Continuous tuning

Evidence is presented for continuous tuning of the band-filling between y - 0.00 and 0.50. In comparison, electrochemical oxidation of monoclinic /)-Ni(Pc) under the same conditions is also accompanied by a significant overpotential in forming tetragonal Ni(Pc)-(BF4)0.48- However, electrochemical undoping produces the monoclinic 7-Ni(Pc) phase with far less band structure tunability than in the silicon polymer. Experiments with tosylate as the anion indicate that tetragonal [Si(Pc)0](tosylate)y n can be tuned continuously between y = 0.00 and 0.67. For the anions PFg,... 

Tunable coherent light sources can be realized in several ways. One possibility is to make use of lasers that offer a large spectral gain profile. In this case, wavelength-selecting elements inside the laser resonator restrict the laser oscillation to a narrow spectral interval and the laser wavelength may be continuously tuned across the gain profile. Examples of this type of tunable laser are the dye lasers were treated in the previous section. 

The differences in formal potentials of different metal hexacyanometalates is the basis of tuning the redox properties of PCMs by synthesis of mixed solutions, as far as that is possible due to the ion radii. Examples for a continuous tuning of the hexacyanoferrate redox potential are mixed nickel/iron hexacyanoferrates [30], mixed copper/iron hexacyanoferrates [56], and mixed cadmium/iron hexacyanoferrates [33]. 

In this chapter, we discuss core-shell semiconductor quantum dots and their applications in biological labeling (Fig. 12.1). In comparison with organic dyes and fluorescent proteins, semiconductor quantum dots represent a new class of fluorescent labels with unique advantages and applications. For example, the fluorescence emission spectra of quantum dots can be continuously tuned by changing the particle size, and a single wavelength can be used for simultaneous excitation of all different-sized QDs. 

The ramifications for a Gedanken experiment at T = 0 K are sketched in Fig. 4a, revealing the d.c. electrical conductivity for a macroscopic system such as Si P in which d, the average distance between one-electron centers, can be continuously tuned by changes in the composition of the system. For values of d below a critical distance, dc, i.e. d < <4) the system is metallic and the electronic wave-function is completely delocalized over the entire sample. For very large d d > dfj, we have an insulator with a valence electron wavefunction that is completely localized at the individual atomic sites. At a critical distance, d we then have, according to Mott, a first-order (discontinuous) metal-insulator transition. Thus, at r = 0 K one either has a non-metal or an insulator, for which the limiting (low temperature) d.c. electrical conductivity is zero, or a metal, with a finite conductivity at this base temperature. Whether the metal-insulator transition in Si P (Fig. 4a) is continuous or discontinuous is still a source of controversy. 

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