International audienc

The emission properties of nanocrystalline ZnO particles prepared following an organometallic synthetic method are investigated. Spherical particles and nanorods are studied. The shape of the particles and the ligands used are shown to influence the luminescence properties in the visible domain. Two different emissions are observed at 440 nm (approximately 2.82 eV) and at 580 nm (approximately 2.14 eV) that are associated with the presence of surface defects on the particles. The first emission corresponds to the well-known yellow emission located at 580 nm (approximately 2.14 eV) with a lifetime of 1850 ns for 4.0 nm size ZnO nanoparticles. The second emission at 440 nm (approximately 2.82 eV) is observed when amine functions are present. This strong blue emission is associated with an excitation energy less than that associated with the yellow emission displaying a lifetime of nine nanoseconds. A possible hole trapping effect by the amine groups on the surface of the ZnO particles is discussed as the origin of this emission. The modification of the intensities between the two visible emissions for different particle shapes is proposed to be related to a specific location of the amine ligands on the surface of the particles.

Three-dimensional fluorescent nanostructures are photoinduced by a near-infrared high repetition rate femtosecond laser in a silver-containing femto-photoluminescent glass. By adjusting the laser dose (fluence, number of pulses, and repetition rate), these stabilized intense fluorescent structures, composed of silver clusters, can be achieved with a perfect control of the luminescence intensity, the emission spectrum, and the spatial distribution at the nanometer scale. This novel approach opens the way to the fabrication of stable fluorescent nanostructures in three dimensions in glass for applications in photonics and optical data storage.

No abstract

Three-dimensional (3D) femtosecond laser direct structuring in transparent materials is widely used for photonic applications. However, the structure size is limited by the optical diffraction. Here we report on a direct laser writing technique that produces subwavelength nanostructures independently of the experimental limiting factors. We demonstrate 3D nanostructures of arbitrary patterns with feature sizes down to 80 nm, less than one tenth of the laser processing wavelength. Its ease of implementation for novel nanostructuring, with its accompanying high precision will open new opportunities for the fabrication of nanostructures for plasmonic and photonic devices and for applications in metamaterials.

Soda lime glasses polarized either with an open or a blocking anode have been characterized by IR reflectance spectroscopy and a combined analysis of second harmonic generation and Raman imaging. The experimental results clearly show that the electrode nature influences strongly (i) the thickness of the space charge layer, (ii) the χ (2) efficiency, and (iii) the structural rearrangements. Besides, using theoretical models accounting for charge carriers' mobilities, the respective influence of two distinct compensation mechanisms, that is an injection of positive charges (H 3 O + /H + ions) or a drift of oxygen ions, have been confirmed.

No abstract

No abstract