Adsorption change with surface pretreatment

Adsorption of small redox-active molecules (e.g. ferrocene [326]) on ITO can be used to probe changes in electrochemical activity of ITO surface as a function of surface pretreatment [314]. Adsorption of ferrocene dicarboxylic add (Fc(COOH)2) and 3-thiophene acetic acid (3-TAA) onto ITO was achieved by soaking ITO in a 1 mM solution of these small molecules in pure ethanol for 10 min and then rinsing briefly with acetonitrile [314-316]. To ensure reproducibility, the adsorption of Fc(COOH)2 on pretreated ITO was repeated a minimum of three times on three separate ITO samples, for each pretreatment condition [314]. Chemisorbed small molecules on ITO will provide for better direct contact of added conducting polymer layers and/or hole transport layers (HTLs) in the devices [316],... 

In summary, the removal of organic matter and Fe oxides significantly changes the physicochemical and surface chemical properties of soils. Thus, this pretreatment affects the overall reactivity of heavy metals in soils. The removal of organic matter and Fe oxides may either increase or decrease heavy metal adsorption. The mechanisms responsible for the changes in metal adsorption in soils with the removal of organic matter and Fe oxides include increases in pH, surface area, CEC and electrostatic attraction, decreases in the ZPC, shifts of positive zeta potentials toward... 

When CHg is produced by the photosensitized decomposition of CH, the abnormal CH did not change implying that the iodine produced during the photolysis of CH I destabilizes the non-planar abnormal radical. Kubota et al were also able to obtain the normal CH radical and its satellites lines on silica gel pretreated at below 300°C. They associated the outer lines with a spin flip-type transition and the inner lines with two different adsorption sites of CHj, such as H C- - 0-Sl and H C HO-Sl. This is partly consistent with the H-D surface exchanged work previously described (41). 

S. W. Weller Houdry Process Corporation) Pretreatment is frequently important not only in determining catalytic activity but also in changing the actual chemical composition of the surface and, therefore, the electronic configuration attributed to the metal ions. With Cr203, for example, pretreatment with O2 at elevated temperature results in substantial coverage of the surface with adsorbed O2, and, in effect, the surface chromium ions have a valence number greater than three. Pretreatment with Ha similarly results in high adsorption of H2 and an effective decrease in the valence number of chromium, probably to two. 

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