Mesoporous transparent films

It has also been demonstrated that mesoporous materials are viable candidates for optical devices [90]. Silicon nanoclusters were formed inside optically transparent, free-standing, oriented mesoporous silica film by chemical vapor deposition (CVD) of disilane within the spatial confines of the channels. The resulting silicon-silica nanocomposite displayed bright visible photoluminescence and nanosecond lifetimes (Fig. 2.12). The presence of partially polymerized silica channel walls and the retention of the surfactant template within the channels afforded very mild 100-140°C CVD conditions for the formation of... 

Ko C.H., Kim J.M., Ryoo R. Mesocrystal engineering using non-bonded interaction to obtain optically transparent mesoporous silica films and plates with uniform orientation. Microporous Mesoporous Mater. 1998 21 235-243... 

Nishiyama N., Tanaka S., Egashira Y., Oku Y., Ueyama K. Vapor-phase s)mthesis of mesoporous silica thin films. Chem. Mate. 2003 15 1006-1011 Noma T., Takada K., Miyata H., lida A. X-ray micro diffraction study on mesostructured silica thin films. Nucl. Instrum. Methods Phys. Res. A 2001 467 1021-1025 Ogawa M. Formation of novel oriented transparent films of layered silica-surfactant nanocomposites. J. Am. Chem. Soc. 1994 116 7941-7942... 

Ogawa M., Ishikawa H., Kikuchi T. Preparation of transparent mesoporous silica films by a rapid solvent evaporation method. J. Mater. Chem. 1998b 8 1783-1786 Ogawa M., Kikuchi T. Preparation of self-standing transparent films of silica-surfactant mesostructured materials and the conversion to porous silica films. Adv. Mater. 1998c 10 1077-1080... 

Ogawa M., Kuroda K., Mori J.-I. Aluminium-containing mesoporous silica films as nano-vessels for organic photochemical reactions. Chem. Commun. 2000a 2441-2442 Ogawa M., Masukawa N. Preparation of transparent thin films of lamellar, hexagonal and cubic silica-surfactant mesostructured materials by rapid solvent evaporation methods. Microporous Mesoporous Mater. 2000b 38 35 1... 

Okabe A., Fukushima T., Ariga K., Aida T. Color-tunable transparent mesoporous silica films Immobilization of one-dimensional columnar charge-transfer assemblies in aligned silicate nanochannels. Angew. Chem. Int. Ed. 2002 41 3414-3417... 

Shioya, Y., Ikeue, K., Ogawa, M., and Anpo, M. (2003) Synthesis of transparent Ti-containing mesoporous silica thin film materials and their unique photocatalytic activity for the reduction of C02 with H20. Applied Catalysis A General, 254 (2), 251-259. 

Figure 9.7. Illustration of the usage of mesoporous films of transparent conducting oxides for novel types of solar cells. The dark gray areas correspond to ITO, the brighter ones to an oxide deposited onto the TCO matrix. The sphere symbolizes a dye. For instance, such films can be used as porous electrodes to include dyes and to deposit semiconductors such as ZnO. 

Fattakhova-Rohfing, D. Brezesinski, T. Rathousky, J. Feldhoff, A. Oekermann, T. Wark, M. Smarsly, B. 2006. Transparent conducting films of indium tin oxide with 3D mesopore architecture. Adv. Mater. 18 2980-2983. 

Dye-sensitized solar cells (DSSCs) are photoelectrochemical solar devices, currently subject of intense research in the framework of renewable energies as a low-cost photovoltaic device. DSSCs are based upon the sensitization of mesoporous nanocrystalline metal oxide films to visible light by the adsorption of molecular dyes.5"7 Photoinduced electron injection from the sensitizer dye (D) into the metal oxide conduction band initiates charge separation. Subsequently, the injected electrons are transported through the metal oxide film to a transparent electrode, while a redox-active electrolyte, such as I /I , is employed to reduce the dye cation and transport the resulting positive charge to a counter electrode (Fig. 17.4). 

The films of organic polymers like polypropylene orpolyethyleneterephta-late, when subjected to mechanical tensions, develop systems of micro- and mesopores that make them transparent for the diffusion of solutions in solvents not dissolving the polymers itself. The counterflow diffusion of solutions ofM02(0C2H40Me)2 (M = Mo, W) in MeOC2H4OH (from one side) and water solutions (from the other side) permitted composites to be obtained where the metal (Mo, W) oxohydroxide particles were formed in situ inside such organic polymer films and remained there after the removal of the solvents [171],... 

Figure 3. Transient-absorption decay kinetics for a 4 pm thick transparent mesoporous film sensitized with AR25. The solid line corresponds to the fitting to a stretched exponential function AO. D. = exp[-(t/T) ]. The excitation wavelength was = 535 nm and the probe wavelength was Ap, = 800 nm.

The morphology of ordered mesostructured carbons is another important factor with respect to their practical applications. Various macroscopic morphologies are required, for example, films (in sensor, separation and optical applications), uniformly sized spheres (in chromatography) or transparent monoliths. Using suitable synthesis strategies, it is possible to control the external shape of the templated mesoporous carbon materials to generate powders, films and membranes, spheres, hollow spheres, rods, fibres, nanowires, nanotubes and monoliths. 

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