Ž . Applied Surface Science 141 1999 148–156 ž /ž / Oxide mediated interaction of Os CO NCCH at 3 11 3 photoelectrochemically oxidized surfaces of MoS : 2 an STM and XPS study Diego J. Dıaz 1 , Raul J. Castro 2 , Carlos R. Cabrera ) ´ ´ Department of Chemistry, UniÕersity of Puerto Rico, Rıo Piedras Campus, P.O. Box 23346, San Juan 00931-3346, Puerto Rico ´ Received 28 July 1998; accepted 18 October 1998 Abstract Metal carbonyl clusters and their interaction with substrates are important for catalytic applications. In this study we Ž . Ž . report on the analysis of MoS surfaces interaction with Os CO NCCH . These modified MoS surfaces are analyzed 2 3 11 3 2 Ž . Ž . by scanning tunneling microscopy STM and X-ray photoelectron spectroscopy XPS . The STM analysis proves to be a very helpful technique to determine the presence, morphology, and size of cluster assemblies on the MoS surface. On the 2 other hand, XPS gives spectroscopic information about the interactions of the cluster with the substrate. Both techniques give evidence on the presence of the Os cluster at imperfections on the MoS surface. The studies on the Os cluster 2 interaction at photoelectrochemically oxidized MoS give reasons to believe that at the MoS imperfections an enhanced 2 2 reactivity occurs. This is due to the presence of dangling bonds. These dangling bonds have oxides or other oxygen Ž . containing groups e.g., OH that act as coordination sites for the clusters. In this way, we show a way of controlling the amount of surface modification by controlling the amount of imperfections on the MoS surface by photoelectrochemical 2 oxidation. q 1999 Elsevier Science B.V. All rights reserved. Ž . Ž . Keywords: Scanning tunneling microscopy STM ; X-ray photoelectron spectroscopy XPS ; Osmium; Molybdenum disulfide 1. Introduction The use of metal supported complexes in hetero- w x geneous catalysis has been widely studied 1–4 . ) Corresponding author. Tel.: q1-787-764-0000, ext. 4807; Fax: q1-787-756-8242; E-mail: cabrera@web.uprr.pr 1 Current address: Department of Chemistry, Cornell Univer- sity, Baker Laboratory a182, Ithaca, NY 14853, USA. 2 Current address: Department of Chemistry, Cayey University College, University of Puerto Rico, Cayey 00736, Puerto Rico. w x Catalysts of the type metal-silica 5–9 , metal- w x w x alumina 10,11 , and metal-substrate 12–18 have been prepared mainly by reacting a metal cluster with one of the mentioned supports. Special interest was devoted in the elucidation of the structure of w x w x these clusters in alumina 19,21 , silica 19,8,20,21 and over other metallic and nonmetallic supports w x 22,23 , where the interactions of these clusters with the substrates were elucidated. It is our interest to study the interaction of metal carbonyl clusters with layered type materials that have shown catalytic applications. Recently, we have studied the surface 0169-4332r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-4332 98 00616-3