Dopants solubility

FIGURE 14 Temperature dependence of the acceptor dopant solubility limit. 

However, dopant solubility and pH level must be considered, as these are also dependant on the choice of solvent. As mentioned previously, conventional sodium sulfonate dopants and anionic biomolecules are easily dissolved in water. Aqueous sodium sulfonate electrolytes have a pH range (pH 7-9) close to the body pH level and this would help to minimize pH-induced cytotoxicity when implanted in the body. Temperature can affect the solubility of dopant and even the viscosity of electrolyte. Generally, low temperature helps to produce smoother, more conductive films, but the reduced dopant solubility and the increased viscosity can be problematic [62]. 

The effect of impurities cannot be ignored. In reality, not only dopants but also impurities can change defect concentrations and the effective diffusivity considerably. Sometimes impurities dominate the overall phenomenon. In particular, this may occur in systems with a very low dopant solubility. 

D. T. J. Hurle, 1999, A comprehensive thermodynamic analysis of native point defect and dopant solubilities in gallium arsenide , j. Appl. Phys. 85, 6957-7022. 

The polyamides are soluble in high strength sulfuric acid or in mixtures of hexamethylphosphoramide, /V, /V- dim ethyl acetam i de and LiCl. In the latter, compHcated relationships exist between solvent composition and the temperature at which the Hquid crystal phase forms. The polyamide solutions show an abmpt decrease in viscosity which is characteristic of mesophase formation when a critical volume fraction of polymer ( ) is exceeded. The viscosity may decrease, however, in the Hquid crystal phase if the molecular ordering allows the rod-shaped entities to gHde past one another more easily despite the higher concentration. The Hquid crystal phase is optically anisotropic and the texture is nematic. The nematic texture can be transformed to a chiral nematic texture by adding chiral species as a dopant or incorporating a chiral unit in the main chain as a copolymer (30). 

If a p-i-n (i.e., LEC) device architecture is used, the choice of the ionic dopant and surfactant additives to the light-emitting organic ink are critical to the print uniformity and resulting device performance and stability. The ionic dopants have limited solubility and can prematurely fall out of solution during the printing process. Most of the previous works in... 

The LEC structure that involves the addition of ionic dopants and surfactants to the printable inks enables the ability to print a top electrode without restriction by the work function of the metal. Silver, nickel, or carbon particle-based pastes are generally the preferred printable electron injecting electrodes however, the shape and size of the particles combined with the softening properties of the solvent can create electrical shorts throughout the device when printed over a thin polymer layer that is only several hundred nanometers thick. For optimal performance, the commercially available pastes must be optimized for printing onto soluble thin films to make a fully screen-printed polymer EL display. 

Cavitating Ultrasound Hydrogenation of Water-Soluble Olefins Emplo5dng Inert Dopants ... 

The atmosphere is also important in sintering. Gas trapped in closed pores will limit pore shrinkage unless the gas is soluble in the grain boundary and can diffuse from the pore. Alumina doped with MgO can be sintered to essentially zero porosity in hydrogen or oxygen atmospheres, which are soluble, but not in air, which contains insoluble nitrogen. The density of oxides sintered in air is commonly less than 98% and often only 92-96%. The sintering atmosphere is also important in that it may influence the sublimation or the stoichiometry of the principal particles or dopants. 

Frequently, growth of crystals from melt involves more than one component, such as impurities, intentionally added dopants, etc., in addition to the major component. In these cases, it is essential to know the distribution of the second component between the growing crystal and the melt. This distribution occurs according to the phase diagram relating the equilibrium solubilities of the second component (impurity) in the liquid and the solid phases. 

Generally speaking, if achiral dopant acid is a strong acid, that is, pKa < 3, and soluble in water, ZV-mcthyl-2-pyrrolidinone, dimethyl sulfoxide, or N,N -dimethylformamide can be used to generate helical polyaniline. 

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