Search results for "surface"

Efficient photovoltaic and electroluminescent perovskite devices.

2015

Planar diode structures employing hybrid organic–inorganic methylammonium lead iodide perovskites lead to multifunctional devices exhibiting both a high photovoltaic efficiency and good electroluminescence. The electroluminescence strongly improves at higher current density applied using a pulsed driving method.

Dielectric and plasmonic waveguides based on quantum dots embedded in polymers

2013

espanolEn este trabajo se propone una revision de la implementacion de guias de onda activas basadas en la dispersion de puntos cuanticos coloidales (QDs) en polimeros. Para ello, guias de onda planas fueron fabricadas embebiendo distintos tipos de nanoestructuras semiconductoras con emision en el visible e infrarrojo (CdS, CdTe, CdSe, PbS) en PMMA, encontrandose las condiciones optimas para el guiado de su fotoluminiscencia y sus propiedades de ganancia y atenuacion. Si varios tipos de puntos son dispersados en la misma capa se propagan varios colores, siendo posible obtener luz blanca con las proporciones adecuadas de rojo, verde y azul. Asimismo, el guiado puede ser mejorado si una cubie…

Thermo- and light responsive micellation of azobenzene containing block copolymers

2010

In this communication, the synthesis and characterization of thermo- and light responsive block copolymers is reported. PEO-b-PNIPAM polymers with azobenzene moieties were prepared and analyzed by turbidimetry, fluorescence, NMR and DLS measurements. A temperature controlled reversible formation as well as a light induced disruption and reformation of micellar structures in water was found.

Glassy dynamics of simulated polymer melts: Coherent scattering and van Hove correlation functions

2001

Whereas the first part of this paper dealt with the relaxation in the β-regime, this part investigates the final relaxation (α-relaxation) of a simulated polymer melt consisting of short non-entangled chains in the supercooled state above the critical temperature of ideal mode-coupling theory (MCT). The temperature range covers the onset of a two-step relaxation behaviour down to a temperature merely 2% above . We monitor the incoherent intermediate scattering function as well as the coherent intermediate scattering function of both a single chain and the melt over a wide range of wave numbers q. Upon approaching the coherent α-relaxation time of the melt increases strongly close to the max…

Cementing agents involved in the macro- and microaggregation of a Mediterranean shrubland soil under laboratory heating

2014

The heating effect on aggregation and cementing agents of a Mediterranean soil was studied in two fractions (macro- and microaggregates) in different environments: under Quercus coccifera soil (UQ), under Rosmarinus officinalis soil (UR) and between plants or bare soil (BS). Samples were heated under laboratory conditions at different temperatures (220, 380, 500, 750 and 1000. °C) to establish their effects on the studied soil properties by comparison with unheated control samples (25. °C). Increasing temperature treatments caused significant changes in most soil variables. In both soil fractions, the presence of vegetation contributed to increase of the soil organic matter (SOM) content, w…

Spatial and short-term temporal variations in runoff, soil aggregation and other soil properties along a Mediterranean Climatological Gradient.

1998

Abstract Physical and chemical soil properties were measured along a mountainous climatological gradient in the province of Alicante (Spain). The objective was to evaluate how the climate affects certain soil properties at different temporal and spatial scales. These properties include infiltration, runoff and sediment concentrations resulting from rainfall simulation experiments performed in winter and in summer. Chemical soil properties like carbonate content, organic matter content and CEC were analysed in reference soil profiles along the gradient. Physical soil properties like soil moisture content, macroaggregation and waterstable microaggregation were measured at monthly intervals du…

2021

Water-in-salt systems, i.e., super-concentrated aqueous electrolytes, such as lithium bis(trifluoromethanesulfonyl)imide (21 mol/kgwater), have been recently discovered to exhibit unexpectedly large electrochemical windows and high lithium transference numbers, thus paving the way to safe and sustainable charge storage devices. The peculiar transport features in these electrolytes are influenced by their intrinsically nanoseparated morphology, stemming from the anion hydrophobic nature and manifesting as nanosegregation between anions and water domains. The underlying mechanism behind this structure-dynamics correlation is, however, still a matter of strong debate. Here, we enhance the apol…

P-chirogenic organocatalysts: application to the aza-Morita–Baylis–Hillman (aza-MBH) reaction of ketimines

2013

The P-chirogenic organocatalysts were found to promote the enantioselective aza-Morita-Baylis-Hillman reaction of ketimines derived from acyclic α-keto esters. In the P-chirogenic organocatalyzed aza-MBH reactions, α,α-disubstituted α-amino acid derivatives were obtained in high yields with high enantioselectivities (up to 97% ee).

Oxamato-based coordination polymers: recent advances in multifunctional magnetic materials

2014

The design and synthesis of novel examples of multifunctional magnetic materials based on the so-called coordination polymers (CPs) have become very attractive for chemists and physicists due to their potential applications in nanoscience and nanotechnology. However, their preparation is still an experimental challenge, which requires a deep knowledge of coordination chemistry and large skills in organic chemistry. The recent advances in this field using a molecular-programmed approach based on rational self-assembly methods which fully exploit the versatility of the coordination chemistry of the barely explored and evergreen family of N-substituted aromatic oligo(oxamato) ligands are prese…

1,3-Dimethylimidazolium-2-carboxylate: the unexpected synthesis of an ionic liquid precursor and carbene-CO2 adductElectronic supplementary informati…

2002

1,3-Dimethylimidazolium-2-carboxylate is formed in good yield, rather than the anticipated organic salt, 1,3-dimethylimidazolium methyl carbonate, as the reaction product resulting from both N-alkylation and C-carboxylation of 1-methylimidazole with dimethyl carbonate; the crystal structure of the zwitterion exhibits π-stacked rings and two-dimensional sheets constructed by hydrogen-bonds from imidazolium-ring hydrogens to the carboxylate group.