Search results for "Surfaces"
showing 10 items of 2837 documents
Entrapping of O2 Molecules in Nanostructured Silica Probed by Photoluminescence
2013
We studied the emission of the O2 molecules embedded in fumed silica (amorphous silicon dioxide) nanoparticles differing for diameters and specific surface. By using a 1064 nm laser as a source we recorded both the O2 emission and the Raman signal of silica. Our experimental data show that the O2 emission/Raman signal (at 800cm-1) ratio decreases with increasing the specific surface both for the as received and the loaded samples. By performing a thermal treatment (600 °C for 2h) we modified the structure and the water content of the smallest nanoparticles without observing any significant change in the O2 emission/Raman signal ratio. Our data are explained by a shell model showing that the…
Optical, structural, and morphological characterisation of epitaxial ZnO films grown by pulsed-laser deposition
2013
We report on ZnO epitaxial growth by pulsed-laser deposition (PLD) on different substrates, such as quartz, sapphire, and GaN template. Approximately 1 mu m-thick films were grown under different substrate temperatures and background oxygen conditions. X-ray diffraction analysis indicated preferential growth along the c-axis direction with a full-width at half maximum(FWHM) of the rocking curve as narrow as 230 arcs in the case of the GaN template. Low-temperature photoluminescence showed A-excitonic emission near 3.36 eV and a FWHM of (DXA)-X-0 emission as small as 2.89 meV at 9 K. Atomic force microscope measurements showed that roughness as low as 18 nm could be obtained. These results p…
Synthesis of multi-color luminescent ZnO nanoparticles by ultra-short pulsed laser ablation
2020
Abstract Crystalline ZnO nanoparticles (NPs) are synthesized by ultra-short femtosecond (fs) pulsed laser ablation (PLA) of a zinc plate in deionized water, and are investigated by optical absorption and time resolved luminescence spectra in combination with the morphology and structure analysis. The comparison with previous experiments based on short nanosecond (ns) PLA highlights that pulse duration is a crucial parameter to determine the size and the optical properties of ZnO NPs. While short PLA generates NPs with average size S ‾ of ~ 30 nm, ultrashort PLA allows to achieve much smaller NPs, S ‾ ⩽ 10 nm, that evidence weak quantum confinement effects on both the absorption edge and th…
Photoluminescence of Point Defects in Silicon Dioxide by Femtosecond Laser Exposure
2021
The nature of the radiation-induced point defects in amorphous silica is investigated through online photoluminescence (PL) under high intensity ultrashort laser pulses. Using 1030 nm femtosecond laser pulses with a repetition rate of 1 kHz, it is possible to study the induced color centers through their PL signatures monitored during the laser exposure. Their generation is driven by the nonlinear absorption of the light related to the high pulse peak powers provided by femtosecond laser, allowing to probe the optical properties of the laser exposed region. The experiment is conducted as a function of the laser pulse power in samples with different OH contents. The results highlight the dif…
Unexpected Epitaxial Growth of a Few WS2 Layers on {11̅00} Facets of ZnO Nanowires
2016
Core–shell nanowires are an interesting and perspective class of radially heterostructured nanomaterials where epitaxial growth of the shell can be realized even at noticeable core–shell lattice mismatch. In this study epitaxial hexagonally shaped shell consisting of WS2 nanolayers was grown on {1100} facets of prismatic wurtzite-structured [0001]-oriented ZnO nanowires for the first time. A synthesis was performed by annealing in a sulfur atmosphere of ZnO/WO3 core–shell structures, produced by reactive dc magnetron sputtering of an amorphous a-WO3 layer on top of ZnO nanowire array. The morphology and phase composition of synthesized ZnO/WS2 core–shell nanowires were confirmed by scanning…
Improved Crystalline Structure and Enhanced Photoluminescence of ZnO Nanolayers in Bi2Se3/ZnO Heterostructures
2019
The Bi2Se3/ZnO heterostructure is a new combination of high- and low-band-gap nanomaterials that can be implemented for optoelectronic devices. The influence of the Bi2Se3 substrate on crystallizat...
Copper coated carbon fiber reinforced plastics for high and ultra high vacuum applications
2014
We have used copper-coated carbon fiber reinforced plastic (CuCFRP) for the construction of high and ultra-high vacuum recipients. The vacuum performance is found to be comparable to typical stainless steel used for this purpose. In test recipients we have reached pressures of 2E-8 mbar and measured a desorption rate of 1E-11 mbar*liter/s/cm^2; no degradation over time (2 years) has been found. Suitability for baking has been found to depend on the CFRP production process, presumably on the temperature of the autoclave curing. Together with other unique properties of CuCFRP such as low weight and being nearly non-magnetic, this makes it an ideal material for many high-end vacuum application…
Photodynamics at the CdSe Quantum Dot–Perylene Diimide Interface: Unraveling the Excitation Energy and Electron Transfer Pathways
2021
Excitation energy and charge transfer processes in perylene diimide dye–CdSe quantum dot complexes have been studied by femtosecond transient absorption spectroscopy. After excitation of the quantu...
Charge Transfer Plasmons in Dimeric Electron Clusters
2020
The tunability of the optical response of dimers of metal clusters and nanoparticles makes them ideal for many applications from sensing and imaging to inducing chemical reactions. We have studied charge transfer plasmons in separate and linked dimers of closed-shell electron clusters of 8 and 138 electrons using time-dependent density functional theory. The simple model clusters enable the systematic study of the charge transfer phenomenon from the electronic perspective. To identify the charge transfer plasmons, we have developed an index, the Charge Transfer Ratio, for quantifying the charge transfer nature of the excitations. In addition, we analyze the induced transition density and th…
Pickering Emulsions of Fluorinated TiO2: A New Route for Intensification of Photocatalytic Degradation of Nitrobenzene
2020
International audience; Fluorination of the TiO2 surface has been often reported as a tool to increase the photocatalytic efficiency due to the beneficial effects in terms of production of oxidizing radicals. Moreover, it is shown that the unique amphiphilic properties of the fluorinated TiO2 (TiO2-F) surface allow one to use this material as a stabilizer for the formulation of Pickering emulsions of poorly soluble pollutants such as nitrobenzene (NB) in water. The emulsions have been characterized in terms of size of the droplets, type of emulsion, possibility of phase inversion, contact angle measurements, and optical microscopy. The emulsified system presents micrometer-sized droplets of…