排序方式: 共有45条查询结果,搜索用时 15 毫秒
1.
Vallée RA Marsal P Braeken E Habuchi S De Schryver FC Van der Auweraer M Beljonne D Hofkens J 《Journal of the American Chemical Society》2005,127(34):12011-12020
Experimental (Single Molecule Spectroscopy) and theoretical (quantum-chemical calculations and Monte Carlo and molecular dynamics simulations) techniques are combined to investigate the behavior and dynamics of a polymer-dye molecule system. It is shown that the dye molecule of interest (1,1'-dioctadecyl-3,3,3',3'-tetramethylindo-dicarbocyanine) adopts two classes of conformations, namely planar and nonplanar ones, when embedded in a poly(styrene) matrix. From an in-depth analysis of the fluorescence lifetime trajectories, the planar conformers can be further classified according to the way their alkyl side chains interact with the surrounding poly(styrene) chains. 相似文献
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van Der Voort M Rella CW van Der Meer LF Akimov AV Dijkhuis JI 《Physical review letters》2000,84(6):1236-1239
We present results of the first vibrational photon-echo, transient-grating, and temperature dependent transient-bleaching experiments on a-Si:H. Using these techniques, and the infrared light of a free electron laser, the vibrational population decay and phase relaxation of the Si-H stretching mode were investigated. Careful analysis of the data indicates that the vibrational energy relaxes directly into Si-H bending modes and Si phonons, with a distribution of rates determined by the amorphous host. Conversely, the pure dephasing appears to be single exponential, and can be modeled by dephasing via two-phonon interactions. 相似文献
3.
J. Cos J. Ferré-Borrull J. Pallarès L. F. Marsal 《Applied physics. B, Lasers and optics》2010,100(4):833-839
We present a theoretical study on two-dimensional photonic crystals composed of silicon and the E7 liquid crystal. We analyze
how the optical axis orientation of the liquid crystal influences the photonic bands and bandgaps, for the case when the Maxwell
equations can be decoupled into the TE and TM modes. We consider two different structures, a triangular lattice of E7 liquid
crystal cylinders in a silicon background and a triangular lattice of silicon cylinders in an E7 liquid crystal background.
The effect of the liquid crystal anisotropy on the geometry of the irreducible Brillouin zone allows us to propose a simplified
way to calculate the photonic bandgaps. Results show that the bandgap width and center frequency have a 60° periodicity for
both structures. Using the plane-wave expansion method, we determined the maximum bandgap and the optimal radius of the cylinders
for each structure. Finally, for the second structure, we propose an optical switch with a 50% duty cycle. These structures
can be applied to design tunable photonic devices. 相似文献
4.
E. Xifré-Pérez L. F. Marsal J. Ferré-Borrull J. Pallarès 《Applied physics. B, Lasers and optics》2009,95(1):169-172
We report on the fabrication and characterization of a porous silicon omnidirectional reflector formed by periodic substructures
stacked together. For these substructures, a low refractive index contrast has been used, resulting in substructures without
omnidirectional reflectivity band. The use of a low refractive index contrast involves the reduction of the requirements to
obtain omnidirectional reflectors. We demonstrate the existence of an omnidirectional reflectivity range with a high gap-to-midgap
ratio by means of reflectivity spectra measurements for a range of incidence angles. The results are in good agreement with
a theoretical model of the reflector. The fabricated structure is the first reported porous silicon reflector suitable for
1.55 μm applications. 相似文献
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Ivan Maksymov Josep Ferré-Borrull Josep Pallarès Lluis F. Marsal 《Photonics and Nanostructures》2012,10(4):459-462
The existence of photonic stop bands in the self-assembled arrangement of pores in porous anodic alumina structures is investigated by means of rigorous 2D finite-difference time-domain calculations. Self-assembled porous anodic alumina shows a random distribution of domains, each of them with a very definite triangular pattern, constituting a quasi-random structure. The observed stop bands are similar to those of photonic quasicrystals or random structures. As the pores of nanoporous anodic alumina can be infiltrated with noble metals, nonlinear or active media, it makes this material very attractive and cost-effective for applications including inhibition of spontaneous emission, random lasing, LEDs and biosensors. 相似文献
7.
P. Granero V.S. Balderrama J. Ferré-Borrull J. Pallarès L.F. Marsal 《Current Applied Physics》2013,13(8):1801-1807
Ordered bulk heterojunction organic solar cells are devices that combine the advantages of the planar bilayer and the bulk heterojunction architectures. They offer uninterrupted pathways to electrodes for effective charge collection and an extended Donor–Acceptor interface for efficient exciton dissociation. Additionally, this interface can also be a potential approach to increase photon absorption by light trapping. Light absorption and charge carrier generation of organic nanostructures are studied by means of finite-element modeling for a wide range of structuring widths, periods and heights for poly(3-hexylthiophene):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (P3HT:PCBM) structures. Results show an increase in light absorption at certain wavelengths in the P3HT region with respect to an equivalent planar bilayer model. This increase can be attributed to two phenomena: for the smallest periods the structures behaves like an effective medium, while for periods of the order of magnitude of the incident light wavelength there is light trapping. The maximum increase in absorption was achieved for a 250 nm-width and 500 nm periodicity structure with a height of 40 nm. Exciton diffusion has also been studied to evaluate the effective amount of absorbed light contributing to photocurrent. In this case, best results correspond to the smallest sizes (1.25–12.5 nm-width) for all the considered heights, achieving an increment in the photocurrent up to more than a factor 6 if compared with that of the reference planar bilayer device. This study can be used to optimize our devices, which are achieved via nanoporous anodic alumina templates. 相似文献
8.
Dr. Pilar Formentin Moritz Tebbe Prof. Miguel A. Correa‐Duarte Pedro Granero Dr. Josep Ferré‐Borrull Prof. Rosana Alvarez Prof. Josep Pallares Prof. Andreas Fery Prof. Angel R. de Lera Prof. Lluis F. Marsal Prof. Ramón A. Alvarez‐Puebla 《Angewandte Chemie (International ed. in English)》2013,52(25):6459-6463
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The oxidation of a number of fatliquoring formulations, of different iodine index, derived from fish oil, rapeseed oil, neatsfoot oil, lecithin, paraffin, sulphited and sulphated variants was studied. The formulations included dispersing agents, stabilizers and/or anti-oxidants. Sheepskins were treated with fatliquoring agents at 5% of fatty matter. The oxidation of the fatliquoring formulations and the fatliquored skins was studied by non-isothermal differential scanning calorimetry (DSC). The onset thermoxidation temperature and the enthalpy of the thermoxidation peak located between 195 and 265 °C were determined and then related to the different fatliquoring standard formulations. The skins were subjected to ageing treatments using UV radiation and temperature. The fall in the denaturation temperature of the skin due to ageing was related to the oxidability of the fatliquoring agent. 相似文献