1,721,338 research outputs found
Sol-gel film containing metal and semiconductor nanoparticles for gas sensing
No full textFunctional nanocomposite films have been obtained by doping sol-gel films with metal and semiconductor nanoparticles for gas sensor application. Three synthetic approaches were adopted, each of them characterized by a systematic increase of the final materials morphology, structure and micro-structure control. The synthesized layers comprised of an inorganic porous matrix (SiO2, TiO2 and NiO) containing nanosized metal (Au, Pt) or semicon-ductor crystals (NiO), and were shown to be active materials for chemical recognition of H2 and CO. The films were deposited onto different sensing supports, leading to successful gas detection via optical, conductometric and surface acoustic wave interfaces
Detecting H2S oscillatory response using surface plasmon spectroscopy
No full textThe oscillatory change in the optical absorbance of NiO-TiO2 film containing Au nanoparticles in the presence of H2S gas are investigated. The oscillatory phenomena could be monitored by looking at the variation of the surface plasmon resonance peak of the Au nanoparticles embedded in the TiO2-NiO matrix. Au nanoparticles act as optical probes in the detection of H2S, while the oxide matrix is responsible for the catalytic oxidation of H2S. To the best of our knowledge, it is the first time that oscillatory phenomena are monitored by optical spectroscopy
Sol-gel thin films for photonic application
No full textFor the fabrication of photonic devices the sol-gel technique is a potentially lucrative alternative to methods such as physical vapor or chemical vapor deposition because of its solution-processability, low cost and relative ease of production. In this work we harness this potential by developing based photonic devices which incorporate highly luminescent CdSe@ZnS core-shell semiconductor quantum dots (QDs) doped within inorganic (TiO2, ZrO2) or hybrid organic-inorganic sol-gel films. As a pre-requisite to the formation of such devices, luminescent waveguides emitting between green and red have been obtained and their optical properties have been characterized. The photochemical stability of these waveguides was found to highly dependent on the exact sol-gel material used. QDs:Titania based composites were found to be inherently photo-unstable due to photoelectron injection into the bulk matrix and subsequent nanocrystal oxidation. In comparison, zirconia composites were significantly more robust with high photoluminescence retained up to annealing temperatures of 300 °C. Despite this difference in photo-chemical stability, both titania and zirconia composite waveguides exhibited amplified stimulated emission (ASE) with one-photon and two-photon optical pumping, however only zirconia based waveguides exhibited long term photostability. This Zirconia based films have been used for the realization of distributed feedback lasers and Bragg micro-cavities
Au and NiO nanoparticles dispersed inside porous SiO2 sol-gel film: correlation between localized surface plasmon resonance and structure upon thermal annealing
No full textThe favorable lattice matching between Au and NiO crystals made possible the growth of unique cookie-like nanoparticles (25 nm mean diameter) inside a porous SiO 2 film after annealing at 700°C. The unusual aggregates result from the coupling of well distinguishable Au and NiO hemispheres, which respectively face each other through the (100) and (200) lattice planes. The thermal evolution of the Au and NiO nanoparticles structure has been studied by high resolution transmission electron microscopy and UV-visible absorption spectroscopy and correlated with the evolution of the Au surface plasmon resonance peak
Photluminescence properties of orgainic-inorganic sol-gel films doped with semiconductor quantum dots
No full textHybrid organic-inorganic thin films doped with lead sulfide nanocrystallites were synthesized by a combination of colloidal chemistry and sol-gel processing. In order to study the influence on the spectroscopic properties of the crystallite surface, and hence the related defect states, PbS-doped films with different sulfur to lead ratios and different surface capping agent concentrations were fabricated. X-ray diffraction measurements showed the presence of nanoparticles with a mean diameter raging from 3 to 5 nm. The absorption spectra showed a large blue shift of the absorption edge to shorter wavelength, indicating strong quantum confinement. Strong photoluminescence emission in the near infrared was found by pumping at 514 or 532 nm. The emission intensity and its position were found to be dependent on the elaboration parameters. The film fabrication process influences only slightly the good particle size distribution of the colloidal PbS solutions. Best results were obtained for films with low sulfur to lead ratio or with high capping agent concentration
Fabrication of erbium-doped channel waveguides by a combination of ion exchange and sol-gel techniques
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