Chemical nanostructures

I think that the present two Colloid Chemistry issues of Topics in Current Chemistry nicely cover the width and the modern spirit of colloid science which (mostly just recently) has given chemists a whole new toolbox for treating and creating chemical nanostructures in a rational way. With this in mind, I hope that all the readers will find some inspiration and profit in the various contributions. 

In author s opinion, from the fundamental point of view, especially important directions of further progress will be a wider application of artificial chemical nanostructures, micro- and nanomechanics and further progress in the area of application of biomimetic mechanisms and design of biomimetic devices. 

The solution to this problem, which necessarily involves reducing the size of structure and thereby increasing the Coulomb charging energy, seems conceivable if chemical nanostructures are taken into consideration. Accordingly, at present, ligand-stabilized metal nanoparticles with their well defined structure seem to be the most promising candidates. ... 

Despite these promising perspectives one must be aware that the utilization of the minute size requires new and comprehensive fabrication and addressing techniques. Extension of the present-day technologies to smaller structures or the development of techniques which treat chemical nanostructures with conventional technologies will not reach the true molecular size scale and will therefore waste much of the advantage of these structures. But even in arrays which are preformed by lithographic techniques, the self-assembling nature of chemical nanostructure helps overcome current size limits. 

To conclude, we expect that ILs will find, besides organometaUic synthesis, catalysis and electrochemistry, a further rich field of application in the synthesis of nanostructured solids, either to make nano-objects (e.g. particles and fibers) with very special and otherwise non-addressable properties or for the design of nanopores and nanochannels in solids. It was reasoned that it is the quite singular combination of energetic adaptability towards other molecules and phases plus the strong H-bonded driven solvent structure which makes ILs a potential key tool in the realization of a new generation of chemical nanostructures. 

Physical and chemical nanostructure transfer in polymer spin-transfer printing. Adv. Mater., 16 (7), 581-584. 

There are many other experiments in which surface atoms have been purposely moved, removed or chemically modified with a scanning probe tip. For example, atoms on a surface have been induced to move via interaction with the large electric field associated with an STM tip [78]. A scaiming force microscope has been used to create three-dimensional nanostructures by pushing adsorbed particles with the tip [79]. In addition, the electrons that are tunnelling from an STM tip to the sample can be used as sources of electrons for stimulated desorption [80]. The tuimelling electrons have also been used to promote dissociation of adsorbed O2 molecules on metal or semiconductor surfaces [81, 82]. 

An excellent, accessible overview of what surface scientists do, the problems they address and how they link to technological needs is in a published lecture by a chemist, Somorjai (1998). He concisely sets out the function of numerous advanced instruments and techniques used by the surface scientist, all combined with UHV (LEED was merely the first), and exemplifies the kinds of physical chemical issues addressed - to pick just one example, the interactions of co-adsorbed species on a surface. He also introduces the concept of surface materials , ones in which the external or internal surfaces are the key to function. In this sense, a surface material is rather like a nanostructured material in the one case the material consists predominantly of surfaces, in the other case, of interfaces. 

The engineering of novel deviees requires, in many eases, materials with finely seleeted and preestablished properties. In partieular, one of the most promising lines of synthetic materials research consists in the development of nanostructured systems (nanocomposites). This term describes materials with structures on typical length scale of 1-100 nm. Nanometric pieces of materials are in an intermediate position between the atom and the solid, displaying electronic, chemical and structural properties that are distinct from the bulk. The use of nanoparticles as a material component widens enormously the available attributes that can be realised in practice, which otherwise would be limited to bulk solid properties. 

In addition to chemical or physical properties, a fascinating aspect of fullerene related materials is their central empty space, where atoms, molecules or particles can be enclosed. The enclosed particles are then protected by the robust graphitic layers from chemical or mechanical effects. The very long cavities of CNTs have a special potential due to their high aspect ratio and they can be used as templates to fabricate elongated nanostructures. 

Nano-composites (NCs) are materials that comprise a dispersion of particles of at least one of their dimentions is 100 nm or less in a matrix. The matrix may be single or multicomponent. It may include additional materials that add other functionalities to the system such as reinforcement, conductivity and toughness (Alexandre and Dubois, 2000). Depending on the matrix, NCs may be metallic (MNC), ceramic (CNC) or polymeric (PNC) materials. Since many important chemical and physical interactions are governed by surface properties, a nanostructured material could have substantially different properties from large dimensional material of the same composition (Hussain et ah, 2007). 

Electrochemistry provides routes to directly prepare nanostructures both delocalized in a random or organized way and localized at predefined surface sites with adjustable aspect ratios. Purity, monodispersity, ligation, and other chemical properties and treatments are definitely important in most cases. By delocalized electrodeposition it is possible to decorate large areas of metal or semiconductor surfaces with structures of a narrow size distribution stable nuclei-clusters can be... 

Penner RM (2001) Hybrid electrochemical/chemical synthesis of semiconductor nanocrystals on graphite. In Hodes G (ed) Electrochemistry of Nanostructures, Wiley-VCH,... 

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