Nanoelements

Metallic nanoparticles and single-walled carbon nanotubes (SWCNTs) exhibit nanoscale dimensions comparable with the dimensions of redox proteins. This enables the construction of NP-enzyme or SWCNT-enzyme hybrids that combine the unique conductivity features of the nanoelements with the biocatalytic redox properties of the enzymes, to yield wired bioelectrocatalyts with large electrode surface areas. Indeed, substantial advances in nanobiotechnology were achieved by the integration of redox enzymes with nanoelements and the use of the hybrid systems in different bioelectronic devices.35... 

Methods to electrically wire redox proteins with electrodes by the reconstitution of apo-proteins on relay-cofactor units were discussed. Similarly, the application of conductive nanoelements, such as metallic nanoparticles or carbon nanotubes, provided an effective means to communicate the redox centers of proteins with electrodes, and to electrically activate their biocatalytic functions. These fundamental paradigms for the electrical contact of redox enzymes with electrodes were used to develop amperometric sensors and biofuel cells as bioelectronic devices. 

High enhancement of the copper localized surface plasmon absorbency was recorded at the two-layer planar system consisted of copper and silver nanoparticles prepared with successive vacuum evaporation. The result obtained may be caused by strong near-field coupling in the close-packed binary system. The effect may be used for the development of high-absorptive coatings and spectral selective nanoelements in the visible and near infrared spectral ranges. 

Figure 1. Tvw) approaches in the metal-oxide-based gas sensor development (on the left) the recognition functionality is based on an individual nanoelement and (on the right) the metal-oxide-based gas sensor takes advantage of the unique properties of nanomaterials but is not nanoscale in dimensions.

Vaia and Giannelis [19] emphasized that the main fundamental aspects differentiating nanocomposites from conventional composites are their vast interfacial areas per unit volume and the nanoscopic dimensions between the nanoelements. The presence of many chains at interfaces means that much of the polymer is really interphase-like instead of having bulk-like properties. Furthermore, the polymer chains are quite often confined between the surfaces of nanoplatelets which are closer to each other than the radius of gyration of a chain. Both adjacency to a nanoplatelet surface and confinement between such surfaces clearly modify the thermodynamics of polymer chain conformations and the kinetics of chain motions. These two factors may potentially also modify the effective mechanical properties of the polymer. Such... 

The properties of a nanocomposite are determined by the stmcture and properties of the nanoelements, which form it. One of the main tasks in making nanocomposites is building the dependence of the stmcture and shape of the nanoelements forming the basis of the composite on their sizes. This is because with an increase or a decrease in the specific size of nanoelements (nanofibers, nanotubes, nanoparticles, and so on), their physical— mechanical properties such as coefficient of elasticity, strength, deformation parameter, and so on, are varying over one order [1-5]. 

The calculations and experiments show that this is primarily due to a significant rearrangement (which is not necessarily monotonous) of the atomic stmcture and the shape of the nanoelement. The experimental investigation of the aforementioned parameters of the nanoelements is technically complicated and laborious because of their small sizes. In addition, the experimental results are often inconsistent. In particular, some authors have pointed to an increase in the distance between the atoms adjacent to the surface in contrast to the atoms inside the nanoelement, whereas others observe a decrease in the aforementioned distance [6]. 

Thus, further detailed systematic investigations of the problem with the use of theoretical methods, i. e., mathematical modeling, are required. The atomic stmcture and the shape of nanoelements depend both on their sizes and on the methods of obtaining which can be divided into two main groups ... 

Obtaining nanoelements by breaking or destmcting more massive (coarse) formations to the fragments of the desired size (the so-called up—down processes). 

THE CALCULATION OF THE INTERNAL STRUCTURE AND THE SHAPE OF THE NON-INTERACTINC NANOELEMENT... 

At this stage of solving the problem, we consider two interacting nanoelements. First, let us consider the problem statement for symmetric nanoelements, and then for arbitrary shaped nanoelements. 

First of all, let us consider two symmetric nanoelements situated at the distance S from one another (Figure 9.1) at the initial conditions... 

We obtain the coordinates x,o from Eq. (9.2) solution at initial conditions (9.1). It allows calculating the combined interaction forces of the nanoelements... 

In the general case, the force magnitude of the nanoparticle interaction 1 4,1 can be written as product of functions depending on the sizes of the nanoelements and the distance between them ... 

The Pbi vector direction is determined by the direction cosines of a vector connecting the centers of the nanoelements. 

Now, let us consider two interacting as5mimetric nanoelements situated at the distance between their centers of mass (Figure 9.2) and oriented at certain specified angles relative to each other. 

In contrast to the earlier problem, the interatomic interaction of the nanoelements leads not only to the relative displacement of the nanoelements but also to their rotation as well. Consequently, in the general case, the sum of all the forces of the interatomic interactions of the nanoelements is brought to the principal vector of forces and the principal mo-... 

The main objective of this calculation stage is building the dependences of the forces and moments of the nanostructure—nanoelement interactions on the distance S between the centers of mass of the nanostructure nanoelements, on the angles of mutual orientation of the nanoelements... 

For spherical nanoelements, the angles of the mutual orientation do not influence the force of their interaction therefore, in Eq. (9.12), the moment is zero. 

In the general case, functions in Eqs. (9.11) and (9.12) can be approximated by analogy with Eq. (9.8) as the product of functions 5 o,0j,02, 3,i9, respectively. For the further numerical solution of the problem of the self-organization of nanoelements, it is sufficient to give the aforementioned functions in their tabular form and to use the linear (or non-linear) interpolation of them in space. 

When the evolution of the nanosystem as whole (including the processes of ordering and self-organization of the nanostructure nanoelements) is investigated, the movement of each system nanoelement is considered as the movement of a single whole. In this case, the translational motion of the... 

Nanoelements kind of interaction depends strongly on the temperature. Figure 9.21 shows the picture of the interaction of nanoparticles at different temperatures It is seen that with increasing temperature the interaction of changes in sequence occurs (Figure 9.22) coupling (1,2) and merging (3,4). With further increase in temperature the nanoparticles dispersed. 

The nanoscopic fillers, as mentioned above, have at least one characteristic length that is of the order of nanometers. Uniform dispersion of these nanoscopically sized particles or nanoelements can lead to ultra-large interfacial area between the constituents (approaching 700 m /cm in dispersions of layered silicates in polymers) and also to ultrasmall distance between the nanoelements (approaching molecular dimensions at extremely low loadings of the nanoparticles). 

The dimensions of the added nanoelements also contribute to the characteristic properties of PNCs. Thus, when the dimensions of the particles approach the fundamental length scale of a physical property, they exhibit unique mechanical, optical and electrical properties, not observed for the macroscopic counterpart. Bulk materials comprising dispersions of these nanoelements thus display properties related to solid-state physics of the nanoscale. A list of potential nanoparticulate components includes metal, layered graphite, layered chalcogenides, metal oxide, nitride, carbide, carbon nanotubes and nanofibers. The performance of PNCs thus depends on three major attributes nanoscopically confined matrix polymer, nanosize inorganic constituents, and nanoscale arrangement of these constituents. The current research is focused on developing tools that would enable optimum combination of these unique characteristics for best performance of PNCs. 

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