Nanoporous structure

A nanoporous structure on the surface of the micro channels can be realized via anodic oxidation, thereby considerably enlarging the catalyst surface [17]. Catalysts... 

According to Ref. [12], template for synthesis of nanomaterials is defined as a central structure within which a network forms in such a way that removal of this template creates a filled cavity with morphological or stereochemical features related to those of the template. The template synthesis was applied for preparation of various nanostructures inside different three-dimensional nanoporous structures. Chemically, these materials are presented by polymers, metals, oxides, carbides and other substances. Synthetic methods include electrochemical deposition, electroless deposition, chemical polymerization, sol-gel deposition and chemical vapor deposition. These works were reviewed in Refs. [12,20]. An essential feature of this... 

Of the various semiconductors tested to date, Ti02 is the most promising photocatalyst because of its appropriate electronic band structure, photostability, chemical inertness and commercial availability. But currently, a variety of nanostmctured Ti02 with different morphologies including nanorods, nanowires, nanostmctured films or coatings, nanotubes, and mesoporous/nanoporous structures have attracted much attention. 

In addition to popular mesoporous silica materials, mesoporous silica supports with various morphologies have also been used for protein immobilization. Tang and coworkers synthesized lotus-leaf-like silica flakes with a three-dimensionally connected nanoporous structure and controllable thickness, which were used for immobilization of ribonuclease A [126]. The synthesized silica flakes have a thickness of200 nm, and a diameter of 3 mm, showing a much higher initial adsorbing rate of... 

The presence of sulfate ions markedly affects the nanopore structure of titania-sulfate aerogels. In Ti02-S042 materials, unlike in zirconia-sulfate aerogels, the larger sulfate load stimulates formation of a more consolidated structure. The XRD analysis shows that even a crystalline phase (anatase) may be present in fresh, dry aerogels, which, perhaps, is the first observation of this phase in sol-gel titania obtained from the low temperature drying process. 

Figure 4 Model of the nanopore structure (cut through a (001) plane), evolution of the inter pore distances with treatment at 620 K, involving shrinkage in the direction normal to the substrate surface.

Specifically, this volume focuses on the synthesis, processing, and structural tailoring of nanocrystalline and nanoporous materials. Nanocrystalline materials possess unique hybrid properties characteristic of neither the molecular nor the bulk solid-state limits and may be confined in nanometersized domains in one, two, or three dimensions for unusual size-dependent behavior. Nanoporous materials, characterized by well-defined pores or cavities in the nanometer size regime and controlled pore diameter and structure, give rise to unique molecular sieving capabilities and ultrahigh internal surface areas. Nanoporous structures also act as hosts and templates for the fabrication of quantum dots and quantum wires. 

The synthesis of novel materials (particularly multicomponent materials) with unusual properties for uses as catalytic converters is gaining interest [72]. Thus, nanoporous structures of materials obtained by high-US agglomeration of monodispersed nanoparticles exhibit excellent properties and do not require the thermal post-treatment usually needed for the crystallization of amorphous materials or removal of surfactants [73]. 

Figure 13.16 Variation of the fluorescence intensity of Eu-35 at 619 nm under alternating streams of air saturated with ethanol (signal intensity decreases) and ethanol-free air (signal intensity increases) [56]. (Reproduced with permission from B.V. Harbuzaru et ah, Metal-organic nanoporous structures with anisotropic photoluminescence and magnetic properties and their use as sensors, Angewandte Chemie International Edition, 2008, 47, no. 6, 1080-1083. Wiley-VCH Verlag Gmbh Co. KGaA.)...

NMR should be powerful to characterize nanopore structures. Fraissard et al proposed Xe NMR technique. [23] Although the chemical shift of Xe is associated with the pore width, its application to unknown porous system is not established yet. 

---