Graphene has been recognized as a promising gas sensing material. The response of graphene-based sensors can be radically improved by introducing defects in graphene using, for example, metal or metal oxide nanoparticles. We have functionalised CVD grown, single-layer graphene by applying pulsed laser deposition (PLD) of V2O5 which resulted in a thin V2O5 layer on graphene with average thickness of ≈0.6 nm. From Raman spectroscopy, it was concluded that the PLD process also induced defects in graphene. Compared to unmodified graphene, the obtained chemiresistive sensor showed considerable improvement of sensing ammonia at room temperature. In addition, the response time, sensitivity and reversibility were essentially enhanced due to graphene functionalisation by laser deposited V2O5. This can be explained by an increased surface density of gas adsorption sites introduced by high energy atoms in laser ablation plasma and formation of nanophase boundaries between deposited V2O5 and graphene.
Thin solid films consisting of ZrO 2 and Fe 2 O 3 were grown by atomic layer deposition (ALD) at 400 °C. Metastable phases of ZrO 2 were stabilized by Fe 2 O 3 doping. The number of alternating ZrO 2 and Fe 2 O 3 deposition cycles were varied in order to achieve films with different cation ratios. The influence of annealing on the composition and structure of the thin films was investigated. Additionally, the influence of composition and structure on electrical and magnetic properties was studied. Several samples exhibited a measurable saturation magnetization and most of the samples exhibited a charge polarization. Both phenomena were observed in the sample with a Zr/Fe atomic ratio of 2.0. 119
Nanolaminates of ZrO2 and HfO2 were grown by atomic layer deposition, using metal halides and water as precursors, on silicon and fused quartz substrates at 300 °C. The crystalline phase composition, optical refraction, and mechanical performance of the multilayers were influenced by the relative contents of the constituent metal oxides. The crystal growth in as-deposited HfO2 dominantly led to the monoclinic phase, whereas ZrO2 was partially crystallized as its metastable and hard tetragonal polymorph. The hardness and elasticity of the nanolaminate structures could be modified by varying the amounts of either oxide contributing to the crystallographic order formed in the solid films. The refractive indexes depended on the nanolaminate structure.
Cobalt-and iron-containing nitrogen-doped carbon nanomaterials are synthesised from 5-methylresorcinol-formaldehyde resin nanospheres by pyrolysis in the presence of nitrogen and metal precursors. Two approaches used for the synthesis yield the catalysts of different morphology, consisting of spherical or irregular porous carbon structures. The electrocatalytic properties of the materials towards the oxygen reduction reaction (ORR) in alkaline solution are evaluated by thin-film rotating disk electrode method. The catalysts containing transition metals exhibit enhanced electrocatalytic activity for ORR as compared to the metal-free nitrogen-doped materials, cobaltcontaining catalysts being slightly more active than iron-based materials. The structure and surface composition of the materials are characterised by scanning electron microscopy, N 2 adsorption studies and X-ray photoelectron spectroscopy.was calculated by using a quenched solid density functional theory (QSDFT) equilibria model for slit type pores.
Introduction Nanostructured Co3O4 in thin film form may possess and demonstrate a variety of properties making the material attractive for several applications. Co3O4 has been investigated as an important electrode material [1-4], gas sensor [5, 6], catalyst [7, 8], or superhydrophobic coating [9]. Co3O4 films have demonstrated resistive switching properties potentially enabling their application in resistive random access memory devices [10, 11]. Cobalt oxide, Co3O4, containing Co 2+ and Co 3+ ions, is recognized as magnetic semiconductor material [12]. Antiferromagnetic behavior with characteristic magnetization-field curves can be demonstrated by Co3O4 nanoparticles [13]. Regarding the possible applications in spintronics, it may occur necessary to activate ferromagnetic coupling in Co3O4 nanoparticles by hybridization with foreign materials, e.g. graphene oxide [14]. Co3O4 films have been grown by oxidation of electron-beam evaporated Co layers [15], pulsed laser deposition [5, 10] chemical bath deposition [1, 6], chemical solution deposition [8, 11], hydrothermal method [2, 13], solvothermal synthesis [9], spray pyrolysis [16]
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