Doped spectral properties

In the case of fluorescence spectra, it is the emission of the radiation from the excited state that is measured, rather than its absorption. This also provides valuable information. As an example, tetraethylorthosilicate (TEOS)-based gels were doped with two optically active organic indicators, thionin and nile blue A. Before trapping in a solgel host, thionin and nile blue A were both evaluated for solvent and protonation effects on their spectral properties. Only extreme pH values provided by HCl, NaOH, and NH4OH produced new absorption and/or fluorescence bands. The absorption and fluorescence spectra revealed a decrease in a pH 11 solution of NH4OH compared to neutral conditions (Krihak et al., 1997). 

In MgO thin films, O vacancies can be generated by electron bombardment or sputtering with Ar. In polycrystalline MgO samples, O vacancies can be created by thermal treatment of hydroxylated surfaces. The dehydroxylation occurs at the expense of a lattice O anion with consequent formation of a surface vacancy or F center. Anion vacancies on the MgO surface, the centers corresponding to the removal of O, are difficult to observe, as these centers do not have specific spectral properties. However, they can act as electron traps and their existence can be deduced by doping the material with excess electrons to form the corresponding Fg and Fg centers which can be detected either by EPR (Fg" ") [130-133] or by optical (Fg+ and Fg) [134-137] spectroscopies. In the F+ or F centers one or two electrons are associated with the defect they are localized in the vacancy [39-43,50] by the MP. 

L. Rebbouh, V. Rosso, Y. Renotte, Y. Lion, F. Grandjean, B. Heinrichs, J.-P. Pirard, J. Delwiche, M.-J. Hubin-Franskin, and G. J. Long, The Nonlinear Optical, Magnetic, and Mossbauer Spectral Properties of Some Iron(III) Doped Silica Xerogels, J. Mater. Sci., 41, pp. 2839-2849, 2006. 

Figures 3 a, b, c summarize the typical spectral IR and Visible region spectral properties of devices. The large light/dark variation ( dynamic range ) is clearly seen therein as well. An interesting property, discussed at length in conjunction with electrochemical data in one of our earlier communications (4), is that the Visible- and IR-region reflectances vary in tandem between applied potentials of -1.1 V and 0.0 V, but behave in an opposite fashion between 0.0 and +0.8 V. As we discussed earlier (5a), this is due to transitions between die various poly(aniline) states reduced non-conductive leuco-emeraldine, partially oxidized conductive doped-emeraldine, and highly oxidized and again non-conductive pemigraniline.

Wen J, Ning L, Duan CK, Chen Y, Zhang Y, Yin M. A Theoretical Study on the Structural and Energy Spectral Properties of Ce + Ions Doped in Various Fluoride Compounds. J Phys Chem C. 2012 116 20513. 

It is difficult to predict the effect of surface functionalization on the optical properties of nanoparticles in general. Surface ligands have only minor influence on the spectroscopic properties of nanoparticles, the properties of which are primarily dominated by the crystal field of the host lattice (e.g., rare-earth doped nanocrystals) or by plasmon resonance (e.g., gold nanoparticles). In the case of QDs, the fluorescence quantum yield and decay behavior respond to surface functionalization and bioconjugation, whereas the spectral position and shape of the absorption and emission are barely affected. 

Numerous studies about phases and phase transitions detected by optical investigations of f elements have been published by Haire, Peterson, and co-workers. In many cases they used the Eu3+ ion to correlate the luminescence properties with structural changes. The Eu3+ ion exhibits a variety of characteristic transitions serving as a fingerprint for the structure (Chen et al., 1992e). However, in view of the problematic situation with respect to the local symmetry in the case of doped ions mentioned above, there has been some discussion on whether the Eu3+ ion or f elements in general can be used as indicators of the actual host structure or not (Tanner and Rudowicz, 1993 Stump et al., 1993). In summary, it must be concluded that the spectral/structural correlation has limitations especially in the case of doped ions where deviations between local and real site symmetry may readily occur. 

Some important deposition parameters to control ZnO Al film properties are deposition pressure, substrate temperature, and amount of oxygen in the sputter gas mixture (see e.g. [93,96,100,101]). Doping concentration in ZnO films plays another important role for opto-electronic properties [97,100,102]. Figure 8.13 shows the spectral transmission of films that were reactively sputtered from targets with different aluminum concentration at optimized conditions [93]. Sputter conditions and film properties are given in Table 8.2. 

Fig. 8.13. Spectral transmission of differently doped ZnO Al films. The films were prepared in an in-line system by reactive MF sputtering. The subscripts denote the aluminum concentration of the corresponding metallic targets in at. %. Deposition conditions and film properties are given in Table 8.2...

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