In this work, we report the synthesis and characterization of new amorphous graphene-like TiO2/chitosan carbon microspheres and its performance as photocatalyst. Four different carbon chitosan microspheres materials were obtained based on the distinctive procedure to incorporate TiO2 and TiOSO4 to chitosan structure by pyrolysis at 600 °C. Detailed characterizations were carried out using many different techniques, as thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), scanning electron miscroscopy/energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), N2 adsorption-desorption, and the obtained materials show an amorphous and a graphene-like structure, which improve the photocatalytic activity. The synthesized materials promoted a fast degradation of three micropollutants under UV-A radiation and, in all cases the degradation rate was approximately 98% at 30 min of reaction, being superior to the P-25 TiO2 efficiency. Due to the amorphous graphene-like structure, all the materials present low adsorption capacity, the high photocatalytic efficiency can be attributed to the material structure that promotes the effective charge separation which reduces the recombination electron/hole, enhancing the photocatalytic efficiency.

Biochar is a rich-carbon material highly functionalized, which allows the use as electrodes modifier for preconcentration and voltammetric determination of several species. This work describes a castor cake biochar production and chemical activation with different reaction conditions using HNO3 and/or H2O2. Biochar samples were characterized using scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, Raman and zeta potential. Carbon paste modified electrodes (CPME) have been constructed using different biochar samples to evaluate the adsorptive capacity for the spontaneous preconcentration and voltammetric determination of Pb2+, Cd2+, Cu2+ and Ni2+ ions, paraquat and methyl parathion pesticides. The activation treatments promoted modifications in the elemental, morphological and structural biochar characteristics. Activated biochar CPMEs showed increase in the current signal around 15 and 2.5 times higher than unmodified and precursor biochar electrode, respectively. N2 sample (HNO3, 60 °C for 3.0 h) presented the better response signals for all compounds. This was attributed to the more effective surface oxidation, promoting a high porosity, acid character and amount of acid functional groups. Besides that, this greater analytical response allows the CPME-N2 application as a passive sampler for the voltammetric determination of inorganic and organic contaminants for environmental management in aqueous matrices.

Rice husk ash (RHA) is a waste material produced in large quantities in many regions worldwide, and its disposal can be problematic. This work describes a method for using RHA to synthesize silicon and potassium slow-release fertilizer. The extraction of silica from RHA was accomplished by alkaline leaching with KOH. Different KOH concentrations and reaction times were evaluated and the best production of K2SiO3 solution was achieved using 6 mol L-1 and 6 h, respectively. The fertilizer was synthesized by the reaction of K2SiO3 with KAlO2 in aqueous medium, followed by calcination at 500 °C. X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses indicated that the fertilizer composition was similar to mineral kalsilite. Solubility essays indicated lower K+ and Si4+ release percentage in neutral medium. Kinetic mechanisms of release tests can be well explained by the pseudo-second order model. The proposed synthesis seems to be a viable process offering economic and environmental benefits.

In Brazil, Gmelina arborea is a common tree to produce char and the content of carbon is an important factor to correlate with the energy content or carbon sequestration capability, whereas Araucaria angustifolia occupies 6 % of its original territory and Brazilian laws protect old native specimens, since the commercial use of wood is restricted for young cultivated specimens. Electron paramagnetic resonance (EPR) spectroscopy is used for detection and quantification of organic free radicals (OFR) and, in this study, it was utilized for exploring OFR content along the rings of one log from G. arborea and A. angustifolia trees, both randomly chosen. The amount of OFR correlated with the carbon content in G. arborea and the age of rings in G. arborea and A. angustifolia. The content of OFR in rings of Gmelina arborea was compared with previous analyses of carbon sequestration in the same tree. Without statistical treatment, an inverse relationship between the carbon and OFR content was found. The concentration of OFR in inner rings (older ages) of A. angustifolia was higher than in outer rings (younger ages). This trend was also observed in G. arborea, suggesting that EPR provides qualitative information about the age. Additionally, a Pleistocene sample of A. angustifolia was analyzed and the content of OFR was one order of magnitude higher than that in the young sample. In conclusion, EPR spectroscopy is proposed as a fast qualitative method to identify the age of wood, especially for confiscated wood loads in protected areas of A. angustifolia and to determine the carbon content in wood.

En Brasil, Gmelina arborea es un árbol para producir carbón y el contenido de carbono es un factor importante correlacionado con el contenido de energía o la capacidad de secuestro de carbono, mientras que la Araucaria angustifolia ocupa el 6 % de su territorio original y las leyes brasileñas protegen los viejos especímenes nativos, ya que el uso comercial de la madera está restringido para ejemplares jóvenes cultivados. La espectroscopia de resonancia paramagnética electrónica (EPR) se usa para la detección y cuantificación de los radicales orgánicos libres (OFR, siglas en inglés) y en este estudio se usó para explorar el contenido de OFR en los anillos de un tronco de árbol de G. arborea y otro de A. angustifolia elegidos al azar. La cantidad de OFR se correlacionó con el contenido de carbono en G. arborea y con la edad de los anillos de G. arborea y A. angustifolia. El contenido de OFR en los anillos de G. arborea se comparó con análisis previos de secuestro de carbono en el mismo árbol. Sin tratamiento estadístico, se encontró una relación inversa entre el contenido de carbono y OFR. La concentración de OFR en los anillos internos (de más edad) de A. angustifolia fue mayor que en los anillos externos (de menor edad). Esta tendencia también se observó en G. arborea, lo que sugiere que EPR proporciona información cualitativa acerca de la edad. Además, se analizó una muestra del Pleistoceno de A. angustifolia y el contenido de OFR fue de una magnitud mayor que en la muestra más joven. En conclusión, la espectroscopia EPR se propone como un método cualitativo rápido para identificar la edad de la madera, especialmente para cargas de madera confiscadas en áreas protegidas de A. angustifolia y para determinar el contenido de carbono en la madera.

The use of probes, such as paramagnetic species diluted in diamagnetic materials in EPR spectroscopy, and mathematical tools such, as the Kubelka-Munk function in DRUV-VIS spectroscopy are strategies in the analysis of complex mixtures of solid materials. The results obtained here show that the solid state reaction between the complex, [VO(acac)(BMIMAPY)] [ClO4], BMIMAPY = [(bis(1-methylimidazole-2-yl)methyl)(2-(pyridyl-2-yl)ethyl) amine] and acac = acetilacetonate, with kaolinite turns possible to obtain anisotropic EPR spectrum of the complex with a reasonable level of resolution. The study by DRUV-VIS using the method of second derivative mode of the Kubelka-Munk function revealed new complex structural arrangements, a solid hitherto unknown.

Este trabalho relata a síntese e a caracterização dos complexos de manganês(II) [MnII(Hbpeten)] e [MnII(Hbnbpeten)], respectivamente [N,N'-bis-(2-hidroxibenzil)-N-(2-piridilmetil)-N'-(2-hidroxietil)etano-1,2-diamine]manganês(II) e [N,N'-bis-(5-nitro-2-hidroxibenzil)-N'-(2-hidroxietil)etano-1,2-diamin]manganês(II), por análise elementar, voltametria cíclica, espectroscopias eletrônica (UV-Vis) e vibracional (FTIR), ressonância magnética nuclear de hidrogênio (¹H NMR) e espectroeletroquímica de ressonância paramagnética eletrônica (EPR). Os dados de espectroeletroquímica de EPR foram consistentes com a redução de um grupo nitro, tanto no H3bnbpeten livre quanto no complexo de manganês. Além disso, os cálculos teóricos foram consistentes com os resultados experimentais, mostrando que somente um grupo nitro contribui para a formação dos orbitais LUMO e sugerindo que os resultados teóricos são adequados para explicar as propriedades eletrônicas dos complexos.

The synthesis and characterization of the manganese(II) complexes [MnII(Hbpeten)] and [MnII(Hbnbpeten)], where H3bpeten and H3bnbpeten are respectively [N,N'-bis-(2-hydroxybenzyl)-N-(2-pyridylmethyl)-N'-(2-hydroxyethyl)ethane-1,2-diamine] and [N,N'-bis-(5-nitro-2-hydroxybenzyl)-N'-(2-hydroxyethyl)ethane-1,2-diamine], are reported. The characterization was carried out by elemental analyses, cyclic voltammetry, spectroscopic methods (UV-Vis, FTIR, ¹H NMR), electronic paramagnetic resonance spectroelectrochemistry (EPR) and theoretical DFT calculations. The electrochemistry and EPR espectroelectrochemistry data were consistent with the reduction of one of the nitro groups in free H3bnbpeten and in the respective manganese(II) complex. These results were supported by DFT calculations, which showed that only one nitro group contributes to the LUMO. The theoretical data appear to be suitable to describe the electronic properties of the compounds.

Cálculos teóricos utilizando os funcionais B3LYP e PBE1PBE e as bases 6-31G(d) e 6-311+G(2d,p) para o sistema 3-(2-fenil-hidrazona)-naftaleno-1,2,4-triona, em solução (dmso) e em fase gasosa, evidenciaram, em ambos os casos, a maior estabilidade da forma ceto-hidrazona (rotâmeros Ia e Ib) comparada às formas enol-azo (rotâmeros IIa/IIb, por volta de 14 kcal mol-1) e III (aproximadamente 6 kcal mol-1). A natureza do substituinte no grupo fenil não influenciou a estabilidade relativa dos tautômeros. Estes resultados foram confirmados por dados espectroscópicos dos derivados HL1-HL13, sintetizados a partir da 2-hidroxi-1,4-naftoquinona e arilaminas (R = 4-OMe, 4-N2-C6H5, 4-Cl, 4-I, 3-I, 2-I, 4-COOH, 3-COOH, 4-CN, 3-CN, 4-NO2, 3-NO2, 2-NO2). A avaliação da atividade anticâncer in vitro (contra linhagens de células cancerosas SF-295, HCT-8, MDAMB-435 e HL-60) e bactericida (Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia e Pseudomonas aeruginosa) dos compostos HL1-HL13 e dos seus respectivos complexos de cobre(II), [Cu(L1-13)2], foi avaliada. Em geral a atividade bactericida foi baixa, exceto para o derivado HL5 (R = 3-I), mais ativo do que o controle; entretanto, seu complexo não foi ativo. Por outro lado, a complexação levou, em geral, ao aumento da atividade antitumoral dos pré-ligantes. O complexo [Cu(L13)2] (R = 3-NO2) apresentou moderada citotoxicidade contra leucemia humana (HL-60).

DFT calculations using the B3LYP and PBE1PBE functionals with the standard 6-31G(d) and 6-311+G(2d,p) basis sets were carried out for the 3-(2-phenylhydrazone)-naphthalene-1,2,4-trione system in solution (dmso) and in the gas phase, and showed the keto-hydrazone forms (rotamers Ia and Ib) to be more stable than the enol-azo forms (rotamers IIa and IIb, by about 14 kcal mol-1) and III (by approximately 6 kcal mol-1), independently of the nature of the substituent in the phenylene ring. These results were confirmed by spectroscopic data on the derivatives HL1-HL13, obtained from 2-hydroxy-1,4-naphthoquinone and arylamines (R = 4-OMe, 4-N2-C6H5, 4-Cl, 4-I, 3-I, 2-I, 4-COOH, 3-COOH, 4-CN, 3-CN, 4-NO2, 3-NO2, 2-NO2). The in vitro antitumor (against SF-295, HCT-8, MDAMB-435 and HL-60 cancer cell lines) and antibacterial activities (Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa) of compounds HL1-HL13 and of their respective copper(II) complexes, [Cu(L1-13)2], were tested. In general, these compounds exhibited low antibacterial activity, except for HL5 (R = 3-I), more active than the control; however, the corresponding complex was inactive. In contrast, increased cytotoxicity was observed upon complexation. Complex [Cu(L13)2] (R = 3-NO2) presented moderate cytotoxicity against human leukemia (HL-60).

Dois ligantes tridentados, HL1, [(2-hidroxibenzil)(2-(imidazol-2-il)etil)]amina, e HL2, [(2-hidroxibenzil)(2-(piridil-2-il)etil]amina, foram usados na síntese dos complexos binucleares [Cu2(L1)2]Cl2•2H2O, complexo 1, e [Cu2(L2)2](ClO4)2•1.5H2O, complexo 2,para serem empregados como catalisadores em processos de oxidação. Os complexos foram caracterizados por análise elementar e espectroscopias na região do infravermelho, ultravioleta-visível e ressonância paramagnética eletrônica. Foram também estudados por voltametria cíclica e titulação potenciométrica, a fim de caracterizar seus comportamentos em solução. A resolução da estrutura cristalina do complexo 1 mostrou um cátion binuclear contendo dois grupos fenóxido em ponte. Este arranjo possui uma distância Cu...Cu de 3.043(10) Å, similar à observada na catecol oxidase (2.90 Å). Os comportamentos catalíticos destes complexos foram investigados nas oxidações de cicloexano e de catecol. Na oxidação de cicloexano observou-se baixa atividade para ambos os complexos, que pode ser atribuída ao estereoimpedimento produzido pela falta de coplanaridade entre os anéis aromáticos do arcabouço dos ligantes, sugerindo que a aproximação entre o substrato e o centro ativo binuclear é uma etapa determinante no mecanismo da reação. Com relação à atividade de catecolase, foram observadas altas eficiências, com o complexo 2 sendo mais ativo que o complexo 1. Isto indica que o ligante piridina é capaz de estabilizar melhor o intermediário proposto para esse processo, que contém o centro CuI CuI. Isto é corroborado pela grande participação da piridina no LUMO (lowest unoccupied molecular orbital) do complexo 2, que pode ajudar a acomodar a carga negativa adicional quando o complexo é reduzido da forma CuII CuII para CuI CuI.

The tridentate ligands HL1, [(2-hydroxybenzyl)(2-(imidazol-2-yl)ethyl)]amine, and HL2, [(2-hydroxybenzyl)(2-(pyridil-2-yl)ethyl]amine, were used to synthesize binuclear CuII complexes, [Cu2(L1)2]Cl2•2H2O, complex 1, and [Cu2(L2)2](ClO4)2•1.5H2O, complex 2, in order to obtain catalysts for oxidative processes. Both complexes were characterized by elemental analysis, IR, UV-Vis and EPR spectroscopies. In addition, they were studied by cyclic voltammetry and potentiometric titration in order to investigate their behavior in solution. The crystal structure of complex 1 revealed a binuclear cation where the metal centers are bridged by two phenoxo groups. This arrangement provides a Cu...Cu distance of 3.043(10) Å, which is similar to the observed for catechol oxidase (2.90 Å). The catalytic reactivities of both complexes were investigated for hydrocarbon and catechol oxidations. Complexes 1 and 2 led to low overall hydrocarbon oxidation conversion values of 6.34 % and 7.15 %, respectively. However, for complex 1, only cyclohexanol (Cy-OH) and cyclohexanone (Cy=O) were isolated as reaction products, with selectivities of 68.1% for Cy-OH. This low overall conversion is tentatively attributed to steric hindrance effects produced by the non-coplanar aromatic rings of the ligand scaffolds, which suggest that the access of the hydrocarbon molecule to the binuclear active center is a determinant step in the reaction mechanism. Investigation of catecholase activities has shown high efficiencies, with complex 2 being more active than complex 1. It indicates that the pyridine-containing ligand is able to stabilize the intermediate CuI CuI center which is proposed to be formed in this process. This is corroborated by the strong participation of pyridine in the LUMO (lowest unoccupied molecular orbital) of complex 2, which can help to accommodate the additional negative charge when the complex is reduced from CuII CuII to CuI CuI.

In this review is presented an innovative technology for use of animal and vegetable waste with high pollution levels in microbial fuel cell (MFC) as an alternative to waste remediation and simultaneously producing electricity and fertilizer for agriculture. A brief history of MFC, the studies about the electron transfer mechanisms, discussion of the biological nanowires in bacteria and the use of chemical mediators or carriers of electrons are explained. The factors influencing the performance of MFCs, the application in waste and sewage treatment and power generation are also discussed.

O objetivo deste estudo foi o de monitorar o nível de poluição de sedimentos subaquáticos de florestas de mangue utilizando espectroscopias de ressonância paramagnética eletrônica (EPR) e de infravermelho próximo (NIR) e análises químicas. A espectroscopia de EPR foi útil para determinar a presença de radicais livres orgânicos de semiquinonas, bem como, fornecer informações sobre a presença de ferro trivalente em domínios diluídos e concentrados nos espectros das amostras. Concluiu-se que, o uso de EPR e NIR, no intervalo espectral adequado, tornou possível avaliar, de forma não destrutiva, o nível de poluição ambiental em sedimentos subaquáticos costeiros de florestas de mangue. Assim, em um período relativamente curto e imprescindível, as autoridades podem tomar as decisões necessárias a fim de evitar danos ambientais.

The objective of this study was the monitoring of the pollution level of underwater mangrove sediments using electron paramagnetic resonance (EPR), near-infrared (NIR) spectroscopy and chemical analyses. EPR spectroscopy was useful to determine the presence of organic free radical semiquinone, as well as, to provide information about the presence of trivalent iron in diluted and concentrated or clustered dominion in the sediment samples spectra. It was concluded that by using EPR and NIR spectroscopy measurement, in the appropriate spectral range, it was possible to nondestructively assess the environmental pollution level of coastline underwater mangrove sediments. Though, in a relatively small period of time, the authorities can take the necessary decisions to avoid environmental damages.

Neste trabalho faz-se a divulgação do potencial de carvões e resíduos orgânicos parcialmente carbonizados visando obter materiais que mimetizam a matéria orgânica do solo das Terras Pretas de Índio da Amazônia, e que sirvam como condicionadores de solo e seqüestrem carbono de forma recalcitrante e reativa. Pesquisas desenvolvidas por grupos brasileiros e estrangeiros têm contribuído para o entendimento do surgimento e utilização das Terras Pretas de Índio da Amazônia. Aqui são divulgados resultados de estudos químicos no sentido do desenvolvimento do conhecimento científico e tecnológico e de inovação no aproveitamento de subprodutos orgânicos, principalmente de indústrias de biocombustíveis, carvão vegetal metalúrgico e outros, buscando imitar a excelente performance da chamada Terras Pretas de Índio da Amazônia.

The potential of charcoal and of partially combusted organic waste to mimic the soil organic matter of the Terras Pretas de Índios (Amazonian Dark Earths) from the Amazon Region is discussed. These materials serve as soil conditioners and as sequesterers of carbon in recalcitrant and in reactive forms. Studies carried out by Brazilian and by international groups have contributed to the emergence of an awareness of the compositions and of the uses of these materials. In this contribution we report on chemical studies that are leading to the development of a scientific and technological awareness, and of innovations that will have value in finding novel uses in applications to soil of chars from organic wastes such as those from the biofuel industry, and from metallurgical and various coal plant residues.

This paper presents some aspects involved in the internationalization of SBQ. The importance of journals, meetings and agreements in this process is discussed.

A estrutura dos sítios metálicos na rede de CuI2SO3.CdII SO3.2H2O foi avaliada pela técnica de ressonância paramagnética eletrônica (EPR), empregando o íon paramagnético CuII como íon sonda. Essa metodologia foi capaz de distinguir os sítios de complexação dos íons M I e M II na estrutura de CuI2SO3.CdII SO3.2H2O. Os resultados indicam que CuI2SO3.CdII SO3.2H2O é dopado com íons CuII nas duas posições dos íons metálicos. Os valores baixos da razão g<FONT FACE=Symbol>||</FONT>/A<FONT FACE=Symbol>||</FONT> para o íon sonda no sítio octaédrico resultam da interação do cobre com átomos de oxigênio em ambiente tetragonal distorcido com alongamento da molécula na direção z. A baixa constante de acoplamento hiperfino A33 é explicada considerando a mistura dos orbitais d x² -y² e d z² e uma estrutura quase piramidal trigonal para o outro sítio.

An evaluation was made of the presence of paramagnetic ions in the host lattice of CuI2SO3.CdII SO3.2H2O by the electron paramagnetic resonance (EPR) technique, using copper(II) ions as paramagnetic probes. The existing M I and M II complexation sites in the double sufite structure were successfully differentiated. The results indicate that the CuI2SO3.CdII SO3.2H2O structure was doped with CuII ions in the two metal ion substitutional positions. The low g<FONT FACE=Symbol>||</FONT>/A<FONT FACE=Symbol>||</FONT> ratio for the CuII probe in the distorted octahedral site resulted from the interaction of copper ions with oxygen donor atoms in a distorted tetragonal environment, with elongation of the molecule in the z direction. The very low value of the A33 hyperfine coupling constant was explained considering the admixture of the d x² -y² and d z² orbitals and the almost trigonal pyramidal structure of the other site.

Três complexos inéditos do tipo [Cu(HL)Cl2] foram obtidos com N(4)-orto (H2Bz4oT, HL1), N(4)-meta (H2Bz4mT, HL2) e N(4)-para-toluil-2-benzoilpiridina tiossemicarbazona (H2Bz4pT, HL3), nos quais a tiossemicarbazona coordena-se ao metal por meio do sistema quelante Npy-N-S. H2Bz4pT (HL3) cristaliza-se no grupo espacial P1, a = 9,509(3) Å, b = 9,807(4) Å, c = 11,564(4) Å; alfa = 100,76(2)°, beta = 105,99(2)°, gama = 114,59(2)°. Tanto as tiossemicarbazonas quanto seus complexos de cobre(II) apresentaram atividade antifúngica pronunciada contra Candida albicans, com valores baixos de concentração inibitória mínima (CIM), entre 8 e 0,3 µg mL-1 (23 a 0,7 µmol L-1) para as tiossemicarbazonas e entre 1 e 0,1 µg mL-1 (2 a 0,3 µmol L-1) para os complexos. Nossos resultados sugerem que a coordenação ao cobre constitui estratégia interessante de redução da dose necessária à atividade.

Three new copper complexes of general formula [Cu(HL)Cl2] have been obtained with N(4)-ortho (H2Bz4oT, HL1), N(4)-meta (H2Bz4mT, HL2) and N(4)-para-tolyl-2-benzoylpyridine thiosemicarbazone (H2Bz4pT, HL3), in which the thiosemicarbazone attaches to the metal through the Npy-N-S chelating system. H2Bz4pT (HL3) crystallizes in the P1 space group, with a = 9.509(3) Å, b = 9.807(4) Å, c = 11.564(4) Å; alpha = 100.76(2)°, beta = 105.99(2)°, gamma = 114.59(2)°. The thiosemicarbazones and their copper(II) complexes exhibit high antifungal activities against Candida albicans with low values of minimum inhibitory concentration (MIC), in the 8-0.3 µg mL-1 (23 - 0.7 µmol L-1) range for the free bases and in the 1-0.1 µg mL-1 (2 - 0.3 µmol L-1) range for the complexes. Our results suggest that coordination to copper(II) could be an interesting strategy for dose reduction.