Sulfur surface structures

Jentz D, Rizzi S, Barbieri A, Kelly D, Van Hove M A and Somorjai G A 1995 Surface structures of sulfur and carbon overlayers on Mo(IOO) a detailed analysis by automated tensor LEED Surf. Sc 329 14-31... 

As an example we consider the Au(100) surface of a single crystal Au electrode [3]. This is one of the few surfaces that reconstruct in the vacuum. The perfect surface with its quadratic structure is not thermodynamically stable it rearranges to form a denser lattice with a hexagonal structure (see Fig. 15.3), which has a lower surface energy. In an aqueous solution the surface structure depends on the electrode potential. In sulfuric acid the reconstructed surface is observed at potentials below about 0.36 V vs. SCE, while at higher potentials the reconstruction disappears, and the perfect quadratic structure is ob-... 

Functionalities on the sulfur surface - ToF-SIMS was applied to both the untreated sulfur and the plasma polymer-encapsulated sulfur to obtain structural information on the outermost layer of the samples. The positive and negative spectra of untreated sulfur are presented in Fig. 13. Compared to Fig. 13b, there are clearly more peaks in the positive spectra in Fig. 13a, which come from hydrocarbon ions in the low molecular weight range. It is interesting to see that sulfur forms almost identical characteristic peaks of Si, S2 up to Sn in both the positive and the negative spectra. 

Comparing the three substrates that were plasma-coated in this study, it has become clear that silica is very easy to encapsulate with a plasma coating, whereas carbon black is difficult to treat because of its inert chemical surface structure. Sulfur is also more difficult to handle, but in this case the incomplete coating is an advantage because the sulfur has to be released from the encapsulation shell in order to be efficient as curing agent. In all cases, the polarity of the substrate is reduced. 

What is the mechanistic nature of sulfur adsorption on metal surfaces and what are the surface structures formed ... 

Fig. 10. Surface structures of sulfur on Pt(l 11) as a function of coverage and temperature (Ref. 84).

Based on these analyses of EXAFS data, we propose that the structure of CdS-DMF nanocrystallites changes as shown in Scheme 1. When 0.2 equivalent of excess Cd + was added into the system, the adsorption of Cd + solvated by DMF occurred to the CdS-DMF surface and resulted in the formation of the sulfur surface vacancy on the surface of CdS-DMF. The change in the coordination number and the square of the Debye-Waller factor of the Cd-S and Cd-O shell support such changes in the surface structure on CdS-DMF nanocrystallites. 

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