Nanostructured Metal Oxide Films

The presence of alkali metal ions is crucial for the stabilization of excess charge trapped within the nanopartides. Intercalation of metal ions within the nanoparticle thus becomes a limiting factor as the rate of transport of these ions becomes slower in thicker metal oxide films. This in turn controls the rate of coloration and recovery of the electrochromic effects. Limited efforts have also been made to employ mixed Ti02/W03 [145], WO3/V2O5 [146], and WO3/M0O3 [147] systems to enhance the efficiency of electrochromic effects. The beneficial aspect of these nanostructured semiconductor films in electrochromic devices is yet to be explored in a systematic way. 

Nanostructured Oxide Films Modified with Dyes and Redox Chromophores 

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These motivations strengthen the interest for eatalysis towards the development of ordered assemblies of ID nanostruetures for oxide materials, e.g. metal-oxide catalysts in which the 3D macro-structure is constituted by an ordered assembling of regular ID structures with nanometric size. Note that this type of structure is significantly different from that of metal-oxide supported over other metal-oxides, such as monolayer-type V202/Ti02 materials. See also later, when the concept of nanostructured metal-oxide films is defined. 

Nanostructured metal oxide film deposition can also be prepared by hydrothermal decomposition, film casting method (sonication of nanoparticles in aqueous solution (H20) or preparation of aqueous suspension of nanoparticles for spread on conducting glass plate) and nanosized metal nanoparticles prepared by controlled hydrolysis [16,18,19,21,26],... 

Abstract In the last decade, the sonoelectrochemical synthesis of inorganic materials has experienced an important development motivated by the emerging interest in the nanostructures production. However, other traditional sonoelectrochemical synthesis such as gas production, metal deposits and metallic oxide films have also been improved with the simultaneous application of both electric and ultrasound fields. In this chapter, a summary of the fundamental basis, experimental set-up and different applications found in literature are reported, giving the reader a general approach to this branch of Applied Sonoelectrochemistry. 

With the advent of synthetic methods to produce more advanced model systems (cluster- or nanoparticle-based systems either in the gas phase or on planar surfaces), we come to the modern age of surface chemistry and heterogeneous catalysis. Castleman and coworkers demonstrate the large influence that charge, size, and composition of metal oxide clusters generated in the gas phase can have on the mechanism of a catalytic reaction. Rupprechter (Chap. 15) reports on the stmctural and catalytic properties of planar noble metal nanocrystals on thin oxide support films in vacuum and under high-pressure conditions. The theme of model systems of nanoparticles supported on planar metal oxide substrates is continued with a chapter on the formation of planar catalyst based on size-selected cluster deposition methods. In a second contribution from Rupprecther (Chap. 17), the complexities of surface chemistry and heterogeneous catalysis on metal oxide films and nanostructures, where the extension of the bulk structure to the surface often does not occur and the surface chemistry is often dominated by surface defects, are discussed. 

X-ray diffraction technique is a non-destructive analytical technique that reveals information about crystallographic structure, chemical composition and physical properties of nanostructured materials. UV/Vis spectroscopy is routinely used in the quantitative determination of films of nanostructured metal oxides. The size, shape (nanocomb and nanorods etc,) and arrangement of the nanoparticles can be observed through transmission electron microscope (TEM) studies. Surface morphology of nanostructured metal oxides can be observed in atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies. 

The development of nanostructured platforms based on novel metal-oxide films can provide insight into cell-material interactions for the development of improved implant surfaces. In this... 

Oxide surfaces, and in particular oxide films, are versatile substrates for the preparation of model catalysts. Quite a few of these systems show nanoscale reconstructions, which can be employed as templates for the growth of ordered model catalysts of reduced complexity. In order to efficiently control the growth of nanostructured metal particle arrays, two conditions have to be met. First, the template must provide sites of high interaction energy that trap the deposited metals. Second, the kinetics of the growth process must be carefully controlled by choosing... 

As an example of metal oxide NPs, nanostructured Ti02 film, often used in photocatalytic reactions, is suitable for the activation of C02 as chemical feedstock [172]. It was shown that C02 can be converted into low-density polyethylene (LDPE) under electrochemical conditions in the presence of a nanoscale Ti02 electrode using a mixture of EMI.BF4 and water. 

Demokritos" (NCSR) Institute of Materials Science works on preparation characterization of nanostructured materials, metallic and metal - oxide contacts, preparation of thin/thick films, and hydrogen storage. 

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