Atomic force microscopy barriers

Lee CK, Wang YM, Huang LS, Lin SM. 2007. Atomic force microscopy Determination of unbinding force, off rate and energy barrier for protein-ligand interaction. Micron 38 446-461. 

First, it is the experimental and theoretical (including computer modeling) investigation of adsorption layers formed on solid surfaces by natural and synthetic polymers, especially by poly electrolytes. Such studies, and in particular those involving the use of Atomic Force Microscopy (AFM, see Chapter VII), provide important information regarding the optimal conditions for the use of polymers for flocculation or stabilization of disperse systems (Chapter VII), and establish the theoretical basis for understanding the mechanism behind the action of structural-mechanical barrier. 

LEDs were fabricated with TA-PPP as the emissive layer. Single-layer devices of ITO/PEDOT/TA-PPP/Ca/Al were fabricated. PEDOT, poly(3,4-ethylenedioxythiophene), was used to enhance hole injection from the anode. Charge injections of the single layer LEDs were clearly hole dominant The barrier for electron injection, around 1.0 eV, is too high. Electron dominant materials such as DO-PF and 2-(4-t-butylphenyl)-5-biphenyloxadiazole (t-PBD) were used to enhance electron injection. The thin film of a TA-PPP and PF blend (95 5 weight ratio) was phase separated. Atomic force microscopy (AFM) showed PF spheres, close to 1 pm in diameter, dispersed in the TA-PPP matrix (Figure 6). This type of phase separation is common in blends of stiff and soft polymers. The PL emission of die blend film was characteristic of TA-PPP. However, once thermally treated, the spectrum shifted bathochromically much like PF. The EL spectrum from LEDs based on the blend thin film contained much emission from PF in the 500-700 nm regime. The device efficiency was about 0.43 cd/A. TA-PPP/PF double layer LEDs were also fobricated. But the efficiency was not improved because when PF was spin coated onto TA-PPP, the PF solution washed out most of the TA-PPP layer. 

Atomic force microscopy (AFM) scans obtained on the cerium- and zirconium-modified silane coatings revealed a very uniform and nanostructured surface, free of cracks and other defects [62]. Scanning electron microscopy (SEM) measurements revealed that the thicknesses of the modified silane coatings were about 2-3 times higher than those of an unmodified silane, which partially explains the improved barrier properties. 

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