Spectroelectrochemical Behaviour of 4-Aminobenzenethiol on Nanostructured Platinum and Silver Electrodes

The adsorption of 4-aminobenzenethiol (4-ABT) on Ag and Pt nanoparticles is studied by spectroelectrochemical means (cyclic voltammetry, Surface-Enhanced Raman Spectroscopy (SERS) and Surface-Enhanced Infrared Reflection Absorption Spectroscopy (SEIRAS). Similar SERS spectra are obtained when 4-ABT is adsorbed on platinum and silver nanostructured substrates. In addition, unless a low power density of the laser is used, these spectra show, both under open circuit conditions and when applying electrode potentials above -0.50 V, bands not observed in the normal Raman spectrum of 4-ABT. These bands disappear when the electrode potential is shifted to more negative values. Conversely, the SEIRA spectra of 4-ABT adsorbed on Ag do not show any significant change with the electrode potential, which indicates that there are not new species electrochemically formed in the range of potentials considered, which include some anodic and cathodic processes as shown in the corresponding cyclic voltammograms. In this regard, SERS measurements put in evidence the time dependence of the spectra obtained at potentials above -0.50 V just after switching on the laser suggesting the formation of new species, probably dimercaptoazobenzene (4-4’-DMAB), formed by a photochemical process of the adsorbed 4-ABT.Financial support from Ministerio de Ciencia e Innovación (projects CTQ2010-16271, CTQ2009-13142, and Fondos Feder), Generalitat Valenciana (Prometeo/2009/045 and ACOMP/2011/200), and University of Alicante is greatly acknowledged

Surface Acid–Base Properties of Anion-Adsorbed Species at Pt(111) Electrode Surfaces in Contact with CO2-Containing Perchloric Acid Solutions

Carbonate and bicarbonate adsorption on Pt(111) electrodes from CO2-saturated acidic solutions is investigated by cyclic voltammetry and Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). Spectroscopic results show carbonate and bicarbonate adsorption even at pH = 1, where bulk concentration of these anions is negligible. Moreover, analysis of the potential dependence of band intensities corresponding to adsorbed carbonate and bicarbonate reveals an effect of the electrode potential on the surface acid–base equilibrium. In this regard, increasing potentials favor bicarbonate deprotonation, leading to carbonate formation. A tentative thermodynamic analysis is given to rationalize these trends.Support from MINECO (Spain) through project CTQ2013-44083-P is greatly acknowledged. RMH thankfully acknowledges support from Generalitat Valenciana under the Santiago Grisolía Program (GRISOLIA/2013/008)

Assessment of climate change impacts on soil water balance and aquifer recharge in a semiarid region in south east Spain

Climate change forecasts in a semiarid region are of much interest to academics, managers and governments. A significant decrease in annual precipitation and an increase in mean annual air temperature are expected; consequently, changes in the soil water balance and groundwater recharge to aquifers are expected as a response to climate change forecasts. In this context, our study aimed to assess the impact of climate changes on the soil water balance and natural groundwater recharge in a semiarid area (Ventós-Castellar aquifer, SE, Spain). To this end, we selected Global Climate Model HadCM3 after comparing it with two other models (ECHAM4 and CGCM2). The HadCM3 model climate data (air temperature and precipitation in two emission scenarios: A2-high and B2-low; 2011–2099) were coupled to a HYDROBAL hydrological model to determine the soil water balance. The HYDROBAL model results showed that climate change will have a significant impact on the soil water balance in the study area, especially on groundwater recharge during the latter period. In both the A2-high and B2-low scenarios, the selected years to run the HYDROBAL model showed a decrease in water balance components (precipitation, actual evapotranspiration, aquifer recharge and runoff) in relation to the baseline period (1961–1990). Over the projected period (2011–2099), we expect fewer rainfall events (>15 mm), which promote aquifer recharge, longer dry summer seasons and, consequently, reduced average annual recharge that ranged from 3% to 17%; 10–49 mm, if compared to the baseline period. The methodology developed in the present study can be beneficial for assessing the impact of predicted climate change on groundwater recharge, and can help managers and planners to devise strategies for the efficient use and conservation of freshwater resources.This research has been supported by the United Nations Educational, Scientific and Cultural Organization – France (IGCP-513), the European Commission – Belgium (PRACTICE project), the Spanish Government through the Ministry of Economy and Competitiveness – Spain (ECOBAL Project, CGL2011-30531-C03-01 and SURVIVE project, CGL 2011-30531-C02-02), the Consolider programme INGENIO 2010 (GRACCIE Project, CSD2007-00067), and the Generalitat Valenciana – Spain (FEEDBACKS-PROMETEO; ACOMP/2010/272 and GV07/143)

Tsunami audiovisual resources on the Internet

Presentamos una selección de páginas web que contienen recursos audiovisuales sobre tsunamis (esquemas, mapas, animaciones, vídeos, imágenes de satélite, fotografías, etc.). Este material gráfico puede ser utilizado por los docentes, como complemento a las tradicionales clases teóricas, para la preparación de seminarios, talleres, presentaciones por ordenador, entre otros. La avalancha de información publicada en Internet sobre el tsunami del Índico de 2004 ha puesto de manifiesto el gran potencial que tiene en la docencia de las Ciencias de la Tierra.We present a web site selection which contains audiovisual resources on tsunamis (diagrams, maps, animations, videos, satellite images, photographs, etc.). This graphic material can be used by lecturers as a complement to traditional theory classes, in order to prepare seminars, workshops, computer-aided presentations, etc. The enormous amount of information published about the 2004 Indian Ocean tsunami on the Internet reveals the great potential of this resource in teaching Earth Sciences

Spectroelectrochemical Study of the Photoinduced Catalytic Formation of 4,4′-Dimercaptoazobenzene from 4-Aminobenzenethiol Adsorbed on Nanostructured Copper

Surface-enhanced raman scattering (SERS) spectra of self-assembled monolayers of 4-aminobenzenethiol (4-ABT) on copper (Cu) and silver (Ag) surfaces decorated with Cu and Ag nanostructures, respectively, have been obtained with lasers at 532, 632.8, 785, and 1064 nm. Density functional theory (DFT) has been used to obtain calculated vibrational frequencies of the 4-ABT and 4,4′-dimercaptoazobenzene (4,4′-DMAB) molecules adsorbed on model Cu surfaces. The features of the SERS spectra depend on the electrode potential and the type and power density of the laser. SERS spectra showed the formation of the 4,4′-DMAB on the nanostructured Cu surface independently of the laser employed. For the sake of comparison SERS spectra of a self-assembled monolayer of the 4-ABT on Ag surfaces decorated with Ag nanostructures have been also obtained with the same four lasers. When using the 532 and 632.8 nm lasers, the 4,4′-DMAB is formed on Cu surface at electrode potentials as low as −1.0 V (AgCl/Ag) showing a different behavior with respect to Ag (and others metals such as Au and Pt). On the other hand, the surface-enhanced infrared reflection absorption (SEIRA) spectra showed that in the absence of the laser excitation the 4,4′-DMAB is not produced from the adsorbed 4-ABT on nanostructured Cu in the whole range of potentials studied. These results point out the prevalence of the role of electron–hole pairs through surface plasmon activity to explain the obtained SERS spectra.Financial support from Ministerio de Economía y Competitividad (Projects CTQ2013-48280-C3-3-R and CTQ2013-44083-P), Fondos Feder, and the University of Alicante are greatly acknowledged

Early research on the effect of climate change on groundwater recharge of Ventós (Alicante)

Las predicciones sobre cambio climático tienen un gran interés en regiones como la provincia de Alicante cuya economía está basada en gran medida en las aguas subterráneas. A priori un descenso en la precipitación y un aumento de la temperatura podría generar impactos sobre la recarga de los acuíferos. En este contexto, el objetivo de este estudio ha sido explorar el posible impacto sobre la recarga de un pequeño acuífero. Para lograr este objetivo, técnicas de regionalización han sido utilizadas a partir del modelo HadCM3. Se han estimado las series de precipitaciones y temperaturas para los escenarios de cambio climático A2 y B2. Estas bases de datos han sido introducidas en un modelo hidrológico HYDROBAL para establecer los balances de agua en el suelo. Los resultados han mostrado un aumento de la temperatura de 4ºC y un descenso de la precipitación del 10% a final de siglo para ambos escenarios. El modelo hidrológico indica un balance de agua negativo en relación al periodo base (1961-1990), obteniéndose las mayores diferencias para el escenario A2. Esto podría producir un fuerte impacto sobre la recarga del acuífero Ventós, aspecto que deber ser corroborado en futuros estudios.Predictions of climate change have a high interest in regions like the province of Alicante whose economy is largely based on groundwater. It is expected that the decrease of precipitation and the increase of temperature according to climate change forecasts, could impact on the recharge to aquifers. In this context, the aim of this study was explore the possible impact of climate changes forecasts on recharge in a small aquifer. In order to achieve it downscaling techniques have been used from the HadCM3 Global Climate Model. Air temperature and precipitation data in two climate change scenarios, B2 and A2 have been estimated. These databases have been coupled to HYDROBAL a hydrological model, to determine the soil water balance. Results have showed increase of 4º C of temperature and decrease of 10% precipitation in both scenarios at the end century. The hydrological model shows a negative water balance in relation to baseline period (1961-1990), being the higher differences with the A2 scenario. It could produce an important impact on the recharge of the Ventós aquifer, but it must be checked in future studies.Este trabajo ha sido financiado con una beca del MAEC-AECID, y realizado en el marco de los proyectos ECOBAL CGL2011-30531-C03-01 y SURVIVE CGL 2011-30531-C02-02