Stability, nanosystem

In this paper we present a comprehensive first-principles study of the structural, electronic and optical properties of undoped and doped Si nanosystems. The aim is to investigate, in a systematic way, their structural, electronic and stability properties as a function of dimensionality and size, as well as pointing out the main changes induced by the nanostructure excitation. A comparison between the results obtained using different Density Functional Theory based methods will be presented. We will report results concerning two-dimensional, one-dimensional and zero-dimensional systems. In particular the absorption and emission spectra and the effects induced by the creation of an electron-hole pair are calculated and discussed in detail, including many-body effects. 

We present experimental results on the ability of water-in-oil reverse micelles for synthesis and stabilization of Au, Agl and dye J-aggregate nanoparticles as well for selfassembling of hybrid nanosystem, consisting of semiconductor nanoparticles and dye J-aggregate. The preparation, spectral behaviour and properties of this nanoparticles are discussed. 

A hybrid nanosystem which consists of semiconductor nanoparticles and organic dye J-aggregate may be self-assembled in RMs (Fig. 5) [4], In this structure, the dye adsorbed to the nanoparticle surface operates as spectral sensitizer and nanocrystal size stabilizer simultaneously. The hybrid nanosystem of this kind may be a key element of solar cells. 

An interesting consequence of the described mechanism, is the fact that precipitation in solutions yields, as a rule, nanosized particles. If the process is arrested at this stage by additives, such as surfactants or microemulsions, one obtains stable nanosystems. However, in the absence of stabilizers, these particles aggregate (rather than to grow) into larger final products, which under appropriate conditions consist of monodispersed colloids. Thus, here we have established the bridge between the two worlds mentioned earlier ... 

Among different (like flexoelectric, flexomagnetic etc.) flexoeffects, the influence of flexoelectric effect on the nanosystem properties had been studied in most details. One can conclude that even rather moderate flexoelectric effect significantly renormalizes all the polar, piezoelectric and dielectric properties and the correlation radius in particular. The effect also suppresses the size-induced phase transition from ferroelectric to paraelectric phase and thus stabilizes the ordered phase in ferroic nanoparticles. 

The use of DNA as a template for the construction of nanosystems offers chemists the abiUly to further expand its self-recognition properties by the incorporation of metals to natural or chemically modified DNA bases, backbones, and ligands to allow the creation of functional molecular architectures. Such systems further expand Ihe DNA code by increasing the information content via the addition of new letters to the DNA alphabet, which can then ideally reduce errors while increasing fimctionalily. Access to not just double-strand oligonucleotides but also the formation of triple and quadruple strands as branched or hairpin structures can also be achieved. The ability to alter the properties of DNA via metal interactions has shown to enhance stability, electrical conductivity, and magnetic and catalytic properties and therefore forms the basis of novel prototypical nano materials. 

From the limits of Eq. (1.86) one observes the major role the topological index plays in predicting the characteristic temperature T = 2E/k at which a given nanosystems (topology) is stabilized (either as ideal or with defects) by the bondonic motion through it otherwise, for an absent topology the bondonic motion is purely entropic at T = OK, without observable character, according with Eq. (1.86) for the indefinite limit — oo x o. 

Altogether, one can presume that, from the viewpoint of structural stability, four fundamental problems should be addressed (i) the effect of size on the properties of nanosystems (ii) the effect of defects in nanomaterials on their internal structures (iii) the evolution of nanomaterials at the beginning of their synthesis, (iv) the stability of nanosystems under varying external conditions and fields. All these problems have not been completely solved yet both from theoretical and experimental points of view. 

Thus, sinee the reactivity indices are placed at the informational interface between the electronie systems stability and their tendency to transform and combine they are mathematieally introduced as the integral functions of the electronie density fimction, releasing the so called electronic density functionals as the effieient tool for the global prediction of the eleetronie properties of the investigated nanosystems. 

Before having in hands metal NPs of interest for a given catalytic application it is necessary to develop efficient synthesis methods to provide controlled nanosystems that will display reproducible properties. To achieve this aim, intensive research in nanochemistry is currently devoted to the bottom-up strategy that consists in building metalUc NPs from monometallic species in solution in the presence of stabilizing agents [15-17]. This approach can benefit... 

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