Prediction of band edge potentials and reaction products in photocatalytic copper and iron sulfides.

The prediction of band edge potentials in photocatalytic materials is an important but challenging task. In contrast, bandgaps can be easily determined through absorption spectra. Here, we present two simple theoretical approaches for the determination of band edge potentials which are based on the electron negativity and work function of each constituent atom. We use these approaches to determine band edge potentials in semiconducting metallic oxides and sulfides, such as titanium dioxide (TiO2), chalcopyrite (CuFeS2), pyrite (FeS2), covellite (CuS), and chalcocite (Cu2S) with respect to an absolute scale (eV) and an electrochemical scale (V). Until now, there is little information on iron and copper sulfides referring to these thermodynamic parameters. TiO2 (Titania p25) was used as reference semiconductor to validate the calculation procedures using experimental values by X-ray diffraction analysis (XRD), diffuse reflectance spectrometry (DRS), and electron paramagnetic resonance spectroscopy (EPR). The production of key chemical species such as reactive oxygen species (ROS) and reactive sulfur species (RSS) has been theoretically and experimentally determined by EPR.

Covalently Bonded Chitosan on Graphene Oxide via Redox Reaction.

Carbon nanostructures have played an important role in creating a new field of materials based on carbon. Chemical modification of carbon nanostructures through grafting has been a successful step to improve dispersion and compatibility in solvents, with biomolecules and polymers to form nanocomposites. In this sense carbohydrates such as chitosan are extremely valuable because their functional groups play an important role in diversifying the applications of carbon nanomaterials. This paper reports the covalent attachment of chitosan onto graphene oxide, taking advantage of this carbohydrate at the nanometric level. Grafting is an innovative route to modify properties of graphene, a two-dimensional nanometric arrangement, which is one of the most novel and promising nanostructures. Chitosan grafting was achieved by redox reaction using different temperature conditions that impact on the morphology and features of graphene oxide sheets. Transmission Electron Microscopy, Fourier Transform Infrared, Raman and Energy Dispersive spectroscopies were used to study the surface of chitosan-grafted-graphene oxide. Results show a successful modification indicated by the functional groups found in the grafted material. Dispersions of chitosan-grafted-graphene oxide samples in water and hexane revealed different behavior due to the chemical groups attached to the graphene oxide sheet.

Resíduos de azevém na superfície de um Planossolo alagado e seus efeitos na concentração de nutrientes na solução do solo e em plantas de arroz / Ryegrass residues on soil surface of a flooded Albaqualf soil and their effects on nutrients concentration in soil solution and rice plants

A incorporação de resíduos de culturas ao solo em lavouras de arroz irrigado tem o potencial de melhorar as características físicas, químicas e biológicas do solo e acelerar as reações de oxirredução durante o alagamento, proporcionando maior disponibilidade de nutrientes para as plantas, que respondem com maior crescimento e maior absorção de nutrientes. Com o objetivo de determinar a concentração de nutrientes na solução do solo e quantificar a absorção de nutrientes e o crescimento de plantas de arroz submetidas a quantidades crescentes de resíduos de azevém aplicadas na superfície do solo, foi conduzido um experimento em casa de vegetação. O experimento foi delineado em blocos ao acaso, com três repetições, sendo utilizadas como tratamentos doses de resíduos de azevém (0,0; 1,25; 2,5; 5,0; 7,5 e 10,0Mg ha-1) aplicadas na superfície de um Planossolo. Sementes de arroz pré-germinadas da cultivar 'BRS 7 Taim' foram semeadas na superfície do solo, que foi alagado 15 dias após, e as plantas foram cultivadas por um período de 45 dias. Nas plantas de arroz, foram avaliados a massa seca da parte aérea e os teores dos nutrientes: N, K, P, Ca, Mg, Fe, Mn, Cu e Zn. Na solução do solo, foram avaliados o potencial redox (Eh), o pH e as concentrações de Mn, Fe, K, Ca e Mg. Os resultados mostraram que a adição de doses crescentes de resíduos de azevém na superfície do solo alagado, até a dose máxima de 10Mg ha-1, intensificou o processo de oxirredução do solo, aumentando a concentração de Mn, Fe, Ca, Mg e K na solução do solo, aumentou os teores de K e Fe na parte aérea das plantas de arroz e aumentou a massa seca de arroz.

The incorporation of ryegrass residues on the soil in rice irrigated fields can improve the physical, chemical and biological soil properties. It can also accelerate the redox reaction during the soil flooding, allowing a higher availability of nutrients to the plants, which responds with a higher growing and nutrient absorptions. The objectives of this research are to quantify the nutrient absorptions, the rice crop growing, and to determine the concentration of nutrients in the soil solution on a flooding Albaqualf soil. For this, increasing doses of ryegrass residues were applied in the soil surface. A greenhouse experiment was carried out using a randomized complete block design with six doses of ryegrass residues (0.0; 1.25; 2.5; 5.0; 7.5 and 10.0Mg ha-1) applied to the soil surface. Cultivar 'BRS 7 Taim' pre-germinated seeds were sown in plastic pots. The soil in the pots was flooded 15 days after this procedure and plants were hept in this condition for an additional 45 days. In the rice plants were evaluated the dry matter weight of the shoots and the following nutrients: N, K, P, Ca, Mg, Fe, Mn, Cu and Zn. In the soil solution were evaluated the redox potential (Eh), pH, and the concentration of Mn, Fe, K, Ca, Mg. Results show that the addition of increasing doses of ryegrass residues in the flooded soil surface until 10Mg ha-1 strengthened the soil redox reaction process increasing the concentration of Mn, Fe, Ca, Mg and K in the soil solution. It also increased the K and Fe contents in the aerial part of rice plants as well increased their dry matter weight.

Resíduos de azevém na superfície de um Planossolo alagado e seus efeitos na concentração de nutrientes na solução do solo e em plantas de arroz

The incorporation of ryegrass residues on the soil in rice irrigated fields can improve the physical, chemical and biological soil properties. It can also accelerate the redox reaction during the soil flooding, allowing a higher availability of nutrients to the plants, which responds with a higher growing and nutrient absorptions. The objectives of this research are to quantify the nutrient absorptions, the rice crop growing, and to determine the concentration of nutrients in the soil solution on a flooding Albaqualf soil. For this, increasing doses of ryegrass residues were applied in the soil surface. A greenhouse experiment was carried out using a randomized complete block design with six doses of ryegrass residues (0.0; 1.25; 2.5; 5.0; 7.5 and 10.0Mg ha-1) applied to the soil surface. Cultivar 'BRS 7 Taim' pre-germinated seeds were sown in plastic pots. The soil in the pots was flooded 15 days after this procedure and plants were hept in this condition for an additional 45 days. In the rice plants were evaluated the dry matter weight of the shoots and the following nutrients: N, K, P, Ca, Mg, Fe, Mn, Cu and Zn. In the soil solution were evaluated the redox potential (Eh), pH, and the concentration of Mn, Fe, K, Ca, Mg. Results show that the addition of increasing doses of ryegrass residues in the flooded soil surface until 10Mg ha-1 strengthened the soil redox reaction process increasing the concentration of Mn, Fe, Ca, Mg and K in the soil solution. It also increased the K and Fe contents in the aerial part of rice plants as well increased their dry matter weight.

A incorporação de resíduos de culturas ao solo em lavouras de arroz irrigado tem o potencial de melhorar as características físicas, químicas e biológicas do solo e acelerar as reações de oxirredução durante o alagamento, proporcionando maior disponibilidade de nutrientes para as plantas, que respondem com maior crescimento e maior absorção de nutrientes. Com o objetivo de determinar a concentração de nutrientes na solução do solo e quantificar a absorção de nutrientes e o crescimento de plantas de arroz submetidas a quantidades crescentes de resíduos de azevém aplicadas na superfície do solo, foi conduzido um experimento em casa de vegetação. O experimento foi delineado em blocos ao acaso, com três repetições, sendo utilizadas como tratamentos doses de resíduos de azevém (0,0; 1,25; 2,5; 5,0; 7,5 e 10,0Mg ha-1) aplicadas na superfície de um Planossolo. Sementes de arroz pré-germinadas da cultivar 'BRS 7 Taim' foram semeadas na superfície do solo, que foi alagado 15 dias após, e as plantas foram cultivadas por um período de 45 dias. Nas plantas de arroz, foram avaliados a massa seca da parte aérea e os teores dos nutrientes: N, K, P, Ca, Mg, Fe, Mn, Cu e Zn. Na solução do solo, foram avaliados o potencial redox (Eh), o pH e as concentrações de Mn, Fe, K, Ca e Mg. Os resultados mostraram que a adição de doses crescentes de resíduos de azevém na superfície do solo alagado, até a dose máxima de 10Mg ha-1, intensificou o processo de oxirredução do solo, aumentando a concentração de Mn, Fe, Ca, Mg e K na solução do solo, aumentou os teores de K e Fe na parte aérea das plantas de arroz e aumentou a massa seca de arroz.

Resíduos de azevém na superfície de um Planossolo alagado e seus efeitos na concentração de nutrientes na solução do solo e em plantas de arroz

The incorporation of ryegrass residues on the soil in rice irrigated fields can improve the physical, chemical and biological soil properties. It can also accelerate the redox reaction during the soil flooding, allowing a higher availability of nutrients to the plants, which responds with a higher growing and nutrient absorptions. The objectives of this research are to quantify the nutrient absorptions, the rice crop growing, and to determine the concentration of nutrients in the soil solution on a flooding Albaqualf soil. For this, increasing doses of ryegrass residues were applied in the soil surface. A greenhouse experiment was carried out using a randomized complete block design with six doses of ryegrass residues (0.0; 1.25; 2.5; 5.0; 7.5 and 10.0Mg ha-1) applied to the soil surface. Cultivar 'BRS 7 Taim' pre-germinated seeds were sown in plastic pots. The soil in the pots was flooded 15 days after this procedure and plants were hept in this condition for an additional 45 days. In the rice plants were evaluated the dry matter weight of the shoots and the following nutrients: N, K, P, Ca, Mg, Fe, Mn, Cu and Zn. In the soil solution were evaluated the redox potential (Eh), pH, and the concentration of Mn, Fe, K, Ca, Mg. Results show that the addition of increasing doses of ryegrass residues in the flooded soil surface until 10Mg ha-1 strengthened the soil redox reaction process increasing the concentration of Mn, Fe, Ca, Mg and K in the soil solution. It also increased the K and Fe contents in the aerial part of rice plants as well increased their dry matter weight.

A incorporação de resíduos de culturas ao solo em lavouras de arroz irrigado tem o potencial de melhorar as características físicas, químicas e biológicas do solo e acelerar as reações de oxirredução durante o alagamento, proporcionando maior disponibilidade de nutrientes para as plantas, que respondem com maior crescimento e maior absorção de nutrientes. Com o objetivo de determinar a concentração de nutrientes na solução do solo e quantificar a absorção de nutrientes e o crescimento de plantas de arroz submetidas a quantidades crescentes de resíduos de azevém aplicadas na superfície do solo, foi conduzido um experimento em casa de vegetação. O experimento foi delineado em blocos ao acaso, com três repetições, sendo utilizadas como tratamentos doses de resíduos de azevém (0,0; 1,25; 2,5; 5,0; 7,5 e 10,0Mg ha-1) aplicadas na superfície de um Planossolo. Sementes de arroz pré-germinadas da cultivar 'BRS 7 Taim' foram semeadas na superfície do solo, que foi alagado 15 dias após, e as plantas foram cultivadas por um período de 45 dias. Nas plantas de arroz, foram avaliados a massa seca da parte aérea e os teores dos nutrientes: N, K, P, Ca, Mg, Fe, Mn, Cu e Zn. Na solução do solo, foram avaliados o potencial redox (Eh), o pH e as concentrações de Mn, Fe, K, Ca e Mg. Os resultados mostraram que a adição de doses crescentes de resíduos de azevém na superfície do solo alagado, até a dose máxima de 10Mg ha-1, intensificou o processo de oxirredução do solo, aumentando a concentração de Mn, Fe, Ca, Mg e K na solução do solo, aumentou os teores de K e Fe na parte aérea das plantas de arroz e aumentou a massa seca de arroz.