XPS results

Effectiveness of selective adsorption of phenanthrene in Triton X-100 solution depends on surface area, pore size distribution, and surface chemical properties of adsorbents. Since the micellar structure is not rigid, the monomer enters the pores and is adsorbed on the internal surfaces. The size of a monomer of Triton X-100 (27 A) is larger than phenanthrene (11.8 A) [4]. Therefore, only phenanthrene enters micropores with width between 11.8 A and 27 A. Table 1 shows that the area only for phenanthrene adsorption is the highest for 20 40 mesh. From XPS results, the carbon content on the surfaces was increased with decreasing particle size. Thus, 20 40 mesh activated carbon is more beneficial for selective adsorption of phenanthrene compared to Triton X-100. 

In contrast to MoSx/NaY, the Fourier transform for MoSj/NaY clearly showed Mo-O bondings as well as Mo-S and Mo-Mo bondings as summarized in Table 1. It is evident that Mo oxide species in calcined MoOj/NaY are only partially sulfided. XPS results corroborated the EXAFS results. The incomplete sulfidation of the Mo species in MoS /NaY may explain in part the relatively low HDS and HYD activities of the cat ysts in Figs.l and 2. 

MoSx-CoSx/NaY catalysts, which were prepared by introducing Mo(CO) into CoSx/NaY (l.lCo/SC), showed the identical HDS activities with those of CoSx-MoSx/NaY at the same compositions, as illustrated in Fig.4. Figure-4 suggests that the dispersions of Mo and Co sulfides are not mutually affected by the presence of the other sulfide species or that the formation of catalytically active species, e.g. Co-Mo mixed sulfide species, is independent of the accommodation order. As shown telow, FTIR of NO adsorption, EXAFS, and XPS results supported the latter pwssibility. 

The EPR spectrum shows, in accordance with the XPS results, no feature that can be attributed to Ti centers. What is the nature of the radical observed in the EPR spectrum It might be thought that methyl radicals are the most natural products in the reduction of a mixed titaniiun-chlorine-methyl species according to the following simple reaction scheme ... 

The previously discussed XPS results, despite being obtained from films deposited from deposition methods other than usual plasma deposition, give valuable information on a-C(N) H film structure. Results reported in the works of Mansur and Ugolini [45] Souto and Alvarez [83] and Hammer, Victoria, and Alvarez [60] are in total accordance with the picture that emerges from IR results hydrogen bonds preferentially to nitrogen atoms, which are bonded mainly to sp -carbon atoms. 

The XPS results obtained by Kolb and Hansen are reproduced in Fig. 6 and they clearly demonstrate not only that cations as well as anions stay on the surface but also that the amount of ions exhibits the expected potential dependence even in the case of specific adsorption. The preservation of the double layer charge after emersion was also shown by other techniques like charge monitoring [28] and electroreflectance measurements [29],... 

While the above XPS results give the impression, that the electrochemical interface and the metal vacuum interface behave similarly, fundamental differences become evident when work function changes during metal deposition are considered. During metal deposition at the metal vacuum interface the work function of the sample surface usually shifts from that of the bare substrate to that of the bulk deposit. In the case of Cu deposition onto Pt(l 11) a work function reduction from 5.5 eV to 4.3 eV is observed during deposition of one monolayer of copper [96], Although a reduction of work function with UPD metal coverage is also observed at the electrochemical interface, the absolute values are totally different. For Ag deposition on Pt (see Fig. 31)... 

Lee et al. [30] used in situ X-ray photo electron spectroscopy (XPS) measurement on La0 9Sr0 Mn03 as a function of cathodic polarization. The XPS results showed the peaks of Mn 2p spectra were shifted to the lower binding energy as the applied potential became more cathodic, indicating the reduction of Mn ions. The oxygen reduction and the concomitant formation of Mn2+ ions and oxygen vacancies are proposed as ... 

These XPS results cause great uncertainty as to the chemical state of emersed Pb(UPD) films on Ag and validate questions raised about partial desorption of UPD films after potential control is lost (3,9). Nevertheless, XPS chemical shifts of the Pb(4f) peaks show a dependence on the emersion potential i.e. the Pb coverage before emersion. Some emersed films also displayed at least two different chemical states of the UPD Pb (Figures 4b an 5b). 

Bera and co workers421 reported on a combustion-synthesized Cei xPtx02 catalyst, where a high fraction of Pt was suggested to be dispersed as Pt2+ ions. Based on XPS results before and after reaction, the authors concluded that the Pt ions were likely the active sites for the WGS reaction. The l%Pt/ceria catalyst was prepared using a combustion mixture of (NH4)2Ce(N03)6, H2PtCl6 and C2H6N402 in the... 

Table 18.5. The XPS Results of Poly(Octafluorobisbenzocyclobutene) from UV-Assisted...

The (8X2)-TiOr film can also be synthesized by the stepwise direct deposition of Ti onto an oxygen-covered Mo(112) surface followed by subsequent oxidation-annealing cycles. However, the quality and reproducibility are not comparable with growth on the SiOz film. In either case, analysis of the HREELS and XPS results indicate that the oxidation state of the Ti is probably +3. This reduced Ti state is apparently responsible for the ability of Au and other metals to wet the surface. 

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