride catalyzed by AlCl3and Al2Cl6species was studied using the same level of theory used in phenol alkylation reactions. We evaluatedthe formation of dimers, trimers, tetramers and pentamers and showed that Al2Cl6dimers exist in greater proportion, according to experimental observations. The experimental solubility of Al2Cl6in benzene was also included in the theoretical kinetic analysis. The reaction catalyzed by the AlCl3 species presents the greatest barrier, in part due to the unfavorable dissociation of the Al2Cl6 species. The mechanism via catalysis with Al2Cl6is more efficient and, even considering its low solubility, the calculated observed ∆G‡is only 20.6 kcal/mol, indicating a high reaction rate. The mechanism involves the formation of the ionic pair CH3CHCH3+...Al2Cl7-, which reacts with benzene to form a Wheland intermediate, and this carbon-carbon bond formation step corresponds to the rate-determiningstep.

Due to the growing global demand for energy, renewable energy becomes of great interest. In addition to being an inexhaustible source of energy, renewable energy uses non-polluting materials. Research related to the use of solar energy has intensified in recent years and a breakthrough in photovoltaic energy is only possible with low production costs. Characterization and optimization studies of solar cells help in the development of more efficient and low-cost cells. This work aims to characterize flexible solar cells using natural dyes without purification process. The characterization was also carried out on the components of the DSSC (Dye Solar Sensitized Cels). Before the assembly of the DSSCs, a study of the energies of the components of the solar cell was carried out in order to verify the feasibility of assembling each of the cells analyzed For the assembly of the DSSC photoanode, the following semiconductors were used: V2O5 and VO2 and the dyes: strawberry, blackberry, blueberry and jabuticaba wine extracts deposited on the surface of the PET-ITO. The counter electrode (cathode) was produced using PANI electrodeposited on the surface of the PET-ITO and the electrolyte used was the iodide/triiodide pair. Several conditions of PANI electrodeposition were evaluated, with condition 1 being selected for the assembly of the DSSC because it presents some favorable conditions, such as: macrovisual uniformity of the film, values of the appropriate HOMO, LUMO and bandgap orbitals. Through the UV-VIS spectrophotometry technique it was possible to determine characteristic absorption bands of the PANI in its conductive form (emeraldine salt), demonstrating that the PANI could be used as a counter electrode of the DSSC, replacing platinum, thus reducing the cost of the DSSC. extracts for mounting the DSSC: strawberry, blackberry and blueberry. Jabuticaba wine was not selected because it is not energetically favorable for DSSC with the other components used in this work. Solar cells without the presence of dye were also mounted for comparison with DSSCs. As a result, DSSCs using V2O5 as a semiconductor were those with the highest efficiency. This fact may be related to the greater crystallinity of the film in relation to VO2, demonstrated in X-ray diffraction analysis. Comparing the efficiency of solar cells without dye and solar cells using dye, it was possible to state that the dyes were able to sensitize the DSSCs, with the exception of the CS3 solar cell. Thus, in addition to the blueberry not being able to sensitize the DSSC, it still served as a physical barrier to electrons, as can be seen by the fact that the efficiency of the CS3 solar cell was lower than the respective solar cell without dye (CS1). Flexible solar cells using natural dyes have low efficiencies (less than 1%) compared to flexible cells, however, their cost tends to be very low. Changes to DSSCs components, in addition to the study of new materials and compositions, can increase the efficiency of flexible solar cells, such as: replacing the liquid electrolyte, semiconductor doping, post-treatment in the photoyear, among others.

Theoretical methods are an important tool in elucidating reaction mechanisms and understanding experimental results. We can also use them to exclude mechanisms and infer about experimental observations, such as the presence of traces of a contaminant that, as for some of the reactions investigated here, has a potential catalytic effect. Increasingly, these methods are useful for the rational design of more effective catalysts. In this context, this work had as its main objective the complete elucidation of the iminium ion mechanism of conjugated addition of nitromethane to 4-phenilbut-3-en-2-one catalyzed by primary amino-thiourea (APTB) in an aprotic solvent. This system presented such mechanistic complexity, which led us to the need to investigate simpler imine formation mechanisms, how the nature of the solvent would impact it, and the effect that the presence of contaminants in the reaction medium has on the reaction. According to our results, the formation of imines in aqueous solution has the formation of a zwitterion as a rate-determining step, followed by the formation of carbinolamine catalyzed by water molecules and then, through elimination of hydroxide ion, there is the formation of iminium ions. The formation of imines and unsaturated imines in the aprotic solvent has its kinetic viability conditioned to the presence of acids as contaminants in the reaction medium, which, of the species investigated here, are the only ones capable of leading to a lowering of the free energy barriers consistent with what is experimentally observed. Understanding the formation of imines provided us a more solid basis for elucidating the mechanism via iminium ion of the Michael reaction catalyzed by APTB, which has as a rate-determining step the formation of the iminium-nitronate ion pair, followed by enantioselective step, and despite not participating in these two main steps, the presence of acetic acid is essential for the other steps to have kinetic viability for continuity, as well as to allow the catalytic cycle to complete. Finally, to design a catalyst that acts exclusively via base, we used an iminophosphorane-thiourea as a reference structure, and through targeted structural modifications, we designed a new catalyst for the Michael reaction, which allowed conversion of up to 96% at 1 day of reaction time and enantiomeric excess of 97% for S isomer.

The α-galactosidase enzyme is responsible for the hydrolysis of the galactose terminal bond in complex oligosaccharides, converting them into simpler sugars such as glucose and galactose. This property allows the use of this enzyme in the treatment of non-nutritive α-galacto-oligosaccharides (GOS), recognized and used in the treatment of soy-based products, which have high concentrations of these oligosaccharides. Which ingested in large amounts can cause stomach pain, diarrhea and flatulence. This study aims at the extraction and partial purification of Trichoderma virens for characterization and use in the treatment of soy milk. The enzyme is able to act in a wide range of temperature and pH, maintaining significant activity and stability, having an optimal pH and temperature of 4,5 and 55 ºC, greater stability at temperatures of 45 ºC and acidic pHs. In the presence of the K+ ion, its activity is increased by about 20%. It presents competitive inhibition in the presence of galactose, a product of its oligosaccharide hydrolysis reaction.

Perovskite nanocrystals (PNCs) have emerged as promising candidates for optoelectronic and photovoltaic applications due to their exceptional optoelectronic properties. A critical problem presented by these nanomaterials is their low chemical stability, and several efforts have been made in order to improve the stability of PNCs. Recently, the coating of the surface of CsPbBr3 perovskite (3D phase) with another phase derived from Cs4PbBr6 perovskite (0D phase) has been evaluated, forming a core-shell system with improved optical properties and greater stability. but little attention has been paid to the charge-extraction properties of the core-shell system, which is continually being reported as promising for applications in optoelectronic and photovoltaic devices. Through a combination of spectroscopic and electrochemical techniques, the electron extraction properties of the 3D and 0D@3D systems were evaluated. Furthermore, a phase change reaction induced by polar solvent was evidenced, confirmed by HRTEM/SAED.

Ractopamine (RAC) is a food additive widely used in animal production whose main objective is to enhance meat production and improve product quality. However, the indiscriminate use of this growth stimulant can lead to the production of meats with a high level of residue from this drug, which can pose a health risk in addition to arousing the attention of more demanding consumers. Based on this premise, a simple and fast method was developed for the determination of RAC in food samples of animal origin, using magnetic solid phase extraction (MSPE) with molecularly printed polymer with restricted access, and capillary electrophoresis (CE). Firstly, it was performed the synthesis of magnetic nanoparticles by the method of co-precipitation of Fe2+ and Fe3+ ions in a basic medium, and these particles were later functionalized with tetraethylorthosilicate. Then, the imprinted polymer was synthesized on the surface of the functionalized magnetic particle by the precipitation method, using RAC as template, acrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinking agent and benzalkonium chloride as surfactant. Then the magnetic MIP was double coated, firstly with the hydrophilic monomers 2-hydroxyethyl methacrylate and glycerol dimethacrylate and then with bovine serum albumin, in order to transform the MIP into an adsorbent with restricted access. The characterization of the synthesized material was carried out by the techniques of DRX, FTIR, TGA, SEM, TEM, wettability test, zero charge point tests, presenting results consistent with the synthesis processes and suggesting that the double coating on the imprinted polymer was successful. For the analysis and quantification of RAC, a reverse injection CE method was optimized, which showed to be very promising for ultra-fast RAC analysis, since the analyte migration times were less than 1 min and the analytical signals obtained had good peak asymmetry, and peaks free from interfering and/or baseline noise. The MSPE showed good applicability, since, in addition to the ease of application, after the optimization process it was possible to reach recovery values of the analyte close to 90% in samples of bovine milk, bovine muscle and muscle pig. The method validation process showed satisfactory results, and the parameters related to selectivity, analytical curve quality, precision, accuracy and robustness of the method that were found are within acceptable limits according to ANVISA resolution 166/2017. The developed method was then applied to real samples of bovine milk and bovine and porcine muscle, with a
iv relative error being observed for fortified samples of less than 15%, mainly in porcine muscle samples, where it was possible to observe an electropherogram with less interference compared to to the electropherograms referring to the other matrices.

Since its discovery, Carbon Dots (CDs) have attracted attention due to their particular optical properties such as intense fluorescence and photostability, in addition to low toxicity, low processing costs and solubility in aqueous media at different pHs. Because they are materials easy to synthesize, several studies have been carried out varying the method of preparation and the precursors used, aiming to obtainthe best set of optical properties. In the literature, CDs have been used in different technological applications, among which the sensing stands out for the high sensitivity of photoluminescence detection. The development of CDs-based sensors takes into account three main factors: the direct interaction of the analyte with the CDs, post-functionalization and the interaction with other fluorophores as sensory materials. CDs can serve as sensors for a wide range of analytes, such as ions, small molecules, macromolecules, cells and bacteria. In addition, they assist in the monitoring and treatment of wastewater. In this work, CDs were synthesized by two routes of synthesis, pyrolysis and hydrothermal, using citric acid and thiourea as precursors in different mass ratio. The structural and optical properties were investigated and used as parameters for choosing two samples to be applied in the sensing of two analytes: water contaminated with diesel oil and naphthalene. The samples chosen for the sensing tests showed a φf of 13.40% and 3.11% for PAC1: T1 (pyrolysis 250°C) and H4AC2: T1 (hydrothermal 175°C,4 hours), respectively. Two studies were carried out: the sensing tests and the study of the influence of the CDs concentration on the sensing. Tests for naphthalene detection showed a good linear correlation and a detection limit of 0.20 mg/L for pyrolysis and 0.10 mg/L for hydrothermal. In contrast, in the test for detecting water contaminated with diesel oil, the sample synthesized via hydrothermal did not show sufficient variation for detection and the sample synthesized via pyrolysis showed a good linear fit and the detection limit was calculated at 0.01 μL of the analyte. To understand the influence of concentration on sensing, the sample that showed the best results in the previous PAC1: T1 test was studied. A very detailed concentration versus emission curve was performed and three points were chosen. For each sample, a standard addition (in this case, water) and an analyte (water contaminated with diesel oil) were added. Each point presented a different behavior both for the addition of water and for the addition of the analyte. Thus,confirming the importance of choosing the concentration for the sensing using CDs.

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