105 research outputs found
Single-step fabrication process of 1-D photonic crystals coupled to nanocolumnar TiO2 layers to improve DSC efficiency
The present work proposes the use of a TiO2 electrode coupled to a one-dimensional photonic crystal (1DPC), all formed by the sequential deposition of nanocolumnar thin films by physical vapor oblique angle deposition (PV-OAD), to enhance the optical and electrical performance of DSCs while transparency is preserved. We demonstrate that this approach allows building an architecture combining a non-dispersive 3 µm of TiO2 electrode and 1 µm TiO2-SiO2 1DPC, both columnar, in a single-step process. The incorporation of the photonic structure is responsible for a rise of 30% in photovoltaic efficiency, as compared with a transparent cell with a single TiO2 electrode. Detailed analysis of the spectral dependence of the photocurrent demonstrates that the 1DPC improves light harvesting efficiency by both back reflection and optical cavity modes confinement within the TiO2 films, thus increasing the overall performance of the cellEuropean Union FP7/2007- 2013Ministerio de Economía y Competitividad CSD2008-00023, CSD2007-00007, MAT2011-23593, MAT2013-40852-R, MAT2013-42900-PJunta de Andalucía TEP8067, FQM-6900, FQM 2265, FQM 57
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Sacrificial ligand route to hybrid polythiophene-silver nanoparticles for sinter-free conductive inks
We report the synthesis of AgNP@PEDOT:PSS hybrid conductive particles with silver cores and polythiophene shells that can be used to formulate sinter-free inks for printing electronics. First, Ag nanocrystals capped with the weakly bound ligand aminohexanoic acid (ϵ-Ahx) are prepared. The ligand shell is exchanged by reacting the dispersion with the polymer ionomer mixture poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS). The particles are characterized by electron microscopy, dynamic light scattering, Z potential, and Raman spectroscopy, confirming the replacement of the ligands on the metal particle surface. The resulting dispersion is colloidally stable as confirmed by DLS. Inks with a solid content of the hybrid particles of 300 mg mL−1 were prepared and deposited on different substrates. The new particles are components for hybrid inks that become electrically conductive without any chemical or thermal post-deposition treatment. We show that silver-based hybrid inks can be deposited on different substrates and possess an average conductivity after 24 h of drying at room temperature of 1.726 × 106 S m−1 ± 0.326 × 106 S m−1, only one order of magnitude lower than elemental silver and within the same order of magnitude as their gold ink counterpart
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Surface polarization, field homogeneity, and dielectric breakdown in ordered and disordered nanodielectrics based on gold-polystyrene superlattices
Hybrid dielectrics were prepared from dispersions of nanoparticles with gold cores (diameters from 2.9 nm to 8.2 nm) and covalently bound thiol-terminated polystyrene shells (5000 Da and 11 000 Da) in toluene. Their microstructure was investigated with small angle X-ray scattering and transmission electron microscopy. The particles arranged in nanodielectric layers with either face-centered cubic or random packing, depending on the ligand length and core diameter. Thin film capacitors were prepared by spin-coating inks on silicon substrates, contacted with sputtered aluminum electrodes, and characterized with impedance spectroscopy between 1 Hz and 1 MHz. The dielectric constants were dominated by polarization at the gold-polystyrene interfaces that we could precisely tune via the core diameter. There was no difference in the dielectric constant between random and supercrystalline particle packings, but the dielectric losses depended on the layer structure. A model that combines Maxwell-Wagner-Sillars theory and percolation theory described the relationship of the specific interfacial area and the dielectric constant quantitatively. The electric breakdown of the nanodielectric layers sensitively depended on particle packing. A highest breakdown field strength of 158.7 MV m−1 was found for the sample with 8.2 nm cores and short ligands that had a face-centered cubic structure. Breakdown apparently is initiated at the microscopic maxima of the electric field that depends on particle packing. The relevance of the results for industrially produced devices was demonstrated on inkjet printed thin film capacitors with an area of 0.79 mm2 on aluminum coated PET foils that retained their capacity of 1.24 ± 0.01 nF@10 kHz during 3000 bending cycles
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Microscopic Softening Mechanisms of an Ionic Liquid Additive in an Electrically Conductive Carbon-Silicone Composite
The microstructural changes caused by the addition of the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide to polydimethylsiloxane (PDMS) elastomer composites filled with carbon black (CB) are analyzed to explain the electrical, mechanical, rheological, and optical properties of IL-containing precursors and composites. Swelling experiments and optical analysis indicate a limited solubility of the IL in the PDMS matrix that reduces the cross-linking density of PDMS both globally and locally, which reduces the Young's moduli of the composites. A rheological analysis of the precursor mixture shows that the IL reduces the strength of carbon–carbon and carbon–PDMS interactions, thus lowering the filler–matrix coupling and increasing the elongation at break. Electromechanical testing reveals a combination of reversible and irreversible piezoresistive responses that is consistent with the presence of IL at microscopic carbon–carbon interfaces, where it enables re-established electrical connections after stress release but reduces the absolute conductivity
TiO2-SiO2 one-dimensional photonic crystals of controlled porosity by glancing angle physical vapour deposition
Herein we present a synthetic route to attain porous one-dimensional photonic crystals of high optical quality. The method employed, based on the alternate deposition of TiO2 and SiO2 porous layers by glancing angle physical vapour deposition, yields a highly accessible interconnected pore network throughout the entire multilayer structure. Furthermore, it allows a strict control over the average size and density of the interstitial sites, which results in the precise tuning of the refractive index of the individual layers and thus of the optical response of the ensemble. The controlled environmental response of the multilayer is confirmed by the optical monitoring of the infiltration of liquids of different refractive index.España Ministerio de Ciencia e innovación MAT2008-02166 MAT2007-65764Consolider Projects CSD2007-00007 CSD2008-00023Junta de Andalucía FQM-3579 TEP227
El derecho de objeción de conciencia sanitaria a la interrupción voluntaria del embarazo
Spanish Act 2/2010 on Sexual Health and voluntary end of pregnancy is the first act in Spain in recognize conscientious objection of medicine professionals to practice an abort. In this field is impossible to say that there is no conflict of convictions, ideas, or free exercise of religion. There is an important social conflict, particularly when a woman wants to exercise her right to abort and the professional wants to exercise the conscientious objection. In this article we explain the legal, doctrinal and ethical consequences of conscientious objection of the medicine professionals in Spain, we make a legal analysis of this act at the Jurisprudence. Finally we explain a real case and his solution.Con la entrada en vigor de la Ley Orgánica 2/2010, de Salud Sexual y Reproductiva y de Interrupción Voluntaria al Embarazo, se reconoce por primera vez en un texto legal el derecho a la objeción de conciencia sanitaria en relación con la práctica del aborto, que, al tratarse de un tema en el que han de considerarse ideas, creencias y convicciones morales, culturales y sociales… y al constituir un punto de desencuentro de planteamientos doctrinales e interpretativos, parece justificada e inevitable la importante polémica social suscitada. Con el presente trabajo se pretende incidir en las consecuencias de este reconocimiento, así como poner de manifiesto los conflictos éticos y jurídicos que, a raíz de esta regulación, se plantean. Para ello se ha analizado los diferentes ámbitos del derecho, tanto desde el punto de vista doctrinal como jurisprudencial, así como desde una perspectiva práctica mediante el estudio de algún caso controvertido
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Sintering of ultrathin gold nanowires for transparent electronics
Ultrathin gold nanowires (AuNWs) with diameters below 2 nm and high aspect ratios are considered to be a promising base material for transparent electrodes. To achieve the conductivity expected for this system, oleylamine must be removed. Herein we present the first study on the conductivity, optical transmission, stability, and structure of AuNW networks before and after sintering with different techniques. Freshly prepared layers consisting of densely packed AuNW bundles were insulating and unstable, decomposing into gold spheres after a few days. Plasma treatments increased the conductivity and stability, coarsened the structure, and left the optical transmission virtually unchanged. Optimal conditions reduced sheet resistances to 50 Ω/sq
A proposal of an effective platelet-rich plasma protocol for the treatment of androgenetic alopecia
Background: Platelet-rich plasma (PRP) has emerged as a promising treatment for androgenetic alopecia (AGA). In spite of the several studies previously reported, to date, a standardized protocol for PRP preparation and application, as well as a standard method for evaluating results has not been established. Aims: The aim of this study is to propose a standardized method for preparation and application of PRP for male AGA (MAGA) and female AGA (FAGA) and assess its safety and efficacy as a co-adjuvant therapy. Materials and Methods: Seventy-eight patients, 19 men and 59 women with AGA Grades II-IV in Ebling's scale, currently on treatment with topical minoxidil and/or oral finasteride for more than a year without improvement, were included in this study. PRP was prepared using a single spin method, and injected in affected areas for 3 monthly sessions, followed by 3 bimonthly sessions. A decrease of at least one grade in Ebling's scale was considered a successful result. Results: After the 6° session, 71.4% of MAGA and 73.4% of FAGA patients reached a successful outcome while 21.4% and 16.3%, respectively, remained without changes. Only 7.1% of MAGA and 10.2% of FAGA presented worsening of their condition. Conclusions: PRP together with a periodical application protocol can be considered effective as a coadjuvant therapy in patients who no longer respond to pharmacological treatments. Ebling's scale was a practical and reliable parameter to allow a better evaluation in both MAGA and FAGA
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Multivalent bonds in self-assembled bundles of ultrathin gold nanowires
Ultrathin gold nanowires are unusual colloidal objects that assemble into bundles with line contacts between parallel wires. Each molecule in the contact line interacts with many ligand and solvent molecules. We used X-ray scattering and electron microscopy to study how these interactions control assembly
Growth regimes of porous gold thin films deposited by magnetron sputtering at oblique incidence: from compact to columnar microstructures
Growth regimes of gold thin films deposited by magnetron sputtering at oblique angles and low temperatures are studied from both theoretical and experimental points of view. Thin films were deposited in a broad range of experimental conditions by varying the substrate tilt angle and background pressure, and were analyzed by Field Emission Scanning Electron Microscopy (FESEM) and Grazing Incidence Small-Angle X-ray Scattering (GISAXS) techniques. Results indicate that the morphological features of the films strongly depend on the experimental conditions, but can be categorized within four generic microstructures, each of them defined by different bulk geometrical patterns and pore percolation depth and connectivity. With the help of a growth model, a microstructure phase diagram has been constructed where the main features of the films are depicted as a function of experimentally controllable quantities, finding a good agreement with the experimental results in all the studied cases.Junta de Andalucía P09-CTS- 5189, TEP5283, P10-FQM-6900Comunidad de Madríd S2009/MAT–1726Ministerio de Economía y Competitividad MAT2011-29194-C02-01, CSD2008-00023, MAT2008-06652, MAT2010-21228, MAT2010-1844
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