Dimensionality nanostructured materials

Fig. la. Atomic structure ofa two-dimensional nano-structured material. For the sake of clarity, the atoms in the centers of the crystals are indicated in black. The ones in the boundary core regions are represented by open circles. Both types of atoms are assumed to be chemically identical b Atomic arrangement in a two-dimensional glass (hard sphere model), c Atomic structure of a two-dimensional nanostructured material consisting Of elastically distorted crystallites. The distortion results from the incorporation of large solute atoms. In the vicinity of the large solute atoms, the lattice planes are curved as indicated in the crystallite on the lower left side. This is not so if all atoms have the same size as indicated in Fig. la [13]... 

There exist a variety of methods to synthesize quasi-one-dimensional nanostructured materials, which include but not limited to vapor phase growth, template-assisted synthesis, sol-gel deposition, surfactant-assisted growth, sonochemical method, hydrothermal method, and electrochemical deposition [21], Among the various methods, the electrochemical anodization method is one of the simplest and cheapest methods to synthesize ordered quasi-one-dimensional nanostructure. 

Electrical conduction is also very important for many devices that exploit the huge area of surface or interface per unit volume in zero-dimensional nanostructured materials such as nanoporous materials, granular materials, nanocomposites, and nanoparticle assemblies. Examples of such devices are chemiresistor-type sensors, solar cells, light-emitting diodes, and energy-storage cells. From the point of view of electron... 

Kroto HW, Heath JR, O Brien SC, Curl RF, Smalley RE (1985) C buckminsterfullerene. Nature 318 162-163 Kuchibhatla SVNT, Karakoti AS, Bera D, Seal S (2007) One dimensional nanostructured materials. Prog Mater Sci 52 699-913... 

Knchibhatla SVNT, Karakoti AS, Bera D, Seal S. One dimensional nanostructured materials. Prog Mater Sci 2007 52 699-913. 

C. K. Chan, One-dimensional nanostructured materials for Li-ion batteiy and supercapacitor electrodes. Ph.D. Dissertation, Stanford University (2009). 

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). 

Vaia, R.A., Ishii, H. and Giannelis, E.P. 1993. Synthesis and properties of two dimensional nanostructures by direct intercalation of polymer melts in layered silicates. Chemistry of Material 5 1694-1696. 

Huang, J., Xia, C., Cao, L. and Zeng, X. (2008) Facile microwave hydrothermal synthesis of zinc oxide one-dimensional nanostructure with three-dimensional morphology. Materials Science and Engineering B, 150, 187-193. 

Zhou, Y. and Shimizu, T. (2008) Lipid nanotubes a unique template to create diverse one-dimensional nanostructures. Chemistry of Materials, 20 (3), 625-633. Nogawa, K., Tagawa, Y., Nakajima, M., Arai, F., Shimizu, T., Kamiya, S. and Fukuda, T. (2007) Development of novel nanopipette with a lipid nanotube as nanochannel. Journal of Robotics and Mechatronics, 19 (5), 528-534. 

We use the same approach to classify the different nanostructures for Titania. The term one-dimensional (ID) nanostructures indicate nanocrystals in which elongation only in one direction is above this threshold (about 10 nm). This class of ID nanostructures comprises different types of nano-ordered materials, such as nanorods, -wires, -coils, -fibers, -pillars (or -columns) and -tubes. We prefer to use the term quasi one-dimensional nanostructures, because often the dimensions are larger than the indicated threshold, although elongation along one main axis still exists. When the diameter of the nanorod, nanowire or nanotube becomes smaller, there is often a significant change in the properties with respect to crystalline solids or even two-dimensional systems. A bismuth nanowire is an excellent example, which transforms into a semiconductor, as the wire diameter becomes smaller.145... 

In summary, LB films provide a route to precise two-dimensional molecular architecture and, hence, to advanced nanostructured materials. However, LB films do have disadvantages, such as the experimental difficulties associated with the creation of defect-free, stable, and long-lasting structures in the dimensions and scales required for device construction at an economically viable cost. 

So-called nanostructural materials are divided into three main types one-dimensional (or more commonly known as multilayers ) structures made of alternate thin layers of different composition, two-dimensional structures (more commonly known as wire-type elements suspended within a three-dimensional matrix), and three dimensional constructs that may be made of a distribution of fine particles suspended within a matrix (in either periodic or random fashion) or an aggregate of two or more phases with a nanometric grain size (these are illustrated in Fig. 17.1). 

Synthetic two-dimensional (2D) materials with nanometer textured surfaces have been fabricated by sophisticated technologies, like dip-pen printing [36] or e-beam lithography [37], to elucidate the interactions of cells with defined surfaces. Cell-nanostructure interactions were studied from the gene expression level (cell metabolism) up to the level of microscopic cell behavior. Understanding of the influences of nanostructure on cell adhesion, orientation, motility, proliferation, migration, or differentiation is accessible [38], In terms of adhesion, proliferation... 

In the above sections, our attention was primarily focused on the structural and optical properties of lanthanide doped in nanoparticles such as spherical QDs. Lanthanides doped in some other novel low-dimensional nanostructures including core-shell, one-dimensional (ID) nanowires and nanotubes, two-dimensional (2D) nanofilms, hollow nanospheres, 2D nanosheets and nanodisks have also attracted extensive attention. It is expected that their unique structures could result in unusual mechanical, electronic, optical and magnetic properties. So far few papers have been reported for lanthanide ions other than Eu3+ in these materials. Much attention is focused on the optical properties of Eu3+ ions in view of their very good spectroscopic properties. 

In general, there are two approaches to assemble nanostructured materials, namely, physical assembly and chemical assembly. Physical assembly techniques are based on the assembly of nonfunctionalized nanoparticles on surfaces by physical forces, which include convective or capillary assembly,3,4 spin coating,5 and sedimentation.6 The physical assembly of nanoparticles generally results in relatively simple, closely packed two- or three-dimensional particle arrays. In addition, the physically assembled nanoparticle structures lack long term stability because they were deposited at relatively low surface pressures.7... 

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