Metal oxide bulk doping additives

However, the correlation of the electrical properties of the bulk phase with the catalytic properties of the essentially heterogeneous catalyst surface is a classical difficulty. This may be one of the reasons why no general correlation between these properties is found when a variety of different metal oxide catalysts is compared. A close relationship is often shown, on the other hand, when a particular catalyst is modified or doped with minor amounts of an additional metal oxide. It is very likely that the correlation is successful in this case, because the nature of surface sites is not essentially changed. 

By doping a primary catalyst component with lower-valent metal cations, additional oxygen vacancies will be created which facilitate the incorporation of electrophilic oxygen species chemisorbed on the surface into the bulk where they will not oxidize adsorbed methyl radicals. Also, the promoter oxide should be basic, not be reducible, oxidizablc, or easily volatiz-ablc. It should form a mixed oxide with the main component which may be possible if the ionic radii arc similar. According to these rules, the expert system proposes as potential catalyst components combinations of substances with appropriate chemical and physico-chemical properties (Table 2). Many of these systems already have been described in the literature... 

In an electrochemical experiment the polymer is a film sandwiched between a metal electrode, the working electrode, and a liquid electrolyte (Fig. 1). Electrons can be exchanged between the polymer (2P) and the metal (it). The exchange proceeds across the polymer-metal interface (0V it). In addition, to maintain electroneutrality in the polymer bulk, ions are exchanged between and the electrolyte (%), across the polymer-electrolyte interface ( >/%). In the case of p doping, which corresponds to oxidation of the polymer, electrons are transferred from 0 to it (and the reverse for n doping, which corresponds to a reduction). The cell includes a reference electrode, which is immersed in the electrolyte and connected to a high-impedence voltmeter. It measures the potential of the electrolyte with respect to that of a reference redox couple. Note that no current... 

The term upconversion describes an effect [1] related to the emission of anti-Stokes fluorescence in the visible spectral range following excitation of certain (doped) luminophores in the near infrared (NIR). It mainly occurs with rare-earth doped solids, but also with doped transition-metal systems and combinations of both [2, 3], and relies on the sequential absorption of two or more NIR photons by the dopants. Following its discovery [1] it has been extensively studied for bulk materials both theoretically and in context with uses in solid-state lasers, infrared quantum counters, lighting or displays, and physical sensors, for example [4, 5]. Substantial efforts also have been made to prepare nanoscale materials that show more efficient upconversion emission. Meanwhile, numerous protocols are available for making nanoparticles, nanorods, nanoplates, and nanotubes. These include thermal decomposition, co-precipitation, solvothermal synthesis, combustion, and sol-gel processes [6], synthesis in liquid-solid-solutions [7, 8], and ionothermal synthesis [9]. Nanocrystal materials include oxides of zirconium and titanium, the fluorides, oxides, phosphates, oxysulfates, and oxyfluoiides of the trivalent lanthanides (Ln ), and similar compounds that may additionally contain alkaline earth ions. Wang and Liu [6] have recently reviewed the theory of upconversion and the common materials and methods used. 

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