Edge Positions

Edge Positions. - There are many possible empirical prescriptions for the definition of the edge position within the 

The relationship between the empirically determined edge position to the energy of the orbitals at the metal centre is also often unclear. While the absorption edge position is sometimes considered to represent the energy of the vacuum level (the position of Eo which is the onset of the continuum), this seems by no means general. In cases where the absorption edge energy can be compared to the ionisation potential as measured by x.p.s., then 

Mo) ions have indicated that the onset of the continuum is at the base of the metal K-absorption edges, and therefore at a lower energy than the normal definition of the edge position.Clearly care must be taken in considerations of absorption edge positions, but in some cases they may provide an indication of oxidation 

---

Fig. 6. Band edge positions of several semiconductors ia contact with an aqueous electrolyte at pH 1 ia relation to the redox (electrode) potential regions (vs the standard hydrogen electrode) for the oxidation of organic functional groups (26,27).

Fig. 5.13 Energy level diagram comparing the surface band edge positions of SnS and the energies corresponding to selected redox couples and corrosion reactions involving the semiconductor. (Reproduced from [198])...

Furthermore, one can monitor changes in oxidation state by the shift in the edge position. For example, Fig. 28 shows that upon... 

Fig. 12 Aviram-Ratner rectification with edge-positioned donor and acceptor groups...

Figure 2. Band edge positions obtained over a period of three weeks for p-and n-type WSe2 -CH3CN interfaces containing metallocene redox couples (ferrocene, FER decamethylferrocene, DFER and acetylferrocene, AFER) each at three concentrations (preceding letter refers to high.H medium,M and low, L). Two different electrodes were used to obtain the data for n-WSe2 with doping densities between 1016 -1017 cm-3.

From the Co EXAFS results alone one cannot conclude whether the Co atoms are located at edges or basal planes but a comparison of the Co EXAFS data with the above Mo EXAFS results indicates that the edge position is the most likely one. This Co location is illustrated in Figure T For the unsupported catalysts, many of these "surface" positions may be present at internal edges (i.e., at the "domain" boundaries). Recently, direct evidence confirming the edge position has been obtained by combining MES results (to ensure that Co is present as Co-Mo-S in the samples studied) with ir spectroscopy (lU) or with analytical electron microscopy (l ) ... 

Therefore, the data indicate that Co-Mo-S can be considered as a M0S2 structure with Co atoms located in edge positions. As discussed below, these Co atoms play a direct role in the catalysis. Furthermore, it is generally accepted that the HDS reaction involves adsorption on sulfur vacancies. The low sulfur coordination number (large coordinative unsaturation) estimated from the Co EXAFS may, in fact, reflect that active sites (vacancies) are associated with the Co atoms. 

The effects on the dynamics of photo-injected electrons where not systematically studied, despite scattered reports on the influence of amines, which induce surface deprotonation, and lower surface charge with a resulting negative shift in band edge position and an increase in the open circuit potential, Voc [103], The opposite effect is induced by Li+ ions, which intercalate in the oxide structure. Guanidinium ions increase Voc when used as counterions in place of Li+. Other adsorbing molecules that influence both Voc and short circuit current are polycar-boxylic acids, phosphonic acids, chenodeoxycholate and 4-guanidinobutyric acid. 

The next family to be discussed, i.e., the nine-vertex nido-carboranes, includes the complications of the B10H14 family (i.e., dilFeringly coordinated edge positions) as well as one additional complication not encountered in the B10H14, and B5H9 families. The additional... 

---