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Nanocomposite thin films of poly(lactic acid) (PLA) were produced incorporating small amounts (0.2 to 1 wt%) of graphene oxide (GO) and graphene nanoplatelets (GNP). The films were prepared by solvent‐casting. Mechanical properties were evaluated for plasticized (by residual solvent) and unplasticized films. Plasticized nanocomposite films presented yield strength and Young's modulus about 100% higher than those of pristine PLA. For unplasticized films improvements in tensile strength and Young's modulus were about 15 and 85%, respectively. For both film types, a maximum in mechanical performance was identified for about 0.4 wt% loadings of the two filler materials tested. Permeabilities towards oxygen and nitrogen decreased, respectively, three‐ and fourfold in films loaded with both GO or GNP. The glass transition temperature showed maximum increases, in relation to unloaded PLA films, of 5 °C for 0.4 wt% GO and 7 °C for 0.4 wt% GNP, coinciding with the observed maxima in mechanical properties. Copyright © 2012 Society of Chemical Industry

This review describes the main features of dye-sensitized solar cells (DSCs) and highlights recent breakthroughs in this promising thin-film photovoltaic (PV) technology. After a brief presentation of the commercially available technologies, the general operation principles and the most relevant characteristics of DSCs are summarized. Recent major advances in high efficiency sensitizers, nanostructured semiconductors and robust electrolytes offer an opportunity for DSCs integration into the marketplace. With attractive features, like low-cost potential, simple processing, wide range of applicability -from low-power electronics to semi-transparent windowpanes for electricity generation -and good performance under typical operating conditions, these cells are one step from large-scale commercialization. We describe major strategies that are under way to make DSCs a key technology in the future PV paradigm. PV and DSC position in the global energy marketNow, more than ever before, energy is what makes our world continuously work. World energy consumption is ca. 4.7 Â 10 20 J (450 quadrillion Btu) and is expected to grow about 2% each year for the next 25 years.1 Earth's resources upon which the world economy has sustained its grown are finite and governments are increasingly aware of this, particularly now that peak oil is on a near future.2 In order to maintain social and economic development, society is obliged to find a way of making a suitable transition to renewable fuels. This desired change in our energetic paradigm is also being hastened by environmental issues; 3 mankind cannot afford to continue to progress by relying on sources of energy that release greenhouse gases.Nowadays, renewable sources comprise about 13% of all energy production and photovoltaics (PV) account for no more than 0.04% and most probably only in 2030 will that figure reach 1%.4 Solar PV energy costs are not yet competitive and continued PV grow is mainly based on government support, 5 as is easily perceived by analyzing three major consumers: Germany, Japan and the USA (the three combined share about 90% of the world market). 6 Nevertheless, PV solar cells are clearly very elegant and attractive devices for producing energy: cells are free from chemical and noise pollution; their power output is flexible, producing mW as well as MW; production can be done in situ, it is not dependent on the electrical grid, which makes them uniquely portable; they do not rely on reserves located abroad in geopolitically unstable countries and, of course, their source of energythe Sun -is free and inexhaustible for the next few million years. Moreover, the sun's rays reaching the earth are enough to fulfill global energy demand more than 10 thousand times over, i.e. in theory one hour of sunlight is more than enough for a whole year of global consumption. Also, ad extremum, solar energy is the only way of respecting the second law of thermodynamics towards sustainable development, because it benefits from all the massive creation of entropy in the sta...

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a b s t r a c tThe photocurrent-voltage characteristic of a photoelectrochemical cell for solar hydrogen production via water splitting, using undoped-hematite as photoanode, was obtained.Photoelectrochemical characteristics of the cell were also investigated by electrochemical impedance spectroscopy. Both techniques were carried out in the dark and under illumination. The analysis of the frequency spectra for the real and imaginary parts of the complex impedance allowed obtaining equivalent electrical analogs for the PEC cell operating in the dark and under 1 sun simulated illumination. Additionally, different electrode configurations were used (two and three-electrode arrangements). The twoelectrode configuration allowed the study of the overall charge transfer phenomena occurring at the semiconductor, within the electrolyte and at the counter-electrode side of the cell, whereas the three-electrode configuration gave more detailed information concerning the double charged layer at the semiconductor/electrolyte interface.