Nano-architectures

Thiol-stabilised gold nanoparticles have not only been used as building blocks for larger structures comprising hundreds or thousands of particles but are also of interest as individual large molecules, i.e. so-called monolayer protected clusters (MFCs) [254], They represent nanoscopic metal surfaces and can be regarded as three-dimensional analogues of two-dimensional macroscopic surfaces. This notion 

1) implementing the imique size-dependent physical properties of individual nanocrystals in a device and 

2) eliciting collective electronic and optical properties due to electronic overlap resulting from the relative positioning of the nanocrystals in the array [270] there is 

An alternative strategy for the formation of ordered nanoparticle arrays is the selforganization method based on biomolecular templates by direct or synergistic 

Although atoms can be arranged in almost infinite permutations, we can currently make only an infinitesimal fraction of what is possible. Very roughly, if we can pack 100 atoms into a cubic nanometer and each atom can be any of the approximately 100 elements, then there are something like 100 °° different ways that we can arrange the atoms in just a single cubic nanometer. A cubic micron expands this to 100 000 000 seems possible is to take a healthy bite out of this enormous 

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Molecular Segregation at Periodic Metal Nano-Architectures on a Solid Surface... 

Nano-architecture and reactivity of Titania catalytic materials. 367... 

The multi-functionality of metal oxides1,13 is one of the key aspects which allow realizing selectively on metal oxide catalysts complex multi-step transformations, such as w-butane or n-pentane selective oxidation.14,15 This multi-functionality of metal oxides is also the key aspect to implement a new sustainable industrial chemical production.16 The challenge to realize complex multi-step reactions over solid catalysts and ideally achieve 100% selectivity requires an understanding of the surface micro-kinetic and the relationship with the multi-functionality of the catalytic surface.17 However, the control of the catalyst multi-functionality requires the ability also to control their nano-architecture, e.g. the spatial arrangement of the active sites around the first centre of chemisorption of the incoming molecule.1... 

This review will discuss the possibility to control and improve the reactivity of Titania by design of new tailored nano-architecture. Specifically, analyses quasi-ID Ti02 nanostructures, e.g. nanorods, nanowires and nanofibres, nanotubes and nanopillars. 2D Titania nanostructures, e.g. columnar-type films, ordered arrays of nanotubes or nano-rods/-wires, nanobowl array, nanomembranes (called also nanohole array) and nanosponge, and Ti-based ordered mesoporous matrices will be instead discussed in a consecutive review paper. 

D. Habel, J. B. Stelzer, J. Caro, M.-M. Pohl, E. Feike, H. Schubert, Nano-Architectured and Nanostructured Materials Fabrication, Control and Properties, [Selected Papers presented at the Euromat Conference], Lausanne, Switzerland, Sept. 1-3, 2003 (2004), Meeting Date 2003, 79-87, Wiley-VCH Verlag GmbH Co. KGaA, Weinheim, Germany. 

Centi, G. Perathoner, S., Nano-architecture and reactivity of titania catalytic materials. Part 2. Bidimensional nanostructured films. Catalysis (RSC) 2009,21 82-130. 

Nano-architecture and reactivity of titania catalytic materials. Part 2. Bidimensional nanostructured films... 

A key aspect of metal oxides is that they possess multiple functional properties acid-base, electron transfer and transport, chemisorption by a and 7i-bonding of hydrocarbons, O-insertion and H-abstraction, etc. This multi-functionality allows them to catalyze complex selective multistep transformations of hydrocarbons, as well as other catalytic reactions (NO,c conversion, for example). The control of the catalyst multi-functionality requires the ability to control not only the nanostructure, e.g. the nano-scale environment around the active site, " but also the nano-architecture, e.g. the 3D spatial organization of nano-entities. The active site is not the only relevant aspect for catalysis. The local area around the active site orients or assists the coordination of the reactants, and may induce sterical constrains on the transition state, and influences short-range transport (nano-scale level). Therefore, it plays a critical role in determining the reactivity and selectivity in multiple pathways of transformation. In addition, there are indications pointing out that the dynamics of adsorbed species, e.g. their mobility during the catalytic processes which is also an important factor determining the catalytic performances in complex surface reaction, " is influenced by the nanoarchitecture. 

The nano-architecture is thus an important aspect to consider for the design of novel catalysts and a critical element to consider also in analyzing how to bridge the gap between model and real catalysts. In fact, in addition to the issues of pressure and material gap , the complexity gap exists." Goodman " over ten years ago pointed out that despite the successes in modelling catalysts with single crystals, there is a clear need to develop models with higher levels of complexity and which take into account the 3D nanoarchitecture. 

In general terms, building a defined nano-architecture in oxide-type materials further extends the concept of nanocatalysis, e.g. when the electrons are confined, and physical and chemical properties are not scalable from the bulk properties. Studies have been made mainly on clusters/metal particles in the... 

Although the discussion reported here will be mainly in reference to titania nanostructured films, the opportunities and problems analyzed are of more general interest and regard how to use the concept of bidimensional nanostructured oxide films to prepare novel catalysts with tailored nano-architectures. 

Keywords Block copolymer Controlled-nano architecture Functionalization ... 

The familiar dsDNA is a linear molecule not suitable for forming complex motifs. To build complex DNA nano architectures, branched DNA molecules are needed. Fortunately, this key problem was resolved. By designing appropriate DNA sequences, the branched DNA molecules can be produced by the conventional solid support synthesis. 

Champion, Y., and Fecht, H. (2004), Nano-Architectured and Nanostructured Materials Fabrication, Control and Properties, Wiley, Hoboken, NJ. 

Solvent Modulated Reversible Interconversion between Two Self-Assembled Nano-Architectures... 

In a different reaction scheme, one can take advantage of the fimctional porphyrin macrocycle to create metalloporphyrin compounds and nanoarchitectures in 2D. Upon exposure of regular TPyP arrays self-assembled on Ag(lll) to iron monomers supplied by an atomic beam, selective com-plexation occurs whereby the template structure is strictly preserved [156]. This expands the diversity of metalloporphyrin layers conventionally realized by evaporation of integral species, because in-situ metalation provides a route towards novel metalloporphyrin nano architectures and patterned surfaces [156-158]. In a related reaction pathway, evidence could be obtained for in-situ complexation and metal center-induced switching of phenanthroline-based catenane units deposited the Ag(lll) surface [182]. 

U. Gupta, H.B. Agashe, A. Asthana, N.K. Jain, Dendrimers novel polymeric nano-architectures for solubility enhancement. Biomacromolecules 7 (2006) 649-658. 

Template-Free Methods for Conducting Polymer Nano-Architecture... 

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