Mesoscopic quantum size effect

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... 

Recently, much attention has been paid to the importance of the quantum function realized by micro- and mesoscopically controlled semiconductor heterostructures. Conducting polymer heterolayers, leading to a conducting polymer superlattice exhibiting quantum size effects, should take an important place in both novel electronic and optical devices. 

Potential-Programmed Electropolymerization (PPEP). This technique allows compositional modulation over distances of the order of 100 A. Mesoscopic layered structures with high lateral quality are produced by the PPEP method. An improvement of the flatness and uniformity of the layered structure is achieved by careful choice of an appropriate working electrode (silicon single-crystal wafer), monomer (pyrrole/bithiophene or pyrrole/3-methyl-thiophene) and solvent (propylene carbonate). The PPEP method can produce materials having desirable properties tailored by the quantum size effect [703-705]. 

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. 

Dimensions between the atomic/molecular and the bulk macroscopic scales are sometimes called mesoscopic. Because the mesoscopic scale corresponds roughly to the electron free path, unusual phenomena such as quantum effects can be observed, some of which could be used in the development of single-electron devices or quantum computers. Top-down-type nanofabrication techniques are now capable of producing structures in this size range, and research on this subject has received significant attention, especially in the held of semiconductor science and technology. 

One of the remarkable properties of quantum mechanics is that the wave nature of matter completely escapes perception in our everyday life, although this feature is a cornerstone of the theory. The smallness of Planck s constant and therefore of the de Broglie wavelength of a macroscopic object is certainly largely responsible for the non-observability of quantum effects in the classical world. However, it is important to ask whether there are fundamental limits to quantum physics and how far we can push the experimental techniques to visualize quantum effects in the mesoscopic world for objects of increasing size, mass and complexity. Where are the fundamental limits on the way towards larger objects ... 

P Claus, A Bruckner, C Mohr and H Hofineister, Supported Gold Nanoparticles from Quantum Dot to Mesoscopic Size Scale Effect of Electronic and Structural Properties on Catalytic Hydrogenation of Conkugated Functional Groups, J. Am. Chem. Soc., 122,11430-11439,2000. 

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. 

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