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Nikos Boukos

Bio: Nikos Boukos is an academic researcher from University of Patras. The author has contributed to research in topics: Nanoparticle & Graphene. The author has an hindex of 37, co-authored 191 publications receiving 5208 citations. Previous affiliations of Nikos Boukos include National Centre of Scientific Research "Demokritos" & University of Ioannina.
Topics: Nanoparticle, Graphene, Nanorod, Adsorption, Thin film


Papers
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TL;DR: Light emitting diodes based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed.
Abstract: Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal?organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour?liquid?solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro-?and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I?V characteristics of ZnO:P nanowire/ZnO:Ga p?n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence characteristics aimed at the development of white LEDs are demonstrated. Although some of the presented LEDs show visible emission for applied biases in excess of 10 V, optimized structures are expected to provide the same emission at much lower voltage. Finally, lasing from ZnO nanorods is briefly reviewed. An example of a recent whispering gallery mode (WGM) lasing from ZnO is demonstrated as a way to enhance the stimulated emission from small size structures.

606 citations

Journal ArticleDOI
TL;DR: In this paper, a graphitic carbon nitride/titania composite photocatalysts with different C 3 N 4 /TiO 2 ratios were synthesized by a simple preparation route through annealing the mixtures of melamine and commercial TiO 2 P25 powder at 550°C for 3h under Ar flow.

311 citations

Journal ArticleDOI
TL;DR: In this article, the photocatalytic efficiency of the titania/graphene (ssG and rGO) nanocomposites was investigated in terms of total NOx (NO and NO 2) removal and NO2 emission.
Abstract: Nanocomposite TiO2/graphene photocatalysts were synthesized via solvothermal process using titanium isopropoxide as a TiO2 precursor. Surfactant-stabilized graphene (ssG) prepared via liquid phase exfoliation and graphene oxide (GO) obtained via oxidation of graphite were used for preparation of two types of composites TiO2/G and TiO2/rGO, respectively, each with graphene loadings 0.01%, 0.1% and 1%. Hydrophilic non ionic surfactant Pluronic F127 was employed in order graphene stabilization in water and homogeneous dispersion with the TiO2 precursor to be achieved. The crystalline structure, composition, morphology, porosity and light absorption of the photocatalysts and their photocatalytic activity in NOx oxidation under UV and visible light irradiation were comparatively investigated. The titania/graphene (ssG and rGO) nanocomposites exhibited higher photocatalytic efficiency than pure TiO2 especially under visible light irradiation in terms of total NOx (NO and NO2) removal and NO2 emission. Differences in the photocatalytic efficiency between the TiO2/G and TiO2/rGO composites were observed originating from the type and the loading of the graphene. In general, the TiO2/rGO exhibited superior efficiency than the TiO2/G and the best results were recorded for low 0.1% graphene loading. The findings are discussed taking into consideration the variation in the BET SSA and the Eg values, as well as the differences in the electronic structure of the ssG and the rGO, the former to be a zero-band gap material and the latter a semiconductor with tunable band gap. The presence of graphene component was determined as a key parameter governing the separation of the photogenerated electron–holes pair through interfacial charge transfer. The significantly increased activity of the TiO2/rGO composites under visible light in NOx removal and the very low levels of NO2 release in comparison to the pure TiO2 render these materials promising photocatalysts for efficient air purification.

202 citations

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TL;DR: The commercial azo dye Reactive Red 195 was selected as a model dye in order to examine the adsorption capacity of TiO2 at room temperature, under dark conditions and it was demonstrated that RR195 could be efficiently adsorbed in aqueous suspension ofTiO2.

161 citations

Journal ArticleDOI
TL;DR: In this article, a comparative analysis of chemical and thermal exfoliation of graphitic carbon nitride (g-C3N4) was performed and it was found that chemical exfoliations resulted in wider band gap with more positive VB edge.
Abstract: Graphitic carbon nitride (g-C3N4) has emerged as one of the most promising visible light active photocatalysts for NOx removal. Due to its low efficiency in bulk form though, many methods have been applied in order to improve the optical properties and photocatalytic activity. Among them, exfoliation via chemical and thermal treatment appears to be very effective and easy to perform. In this work, g-C3N4 was exfoliated by high-yield chemical and thermal treatment. A thorough comparative investigation was performed, revealing successful exfoliation of g-C3N4 and significantly enhanced visible light photocatalytic activity. Both methods led to high pore volume and specific surface area. It was established that chemical exfoliation resulted in wider band gap with more positive VB edge in comparison to thermal exfoliation. Furthermore, increased superoxide radical formation and reactivity of photogenerated electrons was demonstrated by EPR measurements in the case of chemical exfoliation. The chemically exfoliated g-C3N4 showed superior photocatalytic performance in NOx removal under visible light irradiation. This outcome was ascribed to the increased superoxide radical formation, the favorable band gap edges and porosity of the materials.

158 citations


Cited by
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Journal ArticleDOI
TL;DR: Nanoalloys of Group 11 (Cu, Ag, Au) 865 5.1.5.2.
Abstract: 5.1. Nanoalloys of Group 11 (Cu, Ag, Au) 865 5.1.1. Cu−Ag 866 5.1.2. Cu−Au 867 5.1.3. Ag−Au 870 5.1.4. Cu−Ag−Au 872 5.2. Nanoalloys of Group 10 (Ni, Pd, Pt) 872 5.2.1. Ni−Pd 872 * To whom correspondence should be addressed. Phone: +39010 3536214. Fax:+39010 311066. E-mail: ferrando@fisica.unige.it. † Universita di Genova. ‡ Argonne National Laboratory. § University of Birmingham. | As of October 1, 2007, Chemical Sciences and Engineering Division. Volume 108, Number 3

3,114 citations

Journal ArticleDOI
TL;DR: In this paper, an extended account of the various chemical strategies for grafting polymers onto carbon nanotubes and the manufacturing of carbon-nanotube/polymer nanocomposites is given.

2,766 citations

Journal ArticleDOI
TL;DR: In this article, a review summarizes the recent significant progress on the design of g-C3N4-based heterostructured photocatalysts and their special separation/transfer mechanisms of photogenerated charge carriers.
Abstract: Photocatalysis is considered as one of the promising routes to solve the energy and environmental crises by utilizing solar energy. Graphitic carbon nitride (g-C3N4) has attracted worldwide attention due to its visible-light activity, facile synthesis from low-cost materials, chemical stability, and unique layered structure. However, the pure g-C3N4 photocatalyst still suffers from its low separation efficiency of photogenerated charge carriers, which results in unsatisfactory photocatalytic activity. Recently, g-C3N4-based heterostructures have become research hotspots for their greatly enhanced charge carrier separation efficiency and photocatalytic performance. According to the different transfer mechanisms of photogenerated charge carriers between g-C3N4 and the coupled components, the g-C3N4-based heterostructured photocatalysts can be divided into the following categories: g-C3N4-based conventional type II heterojunction, g-C3N4-based Z-scheme heterojunction, g-C3N4-based p–n heterojunction, g-C3N4/metal heterostructure, and g-C3N4/carbon heterostructure. This review summarizes the recent significant progress on the design of g-C3N4-based heterostructured photocatalysts and their special separation/transfer mechanisms of photogenerated charge carriers. Moreover, their applications in environmental and energy fields, e.g., water splitting, carbon dioxide reduction, and degradation of pollutants, are also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced g-C3N4-based heterostructured photocatalysts are presented.

1,759 citations

Journal ArticleDOI
TL;DR: In this paper, the surface of inorganic nanoparticles is modified to improve the interfacial interactions between the inorganic particles and the polymer matrix, which improves the properties of polymeric composites.

1,709 citations

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1,682 citations