LEPs, commercial availability

The technical data for a prototype OLED using LEPs are collated in Table 6.18. The brightness and the contrast ratio (>100 1) of monochrome OLEDs with various colours is comparable with that of a standard commercially available TN-LCD with active matrix addressing. The lifetime is clearly... 

To address new researchers entering the field of PLED, especially those, not trained in organic synthesis, we should mention that many LEP are now available commercially from several companies, such as Aldrich (www.sigma-aldrich.com), American Dyes Source (www.adsdyes.com), H.W. Sands (http //www.hwsands.com/), and Dow Chemicals (http //www.dow.com/pled /). 

Immunofixation electrophoresis (IFE) is gradually replacing immunoelectrophoresis (lEP) for detection of. M-components because of its speed and ease of interpretation. Several procedures, including commercial Idts, are available for both IFE and lEP, Although these procedures may differ in detail, their principles are similar. 

The parabola method makes it possible to measure the potential of cell walls. Usually, the cell is made of quartz, and the parabola method thus offers the possibility of determining the lEP of one material that has already been extensively studied. The potentials of macroscopic specimens of other materials can also be determined from the mobility profile [273-275] by replacement of the original cell wall of a commercial electrophoretic cell by a flat specimen of the material of interest. For example, in [276], the lEP of a basal plane of mica found from the mobility profile was different from the lEP of a mica dispersion. Only a few types of electrophoretic devices (most of which are no longer available on the market) can be used to determine potentials by means of electro-osmosis. 

The force between particles is the sum of a pH-independent van der Waals component, which is always attractive, and a pH-dependent electrostatic component, which can be attractive or repulsive. In Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the potential is used to calculate the interaction force or energy as a function of the distance between the particles. Atomic force microscopy (AFM) makes it possible to directly measure the force between the particles as a function of the distance, and commercial instruments are available to perform such measurements. Different approaches have been proposed to utilize the results obtained by AFM to determine the pHq. The quantity obtained by AFM corresponds to the lEP rather than the PZC. AFM was used to measure the force between SiO2 (negative potential over the entire studied pH range) and Si,N4 (lEP to be determined) in [681]. The pH at which the force at a distance of 17 nm was equal to zero was identified with the lEP. The van der Waals forces are negligible at such a distance, and the force is governed by an electrostatic interaction. The experimental results were consistent with DLVO theory. 

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