Nitrogen-doped titanium oxide thin films covered by gold metal nanoparticles were grown on (001) SiO
2
quartz substrates by pulsed laser deposition. A KrF* excimer laser source (
λ
= 248 nm,
τ
FWHM
... ≤ 25 ns,
ν
= 10 Hz) was used for the irradiation of TiO
2
and gold metal targets. The experiments were performed in controlled reactive oxygen or nitrogen atmosphere. The layers were grown for photocatalytic applications. Evaluation of photocatalytic activity was performed by photodegradation of methyl orange under near-UV light irradiation. Our results show that nitrogen doping and addition of gold nanoparticles have complementary effects, photoactivity being significantly improved as compared to that of pure titanium oxide.
Anatase phase titanium dioxide (TiO,) thin films were grown by pulsed laser deposition on (0 0 1) SiO2 substrates. An UV KrF* (lambda = 248 run, tauFWHM approx 20 us, v = 2 Hz) excimer laser was used ...for the irradiation of the TiO2 targets. The substrates were kept at room temperature or heated during the film deposition at values within the 100-500 deg C range. The crystalline quality of the films and their chemical composition were investigated by X-ray diffractometry and energy dispersive X-ray spectroscopy. The optical properties were studied by a double beam spectrophotometer in the spectral range of 400-1200 nm. At substrate temperatures higher than 300 deg C, the structure of the deposited thin films changes from poorly to well crystallised, corresponding to the tetragonal TiO2 anatase phase. The average optical transmittance in the visible-infrared spectral range of the films is higher than 85% which makes them suitable for sensor applications.
Hybrid layers consisting of Fe oxide, Fe hydroxide, and nitrogen doped graphene-like platelets have been synthesized by an eco-friendly laser-based method for photocatalytic applications. The complex ...composite layers show high photodecomposition efficiency towards degradation of antibiotic molecules under visible light irradiation. The photodecomposition efficiency was investigated as a function of relative concentrations of base materials, Fe oxide nanoparticles and graphene oxide platelets used for the preparation of target dispersions submitted to laser irradiation. Although reference pure Fe oxide/Fe hydroxide layers have high absorption in the visible spectral region, their photodecomposition efficiency is negligible under the same irradiation conditions. The high photocatalytic decomposition efficiency of the nanohybrid layer, up to 80% of the initial antibiotic molecules was assigned to synergistic effects between the constituent materials, efficient separation of the electron-hole pairs generated by visible light irradiation on the surface of Fe oxide and Fe hydroxide nanoparticles, in the presence of conducting graphene-like platelets. Nitrogen doped graphene-like platelets contribute also to the generation of electron-hole pairs under visible light irradiation, as demonstrated by the photocatalytic activity of pure, reference nitrogen doped graphene-like layers. The results also showed that adsorption processes do not contribute significantly to the removal of antibiotic molecules from the test solutions. The decrease of the antibiotic concentration under visible light irradiation was assigned primarily to photocatalytic decomposition mechanisms.
Display omitted
•Ternary CNT/GO/ZnO nanohybrid electrodes.•Laser-material processing.•Photocatalyst layers active under visible light irradiation.•Photodecomposition of antibiotic ...molecules.•Electrochemical energy storage.
Carbon nanotube – highly reduced graphene oxide – transition metal oxide (ZnO) nanohybrid layers were synthesized using a one-step laser technique. Commercial multiwall carbon nanotubes (MWCNTs), graphene oxide (GO) platelets and ZnO nanoparticles were used as starting materials. We discuss the influence of carbon/metal oxide ratio on the physico-chemical properties of the nanohybrid layers, geometrical characteristics, shape and dimensions of constituent nanoentities, chemical composition and chemical bonding states, optical properties, UV–visible absorption, band gap values, as well as charge transfer properties. In the followings the relation between these properties and functional characteristics, removal of water contaminants, antibiotic molecules, and charge storage performances of the ternary, MWCNTs/reduced GO/ZnO layers are presented, identifying the optimum relative concentrations of the constituting nanomaterials. The high photocatalytic efficiencies both under UV and visible light irradiations, even after several consecutive degradation cycles, were attributed to effective separation of photogenerated charge carriers by carbon nanomaterials as well as formation of oxygen deficient ZnOx−1 nanocrystals. The enhanced charge storage capacity of ternary nanohybrid electrodes is based on combined electrochemical double layer capacitance and pseudocapacitance implying redox reactions on the surface and subsurface of the layers in contact with the electrolyte. Both functional properties are strongly influenced by the relative concentrations of the nanomaterials constituting the ternary layers.
Transparent nickel oxide thin films were grown by reactive pulsed laser deposition. An ArF* (λ=193 nm, τ=12 ns) excimer laser source was used to ablate the Ni targets in a controlled pressure of ...ambient oxygen. The substrates were either kept at room temperature or heated to a selected temperature within the 200–400 °C range. Post-deposition heat treatment, which was applied to further promote crystallization and overcome any oxygen deficiency, yielded transparent thin films. The surface morphology and crystalline status of the synthesized thin structures were analyzed in correlation with their optical properties. A significant response to several concentrations of hydrogen was demonstrated when heating the nickel oxide films at 185 °C.
Bioactive glass (BG), calcium hydroxyapatite (HA), and ZrO
2 doped HA thin films were grown by pulsed laser deposition on Ti substrates. An UV KrF
* (
λ
=
248
nm,
τ
≥
7
ns) excimer laser was used for ...the multi-pulse irradiation of the targets. The substrates were kept at room temperature or heated during the film deposition at values within the (400–550
°C) range. The depositions were performed in oxygen and water vapor atmospheres, at pressure values in the range (5–40
Pa). The HA coatings were heat post-treated for 6
h in a flux of hot water vapors at the same temperature as applied during deposition. The surface morphology, chemical composition, and crystalline quality of the obtained thin films were studied by scanning electron microscopy, atomic force microscopy, and X-ray diffractometry. The films were seeded for
in vitro tests with Hek293 (human embryonic kidney) cells that revealed a good adherence on the deposited layers. Biocompatibility tests showed that cell growth was better on HA than on BG thin films.
B doped as well as B and N co-doped highly reduced graphene oxide and multiwall carbon nanotubes/Ni oxide and Ni hydroxide nanohybrid layers were synthesized using a one-step laser technique. NiO ...nanoparticles, graphene oxide platelets, and multiwall carbon nanotubes were used as starting materials for the preparation of the composite layers. H3BO3 was used as B precursor and urea as well as NH3 as N precursors for B and N co-doping of the composite layers. The influence of the nature and concentration of the B and N precursors on the physico-chemical properties of the nanohybrid layers, chemical composition and chemical bonding states, crystalline structure, as well as charge transfer properties was systematically investigated. The relation between the physico-chemical properties and functional characteristics of the nanohybrid layers, photocatalytic removal of water contaminants under simulated sun irradiation conditions was studied, identifying the optimum concentrations of the dopant precursor materials. The mechanism of the photodegradation process was explored, based of the band structure of the composites. The main intermediates, reactive oxygen species implied in the photocatalytic degradation processes of organic molecules, was investigated through the addition of scavengers to the organic dye test solutions. The highest photocatalytic activities were achieved for B and N co-doped samples synthesised using H3BO3 as B and urea as N precursors.
Display omitted
