Scientific Papers in SCI


Title: How Important is Working with an Ordered Electrode to Improve the Charge Collection Efficiency in Nanostructured Solar Cells?
Author(s): Gonzalez-Vazquez, JP; Morales-Florez, V; Anta, JA
Source: Journal of Physical Chemistry Letters, 3 (2012) 386-393

abstract | fulltext

The collection efficiency of carriers in solar cells based on nanostructured electrodes is determined for different degrees or morphological one-dimensional order. The transport process is modeled by random walk numerical simulation in a mesoporous electrode that resembles the morphology of nanostructured TiO2 electrodes typically used in dye-sensitized solar cells and related systems. By applying an energy relaxation procedure in the presence of an external potential, a preferential direction is induced in the system. It is found that the partially ordered electrode can almost double the collection efficiency with respect to the disordered electrode. However, this improvement depends strongly on the probability of recombination. For too rapid or too slow recombination, working with partially ordered electrodes will not be beneficial. The computational method utilized here makes it possible to relate the charge collection efficiency with morphology. The collection efficiency is found to reach very rapidly a saturation value, meaning that, in the region of interest, a slight degree of ordering might be sufficient to induce a large improvement in collection efficiency.

February, 2012 | DOI: 10.1021/jz2015988

Title: Evidence of upconversion luminescence contribution to the improved photoactivity of erbium doped TiO2 systems
Author(s): Obregon, S; Colon, G
Source: Chemical Communications, 48 (2012) 7865-7867

abstract | fulltext

Er3+–TiO2 synthesized by a surfactant free hydrothermal method exhibits good photoactivities under sun-like excitation for the degradation of phenol. The presence of Er3+ does not affect the structural and morphological features of the TiO2 significantly. The best photocatalytic performance was attained for the samples with 2 wt% of Er. Different photocatalytic runs indicated that the incorporation of the Er3+ cation would be responsible for the enhanced photocatalytic activity, which participates in different mechanisms under UV and NIR excitation.

August, 2012 | DOI: 10.1039/C2CC33391K

Title: Self-assembly at room temperature of thermally stable discrete and extended oligomers of polycyclic aromatics on Ag(100): induced dipoles and cooperative effects
Author(s): Papageorgiou, AC; Alavi, A; Lambert, RM
Source: Chemical Communications, 48 (2012) 3394-3396

abstract | fulltext

Thermally stable nanoarchitectures are realized on the Ag(100) surface by self-assembly of asymmetrically substituted arenes. The process is instigated by adsorption-induced molecule → surface charge transfer that gives rise to in-plane dipole moments. Observation and calculation indicate that cooperative interactions further enhance the stability of these polarizable systems.

April, 2012 | DOI: 10.1039/c2cc17728e

Title: Nanoecotoxicity effects of engineered silver and gold nanoparticles in aquatic organisms
Author(s): Lapresta-Fernandez, A; Fernandez, A; Blasco, J
Source: TrAC Trends in Analytical Chemistry, 32 (2012) 40-59

abstract | fulltext

Engineered nanoparticles (ENPs) are increasingly being incorporated into commercial products. A better understanding is required of their environmental impacts in aquatic ecosystems.

This review deals with the ecotoxicity effects of silver and gold ENPs (AgNPs and AuNPs) in aquatic organisms, and considers the means by which these ENPs enter aquatic environments, their aggregation status and their toxicity. Since ENPs are transported horizontally and vertically in the water column, we discuss certain factors (e.g., salinity and the presence of natural organic materials), as they cause variations in the degree of aggregation, size range and ENP toxicity. We pay special attention to oxidative stress induced in organisms by ENPs.

We describe some of the main analytical methods used to determine reactive oxygen species, antioxidant enzyme activity, DNA damage, protein modifications, lipid peroxidation and relevant metabolic activities. We offer an overview of the mechanisms of action of AgNPs and AuNPs and the ways that relevant environmental factors can affect their speciation, agglomeration or aggregation, and ultimately their bio-availability to aquatic organisms.

Finally, we discuss similarities and differences in the adverse effects of ENPs in freshwater and salt-water systems.

February, 2012 | DOI: 10.1016/j.trac.2011.09.007

Title: Public concern over ecotoxicology risks from nanomaterials: Pressing need for research-based information
Author(s): Lapresta-Fernandez, A; Fernandez, A; Blasco, J
Source: Environment International, 39 (2012) 148-149

abstract | fulltext

[No abstract available]

February, 2012 | DOI: 10.1016/j.envint.2011.10.012

Title: Superhydrophobic supported Ag-NPs@ZnO-nanorods with photoactivity in the visible range
Author(s): Macias-Montero, M; Borras, A; Saghi, Z; Romero-Gomez, P; Sanchez-Valencia, JR; Gonzalez, JC; Barranco, A; Midgley, P; Cotrino, J; Gonzalez-Elipe, AR
Source: Journal of Materials Chemistry, 22 (2012) 1341-1346

abstract | fulltext

In this article we present a new type of 1D nanostructures consisting of supported hollow ZnO nanorods (NRs) decorated with Ag nanoparticles (NPs). The 3D reconstruction by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) electron tomography reveals that the Ag NPs are distributed along the hollow interior of the ZnO NRs. Supported and vertically aligned Ag-NPs@ZnO-NRs grow at low temperature (135 °C) by plasma enhanced chemical vapour deposition on heterostructured substrates fabricated by sputtered deposition of silver on flat surfaces of Si wafers, quartz slides or ITO. The growth mechanisms of these structures and their wetting behavior before and after visible light irradiation are critically discussed. The as prepared surfaces are superhydrophobic with water contact angles higher than 150°. These surfaces turn into superhydrophilic with water contact angles lower than 10° after prolonged irradiation under both visible and UV light. The evolution rate of the wetting angle and its dependence on the light characteristics are related to the nanostructure and the presence of silver embedded within the ZnO NRs.

January, 2012 | DOI: 10.1039/C1JM13512K

Title: Enhanced diffusion through porous nanoparticle optical multilayers
Author(s): Lopez-Lopez, C; Colodrero, S; Raga, SR; Lindstrom, H; Fabregat-Santiago, F; Bisquert, J; Miguez, H
Source: Journal of Materials Chemistry, 22 (2012) 1751-1757

abstract | fulltext

Herein we demonstrate improved mass transport through nano-particle one-dimensional photonic crystals of enhanced porosity. Analysis is made by impedance spectroscopy using iodine and ionic liquid based electrolytes and shows that newly created large pores and increased porosity improve the diffusion of species through the photonic crystal. This achievement is based on the use of a polymeric porogen (polyethylene glycol), which is mixed with the precursor suspensions used for the deposition of nanoparticle TiO2 and SiO2 layers and then eliminated to generate a more open interconnected void network, as confirmed by specular reflectance porosimetry. A compromise between pore size and optical quality of these periodic structures is found.

February, 2012 | DOI: 10.1039/c1jm15202e

Title: Weakly Interacting Molecular Layer of Spinning C60 Molecules on TiO2 (110) Surfaces
Author(s): Sanchez-Sanchez, C; Lanzilotto, V; Gonzalez, C; Verdini, A; de Andres, PL; Floreano, L; Lopez, MF; Martin-Gago, JA
Source: Chemistry-A European Journal, 18 (2012) 7382-7387

abstract | fulltext

The adsorption of C60, a typical acceptor organic molecule, on a TiO2 (110) surface has been investigated by a multitechnique combination, including van der Waals density functional calculations. It is shown that the adsorbed molecules form a weakly interacting molecular layer, which sits on the fivefold-coordinated Ti that is confined between the prominent bridging oxygen rows (see figure).

June, 2012 | DOI: 10.1002/chem.201200627

Title: Hydrothermal synthesis of BiVO4: Structural and morphological influence on the photocatalytic activity
Author(s): Obregon, S; Caballero, A; Colon, G
Source: Applied Catalysis B-Environmental, 117 (2012) 59-66

abstract | fulltext

BiVO 4 hierarchical heterostructures are synthesized by means of a surfactant free hydrothermal method having good photoactivities for the degradation of methylene blue under UV-vis irradiation. From the structural and morphological characterization it has been stated that BiVO 4 present the monoclinic crystalline phase with different morphologies depending on the pH value, type of precipitating agent and hydrothermal temperature and treatment time. The best photocatalytic performance was attained for the samples with needle-like morphology.

May, 2012 | DOI: 10.1016/j.apcatb.2011.12.037

Title: Effect of the active metals on the selective H-2 production in glycerol steam reforming
Author(s): Araque, M; Martinez, LM; Vargas, JC; Centeno, MA; Roger, AC
Source: Applied Catalysis B-Environmental, 125 (2012) 556-566

abstract | fulltext

The production of hydrogen by glycerol steam reforming was studied using CeZr(Co, CoRh) catalysts. The effect of Co and Rh presence on the properties of the mixed oxides and the effect on the catalytic behavior were considered. The catalysts were characterized before and after testing by XRD, Raman, TPR, H 2-TPD, TPD-TPO and HRTEM. It was observed that the presence of Co allowed the selective H 2 production related with the presence of a metallic phase at the beginning of the reaction. The presence of Rh favored even more the H 2 production and also increased the stability of the catalyst. For CeZrCoRh, the presence of both metals enhanced the catalyst reduction capacity, a characteristic that significantly improved the catalytic behavior for glycerol steam reforming. The selective H 2 production was related to the capacity of the catalyst to activate H 2O under the reaction conditions. The progressive loss of this capacity decreases the production of H 2, and glycerol decomposition is actually favored over glycerol steam reforming. According to the initial distribution of products, and its evolution with time on stream, two main reaction pathways were proposed.

August, 2012 | DOI: 10.1016/j.apcatb.2012.06.028

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