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A silicon/polyaniline/horseradish peroxidase enzyme (n-Si/PANI/HRP) electrode was obtained by potentiostatic electrodeposition processes. PANI thin films were electropolymerized on a silicon substrate at different electric potentials, and an HRP enzyme was electrodeposited on the best PANI thin film. The best PANI thin film was obtained under electrodeposition conditions of + 1.00 V (vs. Ag/AgCl) and 900 s, and the immobilization of the HRP enzyme was performed at an electric potential of − 0.50 V (vs. Ag/AgCl). The n-Si/PANI- and n-Si/PANI/HRP electrodes were characterized using scanning electron microscopy and atomic force microscopy. The detection capacity of the glyphosate of the n-Si/PANI/HRP electrode with the best morphological characteristics was evaluated according to the electric current density responses from the oxidation of hydroquinone molecules in a solution containing different concentrations of glyphosate. The detection was performed because of the inhibition of the HRP enzyme activity by the glyphosate molecules in the solutions with a lower concentration limit of 5.44 μg L−1 over an electric potential range of + 0.65 to + 1.15 V (vs. Ag/AgCl).

O Programa Institucional de Bolsas de Iniciação à Docência - PIBID é uma iniciativacom o intuito de inserir o licenciando no contexto escolar. Nesse sentido, os bolsistasdo PIBID Química do Instituto Federal Catarinense - Campus Araquari, elaboraram10 oficinas didáticas, considerando temáticas apresentadas no livro: Os botões deNapoleão: as 17 moléculas que mudaram a história. Os temas foram desenvolvidosconsiderando a contextualização, a interdisciplinaridade e metodologiasdiversificadas e ativas, tendo como objetivos para os bolsistas, refletir sobre a salade aula e planejar uma sequência de atividades que viabilizasse abordagensconceituais e estratégias didáticas para o favorecimento do aprendizado e debatessobre a função social daquela temática. Ao aplicar as atividades, os alunos sedemonstraram mais apreensivos e interessados ao passo que dinâmicas interativasiam sendo desenvolvidas. Tal situação contribuiu para a identidade docente doslicenciandos assim o senso crítico dos participantes.

Core–shell Fe2O3@C nanoparticles are very studied due to its biocompatibility with plant and animals cells and due its special properties of chemical adsorption. Thus, the definition of an easy synthesis method of these nanoparticles is very important to the scientific studies and to future applications of these materials. For example, the properties of these nanoparticles depend of the combination between some processing parameters, as the temperature, time, chemical composition, atmosphere and others. The mass yield of the synthesis processes depend of these parameters and are important information. In this work the effect of temperature and of the concentration of the iron precursor were evaluated on the characteristics of the proposed nanoparticles. The nanostructures of Fe2O3 coated with carbon (Fe2O3@C) were synthetized by adapted co-precipitation hydrothermal rote. In 40.0 ml of distilled water was added 1.800 g of glucose, 6.006 g of urea, 0.500 g of polyethylene Glycol (PEG 1500) and different concentrations of iron nitrate Fe (NO2)3.9H2O and different temperature values were applied. The Fe2O3@C core-shell were characterized by scanning electron microscopy (SEM/FEG), Energy Dispersive Scanning (EDS) and X-ray Diffractions (XRD). Results showed that nanoparticles form clusters with different sizes that are dependent on the temperature values and Fe (NO3)3.9H2O concentration. The core-shell mass has a linear relation with the iron precursor mass and the reaction temperatures influences the microstructure of the core-shell nanoparticles.

Nanowires of carbon coated ferric oxide (Fe2O3/C) have been studied to be applied at an electrochemical glucose biosensor as a new type of carbon paste electrode (CPE) modifier. The Fe2O3/C was synthesized by adapting co-precipitation hydrothermal route. Firstly, amperometric sensor based on a modified CPE doped with Fe2O3 has been developed and compared with CPE doped with Fe2O3/C for hydrogen peroxide (H2O2) determination. The performance evaluations for the modified materials and sensors were studied in detail through cyclic voltammetry (CV) method. After, the electrochemical sensor performance was also evaluated for glucose oxidase (GOx) response biosensor due to considerable interest in the blood sugar control. The results demonstrate that the GOx retains its biocatalytic activity toward the oxidation of glucose and that the bioelectrode modified by the Fe2O3/C matrix has potential for use in biosensors and other bioelectronics devices.

In this study a biosensor with laccase immobilized in a chitosan matrix was developed. Prior to the laccase immobilization the chitosan was cross-linked with genipin, a naturally-occurring cross-linking agent, and incorporated into a carbon-paste electrode. Analytical parameters for caffeic acid, such as repeatability (2.7 %), reproducibility (3.0 %), linearity (0.27 and 33 µM; r2≥0.9983), limit of detection (LOD=0.18 µM) and recovery (96–103 %), were determined. The method was applied in the determination of the total phenolic content of mate herb samples. The good performance of the method can be attributed to the effective immobilization of laccase in the cross-linked support.

In this study, peroxidase from alfalfa sprout extract (Medicago sativa) was immobilized on a gold electrode, using a solution of the zwitterionic surfactant 3-(1-tetradecyl-3-imidazolio)propanesulfonate (ImS3-14) containing well-dispersed gold nanoparticles. In the presence of hydrogen peroxide, the peroxidase enzyme catalyzes the oxidation of hydroquinone to o-quinone, which is electrochemically reduced at a potential of +0.09 V vs. Ag/AgCl. The hydroquinone biosensor exhibited excellent electrocatalytic activity under the optimized experimental conditions ([peroxidase] = 97 units mL−1, [H2O2] = 7.4 × 10−5 M, pH 7.0, frequency of 100 Hz, pulse amplitude of 60 mV and scan increment of 4.0 mV). Peak current linearity was observed in the range of 6.96 × 10−7 to 8.54 × 10−6 M, and the detection limit was estimated to be 1.88 × 10−7 M. This biosensor demonstrated good repeatability and reproducibility with relative standard deviations of 3.6% and 6.5%, respectively, and an acceptable stability (at least 100 determinations). The method has been applied to the determination of hydroquinone in skin-brightening creams and the recoveries were 98.3–104.5%.

A sol–gel derived carbon ceramic biosensor was used for methomyl determination in vegetable extract samples based on the immobilization of laccase from Aspergillus oryzae. Esculetin was chosen as the substrate for laccase in order to measure inhibition by this pesticide. The analytical curve was linear for methomyl concentrations of 0.5 to 12.2 µM with a detection limit of 0.2 µM. The lifetime of the proposed biosensor was 60 days and the recovery from vegetable extract samples ranged from 98.0 to 104.2 %. The results using the proposed method are in agreement with those using HPLC at the 95 % confidence level.

A gold electrode surface was modified using a dinuclear copper complex [Cu II 2 (Ldtb)(μ-OCH 3 )](BPh 4 ) and then coated with a chitosan film. This biomimetic polymer film-coated electrode was employed to eliminate the interference from ascorbic acid and uric acid in the sensitive and selective determination of dopamine. The optimized conditions obtained for the biomimetic electrode were 0.1 M phosphate buffer solution (pH 8.0), complex concentration of 2.0 × 10 −4 M, 0.1% of chitosan and 0.25% of glyoxal. Under the optimum conditions, the calibration curve was linear in the concentration range of 4.99 × 10 −7 to 1.92 × 10 −5 M, and detection and quantification limits were 3.57 × 10 −7 M and 1.07 × 10 −6 M, respectively. The recovery study gave values of 95.2–102.6%. The lifetime of this biomimetic sensor showed apparent loss of activity after 70 determinations. The results obtained with the modified electrode for dopamine quantification in the injection solution matrix were in good agreement with those of the pharmacopoeia method.

A biosensor based on the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI·Tf 2 N) and a novel source of peroxidase (tissue from the pine nuts of Araucaria angustifolia ) was constructed. This enzyme was immobilized on chitosan crosslinked with citrate and the biosensor used for the determination of rosmarinic acid by square-wave voltammetry. The peroxidase in the presence of hydrogen peroxide catalyzes the oxidation of rosmarinic acid to quinone and the electrochemical reduction of the product was obtained at a potential of +0.15 V vs . Ag/AgCl. Different analytical parameters influencing the biosensor response, that is, peroxidase units, pH, hydrogen peroxide concentration and parameters for the square-wave voltammetry (frequency, pulse amplitude and scan increment), were investigated. The best performance was observed for the biosensor under the following conditions: 1000 units mL −1 peroxidase, pH 7.0 and 8.3 × 10 −4 mol L −1 hydrogen peroxide with a frequency of 30 Hz, pulse amplitude of 100 mV and scan increment of 5.0 mV. The biosensor gave a linear response to rosmarinic acid over the concentration range of 9.07 × 10 −7 to 4.46 × 10 −6 mol L −1 with a detection limit of 7.25 × 10 −8 mol L −1 . The recovery of rosmarinic acid in plant extracts ranged from 97.0% to 109.6% and the determination of this substance in these samples using the biosensor compared favorably with that using the capillary electrophoresis method.

A new bean sprout peroxidase was immobilized on a gold electrode modified with self-assembled monolayers (SAM) of l -cysteine for the determination of dopamine in pharmaceutical samples using square wave voltammetry. In the bean sprout–(SAM)–Au electrode, the peroxidase, in the presence of hydrogen peroxide, catalyzes the oxidation of dopamine to the corresponding quinone, which is electrochemically reduced back to dopamine at +0.15 V vs. Ag/AgCl. The performance and the factors influencing the response of this biosensor were studied in detail. The best performance was obtained using 0.1 mol L −1 phosphate buffer solution (pH 6.0), 6.0 × 10 −5 mol L −1 hydrogen peroxide, frequency of 100 Hz, pulse amplitude of 80 mV and scan increment of 4.0 mV. The analytical curve was linear for dopamine concentrations from 9.91 × 10 −6 to 2.21 × 10 −4 mol L −1 and the detection limit was 4.78 × 10 −7 mol L −1 . The recovery of dopamine ranged from 98.0 to 111.8% and the relative standard deviation was 3.1% for a solution containing 1.30 × 10 −5 mol L −1 dopamine ( n = 6). The lifetime of this biosensor was 15 days (at least 300 determinations). The results obtained for dopamine determination in pharmaceutical formulations using the proposed bean sprout–SAM–Au electrode were in agreement with those obtained with the standard method at the 95% confidence level.

A novel biosensor based on laccase immobilized on microspheres of chitosan crosslinked with tripolyphosphate was developed for rutin determination in pharmaceutical formulations by square wave voltammetry. In the biosensor, laccase catalyzes the oxidation of rutin to the corresponding o-quinone, which is electrochemically reduced back to rutin at +0.35 V vs. Ag/AgCl. The resultant reduction current is used as the analytical response. Under the optimum conditions established (laccase 0.55 units mg−1; pH 4.0; frequency 30 Hz; pulse amplitude 30 mV; and scan increment 2.0 mV), the analytical curve showed two linear ranges: 5.99 × 10−7 to 3.92 × 10−6 mol L−1 and 5.82 × 10−6 to 1.31 × 10−5 mol L−1 rutin with detection limits of 6.23 × 10−8 and 7.12 × 10−7 mol L−1, respectively. The recovery of rutin ranged from 90.7 to 105.0% and the relative standard deviation was 3.1% for a solution containing 2.0 × 10−6 mol L−1 rutin (n = 9). The lifetime of this biosensor was 320 days (at least 930 determinations). The results obtained for rutin in pharmaceutical formulations using the proposed biosensor were in agreement with those obtained with the standard method at the 95% confidence level.

A new green bean (Phaseolus vulgaris) tissue homogenate-based biosensor was developed for the square-wave voltammetric determination of caffeic acid in white wine. The biosensor was constructed by immobilization of green bean tissue homogenate, as a source of peroxidase, in a chemically crosslinked chitin matrix with epichlorohydrin and glutaraldehyde that was incorporated in a carbon paste electrode. In the presence of hydrogen peroxide the peroxidase catalyses the oxidation of caffeic acid to quinone and the electrochemical reduction of the product was obtained at a fixed potential of +0.10 V versus Ag/AgCl (3.0 mol L−1 KCl). The response characteristics and optimization of the bioelectrode design were evaluated. The recovery of caffeic acid from three samples ranged from 91.0 to 103.1% and a rectilinear calibration curve for caffeic acid concentrations from 2.0 × 10−5 to 2.0 × 10−4 mol L−1 (r = 0.9990) was obtained. The detection limit was 2.0 × 10−6 mol L−1 and the relative standard deviation was 2.2% for a solution containing 1.2 × 10−4 mol L−1 caffeic acid and 2.0 × 10−3 mol L−1 hydrogen peroxide in 0.1 mol L−1 phosphate buffer solution at pH 7.0 (n = 10). The long-term stability of the biosensor was 300 days.

A new reagentless biosensor for the square-wave voltammetric determination of rutin in pharmaceutical formulations was developed by immobilization of gilo ( Solanum gilo ) crude extract in chitosan matrix. The gilo tissue acts as a source of peroxidase. The highest biosensor performance was obtained after immobilization of the peroxidase in chemically crosslinked chitosan with epichlorohydrin and glutaraldehyde that was incorporated in a carbon paste electrode. In the presence of hydrogen peroxide this enzyme catalyses the oxidation of rutin to quinone and the electrochemical reduction of the product was obtained at a fixed potential of +124 mV versus Ag/AgCl (3.0 M KCl). The performance and factors influencing the resulting biosensor were studied in detail. The bioelectrode exhibited a linear response for rutin concentrations from 3.4 × 10 −7 to 7.2 × 10 −6 M ( r = 0.9998) and the recovery of rutin from the samples ranged from 96.2 to 102.4%. The detection and quantification limits were 2.0 × 10 −8 and 6.3 × 10 −8 M, respectively. The relative standard deviation was less than 1.0% for solutions containing 3.4 × 10 −7 to 7.2 × 10 −6 M rutin in 0.1 M phosphate buffer solution at pH 7.0 ( n = 10). The lifetime of this biosensor was 8 months (at least 500 determinations).

Uma alternativa viável e eficaz no tratamento de efluentes é o uso de carvão ativado. Este trabalho possui por objetivo a obtenção de um carvão ativado utilizando como material percursor café torrado que passou por um processo prévio de extração, para retirada do óleo bruto, que atue no tratamento do corante azul de metileno. Os materiais foram caracterizados através da determinação da área superficial BET. A cinética de adsorção foi determinada experimentalmente e os modelos comparados aos modelos matemáticos de pseudoprimeira e pseudossegunda ordem, sendo que o modelo de pseudossegunda ordem descreveu mais adequadamente a cinética de adsorção com qe = 103,09 mg.g−1 para C1 e 62,89 mg.g−1 para C2. A capacidade de adsorção de surfactantes aniônicos no equilíbrio obedeceu ao modelo de Langmuir para C1, apresentando K de 2,125 L.mg−1 e qmax de 588,235 mg.g−1 e a isoterma de Freundlich apresentou o melhor ajuste aos dados de equilíbrio para C2, sendo os resultados obtidos para KF e n iguais a 51,019 ((mg.g−1).(L.mg−1)1/n) e 3,104, respectivamente. O ponto de carga zero para C1 está na faixa de 2,001 - 2,009 e C2 de 2,0013. Os resultados demonstraram ambos os carvões ativados são eficientes na remoção de corantes catiônicos.

A biosensor based on the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate containing dispersed iridium nanoparticles (Ir-BMI.PF6) and polyphenol oxidase was constructed. This enzyme was obtained from the sugar apple (Annona squamosa), immobilized in chitosan ionically crosslinked with oxalate. The biosensor was used for determination of chlorogenic acid by square wave voltammetry. The polyphenol oxidase catalyzes the oxidation of chlorogenic acid to the corresponding o-quinone, which is electrochemically reduced back to this substance at +0.25 V vs. Ag/AgCl. Under optimized operational conditions the chlorogenic acid concentration was linear in the range of 3.48 × 10−6 to 4.95 × 10−5 mol L−1 with a detection limit of 9.15 × 10−7 mol L−1. The biosensor was applied in the determination of chlorogenic acid in organic and decaffeinated coffee and the results compared with those obtained using the capillary electrophoresis method. The recovery study for chlorogenic acid in these samples gave values of 93.2–105.7%.

Self-assembled monolayers of a nickel(II) complex and 3-mercaptopropionic acid on a gold electrode were obtained for determination of catechin by square wave voltammetry. The complex [Ni(II)L] with L=[N-(methyl)-N'-(2-pyridylmethyl)-N,N'-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-1,3-propanediamine[nickel(II)] was synthesized and characterized by (1)H NMR, IR, and electronic spectroscopies and electrochemical methods. The optimized conditions obtained for the electrodes were 0.1 mol L(-1) phosphate buffer solution (pH 7.0), frequency of 80.0 Hz, pulse amplitude of 60.0 mV and scan increment of 10.0 mV. Under these optimum conditions, the resultant peak current on square wave voltammograms increases linearly with the concentration of catechin in the range of 3.31 x 10(-6) to 2.53 x 10(-5)mol L(-1) with detection limits of 8.26 x 10(-7)mol L(-1). The relative standard deviation for a solution containing 1.61 x 10(-5)mol L(-1) catechin solution was 2.45% for eight successive assays. The lifetime of the Ni(II) complex-SAM-Au electrode was investigated through testing every day over 4 weeks. The results showed apparent loss of activity after 20 days. The results obtained for catechin in green tea samples using the proposed sensor and those obtained by electrophoresis are in agreement at the 95% confidence level.

A catechol oxidase biomimetic sensor, based on a novel copper(II) complex, was developed for the determination of catechin in green tea and the results were compared with those obtained by capillary electrophoresis. The dinuclear copper(II) complex, [Cu2(HL)(µ-CH3COO)](ClO4), containing the ligand N,N-[bis-(2-pyridylmethyl)]-N',N'-[(2-hydroxybenzyl)(2-hydroxy-3,5-di-tert-butylbenzyl)]-1,3-propanediamine-2-ol (H3L), was synthesized and characterized by IR, ¹H NMR and elemental analysis. The best conditions for the optimization of the biomimetic sensor were established by square wave voltammetry. The best performance for this sensor was obtained in 75:15:10% (m/m/m) of the graphite powder:nujol:copper(II) complex, 0.05 mol L-1 phosphate buffer solution (pH 7.5) and frequency, pulse amplitude, scan increment at 30 Hz, 80 mV, 3.3 mV, respectively. The analytical curve was linear in the concentration range 4.95 × 10-6 to 3.27 × 10-5 mol L-1 (r = 0.9993) with a detection limit of 2.8 × 10-7 mol L-1. This biomimetic sensor demonstrated long-term stability (9 months; 800 determinations) and reproducibility with a relative standard deviation of 3.5%. The recovery of catechin from green tea samples ranged from 93.8 to 106.9% and the determination, compared with that obtained using capillary electrophoresis, was found to be acceptable at the 95% confidence level. Um sensor biomimético catecol oxidase, baseado em um novo complexo cobre(II) foi desenvolvido para determinação de catequina em chá verde e os resultados comparados com os obtidos por eletroforese capilar. O complexo dinuclear de cobre(II) [Cu2(HL)(µ-CH3COO)](ClO4), contendo o ligante N,N-[bis-(2-piridilmetil)]-N',N'-[(2-hidroxibenzil)(2-hidroxi-3,5-di-tert-butilbenzil)]-1,3-propanodiamino-2-ol (H3L), foi sintetizado e caracterizado por IV, ¹H RMN e análise elementar. As melhores condições para otimização do sensor biomimético foram estabelecidas por voltametria de onda quadrada. O melhor desempenho desse sensor foi obtido em 75:15:10% (m/m/m) de pó de grafite:nujol:complexo de cobre(II), tampão fosfato 0,05 mol L-1 (pH 7,5) e freqüência, amplitude de potencial, incremento em 30 Hz, 80 mV, 3,3 mV, respectivamente. A curva analítica foi linear na faixa de concentração 4,95 × 10-6 a 3,27 × 10-5 mol L-1 (r=0,9993) com limite de detecção de 2,8 × 10-7 mol L-1. Esse sensor biomimético demonstrou longo tempo de estabilidade (9 meses; 800 determinações) e reprodutibilidade com um desvio padrão relativo de 3,5%. A recuperação da catequina em amostras de chá verde variou de 93,8 a 106,9% e a determinação, comparada com a obtida usando eletroforese capilar, mostrou-se aceitável a um nível de confiança de 95%.

This paper gives an overview of activities carried out at IPEN, Brazil, in the IAEA-sponsored Coordinated Research Project (CRP) “Corrosion of Research Reactor Al-clad Spent Fuel in Water” and in the Latin American regional project on “Management of Spent Research Reactor Fuel”. In both projects Al alloy coupons in various configurations were exposed to the spent fuel storage pool of the IEA-R1 reactor for various times and then examined. Pitting was the main form of corrosion and pit distribution on coupons revealed the marked influence of settled solids. The AA6061 and AA1050 alloy coupons withdrawn after 2 years were stained with a layer of Bayerite caused by an increase in the average pool water temperature. This observation—part of a normal sequence of activities within the project––enabled reactor operations to explain the perplexing change in color of most in-reactor Al alloy components. It exemplified advantages of conducting a corrosion surveillance program. Analysis of sediments obtained from the pool revealed that the main constituents were oxides of aluminum, iron, silicon, and calcium. Coupons of the Russian alloy SZAV, pitted more inside crevices compared to the alloy AA6061. The former pitted more when coupled with stainless steel. Alloy grain orientation also influenced pitting. Coupons of rolled AA6061 alloy pitted more than coupons made from extruded AA6061 alloy. Details about the spent fuel storage facilities in IPEN and the water purification systems of the IEA-R1 research reactor (RR) are also presented.