Zero-dimensional structures

Zero-Dimensional Structures SET on Single Chemically Tailored Nanoclusters... 

As pointed out by Sessoli and coworker in their review, a possible approach to increasing the energy barrier of lanthanide-based SMMs is by assembling together several lanthanide ions which interact magnetically either in a zero-dimensional structure (SMMs) or in a one-dimensional structure (Single-Chain Magnets) [26]. The last several years have indeed seen a flurry of results from synthetic chemists in this respect. Especially in our recent review about Dy-based SMMs, polynuclear... 

The special effects associated with materials made up of nanosized particles are also due to non-local interactions. Such effects were first noticed in the field of micro-electronics during efforts to decrease the size of devices to quasi one-dimensional or zero-dimensional structures [236]. One possibility for obtaining zero-dimensional structures is the inclusion of spherical semiconductor particles in a transparent dielectric medium. Such isolated microcrystals, typically of nanometer size are known as quantum dots. Best-known examples include particles of CdS and CdSe isolated in silicate glasses. 

Analogous to the period in this sentence, a zero-dimensional structure is the simplest building block that may be used for nanomaterials design. These materials have... 

Interestingly the formation of excitons in nanoparticles stabilized on thin films -a basic cluster formation process in thin film physics - leads to the creation of quantum dots, i.e. quasi-zero dimensional structures that confine carriers in all the three spatial dimensions, thereby enhancing applicable phenomena such as light emission and gas sensing. 

The zero-dimensional structure mainly corresponds to nanoparticle or nanosphere. Conducting polymers can be coated on the surface of inorganic particles, and inorganic layers can also be coated onto polymer nanoparticles. Due to their low dimensions, the diffusion pathways of charges and ions would be reduced, thus enhance the electronic properties of composites. 

Buckyballs can be thought of as zero-dimensional structures. They are a truly nanoscale material, because the diameter of the molecule is about 1 nm (10 m). Assembled into a solid with weak intermolecular bonding, buckyballs have very interesting properties. For example, if C q molecules are charged. 

Fig. 1.1. A categorization of small volume structures in terms of their general shapes and levels of constraints. A film is often called a two-dimensional structure, a line is called a one-dimensional structure and a dot a zero-dimensional structure, but this terminology is not standard and it varies significantly among different technical...

Carbon nanotubes have the same range of diameters as fullerenes, and are expeeted to show various kinds of size effeets in their struetures and properties. Carbon nanotubes are one-dimensional materials and fullerenes are zero-dimensional, whieh brings different effects to bear on their structures as well as on their properties. A whole range of issues from the preparation, structure, properties and observation of quantum effeets in carbon nanotubes in eomparison with 0-D fullerenes are diseussed in this book. 

The problem of accessibility in microporous solids is extreme in zero-dimensional zeolite structures such as clathrasils, that is, zeolite-related materials consisting of window-connected cages. The pore openings in these caged structures are restricted to six-membered rings of [Si04] units at most, which corresponds to pore diameters of approximately 0.2 nm [58]. These pores are too small for the removal of templates and, afterward, are impenetrable to typical sorptive molecules for characterization such as N2 and Ar or reactants such as hydrocarbons. Therefore, the intrinsic... 

There is nothing intrinsically superior about non-zero-dimensional materials compared to lanthanide cages as magnetocaloric materials, but, thus far, synthetic chemists have been unable to realize as many of the required properties in cages simultaneously, as they have done with some chains and lattices. The key advantage is cramming in as many metals as possible into a structure with as few ligands as possible. 

In particular we can identify the set Xtnl(fc) of fc-valued points of Xtn) with the set of closed zero-dimensional subschemes of length n of X which are defined over k. In the simplest case such a subscheme is just a set of n distinct points of X with the reduced induced structure. The length of a zero-dimensional subscheme Z C X is dimkH0(Z, Oz)- The fact that Hilbn(X/T) represents the functor 7iilbn(X/T) means that there is a universal subscheme... 

Let X be a smooth projective variety over an algebraically closed field k. The easiest examples of zero-dimensional subschemes of X are the sets of n distinct points on X. These have of course length n, where the length of a zero-dimensional subscheme Z is dimkH°(Z,Oz)- On the other hand these points can also partially coincide and then the scheme structure becomes important. For instance subschemes of length 2 are either two distinct points or can be viewed as pairs (p, t), where p is a point of X and t is a tangent direction to X at p. 

As another example, the three-dimensional structure of Cytochrome c has been determined on the basis of structural information from pseudocontact paramagnetic chemical shifts, Curie-Dipolar cross-correlation, secondary structure constraints, dipolar couplings and 15N relaxation data [103]. This protein has a paramagnetic center, and therefore the above-mentioned conformational restraints can be derived from this feature. Dipolar couplings do not average to zero because of the susceptibility tensor anisotropy of the protein. The structure determination of this protein without NOE data gives an RMSD (root... 

The methodology used to answer these questions can be classified as either semi-empirical or based on first principles. The confined structure is assumed to be two-dimensional (2D = quantum well), one-dimensional (lD = quantum wire) or zero-dimensional (0D = quantum dot). 

Silicon microstructures can be categorized according to the dimensionality of the confinement. Most PL studies deal with silicon structures confined in three dimensions such dot-like structures are designated zero-dimensional (OD). An overview of size-dependent properties of silicon spheres is given in Table 6.1. Standard methods of generating such microstructures are gas-phase synthesis [Di3, Li7, Scl2], plasma CVD [Ru2, Col, Ta8] or conventional chemical synthesis [Mal5]. 

Similar educational opportunities abound for carbon. The diamond and graphite allotropes of carbon have been mainstays of chemistry classes for generations of students and provide a contrast between a three-dimensional structure of great hardness and a two-dimensional structure with lubricant properties, respectively. We now have what can be regarded as zero- and onedimensional counterparts - buckyballs and carbon nanotubes, respectively - with their rich diversity of structural relatives and physicochemical properties (4). These materials are being employed in a variety of nanoscale devices because of their unusual chemical, mechanical and electrical properties. 

Similar to zero-dimensional metal nanoparticles, most of the work on one-dimensional metal nanostructures focuses almost exclusively on gold nanorods. The high interest in anisometric gold nanoclusters arises from their unique optical and electronic properties that can be easily tuned through small changes in size, structure (e.g., the position, width, and intensity of the absorption band due to the longitudinal surface plasmon resonance is strongly influenced by the shell as well as the aspect ratio of the nanorods), shape (e.g., needle, round capped cylinder, or dog bone), and the inter-particle distance [157]. 

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