Effect of N719–dye adsorption into composition of different sized TiO<SUB>2</SUB> films for photovoltaic performance of the dye-sensitized solar cells

Effect of N719-dye adsorption into TiO films prepared via incorporating small (~15 nm) and large (~300 nm) TiO nanoparticles at several ratios were investigated to improve the photovoltaic efficiency of dye-sensitized solar cell. The photovoltaic efficiency is significantly improved after incorporation of large and small TiO nanoparticles. From experimental result, the composition with 70% small: 30% large TiO is found as an optimum mixing ratio for the best performance (5.57%) of a dye-sensitized solar cell. This high photovoltaic performance is attributed to an effect of following factors. Besides an increase in dye molecules adsorption, the light scattering of over layer large TiO enhances harvesting light of the solar cells and the under layer small TiO ensures good electronic contact between film electrode and the fluorine-doped tin oxide glass substrate. However, we found that the composition with 50% small: 50% large TiO was adsorbed much more N719-dye molecule than that of the other mixtures of TiO and hence resulting in a decrease photovoltaic performance. This decrement of performance may be attributed to the decreased surface area and dye aggregation

Revisiting groundwater chemical processes in a rapidly urbanizing basin

Monterrey procures about 40% of its water supply from groundwater resources, considering several aquifers below and nearby. This city meets semiarid climate conditions with highly variable precipitation rates. The increasing demand for groundwater during drought conditions can deteriorate water quality, raising the energy consumption and costs of lifting, moving, distributing, and treating water. Thus, the major ion content of this resource was assessed, analyzing changes across the Monterrey Basin during the last 11 years to obtain a more robust geochemical concept of the study area. Waters from three wellfields (Buenos Aires, Santiago, Mina) with low mineralization were classified as recharge waters. Waters circulating across evaporite-silicate-carbonate sediments of the Monterrey Basin with gradually increasing salinity were classified as transition zone waters (Metropolitan area) and discharge zone waters (north and northeast of the city). According to this, it can be concluded that groundwater from the different Monterrey sources exhibits high-quality mineralized water, considering the analyzed parameters. Nevertheless, further attention must be paid on nitrate and sulfate occurrence and evolution in the transition and discharge zones

Intensive long-term pumping in the Principal-Lagunera Region aquifer (Mexico) causing heavy impact on groundwater quality

Located in the semi-arid and water-scarce area, Comarca Lagunera is one of the main agricultural and dairy products supplying regions in Mexico. As a consequence of the intensive exploitation of groundwater resources for irrigating purposes over one century, the water table has declined up to 200 meters and developed several cones of depression, aggravating the energy consumption necessary for lifting and distributing the groundwater in the agricultural land. Due to this long-term overdraft pumping, not only the groundwater flow dynamics are constantly changing, but also water quality has deteriorated significantly during the last decades. This study evaluates groundwater dynamics and the evolution of ion element composition and the quality of water from the Principal-Lagunera Region aquifer. Elevated nitrate and sulfate concentrations are ubiquitous near Bermejillo in the northwestern portion. Arsenic concentration exceeds international drinking water recommendations in 80% of the sampled sites and reaches maximum values of up to 349 μg/l in agricultural fields. The distribution of these high values of arsenic overlaps with the location of depression cones. This suggests a geogenic origin of this metalloid