Mesoscopic metals

This new theory of the non-equilibrium thermodynamics of multiphase polymer systems offers a better explanation of the conductivity breakthrough in polymer blends than the percolation theory, and the mesoscopic metal concept explains conductivity on the molecular level better than the exciton model based on semiconductors. It can also be used to explain other complex phenomena, such as the improvement in the impact strength of polymers due to dispersion of rubber particles, the increase in the viscosity of filled systems, or the formation of gels in colloids or microemulsions. It is thus possible to draw valuable conclusions and make forecasts for the industrial application of such systems. 

It will certainly take an integrated examination of chemical structure, microscopic and macroscopic lattice structure to provide the key to unravelling the mysteries of ICP. Our approach in understanding ICPs as mesoscopic metals (cf [68]) might provide a useful basis for further scientific and technological progress. 

Recently the question has been raised as to whether the electrical conductivity of isolated mesoscopic metal particles, that is particles in the submicrometer order of magnitude, and of intrinsic conductive polymers (ICP) have some properties in common. In this section we outline the metallic properties and the origin of mesoscopic conductivity (small metal particles). 

The credit for the finally experimental proof of the old theory goes to Nimtz and Marquardt [23b], who succeeded in creating mesoscopic metals (i.e. metals with a particle size of less than 1 p to approx. 20 nm) and investigated their conductivity as a suspension or colloidal dispersion in a suitable test design with the aid of microwaves. 

It is interesting to note that the temperature dependence of the conductivity of mesoscopic metals is different from that of the same metals in bulk form. Whereas it is well known that temperature dependence is characterised as metallic by the fact that conductivity increases with falling temperature, metals in mesoscopic form exhibit non-metallic behaviour in that their conductivity declines, albeit only slightly as the temperature drops [130],... 

In 1989 we finally suggested a first joint study with the Cologne working group with the aim finding out whether our polyaniline might perhaps display similar behaviour like an artificially produced mesoscopic metal. Our hypothesis was that owing to its spherical... 

Other features in common between mesoscopic metals and conductive polymers (here PAni) are the frequency dependence of conductivity... 

The analysis of the measurements above the critical volume concentration now made it possible to say something about whether the transport mechanism was dominated by these mesoscopic metallic regions (which we now definitely know are not interlinked by bridges of material or amorphous loops of chains, but at most display point-type physical contact above the critical volume concentration). 

This behaviour is characteristic of partial interfacial polarisation induced by conductive paths that are not arranged parallel to the electric field. The same phenomenon has already been observed in heterogeneous combinations of mesoscopic metallic particles in... 

From this it follows in turn that transport is determined by 3D hopping between mesoscopic metallic phases The figure quoted here also agrees with the figure of 6.3 nm mentioned earlier, which was obtained from measurements below the critical volume concentration. 

These mesoscopic metallic phases are quite evidently to be seen in the morphological primary particles of approx. 10 nm diameter found by other methods. 

This is the reason why the conductivity found in mesoscopic metals is not die conductivity familiar from bulk metals, but a much lower conductivity. G. Nimtz... 

Figure 11.116. Mesoscopic metallic particles (like PAni with 10 nm diameter) only allow certain electron wavelengths to occur this is the reason for their limited conductivity.

Metals undergo the most considerable property change by size reduction, and their composites with polymers are very interesting for functional applications. The new properties observed in nano-sized metals (mesoscopic metals) are produced by quantum-size effects (i.e., electron confinement and surface effect). These properties are size-dependent and can be simply tuned by changing the dimension. Since the same element may show different sets of properties by size variation, a Three-dimensional Periodic Table of elements has been... 

Noel S, Batalla E, Rochon P. 1996. A simple method for the manufacture of mesoscopic metal wires. J Mater Res 11(4) 865 867. 

Park, S., Lim, J.H., Chung, S.W., Mirkin, C.A. Self-assembly of mesoscopic metal-polymer amphiphiles. Science 303, 348-351 (2004)... 

Therefore, only certain wavelengths are allowed, i.e., those that have a node plane at the boundaries of the three-dimensional conduction band. Hence, the conductivity is quantum size Kmited. We observe the quantum effects of conductivity. These results motivated us to work together with the Cologne group and to find out whether there are similarities between mesoscopic metals and organic metals [5], as we suspected that the conductivity phenomena in conductive polymers may be better understood taking nanostructures into account. 

Our cooperation with Guenther Nimtz of Cologne University showed very quickly [5] that the conductive polymer (in the first experiments deposited from dispersions onto PC films) behaves principally in the same way as Nimtz s mesoscopic metals, which he had prepared by vapor deposition in oil to form a colloidal dispersion of finest metal droplets in oil. 

Their conductivity is metallic (more precisely comparable with mesoscopic metals or in other words nanometals). 

Mesoscopic Metallic State a metallic state in an inhomogeneous system in which conduction electrons are delocalized over a number of crystalline regions (with disordered polymer regions between them). The size of the localization length is 10 -10 A, smaller than macroscopic dimensions (10 A or greater). 

Penner RM. Mesoscopic metal particles and wires hy electrodeposition. J Phys Chem B 2002 106 3335-8. 

The confinement effects of charge carriers (Koole et al. 2014) appear in nanosize metal (mesoscopic metals) domains, where the conduction of electrons moves within a very small space, comparable to their de Broglie wavelength ( = h/p). Accordingly, their states are quantized in the same way as atoms, and these systems are called artificial atoms. Therefore, the electrons are positioned among the atomic nuclei, behaving as a typical molecule, and the electronic energy levels are not continuous, such as in bulk. Instead, they are discrete (Klabunde et al. 2001). Thus, nanocrystals are also known as quantum dots that exhibit a size quantization effect in at least one dimension. Similar phenomena occur not only in metals but also in any material when its size decreases. 

Colas des Francs, G., Bouhelier, A, Finot, E., Weeber, J. C., Dereux, A., Girard, C, and Dujardin, E. (2008) Fluorescence relaxation in the nearfield of a mesoscopic metallic particle distance dependence and role of plasmon modes. Opt. Express, 16,17654-17666. 

Mesoscopic metals display a conductivity that is several powers of 10 smaller with decreasing particle size [Section VI and Ref. 24J (quantum-me-chanically limited conductivity), and below l/w,m they also display a nonmetallic temperature dependence. Conversely, it Is not yet known what... 

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