Adriano R. V. Benvenho

A novel soluble poly(fluorenylenevinylene) conjugated polymer: synthesis, characterization and application to optoelectronic devices

We report the synthesis and characterization of poly(9,9-dioctyl-1,4-fluorenylenevinylene), PDO14FV. This polymer is a novel poly(arylenevinylene) with fluorene units and long chain substituents that ensure solubility in organic solvents. PDO14FV presents green photoluminescence and yellow–green electroluminescence. The estimated ionization potential of PDO14FV is 5.3 eV and its estimated electroaffinity 2.5 eV. Organic light-emitting diodes based on PDO14FV were constructed, showing electroluminescent intensity onset at ca. 6 V.

Pseudo-metal-base transistor with high gain

We use evaporated C60 fullerene as emitter, a conducting polymer blend as base, and Si as collector in a vertical transistor structure similar to a metal-base transistor. The conducting polymer blend used as a base is poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate). The measured common-base current gain of our pseudo-metal-base transistor (p-MBT) is close to 1.0. The p-MBT is straightforward to fabricate and is compatible with conventional Si-based electronics.

Efficient organic light-emitting diodes with fluorine-doped tin-oxide anode and electrochemically synthesized sulfonated polyaniline as hole transport layer

In this work we report efficiency measurements on light-emitting diodes with electrochemically synthesized sulfonated polyaniline as hole transport layer. The anode used in our devices is fluorine-doped tin oxide, the blocking layer is electrochemically synthesized poly(9,9-dioctyl-1,4-fluorenylenevinylene) and the electron transporting material and emitter is tris-(8-hydroxyquinoline) aluminum. Sulfonated polyaniline based devices presented efficiency of 0.79 cd/A.

Study of poly(3-hexylthiophene)/cross-linked poly(vinyl alcohol) as semiconductor/insulator for application in low voltage organic field effect transistors

In this work we study the cross-linked poly(vinyl alcohol)/poly(3-hexylthiophene) interfacial properties of an organic field effect transistor. We use cross-linked poly(vinyl alcohol) prepared with different ammonium dichromate:poly(vinyl alcohol) proportions, ranging from 0% to 35%, as insulator. Using admittance spectroscopy, we show that the interfacial properties change when the ammonium dichromate concentration is altered. The interfacial properties and the better insulation are responsible for the improvement of the device performance in these organic field effect transistors, achieving best performance in the blend with ammonium dichromate:poly(vinyl alcohol) proportion of 0.25:1.

Analytical Methods for Determining Automotive Fuel Composition

Gasoline, a sub-product from the fractional distillation of petroleum, is a mixture of several hundred organic volatile compounds, mainly hydrocarbons, ranged from four to twelve carbon atoms with boiling points in the range of 30 – 225 °C (Fialkov et al., 2008). The physico-chemical properties depend on the origin and method used to obtain the gasoline (Barbeira et al., 2007). It has been used as fuel for internal combustion engine vehicles for over a century, albeit the possibility of producing alternative sustainable fuels was considered long time ago, as can be learnt from Henry Ford’s statement to the New York Times in 1925 (French & Malone, 2005): “There is fuel in every bit of vegetable matter that can be fermented. There’s enough alcohol in one year’s yield of an acre of potatoes to drive the machinery necessary to cultivate the fields for a 100 years.” In the last decades, there has been a growing concern with regard to some important environmental aspects as, for instance, the vehicle-generated greenhouse gas emissions leading to air pollution and the need for renewable fuels due to energy shortage. Ethanol has been considered as an attractive alternative fuel, because it can be obtained from domestic crops, such as sugar cane, corn, sorghum, wheat and potatoes and presents higher octane number and faster combustion speed than gasoline (Yao et al., 2009). Interestingly, ethanol, as automotive fuel, started to be used in Brazil as early as the 1930s (Szklo et al., 2007), but it was only after the two major oil shocks of the 1970s that its consumption became significant either as a gasoline additive or as a gasoline substitute. Currently, several other countries such as the USA, Thailand, China and Sweden are using blends of gasoline and ethanol, to fuel vehicles. Gasohol is gasoline blended with anhydrous ethanol at different percentages expressed by an E-number, which corresponds to the percentage in volume of alcohol present in the fuel (Muncharoen et al., 2009). For instance, E20 contains ethanol at 20% and gasoline at 80%, by volume. In the last decade, flexible-fuel vehicles (FFV), that can use gasoline, gasohol, hydrated ethanol or any mixture of them, became very popular. Currently, in Brazil, more FFV