Mechanical properties and dimensional effects of ZnO- and SnO(2)-based varistors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Doping saturation in dye-sensitized solar cells based on ZnO:Ga nanostructured photoanodes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electron Transport in Dye-Sensitized Solar Cells Based on ZnO Nanotubes: Evidence for Highly Efficient Charge Collection and Exceptionally Rapid Dynamics

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparative electrical behavior at low and high current of SnO(2)- and ZnO-based varistors

The complete I-V characteristics of SnO(2)-based varistors, particularly of the Pianaro system SCNCr consisting in 98.9%SnO(2)+1%CoO+0.05%Nb(2)O(5)+0.05%Cr(2)O(3), all in mol%, have been seldom reported in the literature. A comparative study at low and high currents of the nonohmic behavior of SCNCr- and ZnO-based varistors (modified Matsuoka system) is proposed in this work. The SCNCr system showed higher nonlinearity coefficients in the whole range of measured current. The electrical breakdown field (E(b)) was twice as high for the SCNCr system (5400 V/cm) than for the ZnO varistor (2600 V/cm) due to a smaller average grain size of the former (4.5 mu m) with respect to the latter (8.5 mu m). Nevertheless, we consider that another important factor responsible for the high E(b) in the SCNCr system is the great number of electrically active interfaces (85%) as determined with electrostatic force microscopy (EFM). It was also established that the SCNCr system might be produced in disks of smaller dimensions than that of commercial ZnO-based product, with a 5.0 cm(-1) minimal area-volume (A/V) ratio. The SCNCr reached the saturation current in a short time because of the high resistivity of the grains, which is five times higher than that of the grains in ZnO-based varistors.

ZnO architectures synthesized by a microwave-assisted hydrothermal method and their photoluminescence properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

First Report on Rotenoids as Neurotoxic Principles of Seeds from Aeschynomene indica (Leguminosae)

Toxic principles from seeds of Aeschynomene indica collected in Brazil were analyzed. Dalpanol, 12 alpha-hydroxydalpanol and 11-hydroxydalpanol were identified using (1)H NMR in A. indica for the first time. 11-hydroxydalpanol has not been previously reported in the existing literature. Furthermore these rotenoids are likely the toxic principles that cause neurological signs in mice.

Synthesis and characterization of ZnO and ZnO : Ga films and their application in dye-sensitized solar cells

Highly crystalline ZnO and Ga-modified zinc oxide (ZnO:Ga) nanoparticles containing 1, 3 and 5 atom% of Ga3+ were prepared by precipitation method at low temperature. The films were characterized by XRD, BET, XPS and SEM. No evidence of zinc gallate formation (ZnGa2O4), even in the samples containing 5 atom% of gallium, was detected by XRD. XPS data revealed that Ga is present into the ZnO matrix as Ga3+, according to the characteristic binding energies. The particle size decreased as the gallium level was increased as observed by SEM, which might be related to a faster hydrolysis reaction rate. The smaller particle size provided films with higher porosity and surface area, enabling a higher dye loading. When these films were applied to dye-sensitized solar cells (DSSCs) as photoelectrodes, the device based on ZnO: Ga 5 atom% presented an overall conversion efficiency of 6% (at 10 mW cm(-2)), a three-fold increase compared to the ZnO-based DSSCs under the same conditions. To our knowledge, this is one of the highest efficiencies reported so far for ZnO-based DSSCs. Transient absorption (TAS) study of the photoinduced dynamics of dye-sensitized ZnO:Ga films showed that the higher the gallium content, the higher the amount of dye cation formed, while no significant change on the recombination dynamics was observed. The study indicates that Ga-modification of nanocrystalline ZnO leads to an improvement of photocurrent and overall efficiency in the corresponding device.

Pelletization of seeds of Raphanus sativus L. cv. Redondo Gigante with graphite for germination under water stress conditions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Germination of Jacaranda mimosifolia (D. Don - Bignoniaceae) seeds: effects of light, temperature and water stress

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

An adapted thermal-gradient block for the germination of photoblastic seeds

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)