Doping cation

K.E. Karakitsou, and X.E. Verykios, Effects of altervalent cation doping of Ti02 on its performance as a photocatalyst for water cleavage, J. Phys. Chem. 97, 1184-1189 (1993). 

Figure 2. Effects of altervalent cation doping of Ti02 on a) CO selectivity and b) H2 selectivity under concentrated feed conditions, CH4/02=66.7/33.3 vol.% (Ti02 doped with lwt% of ZnO A CaO 0 La203 Li O undoped).

The spectra of the doped materials (Cr, Ni, Zn +, Li+, Co +, AP+) are similar to those seen for the nominally stoichiometric materials, and sets of resonances between 500 and 700 ppm are seen on cation doping in addition to that of the normal spinel environment (at ca. 500 ppm). Again, these resonances are assigned to lithium ions near manganese-(IV) cations. The lower intensity of the additional resonances seen on Cr + substitution, in comparison to Zn + or Ni + substitution, is consistent with the oxidation of fewer manganese ions near the depart ions. For the Li- and Zn-doped spinels, resonances at ca. 2300 ppm were also observed, which are assigned to lithium ions in the octahedral sites of the spinel structure. In the case of Zn doping, it is clear that the preference of Zn + for the tetrahedral site of the spinel structure forces the lithium onto the octahedral site. 

Technically important electrochemical reactions of pyrrole and thiophene involve oxidation in non-nucleophilic solvents when the radical-cation intermediates react with the neutral molecule causing polymer growth [169, 191], Under controlled conditions polymer films can be grown on the anode surface from acetonitrile. Tliese films exhibit redox properties and in the oxidised, or cation doped state, are electrically conducting. They can form the positive pole of a rechargeable battery system. Pyrroles with N-substituents are also polymerizable to form coherent films [192], Films have been constructed to support electroactive transition metal centres adjacent to the electrode surface fomiing a modified electrode,... 

In general, doping tends to lead to a loss of x-ray order in polyacetylene and polyphenylene, suggesting that dopant ions may be distributed more or less at random. The structural models shown in Fig. 16 are clearly idealised as only limited order is seen even in cation-doped polymer. The anion dopants are much larger and apparently disrupt the structure too much for any sign of regularity to be seen, except in the case of iodine. 

Mimurada, J., Nakano, M., Sasaki, K., Ykuhara, Y., and Sakuma, T., Effect of cation doping on the superplastic flow in yttria-stabilized tetragonal zirconia poly crystals , J. Am. Ceram. Soc, 2001, 84, 1817-21. 

Nakatani, K., Nagayama, H., Yoshida, H., Yamamoto, T., and Sakuma, T., The effect of grain boundary segregation on superplastic behavior in cation-doped 3Y-TZP , Scrlpta Mater., 2003, 49, 791-5. 

Doping. Studies (52,53) have shown that if substitutional cationic doping at low levels is homogeneous, which can be achieved by the use of a flame reactor (see Sec. II.B.2, Particle Size ), it has a detrimental effect on the photocatalytic activity under UV irradiation. Furthermore, no activity is observed under irradiation in the visible spectral range in spite of an absorption by these samples. These observations regarding various reactions in different media have been attributed to electron-hole recombination at the site of the foreign cations (52,54). 

Serpone, N. (2006). Is the band gap of pristine Ti02 narrowed by anion- and cation-doping of titanium dioxide in second-generation photocatalysts Journal of Physical Chemistry B, 110(48), 24287-24293. 

Another use of the apparent invariance of the electronic spectra is shown in Fig. 27, where the twin peaked electronic spectrum611 of the [Cu(bipy)2(ONO)]+ cation doped in the isomorphous lattice of [Zn(bipy)2(ONO)] [N03] [18]65) is shown to be independent of... 

Figure 11 Band structure of cation-doped photocatalyst with visible light response from a semiconductor with wide band gap (UV response) (Kudo, 2003).

In the final part of this section, the starting materials are small molecules or monomers, and CMs are synthesized through polymerization. For route 7, this is achieved with hexachlorobuta-1,3-diene, which is cathodically polymerized in LiBFV CH3CN to form a cation-doped black polymer [440]. 

Figure 4 Influence of aliovalent cation doping on specific electrical conductivity and activation energy of electron conduction of 0.5% Pt/Ti02(D) at 333 K, in vacuum. (From Ref. 82.)...

The influence of aliovalent cation doping of the support (Ti02) on the catalytic properties of supported Pt and Rh crystallites was also investigated under other reaction conditions, among which the photocatalytic cleavage of water [116] and the reduction of NO by propylene [117] in the presence or absence of oxygen. In the case... 

Fig. 18 EPR spectra of < l%[Ti(OH2)6] cation doped into Cs[Al(0H2)6](S04)2 6H2O with the trigonal axis aligned parallel to the external magnetic field after [50]...

Fig. 21 Variation of the effective magnetic moment with temperature for 8.4% [Ti(OH2)5] cation doped into Cs[Ga(0H2)6](S04)2 6H2O. The curve labelled ligand field theory was calculated from the basis states of the Eg(Ss) term only with X = 130cm and k = 0.88. The curve labelled Jahn-TeUer fit was calculated with the same electronic parameters but allowing for Jahn-Teller coupling to two modes with energies of 53 and 894 cm [50]...

Addition of foreign cations (doping) was achieved by the method of incipient wetness using an aqueous.solution of the nitrate salt of the cation. A drying step (2A hours at 110°C) and a calcination step (1 hour at 600°C) followed for each preparation. 

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