Polythiophenes are a very versatile class of conjugated different polythiophenes. We also present our efforts in preparpolymers. Substituted polythiophenes can be tailored for ing substituted polythiophenes with high luminescence various applications by designing the side groups to give efficiency for use in polymer light-emitting diodes and lasers, the polymer different desired properties. Our work on and present studies of the photophysics of these polymers. preparing polythiophenes designed to have high stability Finally, we highlight design of substituted polythiophenes for in the doped state is described. We also discuss our efforts use in polymer photodiodes. on tuning the colour of the emission from polythiophenes for use in polymer light-emitting diodes. Design criteria Synthesis of polythiophenes for the synthesis of polythiophenes with high luminescence efficiency for use in light-emitting diodes and lasers arePure polythiophene without side chains is neither soluble nor also described. Finally, the design of polythiophenes for fusible. Once the polymer is prepared it is not possible to use in photodiodes is discussed.further process the prepared films or powder. However side chains which give solubility and fusibility to the polymer can be attached to the repeating unit (the thiophene ring).5 The

International audienceWe report single-shot, high aspect ratio nanovoid fabrication in bulk fused silica using zeroth order chirp-controlled ultrafast laser Bessel beams. We identify a unique laser pulse length and energy dependence of the physical characteristics of machined structures over which nanovoids of diameter in the range 200-400 nm and aspect ratios exceeding 1000 can be fabricated. A mechanism based on the axial energy deposition of nonlinear ultrashort Bessel beams and subsequent material densification or rarefaction in fused silica is proposed, intricating the non-diffractive nature with the diffusing character of laser-generated free carriers. Fluid flow through nanochannel is also demonstrate

We present a study of the structural, electronic, vibrational, and elastic properties of the orthorhombic NiSi structure by means of the density-functional theory and the density-functional perturbative theory, with the Perdew-Burke-Ernzerhof generalized gradient approximation of the exchange-correlation functional, within its spin-polarized version. The optimized lattice parameters, the formation energy, and vibrational properties are found in agreement with experimental data. We show that NiSi is not ferromagnetic, with a low density of states at the Fermi level. Elastic constants have been calculated by means of three different approaches for comparison. In the first two, the calculated energy E is fitted as a function of the deformation, atomic positions are either relaxed or not relaxed during the simulations. Atomic relaxations are shown to modify significantly elastic constants. In the third approach we have related acoustic velocities to elastic constants. NiSi is shown to be highly anisotropic. In particular the linear bulk modulus along b axis is much larger than along other axes. Polycrystalline elastic properties and Debye temperature have been also evaluated for a complete description of elastic properties.