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This paper reports citrate-stabilized silver nanoparticles (AgNPs) synthesized by nitrate ion chemical reduction with sodium borohydride, at different pHs (2–9). The AgNPs synthesized by this method exhibited size distribution from 5 to 249 nm, depending on pH, as determined by dynamic light scattering, and morphology spherical, as determined by transmission electron microscopy. In pH range 3–7 occurred aggregation of the nanoparticles. The size distribution depending on pH was determined by dynamic light scattering. The zeta potential was determined, and the colloidal stability was correlated with nanoparticles aggregation at different pHs. The size-dependent antimicrobial activity was evaluated for two solutions, wherein both samples exhibited antimicrobial activity, although the smallest AgNPs without agglomeration have enhanced antimicrobial properties.

Many essential oils and monoterpenes are used therapeutically as relaxing drugs and tranquilizers. In this study, ten structurally related monoterpene alcohols, present in many essential oils, were evaluated in mice to investigate their pharmacological potential in the central nervous system. Isopulegol (1), neoisopulegol (2), (ð)-isopinocampheol (3), (Ð)-myrtenol (4), (Ð)-cis-myrtanol (5), (+)-p-menth-1-en-9-ol (6) and (ð)-neomenthol (8) exhibited a depressant effect in the pentobarbital-induced sleep test, indicating a sedative property. (Ð)-Menthol (7), (+)-dihydrocarveol (9), and (ð)-isoborneol (10) were ineffective in this test. The results show that these psychoactive monoterpenes have the profile of sedative drugs, and this pharmacological effect is influenced by the structural characteristics of the molecules.

Recebido em 31/01/2017; aceito em 7/8/2017; publicado na web em 02/10/2017 PEROVSKITES SOLAR CELLS: A NEW EMERGING TECHNOLOGY. Solar energy has been considered as an important source of clean and safe energy to overcome the problems associate to the burn of fossil fuels (e.g. climate changes, pollution, health problems, etc.). In the area of photovoltaics, devices that convert solar energy into electricity, perovskites solar cells (PSC) have attracted great attention due to their rapid development, high energy conversion efficiency, diversification of the processing methods and different materials. The fantastic properties of the hybrid perovskite materials, such as high absorption coefficient, direct and tunable bandgap, ambipolar charge carrier, simple preparation, etc., have quoted this technology as one the most important in this century. The rapid development of PSC has provided a significant increase in energy conversion efficiency, which was first reported, in 2009, as 3.8% and now reaches up to 22.10%, according to the National Laboratory of Renewable Energy (NREL). Many studies have been carried out to further increase the efficiency of devices and solve problems as the instability of the material, and the presence of lead, so that the PSC can be applied commercially. This paper presents a review on PSC and the major advances reported in device's architecture, preparation methods, novel materials and interface engineering.Keywords: solar cell; perovskites; perovskites solar cells. INTRODUÇÃOHá muitos anos a humanidade tem feito uso de combustíveis fósseis para satisfazer grande parte da demanda de energia. Porém, com a diminuição progressiva das reservas de combustíveis fósseis, deterioração do meio ambiente (devido ao efeito estufa), poluição do ar e água e, consequentemente, com os problemas de saúde humana associados ao aquecimento global, além das questões econômicas e políticas relacionadas à saúde e preservação do meio ambiente, o desenvolvimento de fontes alternativas de energia tem se tornado cada vez mais importante.1,2 Tendo em vista essas preocupações, a energia solar fotovoltaica pode ser considerada umas das fontes de energia alternativa mais promissora, pois provém de uma fonte abundante, limpa e segura, não gera ruídos e ainda permite a geração de energia elétrica em áreas remotas. 3A energia solar é, de uma forma ou de outra, a fonte de quase toda a energia na Terra.4 O sol fornece ao nosso planeta cerca de 10.000 vezes mais energia que o nosso consumo diário global. A energia solar pode ser convertida em calor, o qual pode ser utilizado diretamente para o abastecimento de água quente, ou em eletricidade, através do efeito fotovoltaico, nas células solares. 5,6 A constituição básica de uma célula solar é baseada em duas camadas de semicondutores (junção), sendo uma camada contendo carga positiva (p) e outra contendo carga negativa (n), que geram corrente elétrica quando expostas à radiação solar.7 Atualmente, as células solares são classificadas em três tipos, a saber: Células Solares de...

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Natural polymers are a very interesting matrix to obtain solid polymeric electrolytes (SPE). The principal advantage comes from their particularly interesting biodegradation properties due to the natural origin and also very low cost and good physical and chemical properties. These polymers contain heteroatoms in their structure and for this reason can interact with protons or lithium ions leading to the ionic conduction. Among different natural polymers, starch-based SPEs show good opto-electrochemical characteristics and can be applied to electrochemical devices. This work presents the results of starch and starch derivatives-based electrolytes, which were characterized by impedance spectroscopy and thermal analysis. The ionic conductivity results obtained for these SPEs varied from 10 À6 S=cm to 10 À4 S=cm at room temperature, depending on the sample, and increased following Arrhenius model. The samples showed good stability up to 200 C evidenced by thermal analysis (TGA). Good conductivity results combined with transparency and good adhesion to the electrodes have shown that starchbased SPEs are very promising materials to be used as solid electrolytes in electrochromic devices.

Organo-selenium compounds are already known for their anti-cancer activity, being effective against several kind of tumours. 1,2) These compounds also present other pharmacological properties such as antibacterial, antiviral, anti-fungal, anti-parasitic, antihistamine and anti-inflammatory effects. [3][4][5] Other properties include central nervous system inhibition, anaesthetic, hypnotic, tranquilliser and analgesic activities. 5-7)These facts led us to verify in mice the antinociceptive potential of 2-phenylselenenyl-1,8-cineole (PSC), 8,9) an intermediate obtained in our terpene total synthesis studies.10) To our knowledge this is the first study describing the analgesic effects of PSC. MATERIALS AND METHODS ChemicalCompound PSC was prepared in our laboratory as already described, 8) and dissolved in 5% Tween 20 as an emulsion.Animals Male Swiss mice (26-36 g; 6-8 weeks old) were obtained from the Biology Dept. of this University. The animals were maintained at constant room temperature (23Ϯ1°C) and on a 12/12 h light-dark cycle (light from 7:00 to 19:00 h), with free access to food and water and for a minimum of 7 d before performing the experiments. All behavioural observations were conducted between 13:00 and 19:00 h.Statistical Statistical analysis was performed by means of variance analysis followed by Student's t-test or Dunnet's test. A probability level of 0.01 or 0.05 was accepted as significant.Acute Toxicity and Behavioural Effects The toxicity study was performed with different doses of PSC to groups of mice (nϭ10) administered intraperitoneal (i.p.), and mortality was recorded for 72 h for the determination of LD50. 11)According to the method of Irwin, 12) the behaviour of the mice was observed at 1 and 2 h after i.p. injection of PSC.Pentobarbital-Induced Sleeping Time Sodium pentobarbital at a hypnotic dose of 50 mg/kg was injected i.p. to 2 groups (nϭ10) of mice 60 min after pre-treatment with 0.9% saline (control) and PSC (30 mg/kg) i.p., respectively. The duration of sleep time (loss and recovery of the righting reflex) was recorded. 13)Tail Immersion Method The tail (up to 5 cm) of the mice were dipped into a beaker containing water kept at 50°C. The time for the mice to remove its tail from the hot water was recorded and a maximum 60 s cut-off was used. The mice were divided into 3 groups (nϭ10). Saline 0.9% (control), PSC (30 mg/kg) and morphine (6 mg/kg) were administered i.p. Readings were taken at 60, 120, 180 and 240 min after drug injection. 14)Acetic Acid Induced Writhing The mice were divided into 6 groups (nϭ10) and pre-treated with saline 0.9% (control). PSC (15, 30, 60 mg/kg), 1,8-cineole (150 mg/kg) and morphine (6 mg/kg) were administered i.p. After 60 min an acetic acid solution (0.6%; 0.1 ml/10 g) was i.p. injected. After a further 5 min, the number of constrictions was recorded for 5 min. 15) RESULTS AND DISCUSSIONIn this work, the effects of PSC were evaluated for central pharmacological activity. PSC did not induce mortality up to a dose of 120 mg/kg in mice. On the basis...