Controlled-nano architecture

Keywords Block copolymer Controlled-nano architecture Functionalization ... 

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. 

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. 

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

An interesting observation with respect to the supramolecular organization of 50 and 51 is the difference in the CD spectra in heptane solution. The bisig-nated CD spectrum of OPV 50 is opposite to that of 51 in sign and shape. However, in the case of 51 an inversion of the Cotton effect is observed with time (within 80 min), which is accompanied by a shift in the zero-crossing. The sign reversal of 51 shows first-order kinetics with a rate constant of k = 5.6 X 10 s . The initially formed hehx may be kinetically controlled, whereas the finally formed helix may be the thermodynamically stable form. Thus a variety of nano architectures of different shape, size and properties... 

Sulfiphihc cathode materials w ith a strong affinity for lithium polysulfides are a promising group of candidates to control the dissolution and precipitation reactions in the cell, where the improvement of conductivity and the areal sulfur loading is an important objective. A metallic CogSs material has been described with an interconnected graphene-like nano-architecture that realizes this issue (28). 

The reviews collected in this book convey some of the themes recurrent in nano-colloid science self-assembly, constraction of supramolecular architecture, nanoconfmement and compartmentalization, measurement and control of interfacial forces, novel synthetic materials, and computer simulation. They also reveal the interaction of a spectrum of disciplines in which physics, chemistry, biology, and materials science intersect. Not only is the vast range of industrial and technological applications depicted, but it is also shown how this new way of thinking has generated exciting developments in fundamental science. Some of the chapters also skirt the frontiers, where there are still unanswered questions. 

Tailor-made macromolecules have come into the focus of polymer science to overcome the challenges of a number of complex applications from the nano to the macro scale. Materials scientists have been designing and synthesizing tailor-made macromolecules specific for each application. These materials are composed of different monomeric units, chemical functionalities, and topologies. The challenge has been to control precisely the position of the functionality on the polymer, to determine the necessary ratio of monomeric units, as well as to understand the effect of the molecular architecture on the material performance. 

Moreover, the inner cavity of supramolecular capsules provides a discrete, well-defined environment ideally suited to investigate effects of compartmentalization and processes in confined spaces [8]. To realize technical applications as detection and stabilization of encapsulated molecules or their use as nano-sized reaction vessels, precise control of important factors such as size, stability, porosity of the walls, and functionalization of the inner surface have to be achieved [9-18]. Several capsules have been synthesized and a proof of principle for several applications has been provided, but in most cases their use is restricted to small guest molecules. The development of spacious architectures which are able to encapsulate several bulky molecules and are amenable for decoration of the inner surface with functional groups will constitute an important step on the way to functional systems. 

This article describes recent efforts to develop, characterize, and predict three-dimensional organizations of ordered, covalent connectivity around various picoscopic and sub-nanoscopic reference points (i.e., initiator cores sub-nano-scopic (point-like) reactive organic molecules). The resulting covalent architecture can be systematically controlled by stepwise reiterative reaction sequences (generations) as described below ... 

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